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Susanta Kumar Chakraborty
Riverine Ecology Volume 1 Eco-functionality of the Physical Environment of Rivers
Riverine Ecology Volume 1
Susanta Kumar Chakraborty
Riverine Ecology Volume 1 Eco-functionality of the Physical Environment of Rivers
Susanta Kumar Chakraborty Vidyasagar University Midnapore, West Bengal, India
ISBN 978-3-030-53896-5 ISBN 978-3-030-53897-2 (eBook) https://doi.org/10.1007/978-3-030-53897-2 © Springer Nature Switzerland AG 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland
Dedicated to the fond memories of my Parents Late Mr. Bhupendra Mohan Chakraborty and Late Mrs. Binapani Chakraborty who first taught me to love and learn nature……
Preface
Although, the two thirds of the entire globe are covered with water, fresh water only shares a very negligible fraction of it, but provides considerable ecological services, along with catering to the need for drinking, irrigation, fisheries, aquaculture, energy production, navigation and transportation, industries, tourism, etc. A holistic approach of unraveling intricate relationships among so many structural components (living and nonliving) of fresh water ecosystem, generates necessary scientific inputs for chalking out strategies for the eco-management of several freshwater bodies such as rivers, lakes, and wetlands all over the globe. The prime objective of writing up this textbook is to present a balanced, comprehensive, and contemporary knowledge bases of the underlying science in the functioning of riverine ecosystem, highlighting the eco-potentiality of the physical environment of the lotic aquatic ecosystem. On realizing the need and significance of freshwater river ecosystems, especially for the very existence of human civilization, and also for the sustenance of global environment, integrated management practices based on a holistic approach for nourishment and restoration of river basin ecosystems are necessary, and a number of international efforts viz., the Stockholm conference on the Human Environment (1972), United Nations conference on Environment and Development (1992), International Geosphere-Biosphere Program, International Human Dimension Program, and more recently the European Union’s Water Framework Directive, have been implemented with the prime objective of ensuring the sustainable conservation of rivers and their living and non-living resources. As a corollary to these efforts, this book has highlighted different facets of riverine ecology and its underlying scientific principles, hypotheses, and theories in order to explain complex interactions that operate in the functioning of this unique, dynamic and precious ecosystem of the world. Considering the interconnectedness of river basins as being a unified system, an understanding of the delicate ecological balance among litho-bio-hydro-atmospheric processes within riverine basin is considered as prerequisite for the successful eco- management of rivers and adjoining ecosystems. The demand of the time is to discuss on the multidimensional and multidisciplinary characters of water highlighting the sources, threats, and conservative management. vii
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A river basin is a basic geographic and climatological unit where most of the biogeochemical cycles and trophic interactions occur, the outcomes of which are manifested at different spatiotemporal scales. Integral components of rivers such as drainage channels and different geomorphological, physical, and chemical components within the river basin act as an interconnected unified system through a delicate environmental equilibrium. In the undisturbed normal and pristine state, the river ecosystem maintains its ecological health and stability through its eco-dynamism. The eco-potential and effectiveness of riverine ecosystems can only be evaluated on developing transparent understanding of the ecological functioning of the system in response to a myriads of interactions among physical, chemical, and biotic environmental variables. However, deviation from the normal state of the prevailing ecological factors and processes within the river ecosystem affects the ecological equilibrium and results in detrimental effects on the natural dynamism of rivers and consequently the well-being of mankind. The planning for the water resource development and management by the Government of India could not pay required attention on the need for sustainability and equity even after several decades of independence. Indian planning moved one step forward in undertaking strategy for harnessing the bounty of both surface water and groundwater resources of rivers which initially received unquestioned acceptance. Since 1990s, serious questions began to be raised on the enlightenment of continuing understanding and approach towards the sustainability of rivers and also groundwater reserves in view of the harmful ecological impacts of the green revolution (loss of indigenous species of crops, over dependence on chemical fertilizers and pesticides, more abstraction of surface water, lifting of groundwater for irrigation, etc.). Since 1970, the subject ecology has fully emerged from its roots in the realm of biological sciences to become an integrated discipline of science by way of interlinking living organisms, the physical environment, and humans. A limnological (ecology of freshwater system) approach has been enjoying steady acceptance all over the world in the decision-making process in order to combat the ongoing problems of water pollution, mitigation of dam-mediated ecological disturbances, and for the enhancement and conservation of fish and wildlife of rivers. Streams as the lotic eco-zone in the headwater regions experience a rapid flow of shallow water which impose shearing stress on the stream bed, and result in the development of rocky or gravel or sandy substratum covered by transparent and oxygenated water. In the pursuit of having proper understanding of the limnological properties of the lotic water bodies, emphasis has been laid in identifying the differences among the physical and chemical characteristics of waters of various geomorphological regions and the diversity of different biota and their growth characteristics Writting up this text book on Riverrine Ecology with an emphasis on the ecofunctionality of the physical environment of the riverine ecosystem had an intention to pool some salient ideas (characteristics of water, basic operating principles of ecology, biogeochemical cycles, several geo morphological and geohydrological structural and functional pathways) and also to link up them to understand the physical structure and processes within the river for proper governance, with an aim at
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tackling the adversity in respect of the ecological perturbations and other associated ecological changes. Greater avenues are also expected to be generated for making the resources available starting from various administrative agencies to end users, the private sector, and civil society. The publication of this book is also intended to draw attention to and also enlighten academicians, researchers, administrators, and planners about the multidimensional aspects of river ecology from both theoretical and practical views. This book is dedicated to those interested in the natural and social sciences, especially for the students and researchers of ecology, environmental sciences, environmental planners, and administrators, for their understanding of the elements pertaining to the functioning of river ecosystem, and also to highlight sensitivity, and vulnerability of such functional manifestations through already established relevant underlying scientific principles, hypotheses, theories, and different strategies of eco-restoration alongside sustainable eco-management of rivers and aquatic ecosystems with an emphasis of socio-ecological perspective. Emphasis was given in explaining the gradual evolution of the concepts of river basins, watersheds, floodplains, tributaries, highlands, and foothills along with highlighting the present and past of the river in India especially of the precolonial times. The first chapter of the book is an elaborate introduction that touches upon the main objectives and contents of the book. Instead, each chapter will frame its own meaning in the context of the specific topic covered. The subject river ecology has been dealt with by detailing its multidimensional facets with subject contents distributed in six elaborate chapters starting with Chapter 1: Introduction—briefly highlighting main objectives and contents of this book; Chapter 2: Properties and Distribution of Water, Rivers, and Related Matters; Chapter 3: Basic Principles of Ecology and Their Relevance to Rivers; Chapter 4: Biogeochemical Cycling with Respect to Riverine Ecosystem; Chapter 5: Physiography of the Riverine System in general (international and national) and regional research study sites in particular mainly focusing on ground reality and different relevant theories, hypotheses, etc. This chapter also has included some relevant aspects of Indian rivers with more focus on the river Ganges; Chapter 6: Geohydrology in Riverine Systems highlighting basic research undertaken in the southwestern part of the State West Bengal, India; Chapter 7: Physicochemical Parameters in respect of temporal and spatial variations projecting the case studies of the riverine networks of the southwestern part of the State of West Bengal, India; Chapter 8: Conclusion summarising the major thrust subject contents of all the chapters of the book and commenting on the past, present and future of ecological research on rivers centering mostly on the their physical environments. This book is organized with an introductory chapter (Chap. 1) preceding with other chapters detailing the subjects like properties of water, basic ecology, biogeochemical cycling, physiography, geohydrology, limnological (physico-chemical) parameters (water and soil quality parameters), and an elaborate chapter as conclusion, summing up main thrust areas of each of the previous chapters with an eye to generate knowledge base in documenting, explaining, interpreting the nonliving resources for facilitating the ecoassessment ventures for river ecosystem.
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After Chap. 1 (Introduction), each of the six chapters in between Chapter 1 (Introduction) and Chapter 8 (Conclusion) is organized as: it begins with an abstract, followed by the main contents presented under different headings and subheadings incorporating major developments in the subject in the international panorama substantiated by regional case studies. An overview of the subject components is given at the beginning of every chapter. The entire discussion ends with a brief conclusion followed by references and recommendation for further readings. The introduction part of each chapter begins by explaining why the knowledge on the ecological functioning of rivers and their integrations with the history, culture, and economics of human beings are needed for understanding river science and management. Besides, significance of the rationality and relevance of the contents of other chapters has been highlighted to justify their inclusion in this book. Organizing the book focusing on an application-oriented approach is expected to allow the readers to easily access and locate information along with pertinent interpretations that are needed for their understanding of the subject matters of the relevant chapters. Chapter 1: Introduction: This introductory chapter of this book has touched upon major aspects of the entire book, focusing on their speciality and applicability in the realm of river ecology. Chapter 2: Properties and Significance of Fresh Water: In order to unravel the mystery of the multidimensional properties of water, an interdisciplinary approach involving a range of disciplines across physical, biological, and even social sciences has been highlighted. This chapter has discussed on all those uniqueness of water and applicability. Chapter 3: Basic Ecology: Theories and Practice Relevant to River: This chapter discussing on both basic and applied ecological principles relevant to riverine ecology, has focused mainly on the close interrelationships between water and land. The subject ecology has the distinction of being peculiarly confronted with uniqueness because of the interacting innumerable number of species and genetically distinct individuals, all living in a varied and ever-changing world. The challenge of ecology is to develop an understanding of very basic and apparent problems that recognizes uniqueness and complexity by an integration of three divisions of science, biology, chemistry, and physics, to explain the patterns of ecosystem functioning and often to offer predictions for future ecological changes. Applying ecological principles is not only a practical necessity but also a scientifically challenging task to unfold the preponderating complex relationship at the level of individual organisms, single species populations, whole communities, and ecosystems. It is ascertained that judicious and successful environmental planning and action based on the ecological principles lend successful outcomes in a sustainable manner. Chapter 4: Biogeochemical Cycling and Trophic Interactions: This chapter explains the pathways of the cyclical movement of essential life-supporting components from the living organisms to their nonliving surroundings that drive the trophic cascade, within the food-chains and food web networks of the riverine ecosystems by practicing and manifesting different types of feeding behaviors such as herbivory and predatory.
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Chapter 5: Physiography of Rivers: Relevant Hypothesis and Theories: This chapter deals with the physiography of riverine system with proper interpretation from the global to regional levels mostly citing different hypothesis and theories pertaining to river movements, connectivities, habitat formations, etc. This chapter also has stressed upon different established theories, hypotheses, and scientific principles such as that River Continnum Concept, Environmental Flows, Hydrological Flow Pulse, Hydrogeomorphic Patches and Associated Functional Process Zones (FPZs), and theories on Nutrient Spiraling and River Ecosystem Synthesis, Flood Pulse Concept, Equilibrium vs. Non-equilibrium, Descriptive vs. Mechanistic, Riverscapes vs. Riverine Landscapes, Hypothesis, Regime Shift and Resilience Shift, and Biocomplexity in Riverine Ecosystem Synthesis. Chapter 6: Geohydrological Perspectives of Riverine Flows: This chapter has dealt with hydrodynamics in the riverine ecosystem from the point of view of hydrogeological perspective, sources and origin of different geological formation, water distribution, horizontal and vertical, surface-groundwater interactions, etc. The management of surface water resources is essential for human and ecosystem health and social and economic growth and development. Water resource professionals use a wide range of technical management tools which are firmly based on the physical, biological, mathematical, and social sciences. This work addresses the fundamental physical and biological processes in surface water systems that provide the basis for both deeper understanding and management decision-making. The complexity of the natural surface water environment combined with the everincreasing capabilities of computers to simulate the temporal evolution of systems represented by differential equations has made hydrodynamic and water quality models as essential tools for both science and management. Chapter 7: Physicochemical Parameters and Their Seasonal Dynamics— Special Reference to Riverine Networks of South West Bengal, India: This chapter has highlighted the eco-dynamics of major rivers in respect of their physicochemical variables in temporal and spatial scales highlighting the case studies from the freshwater riverine networks of south West Bengal, India. Chapter 8: Conclusion: Three main messages which have been emerged from the presentation, discussions and analyses of research information pertaining to physical environment or rivers summarized as follows. This book reviews the current scientific developments to make them useful for sustainable river management and to ascertain the society to learn its way into an uncertain future. It starts with a separate chapter dealing with the proper evaluation of riverine water, and its properties, followed by other complete chapters discussing on the basic ecological principles pertaining to biogeochemical cycling and the assessment of the geohydrological potential of rivers so that restoration of the normal functioning of environmental flows and ecosystem services in riverine systems can be possible. The scientific perception, realization, and understanding of the ecology of freshwater riverine ecosystem were developed century years back as this biologically productive and sensitive running water ecosystem represents the lifeline of human being by providing water, and food, alongside shaping the sociocultural profiles of a region. The quest of human being for unraveling the mysteries
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of river and its associated landscapes has not only been restricted to several studies on food resources obtained from rivers but also on the changing ecological status of it with special emphasis on environmental perturbations in the backdrop of the River Continuum Concept. In addition, chalking out appropriate and effective eco-management strategies towards a sustainable future of riverine ecosystems replacing the ongoing economic and technological development (detrimental to the ecological health of rivers, and acting as the disruptive forces against ecological services), have appeared to partially meet the materialistic thrust of human beings but it seems to be increasingly difficult in the present pace of increasing economic and ecological turbulence. This book reviews the current scientific developments in the domain of physical environment of rivers in order to make them useful for sustainable river management and to ascertain the society to learn its way into an uncertain future. It starts with proper evaluation of riverine water and its unique properties, basic ecological principles operating in the ecosystem levels, multidimensional interactive pathways pertaining to biogeochemical cycling and trophic interaction, and different theories and hypothesis in respect of nutrient cycling and habitat developments and assessment of the geohydrological and physicochemical properties within riverscapes so that baseline research information can be generated to support and strengthen the mitigation measures not only to arrest the ongoing damages but also to restore the function of environmental flows and ecosystem services in riverine systems. In a number of ways, it is increasingly difficult to separate scientific pursuit from an emotional and aesthetic bond in unraveling the mysteries of interlinkages and interdependence of different structural components of rivers, their intricate interaction pathways, and eco-management (conservation ethos and rehabilitation practices). This book deliberated the current scientific developments in order to make them useful for sustainable river management and also to ascertain the society to learn its way into an uncertain future. In the quest to develop a logical set of principles for analyzing and interpreting the diversity and complexity of the riverine environment, this book is an attempt to communicate the already developed knowledge and understanding on multidimensional subjects in a holistic but as simple as possible way. Although much emphasis was laid on depicting the regional information with an Indian flavor, but much endeavor was put on global perspective for developing the concept, hypothesis, and theories pertaining to riverine ecology so that useful guidance is provided for the development of core understanding that is required to achieve sustainable outcomes through ecomanagement practices. Duplications, inaccuracies, and inconsistencies may have arisen in cross- disciplinary use of terms and also in dealing with the subjects in different chapters but hopefully it was possible to provide a platform with the help of several photographs, figures, flow charts, and tables to address to the broad objectives of the book. This book will cover state of the art on ecology, hydrodynamics, sediment transport, and water quality in surface waters and also taking into consideration of surface water–groundwater interactions in one comprehensive text. But instead of venturing to cover every detail of water and its qualities, ecological relationships,
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hydrodynamics, and sediment transport, the major thrust of the book is to enable the proper identification and integration of eco-potentiality of hydrodynamics of riverine ecosystem in an holistic manner, which is expected to open up new vistas to counteract different eco-problems in and around riverine flows. The readers are supposed to understand basic ecological principles and ongoing geohydrological interactions shaping and sustaining a riverine ecosystem along with the essence and flavors of different scientific theories and hypothesis that have been put forward to explain such riverine eco-dynamics during last one century. The understanding of all research information are expected to help solving the ongoing problems. All relevant information from different (primary and secondary) are only presented on a need-to-know basis. However, these baseline research information tend to support and strengthen the mitigation measures not only to arrest the ongoing damages but also to restore the function of environmental flows and ecosystem services in riverine systems. Midnapore, West Bengal, India Susanta Kumar Chakraborty
Acknowledgement
No book is conceived without the support and assistance of others and I had the privilege of having more than my fair share of both. First, the authorities of my institute, Vidyasagar University at Midnapore (West), West Bengal, India, made it possible to pursue such time-consuming and painstaking work by providing me with the necessary facilities. Secondly, it is the time for me to recognize and render my best regards to all my senior advisers, and my sincere thanks to all my junior researchers, well-wishers, and friends for their valuable support throughout the entire journey of writing up this book since the time the idea was first conceived and was subsequently crystallized on getting the approval from the publishing house, Springer, USA. Writing of this book could not have been possible without the generous support of Springer Publication House, Springer Nature Switzerland AG, Gewerbestrasse 11, 6330 Cham, Switzerland, especially Ron Doering, Guido Zosimo-Landolfo, Rain, Amelie Von Zumbusch, Schimide, Aaron Schiller, Lavanya Venkatesan and Silembarasan Pannerselvam, who by virtue of their sincere and considerate support acted as the driving force for writing up this book covering multidimensional aspects of riparian ecology, (Volume II of the book Riverine Ecology: Ecofunctionality of Physical Environment of River), which have been discussed and presented in eight complete and comprehensive chapters including one introduction and one conclusion. The first chapter as introduction and last (8) chapter as conclusion have attempted to discuss most of the thrust areas that have been elaborately highlighted in six other chapters unique (properties and distribution of water, basic ecological principles, biogeochemical cycles and trophic interactions, physiography with different pertinent theories and hypothesis, geo-hydrology, and eco-dynamics of rivers based on physicochemical parameters). I shall be failing in my duty not to name some of my research students such as Tridip, Sujoy, Md. Abdullah, Santu, Sayan, Sankarson, Santanu, Ram, Hirulal, Sankarsan, Srinjana, Tilottama, Manjishtha, Sangita, Kishalay, Poulami, Srinjana, Subhasree, Anindita, Jayanti, Srinjana, Arundhuti, and Joydev for their active support and secretarial assistance throughout the entire period of this book preparation. Although I have the privilege to owe to all of them, I must extend my special thanks to Dr. Tridip Dutta, my Ph.D. student, and
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Jagadish Mahata, supporting staff of Vidyasagar University, for their wholehearted assistance in the typing, formatting, and preparation of schematic figures. It is my privilege to acknowledge different research-sponsoring agencies such as University Grant Commission (UGC), Department of Environment and Forest, Indian Council of Agricultural Research (ICAR) National Agriculture Technology Project (NATP), UNIFEM, Department of Biotechnology (Govt. of India), Department of Science and Technology, West Bengal Pollution Control Board, Department of Public Health Engineering, Government of West Bengal, India and many other corporate and industrial agencies for sanctioning consultancy projects on different aspects of Environmental Impact Assessment (EIA). The research outcomes in one form or others have been incorporated in this book as and when required in accordance with the demand of the subjects. A book such as this could also not be written without the unwavering support of countless mentors, colleagues, and friends. I am really indebted to a number of them as my coauthors of several research papers, many among whom happen to be my Ph.D. students and co-supervisors of my Ph.D. students. I must acknowledge the exciting and thought-provoking association with a number of research associates, namely, Professor Sankar Kumar Acharya of Bidhan Chandra Krishi Viswavidyalaya, Professor Sangamitra Raha of Saha Institute of Nuclear Physics, Dr. Phanibhusan Ghosh-Scientist of Wetland Research Institute, Dr. (Mrs.) Priyanka Halder Mallick, Associate Professor of Zoology, Vidyasagar University, Dr. Ashish Kumar Paul Professor of Geography, Vidyasagar University, Dr. Jatisankar Bandopadhyaya, Assistant Professor of GIS and Remote Sensing, Vidyasagar University, Dr. Debdulal Banerjee, Department of Botany, Vidyasagar University, and Professor Bikash Ranjan Pati, Retired professor of Microbiology, Vidyasagar University, for their contributions for publication of research papers and preparation of reports of a number of research projects. I am thankful to Dr. Suman Pratiher, Assistant Professor of Zoology, Keshpur College, Midnapore (West), West Bengal, India for his contribution of several photographs of the Himalayan stretches of the River Ganges. Besides, my two decades long research on river ecology, pollution, and biodiversity have only been made possible because of the very active, sincere, and committed research supports from a number of my research scholars and research assistants; they are Dr. Nandan Bhattacharya, Dr. Subrata Giri, Dr. Siddhartha Mishra, Dr. Prasenjit Pradhan, Mr. Ritwik Majumder, Dr. Barun Dey, Dr. Sunirmal Giri, Dr. Gurudas Chakravorti, Dr. Gautam Chandra, Dr. Gautam Bhunia, Dr. Diptiman Ghosh, Dr. (Mrs.) Sangita Maity Dutta, Dr. Subhasis Chatterjee, Dr. Subrata Giri, Dr. Subrata Jana, Dr. Kartik Bera, Mr. Kishalay Paria, Mr. Prasenjit Sahu, Dr. Hirulal Pakhira, Dr. Manjishtha Bhattacharyya, Dr. Subhasree Middya, Mr. Bapi Doloi, as field Assisstant, Mr. Sahadev Chakraborty as Driver and many others. Although the author writes a book, if it is a textbook, it does not or should not belong as a product of author alone. Thousands of pieces of information generated by a multitude of research activities have been used in one form or another to enrich the subject of each and every chapter of this book. Therefore, writing up a research- based textbook is not that easy as it appears to be because it needs not only highlighting the existing research information on the relevant subjects but also
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presentation of a comparative view of the earlier research outcomes undertaken by different researchers from different corners of the globe. Simultaneously, already established research ideas or findings should be paid proper recognition. This book could not have been made possible without the patient cooperation and encouragement of my family members, especially my wife Jhuma and my son Sunrita, who have never complained about my inadvertent absence and dissociation from daily affairs.
Contents
1 Introduction���������������������������������������������������������������������������������������������� 1 1.1 Water and Rivers ������������������������������������������������������������������������������ 3 1.2 Uniqueness of River Ecosystem ������������������������������������������������������ 4 1.3 Historical Background of Rivers in Respect of Human Beings���������������������������������������������������������������������������������� 5 1.4 Classification of Rivers �������������������������������������������������������������������� 6 1.5 Physicochemical and Biophysical Parameters in River Ecology �������������������������������������������������������������������������������������������� 7 1.6 Biogeochemical Pathways: Cyclical Relationship Among Living and Nonliving Components�������������������������������������������������� 7 1.7 Pulsing of Food Web Dynamics: Roles of Resource Bases and Ecological Factors���������������������������������������������������������������������� 8 1.8 Pulsing of Rivers-Floodplains Hydrology: Top-Down Control of Basal Resources���������������������������������������������������������������������������� 9 1.9 Geomorphology and Flow Variability of Rivers ������������������������������ 10 1.10 Different Dimensions of Hydrogeology and Its Relevance in the River Ecology ������������������������������������������������������������������������ 10 1.11 Environmental Management of River Basin: Integration and Complementation of Land and Water ���������������������������������������������� 11 1.12 Physiography of Rivers and Floodplains: Relevant Theories ���������� 12 1.13 Environmental Flows in River Ecosystem���������������������������������������� 13 1.14 Geomorphology vs. Biotic Activities: Role of Spatial Heterogeneity������������������������������������������������������������������������������������ 13 1.15 Ecological Conditions for Environmental Flows in Rivers�������������� 14 1.15.1 Flow Velocity������������������������������������������������������������������������ 14 1.15.2 Temperature�������������������������������������������������������������������������� 14 1.15.3 Riparian Vegetation�������������������������������������������������������������� 15 1.15.4 Sunlight�������������������������������������������������������������������������������� 15 1.15.5 Oxygen Dissolved in Water (D.O)���������������������������������������� 15 1.15.6 pH Value of Water ���������������������������������������������������������������� 15
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1.15.7 Substrates and Their Roles���������������������������������������������������� 16 1.15.8 Nutrients and Eutrophication of Water �������������������������������� 16 1.16 River Continuum Concept (RCC): A Means of Orderly Arrangement of Ecological Processes���������������������������������������������� 17 1.17 Concluding Remark�������������������������������������������������������������������������� 18 References�������������������������������������������������������������������������������������������������� 18 2 Water: Its Properties, Distribution, and Significance�������������������������� 23 2.1 Water: A Unique Creation of Nature������������������������������������������������ 24 2.1.1 Some Facts of Water ������������������������������������������������������������ 29 2.2 Water Balance Within Living Organisms: A Prerequisite for Survivality of Organisms������������������������������������������������������������ 29 2.3 Hydrological Cycles�������������������������������������������������������������������������� 30 2.3.1 Evaporation �������������������������������������������������������������������������� 31 2.3.2 Condensation������������������������������������������������������������������������ 31 2.3.3 Transpiration ������������������������������������������������������������������������ 31 2.3.4 Percolation���������������������������������������������������������������������������� 32 2.3.5 Precipitation�������������������������������������������������������������������������� 32 2.4 Water Cycles Between Earth and the Atmosphere���������������������������� 32 2.5 Properties of Water���������������������������������������������������������������������������� 33 2.5.1 Physical Properties of Water ������������������������������������������������ 33 2.5.2 Chemical Properties�������������������������������������������������������������� 36 2.6 Flows and Exchange of Materials from Water to Other Environmental Compartments���������������������������������������������������������� 36 2.6.1 Dissolved Substances in Water �������������������������������������������� 37 2.6.2 Humic Substances and Other Organics in Water������������������ 38 2.7 Hydrologic Cycle������������������������������������������������������������������������������ 38 2.8 Relationships Among Water Viscosity, Inertia, and Physical Parameters���������������������������������������������������������������������������������������� 39 2.8.1 Viscosity Is the Resistance to Change in Form, or a Sort of Internal Friction ������������������������������������������������ 39 2.8.2 The Reynolds Number (Re)�������������������������������������������������� 39 2.8.3 Relative and Dynamic Viscosities and Their Effects on Aquatic Organisms���������������������������������������������������������� 40 2.8.4 Movement of Water (Brownian Motion)������������������������������ 40 2.8.5 Solar Heating and Evaporation of Water������������������������������ 41 2.9 Movement of Light, Heat, and Chemicals in Water�������������������������� 41 2.9.1 Diffusion of Chemicals in Water������������������������������������������ 41 2.10 Some Unusual Properties of Water �������������������������������������������������� 42 2.10.1 Density���������������������������������������������������������������������������������� 42 2.10.2 Heat Capacity and Specific Heat������������������������������������������ 43 2.10.3 Heat of Fusion/Melting �������������������������������������������������������� 43 2.10.4 Heat of Vaporization/Condensation�������������������������������������� 43 2.10.5 Isotopes �������������������������������������������������������������������������������� 43 2.10.6 Sublimation�������������������������������������������������������������������������� 44
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2.10.7 Surface Tension and Cohesiveness: Roles of surfactants������������������������������������������������������������������������ 44 2.10.8 Viscosity�������������������������������������������������������������������������������� 45 2.10.9 Colligative Properties������������������������������������������������������������ 45 2.11 Circulation of Water: Influence on Chemical and Biological Processes ������������������������������������������������������������������������������������������ 45 2.11.1 Circulation of Water in Freshwater Bodies (Lentic and Lotic) ���������������������������������������������������������������� 46 2.11.2 Diffusion in Water���������������������������������������������������������������� 46 2.12 Distribution of Water������������������������������������������������������������������������ 47 2.13 Characteristic of Freshwater Systems���������������������������������������������� 47 2.13.1 Running Waters: Lotic Ecosystems�������������������������������������� 47 2.14 The History of Freshwater Systems�������������������������������������������������� 48 2.15 Underground Freshwater������������������������������������������������������������������ 49 2.16 Aboveground Freshwater������������������������������������������������������������������ 49 2.17 Ponds, Lakes, and Other Wetlands���������������������������������������������������� 50 2.18 Rivers and Streams���������������������������������������������������������������������������� 50 2.19 Human Advancements and Water ���������������������������������������������������� 51 2.19.1 Water in Ancient Civilizations���������������������������������������������� 51 2.19.2 Water in Modern Times�������������������������������������������������������� 53 2.19.3 Freshwater Consumption������������������������������������������������������ 53 References�������������������������������������������������������������������������������������������������� 54 3 Ecology and Its Relevance to Environmental Problems���������������������� 57 3.1 Concept and Definition of Ecology�������������������������������������������������� 58 3.2 Ecology vs. Man: An Historical Perspectives���������������������������������� 61 3.3 Biology vs. Ecology: Inter Exchangeable Relationships������������������ 62 3.4 Organizational Ecology: Major Developments in Ecology�������������� 63 3.5 Ecosystem Ecology: Concept, Origin ���������������������������������������������� 63 3.6 Definition and Origin of Ecosystem Concept ���������������������������������� 64 3.6.1 Definitions of Ecosystem������������������������������������������������������ 65 3.7 Structural Components of Ecosystem���������������������������������������������� 66 3.7.1 Major Structural Components in River Ecosystem�������������� 67 3.8 Holistic Approach of Ecosystem Functioning: Relationship with Ecosphere and Biosphere���������������������������������������������������������� 70 3.9 Organisms Ecosystem Interaction: Environmental Perspectives�������������������������������������������������������������������������������������� 71 3.10 Hierarchy of Ecological Systems: Population, Community, Biosphere, and Ecosphere���������������������������������������������������������������� 72 3.11 Functional Ecosystem: Production of Biomass and Flow of Energy������������������������������������������������������������������������������������������ 73 3.11.1 Ecosystem as Cybernetic System����������������������������������������� 75 3.11.2 Stability of Ecosystem: Homeostasis������������������������������������ 75
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3.12 Energy and Ecosystem���������������������������������������������������������������������� 77 3.12.1 Energy ���������������������������������������������������������������������������������� 77 3.12.2 Productivity and Ecological Efficiency�������������������������������� 90 3.13 Primary Productivity: Gross and Net Primary Productivity ������������ 93 3.13.1 Threshold Concentrations and Sustainable Budgeting of Energy������������������������������������������������������������������������������ 94 3.13.2 Energy Balance by Heterotrophic Organisms: Secondary Production ���������������������������������������������������������� 94 3.13.3 The Significance of Transfer Efficiencies as a Determinant of Energy Pathways ���������������������������������������� 95 3.14 Secondary Productivity �������������������������������������������������������������������� 96 3.15 Environmental Factors Determining Biological Productivity���������� 97 3.16 Relationship Between Biodiversity and Productivity ���������������������� 97 3.17 Habitat and Niche Concept �������������������������������������������������������������� 98 3.17.1 Habitat and Its Ecological Significance�������������������������������� 98 3.17.2 Ecological Niche: Definition and Types ������������������������������ 104 3.18 Concept and Applicability of Ecological Niche�������������������������������� 106 3.18.1 Ecological Niche and Inter-Specific Competition: (Resource Partitioning, Niche Overlap)�������������������������������� 106 3.18.2 Types of Niche Differentiation and Resource Partitioning���������������������������������������������������������������������������� 109 3.19 Individual Ecology (Autecology)����������������������������������������������������� 112 3.19.1 Population Ecology�������������������������������������������������������������� 112 3.19.2 Age Structure������������������������������������������������������������������������ 115 3.19.3 Significance of Reproduction and Sex Ratios���������������������� 116 3.19.4 Mortality and Natality���������������������������������������������������������� 116 3.19.5 Population Ecology: Population Dynamics: (Population Growth and Regulation)������������������������������������ 117 3.20 Predation: Lotka–Volterra Model of Predation�������������������������������� 125 3.20.1 Predation ������������������������������������������������������������������������������ 125 3.21 Community and Community Interactions���������������������������������������� 130 3.21.1 Community Interactions: Environmental Gradients ������������ 131 3.21.2 Organismic Concept of Biotic Community�������������������������� 131 3.21.3 Individualistic Concept of Biotic Community���������������������� 132 3.21.4 Ecotypes and Ecoclines�������������������������������������������������������� 132 3.21.5 Ecotones and Edge Effects: Ecological Implications ���������� 134 3.21.6 Relationship among Taxon, Community, and Ecological Guilds������������������������������������������������������������������ 135 3.21.7 Stability, Equilibrium, and Nonequilibrium within Community �������������������������������������������������������������������������� 135 3.21.8 Link Between Diversity and Stability���������������������������������� 136 3.21.9 Life History Strategies���������������������������������������������������������� 136 3.22 Ecological Applications at the Level of Community and Ecosystems���������������������������������������������������������������������������������������� 137
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3.23 Metapopulation Dynamics: A Balance Between Colonization and Extinction ������������������������������������������������������������ 138 3.23.1 Metapopulation Equilibrium������������������������������������������������ 138 3.23.2 Four Conditions: Prerequisite to Justify a Metapopulation �������������������������������������������������������������������� 139 3.24 Community and Ecosystem: Relationships and Interlinkages���������� 141 3.25 Ecological Succession���������������������������������������������������������������������� 142 3.25.1 Types of Ecological Succession�������������������������������������������� 142 3.25.2 Steps of Ecological Succession of the Environmental Gradients: Autogenic and Allogenic Changes���������������������� 143 3.26 Relation of Ecology with Evolution������������������������������������������������� 145 3.27 Evolution, Coevolution, and Adaptation. Evolution of Cooperation�������������������������������������������������������������������������������������� 145 3.27.1 Evolution������������������������������������������������������������������������������ 145 3.27.2 Coevolution�������������������������������������������������������������������������� 146 3.27.3 Adaptations �������������������������������������������������������������������������� 146 3.28 Relation of Ecosystem with the Environment���������������������������������� 150 3.29 Ecosystem Interrelationships������������������������������������������������������������ 150 3.29.1 Disturbance and Resilience�������������������������������������������������� 151 3.30 Eco-evolutionary Attributes�������������������������������������������������������������� 152 3.30.1 Proximate and Ultimate Factors�������������������������������������������� 153 3.31 Aquatic Systems and Their Ecological Uniqueness ������������������������ 154 3.31.1 Ecological Resources������������������������������������������������������������ 155 3.32 Conservation: Roles of Metapopulation and Fragmentation������������ 159 References�������������������������������������������������������������������������������������������������� 161 4 Trophic Interactions and Biogeochemical Cycles in River Ecosystem�������������������������������������������������������������������������������������������������� 167 4.1 Biosphere, Ecosphere, and Biogeochemical Cycles ������������������������ 168 4.1.1 Trophic Relationship������������������������������������������������������������ 169 4.1.2 Trophic Interactions�������������������������������������������������������������� 170 4.1.3 Biogeochemical Cycles: Definition, Concept, and Classification������������������������������������������������������������������ 173 4.1.4 Types of Biogeochemical Cycles������������������������������������������ 174 4.2 Hydrologic Cycle and Identification of Habitats������������������������������ 178 4.2.1 Water Cycle and Water Balance�������������������������������������������� 178 4.2.2 Aquatic Habitats and the Hydrologic Cycle ������������������������ 180 4.2.3 Water Economy: Hydrological Cycles���������������������������������� 182 4.3 Hydrological Cycles and Its Different Components ������������������������ 183 4.3.1 Evaporation and Precipitation���������������������������������������������� 183 4.3.2 Runoff Flow Processes���������������������������������������������������������� 183 4.4 Global Water Balance ���������������������������������������������������������������������� 184 4.5 The Hydrological Cycle and Global Processes�������������������������������� 185 4.6 Human Modification of the Environment ���������������������������������������� 185 4.7 Oxygen Cycle������������������������������������������������������������������������������������ 186
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4.8 Nitrogen Cycle���������������������������������������������������������������������������������� 187 4.9 Carbon Cycle and Conditions for Biosphere Stability���������������������� 188 4.9.1 Carbon Cycle in Streams and Rivers������������������������������������ 189 4.10 Phosphorus Cycle������������������������������������������������������������������������������ 191 4.10.1 Occurrence of Compound Forms of Phosphorus in Nature������������������������������������������������������������������������������� 192 4.10.2 Cycling of Phosphorus���������������������������������������������������������� 192 4.11 Sulfur Cycles and Its Different Dimensions in the Ecosystem Functioning �������������������������������������������������������������������������������������� 193 4.11.1 Sedimentary and Sulfur Cycle���������������������������������������������� 193 4.11.2 Different Pathways of the Sulfur Cycle�������������������������������� 194 4.12 Nutrient Cycles in River Ecosystem ������������������������������������������������ 194 4.12.1 Nutrient Cycling: Role of Mineralization ���������������������������� 195 4.12.2 Decomposition in Aquatic Ecosystem���������������������������������� 195 4.13 Aerobic and Anaerobic Conditions�������������������������������������������������� 196 4.14 Nutrient Cycles and Nutrient Spiraling: Tightly Coupled Systems �������������������������������������������������������������������������������������������� 197 4.14.1 Nutrient Spiraling and Its Contribution in Nutrient Cycling���������������������������������������������������������������������������������� 198 4.14.2 Importance of Autochthonous Versus Allochthonous Contributions������������������������������������������������������������������������ 199 4.14.3 Nutrient Cycling in Streams and Lakes�������������������������������� 199 4.14.4 Stream Invertebrates and Spiraling Length�������������������������� 201 4.14.5 The Effect of Vertebrate Species on Nutrient Cycling in Aquatic Ecosystems���������������������������������������������������������� 201 4.14.6 Relationships Between Nutrient Uptake and Its Potential Determinants ������������������������������������������������������������������������ 202 4.14.7 Hypothesis Pertaining to the Differences of Nutrient Cycling Between Lakes and Streams������������������������������������ 203 4.14.8 Nutrient Cycling in Lotic Systems���������������������������������������� 203 4.14.9 Microbes and Trophic Interactions �������������������������������������� 203 4.14.10 Role of Detritus������������������������������������������������������������������ 206 4.14.11 Biological Decomposition�������������������������������������������������� 206 4.14.12 Common Decomposition Process �������������������������������������� 208 4.15 Trophic Structure of Food Cycles ���������������������������������������������������� 208 4.16 Detritus and Detrital Dynamics�������������������������������������������������������� 210 4.17 Trophic Interrelationships and Microbes: Zooplankton Interaction ���������������������������������������������������������������������������������������� 210 4.18 Bottom-up and Top-down Control on Food Web: Feedbacks of Geomorphology and Nutrient Enrichment ���������������������������������� 212 4.18.1 Case Studies of the Relationship of Bottom-up Phenomenon with Landscape Modification�������������������������� 213 4.19 Nutrient Limitation and Relevant Theory ���������������������������������������� 215 4.20 Biogeochemical Pathways in Between Rivers and Floodplains ������ 216
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4.21 Contributions of Birds and Fishes to Nutrient Loadings and Cycling �������������������������������������������������������������������������������������� 217 4.21.1 Methanogenesis and Its Contribution to River Ecosystem ���������������������������������������������������������������������������� 218 4.22 Degradation of Particulate Organic Matter in Sediments of Lotic System �������������������������������������������������������������������������������� 219 4.23 Degradation of Dissolved Organic Matter in Sediments of Lotic System �������������������������������������������������������������������������������� 220 4.24 Organic Matters and Allochthonous Sources of Nutrients��������������� 221 4.24.1 Types of Humic Substances�������������������������������������������������� 221 4.24.2 Formation of Humic Compounds ���������������������������������������� 222 4.24.3 Allochthonous Organic Matter �������������������������������������������� 223 References�������������������������������������������������������������������������������������������������� 225 5 Physiography of Rivers: Relevant Hypothesis and Theories �������������� 235 5.1 Uniqueness of Riverine Ecosystem�������������������������������������������������� 236 5.2 River Types: Complex Diversity or Confusing Variety?������������������ 241 5.2.1 Rivers and Ecosystems: Formation Spatial Other Geomorphological Structures ���������������������������������������������� 241 5.2.2 Different Spatial Structure and Their Relationships in Riverine Ecosystem���������������������������������������������������������� 243 5.2.3 Types and Characteristics of Channel Patterns �������������������� 245 5.2.4 Fluvial Geomorphology and Characterization of Rivers������ 246 5.2.5 Approaches and Criteria for Characterization���������������������� 247 5.3 River Classification: Stream Orders�������������������������������������������������� 248 5.3.1 Concept and Types���������������������������������������������������������������� 248 5.3.2 Stream Order: An Important Way to Characterize Streams���������������������������������������������������������������������������������� 249 5.4 Classification of Streams Based on Water Budgeting���������������������� 250 5.4.1 Different Associated Landscapes of Streams and Rivers������������������������������������������������������������������������������������ 252 5.4.2 Structural and Functional Significance of Stream Corridor and Watershed�������������������������������������������������������� 253 5.4.3 Classificatory Scheme Based on River Morphology and Hydrology���������������������������������������������������������������������� 254 5.5 Characterization of Rivers and Streams�������������������������������������������� 260 5.6 Habitats Formation in Streams and Rivers���������������������������������������� 260 5.7 Categorization of Streams Based on Water Flow and Geology�������� 261 5.8 Meandering Effect on Development of Flood Plains������������������������ 264 5.9 Multifunctional Roles of Rivers�������������������������������������������������������� 266 5.9.1 Man as a Factor on River Systems���������������������������������������� 267 5.10 Movement of Materials by Rivers and Streams: Interconnectivity Among Landscapes���������������������������������������������� 268 5.10.1 Movement of Dissolved Materials in Riverine Flows: Associated Physical Processes���������������������������������������������� 269
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5.10.2 Models for Depicting Relation of Channels Cross Section with Dispersion�������������������������������������������������������� 269 5.11 Case Study on Detailed Hydro-Geomorphological Studies from South West Bengal, India �������������������������������������������������������� 270 5.11.1 Background Information of the Biogeography of the State of West Bengal, India�������������������������������������������������� 270 5.11.2 Geological Past of West Bengal, India���������������������������������� 272 5.11.3 Types and Mode of Origin of Rocks in West Bengal, India�������������������������������������������������������������������������������������� 272 5.11.4 Origin of Rocks in West Bengal, India �������������������������������� 273 5.11.5 Geological Background of the Rivers of South West Bengal, India: River Basin and Associated Watersheds�������� 274 5.12 Pilot Survey to Identify and Select Study Sites for Detailed Survey and Ecomonitoring of Environmental Changes�������������������� 275 5.12.1 Objectives of the Study: In the Backdrop of Riverine System in West Bengal��������������������������������������������������������� 276 5.12.2 Physiography of Subarnarekha and Kansai Rivers (Figs. 5.9, 5.10, 5.11, 5.12, 5.13, and 5.14)�������������������������� 277 5.12.3 Evolution of Landforms and Associated Resources ������������ 279 5.13 Physiography of Different Rivers of South West Bengal, India�������������������������������������������������������������������������������������������������� 280 5.13.1 Bio-geographical and Environmental Status of the Areas Under Study���������������������������������������������������������������� 281 5.13.2 Geological Formations and Eco-physical Features�������������� 283 5.13.3 Hydrogeology of the Sub-surface Water Flow and Storage���������������������������������������������������������������������������������� 288 5.13.4 Categorization of Riverine System in South West Bengal, India ������������������������������������������������������������������������ 289 5.13.5 Agro Climatic Conditions and Sources of Pollution of the River Basin of the Rivers of South West Bengal Climate���������������������������������������������������������������������������������� 293 5.14 Environmental and Socioeconomic Profiles of Different Studied Water Bodies������������������������������������������������������������������������ 294 5.15 Multifunctionality of River �������������������������������������������������������������� 296 5.16 Recent Perspectives on Theories, Hypothesis, and Concepts on Riverine Ecology�������������������������������������������������������������������������� 296 5.16.1 Continuum Models of River Systems ���������������������������������� 297 5.16.2 Nutrient Spiraling Concept (NSC)���������������������������������������� 297 5.16.3 River Continuum Concept (RCC)���������������������������������������� 298 5.16.4 Serial Discontinuity Concept (SDC)������������������������������������ 298 5.16.5 The Flood-Pulse Concept (FPC)������������������������������������������ 298 5.16.6 Network Dynamics Hypothesis (NDH)�������������������������������� 299 5.16.7 Hyporheic Corridor Concept (HCC)������������������������������������ 299 5.16.8 Hierarchical Framework for Stream Habitat Classification (HFSHC)�������������������������������������������������������� 300
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5.16.9 Patch Dynamics Concept (PDC)������������������������������������������ 300 5.16.10 Process Domain Concept (PrDC) �������������������������������������� 300 5.16.11 Contemporary Concepts of River Systems ������������������������ 301 5.16.12 Hydrosystems Concept (FHC)�������������������������������������������� 301 5.16.13 Riverine Ecosystem Synthesis Concept (RESC)���������������� 301 5.17 Environmental Flows and Its Relevance in River Ecosystem���������� 302 5.17.1 River Regulation as a Global Phenomenon�������������������������� 302 5.17.2 Evolution of the Science of Environmental Flow Assessment���������������������������������������������������������������������������� 303 5.17.3 Holistic Approach of Environmental Flow Assessment�������� 304 5.17.4 Patterns of Biotic Community Along Longitudinal Dimension ���������������������������������������������������������������������������� 305 5.17.5 Hydro-Geomorphic Patches and Associated Functional Process Zones (FPZs) ���������������������������������������� 305 5.17.6 Problems on Designating Different Zones���������������������������� 307 5.17.7 The River as a Continuum: An Ecological Assessment of Riverine Flows and Biotic Association�������� 307 5.18 The Flood-Pulse Concept and Its Applicabilities in Lotic System���������������������������������������������������������������������������������������������� 313 5.18.1 Deficiencies of the Current Hypotheses�������������������������������� 314 5.19 Physical vs. Biological Control: Gradient of Relative Importance���������������������������������������������������������������������������������������� 314 5.20 Pristine vs. Developed Systems�������������������������������������������������������� 315 5.21 Equilibrium vs. Disequilibrium: Relevant Concept and Theories�������������������������������������������������������������������������������������������� 315 5.21.1 Case Studies in Support of Dynamic Equilibrium���������������� 316 5.22 Descriptive vs. Mechanistic Hypotheses������������������������������������������ 316 5.23 Future Directions for Large River Research: Weakness of RCC and FPC ������������������������������������������������������������������������������ 317 5.24 Network Theory and the Structure of Riverine Ecosystems ������������ 317 5.25 Temporal Dimension: Normality or Aberration�������������������������������� 318 5.26 Hierarchical Patch Dynamics Model (HPD) in Riverine Landscapes���������������������������������������������������������������������������������������� 320 5.26.1 Application of the HPD Model to Riverine Ecosystems������ 320 5.27 Hierarchy Theory to Explain Spatiotemporal Complexity of River Ecosystem �������������������������������������������������������������������������� 321 5.28 Hierarchical Patch Dynamics in Riverine Landscapes �������������������� 324 5.29 A Resilience Perspective for Integrated Ecosystem Management: Biodiversity, Landscape, and Climate������������������������ 328 5.29.1 Regime Shift and Resilience: Key Concepts in Ecosystem Management ������������������������������������������������������ 329 5.29.2 Regime Shifts vs. Ontogenetic Niche Shifts������������������������ 330 5.29.3 Effects of Ecological Contexts on the Occurrence of Regime Shifts and Ontogenetic Niche Shifts ������������������ 330
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5.30 The Riverine Ecosystem Synthesis: Biocomplexity in Riverine Networks Across Space and Time���������������������������������������������������� 331 5.31 Historical Perspectives and Philosophical Foundation �������������������� 331 5.32 A contribution to Conceptual Cohesiveness in Lotic Models���������� 332 5.33 Major Rivers in India: Uniques of Environmental Changes in the Ganga River���������������������������������������������������������������������������� 337 5.33.1 Physiography of Rivers of India: Ganges Being the Lifeline of Indian Civilization���������������������������������������������� 338 References�������������������������������������������������������������������������������������������������� 357 6 Geo-hydrological Perspectives of Riverine Flows �������������������������������� 375 6.1 Hydrogeology vs. Geohydrology������������������������������������������������������ 377 6.2 Definition of Hydrogeology and Its Relation with Other Sciences�������������������������������������������������������������������������������������������� 380 6.2.1 Geomorphological Approach to River Ecosystem���������������� 380 6.2.2 Geomorphology as Organizer of River Systems in a Hierarchical Manner ������������������������������������������������������������ 381 6.2.3 Characteristics of Hydrological Behavior���������������������������� 381 6.3 The Application of Hydrogeology���������������������������������������������������� 382 6.4 Present and Previous Perspectives of Riverine Hydrogeology �������� 382 6.4.1 Current Concepts in Fluvial Geomorphology���������������������� 383 6.4.2 River as a Fluvial System or Fluvial Geomorphology���������� 383 6.5 Morphology and Flow in River Ecosystem�������������������������������������� 387 6.5.1 Patterns of Movement: The Water of Surface Waves Moving in a Circular Path���������������������������������������������������� 388 6.5.2 The Coriolis Force: Determinant of Current������������������������ 388 6.6 River Drainage Basin������������������������������������������������������������������������ 389 6.6.1 Driving Forces of Water Movement and Water Influx���������� 389 6.6.2 Channel Morphology: Functional Approach������������������������ 390 6.7 Roles of Water Engineering in Hydrogeology���������������������������������� 391 6.8 Ground Water: Characteristics and Classification���������������������������� 391 6.9 The Water Cycle (Hydrological Cycle): Relationship with Water Budgeting������������������������������������������������������������������������������������������ 392 6.10 Groundwater as a Natural Resource ������������������������������������������������ 393 6.11 Movement of Water Through Soil and Aquifers ������������������������������ 394 6.11.1 Role of Sediment Profiles on Vertical Movement of Water�������������������������������������������������������������������������������� 394 6.11.2 Groundwater Habitats: Different Forms of Aquifers������������ 395 6.12 Interaction of Groundwater with Surface Water ������������������������������ 397 6.13 Ground Water Quality: Determining Factors������������������������������������ 397 6.14 Hydrological Cycle: Main Determining Attribute for Hydrology ���������������������������������������������������������������������������������������� 398 6.15 Watershed and Its Implication on Hydrogeology ���������������������������� 399 6.16 Water Balancing Climatic Parameters: Determining Influence on Hydrogeology������������������������������������������������������������������������������ 400
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6.16.1 Precipitation: A Determining Factor for Hydrogeology ������ 401 6.16.2 Evapotranspiration: A Major Factor for Hydrogeology�������� 401 6.16.3 Evaporation and Transpiration���������������������������������������������� 402 6.17 Movements or Infiltration of Water Through Soil���������������������������� 402 6.18 Stratification of Water: Geohydrological Properties of Surface and Ground���������������������������������������������������������������������� 402 6.18.1 Surface Water System ���������������������������������������������������������� 402 6.18.2 The Unsaturated Zone and Its Uniqueness �������������������������� 403 6.19 Surface Water in Rivers and Streams������������������������������������������������ 404 6.20 Groundwater: Sources and Distribution�������������������������������������������� 404 6.21 Groundwater-Surface Water junction (Ecotones): Hydrogeological Influence on Composition and Retention of Nutrients �������������������������������������������������������������������������������������� 405 6.22 The Lifting of Groundwater by Pumping: Impact on Hydrogeology ���������������������������������������������������������������������������������� 406 6.22.1 Reasons Behind Water Pumping and Consequences������������ 406 6.22.2 Natural Balance of Water and Water Flow Patterns vs. Groundwater Pumping���������������������������������������������������������� 406 6.22.3 Controlling Measures of Ecological Damage Caused by Groundwater Pumping���������������������������������������������������������� 407 6.22.4 Groundwater Resources in Developing Countries���������������� 408 6.23 Water Balance: An Interpretation������������������������������������������������������ 410 6.24 Aquifer Properties: Factors �������������������������������������������������������������� 410 6.24.1 Unconfined Aquifer: Characteristics������������������������������������ 411 6.24.2 Confined Aquifers: Characteristics �������������������������������������� 411 6.24.3 Semi-Confined Aquifers: Characteristics������������������������������ 412 6.24.4 Aquifers Based on Position of the Groundwater System���������������������������������������������������������������������������������� 412 6.24.5 Recharge Processes: Governing Factors ������������������������������ 412 6.25 Groundwater Scenario of India�������������������������������������������������������� 413 6.25.1 Groundwater Systems: Recharge Patterns���������������������������� 413 6.25.2 Ground Water System: Discharge Patterns �������������������������� 414 6.26 Physical Properties of Water and Rock�������������������������������������������� 416 6.26.1 Density of Water ������������������������������������������������������������������ 416 6.26.2 Viscosity of Water ���������������������������������������������������������������� 416 6.26.3 Permeability: Relation Between Soil and Water������������������ 416 6.26.4 Storativity of Aquifer������������������������������������������������������������ 417 6.26.5 Viscosity of Water ���������������������������������������������������������������� 417 6.26.6 Porosity of Sediment������������������������������������������������������������ 417 6.27 Groundwater and Surface Water Interactions ���������������������������������� 418 6.27.1 Distribution of subsurface water ������������������������������������������ 419 6.28 Runoff Generation and Streamflow�������������������������������������������������� 419 6.28.1 Mechanism of Erosional Deposition������������������������������������ 420 6.28.2 Physiographic Factors���������������������������������������������������������� 421
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6.29 Water Current: Adaptability of Organisms �������������������������������������� 421 6.29.1 Water Depth and Width: Adaptability of Organisms������������ 422 6.29.2 Infiltration and Percolation: Determining Factors (Substrates, Temperature; Dissolved Oxygen, Dissolved Salts; Vegetation) ������������������������������������������������ 423 6.29.3 Tools for River Basins Demarcation: Flow of Water and Transport of Sediment���������������������������������������������������������� 423 6.30 Hydrogeological Survey of Availability of Surface and Subsurface Water: A Case Study from the South West Bengal, India (Figs. 6.6, 6.7, 6.8, 6.9, 6.10, 6.11, 6.12, 6.13, and 6.14; Tables 6.5, 6.6, 6.7, 6.8, and 6.9)������������������������������������������������������ 424 6.30.1 Geological Background of the Proposed Study Sites ���������� 428 6.30.2 Drainage System of the Study Area�������������������������������������� 435 6.30.3 Geomorphology of the Study Area �������������������������������������� 435 6.30.4 Groundwater Aquifers in the Kansai and Subarnarekha Rivers of South West Bengal, India�������������������������������������� 437 6.31 Channel in Relation to Topography of the River Networks of South West Bengal, India�������������������������������������������������������������� 439 6.31.1 Geomorphology of Subarnarekha River: The Major Freshwater Transboundary River Estuary of South West Bengal, India���������������������������������������������������������������� 440 6.31.2 Methodology for Environmental Assessment ���������������������� 443 6.31.3 Selection of Study Sites and Design of Boring Activity at Onda, Bankura���������������������������������������������������� 443 6.31.4 Sloping Pattern of Riverbed�������������������������������������������������� 444 6.31.5 Design of Boring Activities�������������������������������������������������� 444 6.31.6 Outcome of Research Information���������������������������������������� 444 6.32 Microbiological Application for Ensuring Good Water Quality in the Drought-Prone Areas of Southern West Bengal�������� 446 6.33 Wastewater Management������������������������������������������������������������������ 446 6.33.1 Metal Leaching Microbes: Roles of Metals Decontamination ������������������������������������������������������������������ 447 6.33.2 Endophytic Fungi: Geo-ecological Significance������������������ 447 6.34 Concluding Remarks on Geomorphological and Hydrobiological Research���������������������������������������������������������������� 448 6.35 Sustainable Water Management in the Drought-Prone Riverine Tracts of South West Bengal, India������������������������������������ 448 6.36 Selection of Study Sites on Four Rivers, viz., Shilabati, Kansai, Dwarakeswar, and Subarnarekha ���������������������������������������� 449 6.36.1 Water Quality Assessment���������������������������������������������������� 450 6.36.2 Geological Background of the Proposed Study Sites ���������� 450 6.36.3 Boring Process���������������������������������������������������������������������� 450 6.36.4 Collection of Ground Truth Information of Land Use: Analysis with Satellite Imageries����������������������������������������� 451 6.37 Sustainability of Water Resources���������������������������������������������������� 451
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6.37.1 Sources and Values of Ground and Surface Water in the Studied River Basin of South West Bengal, India������ 452 6.37.2 Potential and Trend of Water Use ���������������������������������������� 452 6.37.3 Values of Ground and Surface Water������������������������������������ 452 6.37.4 Water Received as Runoff from Upstream Region�������������� 453 6.37.5 Water Use Potential of Flood-affected and Drought-Prone Areas of Eastern India���������������������������������� 453 6.37.6 Water Resource and Its Usage, Population and Demography in the Studied Districts������������������������������������ 454 6.37.7 Annual Rainfall in India, West Bengal and Studied Areas ������������������������������������������������������������������������������������ 455 6.38 Background of the Study Areas�������������������������������������������������������� 455 6.39 Hydrogeology and Geomorphology ������������������������������������������������ 456 6.39.1 Hydrogeology ���������������������������������������������������������������������� 456 6.39.2 Land Use and Water Management���������������������������������������� 457 6.40 Soil Characteristics �������������������������������������������������������������������������� 460 6.40.1 Riverine Tract of Kansai Rivers Section at Manbazar-I of Purulia District, West Bengal, India�������������� 460 6.40.2 Riverine Tract of Dwarakeswar River at Onda, Joypur, and Indus Blocks of District Bankura���������������������������������� 461 6.40.3 Sediment Profiles and Granulometric Analysis of the Study Sites���������������������������������������������������������������������������� 463 6.41 Groundwater–Surface Water Relationship���������������������������������������� 463 6.42 Recharge and Discharge of Aquifers������������������������������������������������ 464 6.42.1 Physical Properties of Aquifers�������������������������������������������� 464 6.43 Details of Boring Information and Sediment Characteristics ���������� 465 6.44 Conjunctive Use of Water Resources������������������������������������������������ 466 6.45 Concluding Remarks and Recommendation on Water Management�������������������������������������������������������������������������������������� 466 References�������������������������������������������������������������������������������������������������� 470 7 Physicochemical Parameters and Their Seasonal Dynamics: Special Reference to Riverine Networks of South West Bengal, India���������������������������������������������������������������������������������������������������������� 477 7.1 Water Quality Parameters: Significance and Uses���������������������������� 478 7.1.1 Definition and Concept �������������������������������������������������������� 478 7.1.2 Uses of Water������������������������������������������������������������������������ 479 7.1.3 Human Crisis Out of Water Quality�������������������������������������� 479 7.1.4 Reference-Based Water Quality Standards �������������������������� 480 7.1.5 Ecological Theory and Water Quality Management������������ 481 7.2 Water Quality Parameters of River �������������������������������������������������� 481 7.2.1 Physical Properties���������������������������������������������������������������� 482 7.3 Fluvial Processes: Sediment Transport and Storage ������������������������ 487 7.4 Properties of Surface Water�������������������������������������������������������������� 488 7.4.1 Surface Water and Water Quality Parameters ���������������������� 488
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7.5 Physicochemical Parameters: Determinants and Processes�������������� 489 7.5.1 Chemical Properties of Water ���������������������������������������������� 490 7.5.2 Dissolved Oxygen (DO) ������������������������������������������������������ 490 7.6 Sediment Fluxes�������������������������������������������������������������������������������� 493 7.7 Nutrients Dynamics�������������������������������������������������������������������������� 493 7.8 The Influence of the Climate and Watershed on Water Quality�������� 494 7.9 Hydrodynamic Effects���������������������������������������������������������������������� 494 7.10 Seasonal Dynamics of Physicochemical Parameters of Water: An Eco-Assessment Approach for Rivers���������������������������������������� 495 7.10.1 Interpretation of Results on Water Quality Parameters�������� 506 7.11 Seasonal Fluctuation of Soil Parameters in Different Rivers of South West Bengal, India�������������������������������������������������������������� 511 7.11.1 Soil Temperature (°C)������������������������������������������������������������ 512 7.11.2 Soil pH���������������������������������������������������������������������������������� 512 7.11.3 Soil Salinity (%)�������������������������������������������������������������������� 513 7.11.4 Organic Carbon (%)�������������������������������������������������������������� 513 7.11.5 Soil Texture: Sand, Silt, and Clay (%)���������������������������������� 513 7.12 Research Outcomes with Concluding Remarks�������������������������������� 514 7.13 Deduction of Water Quality Index (WOI)���������������������������������������� 516 7.14 Interpretation of Seasonality of Water Quality Parameters of Freshwater Rivers ������������������������������������������������������������������������ 517 References�������������������������������������������������������������������������������������������������� 518 8 Conclusion������������������������������������������������������������������������������������������������ 523 8.1 Riverine Research: An Interpretation Emphasizing Historical Perspective���������������������������������������������������������������������������������������� 524 8.2 Geomorphological Factors and Habitats Formation ������������������������ 525 8.3 Geomorphological Structure and Riverine Ecological Processes ������������������������������������������������������������������������������������������ 526 8.4 Rivers as Continua: Complexity in the Physical and Biological Realms���������������������������������������������������������������������������� 527 8.5 Groundwater–Surface Water Interactions ���������������������������������������� 528 8.6 River-Floodplain Wetlands and Ecological Significance������������������ 528 8.7 Unwinding of Complexity of Riverine Ecosystem: New Approach in River Study������������������������������������������������������������������ 529 8.8 Models and Theories: Relevant for Lotic Ecosystem and Its Biodiversity���������������������������������������������������������������������������������� 531 8.9 The River-Continuum Concept (REC): Synthesis of New Ideas on the Ecological Changes���������������������������������������������������������������� 533 8.9.1 Concept on “Riverine Ecosystem Synthesis” (RES)������������ 533 8.9.2 River-Continuum Concept (RCC) and Other Relevant Major Theories and Hypothesis�������������������������������������������� 533 8.10 Eco-dynamics of River Floodplains : Relevance of Flood Pulse Concept (FPC)������������������������������������������������������������������������ 535
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8.11 Quantification of Ecosystem Flows: A Prerequisite for River Management�������������������������������������������������������������������������������������� 536 8.12 Future Directions for Large River Research in Respect of RCC and Flood-Pulse Concept���������������������������������������������������� 537 8.13 Conclusions and Perspectives ���������������������������������������������������������� 539 References�������������������������������������������������������������������������������������������������� 539 About the Author��������������������������������������������������������������������������������������������� 547 Index������������������������������������������������������������������������������������������������������������������ 549
Chapter 1
Introduction
Abstract The moving freshwater bodies, ecologically designated as lotic aquatic ecosystem, are represented by rivers, streams, springs, tributaries, etc. and exhibit variability across the world in different periods of an annual cycle mainly because of variable geo-eco-physico-chemical attributes such as their sizes, shapes, carrying capacity, depth and volume of water, discharge potential, and abilities to connect with the water cycle in the watersheds. However, these freshwater ecosystems are in the brink of eco-degradation mainly due to non-judicious handling of this fascinating landscape of the world. This volume (I) of the book in its six (6) capacious chapters along with an elaborate introduction and conclusion has attempted to highlight multidimensional facets of the physical environment (geomorphology, geohydrology, physicochemical factors and processes) of the riverine ecosystem in the backdrop of an analytical discussion of the properties and distribution of the wonder molecule of this planet, the water, basic ecological concepts and principles with special reference to energy flows, trophic relationships, biogeochemical cycling and interactions among different components within biotic community in an integrated and holistic manners citing original research outcomes of the long-term research studies undertaken in the riverine networks of South West Bengal, India. These detailed and in-depth analyses are expected to unravel the avenues not only for sustainable utilization of fresh water along with its resource bases from the riverine ecosystem but also to identify the causes of eco-degradation so that appropriate mitigation strategies can be chalked out. Besides, types and classificatory schemes for the rivers in the global perspectives have been dealt with in order to understand the mode of ecological processes linking up the biotic and abiotic structural components of the riverine ecosystem with the help of a considerable number of concepts, models, theories, and hypothesis [River continuum concept (RCC), Nutrient spiraling concept (NSC), Serial discontinuity concept (SDC), The flood pulse concept (FPC), Network dynamics hypothesis (NDH), Hyporheic corridor concept (HCC), Patch dynamics concept (PDC), Process domain concept (PrDC), Hydrosystems concept (FHC), Riverine ecosystem synthesis concept (RESC), Hydro-geomorphic patches, Functional Process Zones (FPZs), Environmental Flows, Equilibrium versus disequilibrium theories, Hierarchical patch dynamics model (HPD)], all of which have been put forward by different research scientists from the different corners of the globe.
© Springer Nature Switzerland AG 2021 S. K. Chakraborty, Riverine Ecology Volume 1, https://doi.org/10.1007/978-3-030-53897-2_1
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1 Introduction
Keywords Physicochemical properties of water · Ecological concepts · Trophic interactions · Biogeochemical cycling · Geohydrology · Geomorphology · Theories · Hypothesis on riverine processes The land area that a river drains is called a watershed. All the runoff, streams, and rivers of the watershed ultimately flow into the same body of water, the ocean. The rivers and streams often constitute important hydrographic networks within the watershed, characterized by temporary flowing water only during certain period of the year, especially in the areas and time having higher temperatures coupled with less rainfall and they are called intermittent streams, rivers, and tributaries (smaller rivulets or rivers feeding another). Fast-moving streams and rivers provide excellent shelters for the moving animals such as fishes, while the fast-moving clear water support little plant life. In contrast, the slow-moving rivers carrying sediments with more silts and clays exhibit murky look of the flowing water and facilitate the settlement, colonization, and propagation of vegetations along with the associated faunal components at the riverbanks. These slow-moving rivers can also result in the formation of deltas in the continuous process of deposition of sediments because of the interactions of the currents from the sea and rivers at confluence of both of them. Without realizing almost nothing about the structure and function of rivers, human beings have been continually reaping the benefits provided by rivers for centuries (Ayivor and Gordon 2012; Naiman et al. 1988, 2012; Naiman and Bilby 1998; Petts and Amoros 1996). The ever-increasing dependence of the human civilization on different natural resources for securing direct and indirect benefits has pushed the freshwater river systems almost to the brink of the sad demise of this fascinating landscape of the world, justifying “point of no return “to the earlier pristine state of riverine environment. Proper assessment of ecological changes and remediation of eco-degradation of river ecosystems are the demands of the day for ensuring sustainability of the threatened aquatic environment. This can only be possible by adhering strictly to the relevant ecological principles pertaining to such ecosystem functioning. This book is expected to fulfill these requirements by way of highlighting basic ecological and limnological foundations representing the uniqueness of physical environment of riverine ecosystem in the backdrop of basic ecological principles and physical- chemical properties of water which are expected to unravel the avenues not only for sustainable utilization of fresh water from the riverine ecosystem but also to identify the causes of eco-degradation and their mitigation on the other. Besides emphasizing the ecological messages in respect of the synergistic impacts of human intervention coupled with natural disasters on the regional riverine flows, which imposed multitude of stresses on different structural components of this very sensitive but productive ecosystem, this book aims at fulfilling the gap in the existing and relevant knowledge bases for the international community from the perspective of the tropical ecological dynamics of river ecosystems from a developing country, like India. Apart from highlighting the basic ecological
1.1 Water and Rivers
3
concepts, hypotheses, and theories pertaining to the flow patterns shaped and determined by the topography and geomorphology, and also through the interactions among an array of physicochemical factors of freshwater river systems of tropical biogeographic zones, this book also tends to develop understandings on the resistance and resilience of riverine ecosystem’s functioning, based on original research outcomes of the long-term research studies undertaken in the riverine networks of South West Bengal, India. To justify the study of river ecology highlighting mostly of its physical environmental set ups in association with a broad spectrum of different related field of research priorities and components under major established subjects such as geohydrology, geomorphology, physiography, and limnological parameters (water and soil), changes in the land uses, and other river associated landscapes, for developing proper strategies for river management and conservation, on the basis of basic and baseline information, the present book has highlighted fundamental research conceptual facts on physical environment of rivers (properties of water and eco-dynamics of physicochemical parameters of riverine flows), bio-geo-chemical cycling, and trophic relationships, citing different scientific principles, hypotheses, and theories as put forward by different researchers from different corners of the globe alongside discussing research outcomes from different research efforts from the riverine networks of south-western parts of the state of West Bengal, India. The book has also attempted to integrate and correlate apparently diverse fields pertaining to the basic principles of ecology, unique properties of the wonder molecule of water, along with geomorphological and hydrogeological research on river ecosystem with a holistic approach.
1.1 Water and Rivers Water, being an essential life-sustaining universal solvent of dissolving gases, nutrients, and minerals substance, mostly comprise 90% of living materials, and is distributed widely, covering nearly three-fourths of the Earth’s surface. Based on the solute concentration of water, it is categorized as fresh water (in rivers, streams, lakes, etc.) and saline water (estuary, sea, etc.). The availability of water from the natural sources within a river basin hardly coincide with the growing demand of water to keep pace with the ongoing socioeconomic development which impose several constraints on the sustainable environment management practices on the same river basin. Consequently, there is a need for establishing a continuous balance between the demand for human beings and natural supply of water to meet it the needed requirement over time and space, maintaining the quality, quantity, and energy. This balance is expected to be achieved by establishing and following the integrated river basin development strategy, which involves a large number of environmentally sound water management and conservation activities. Identification of the criteria for developing such requirements must take into considerations several ongo-
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1 Introduction
ing perturbations of the riverine ecosystems due to the socioeconomic growth and different environmental developments as a part of eco-management strategies (Connel 1978; Barbour et al. 1999; Gopal 1997; Minshall 1984; Minshall and Minshall 1977; Minshall et al. 1982, 1983, 1985; Naiman et al. 1988; Tabacchi et al. 1996).
1.2 Uniqueness of River Ecosystem Rivers, being one of the dynamic and complex ecosystems of the world, is marked by their very unstable and changing ecological dimensions from the places of their origins to large lowland rivers in the temporal and spatial scales. Oscillation of riverine environment is observed diurnally, monthly, seasonally, and annually. Such dynamism has drawn the human attention since the time immortal as the human civilization has not only evolved on the bank of rivers but also flourished through mutual interactions with rivers to derive continuous benefits from riverine system in the form of pure water for the domestic, industrial, and agricultural uses, generation of energy, facilitation of navigation, production of food, and development of recreational avenues. Besides, rivers and streams act as centers of all kinds of ecological interactions by accommodating and integrating all structural components of river ecosystem and its associated landscapes. In addition, different facets of human culture have not only been originated from rivers but still rely on this unique landscape, as river touch all most all constituent components of the natural environment in its journey from the regions of its origin to the point of its confluence with the sea. However, the functional mechanism of the lotic water ecosystem through the interactions among an array of structural components, both living and nonliving ones, is still not clearly known. For centuries, the pursuit of human societies for exploiting natural resources and other ecological services provided by running waters without knowing and understanding the mode of functioning of the ecosystems to maintain their stability and vitality, have caused eco-degradation of this sensitive landscape profusely. In the present era, an exponential rise of human population has resulted in increasing dependence and demands of human society on streams and rivers, and thereby a comprehensive but basic ecological understanding of the structure and dynamics of running water has appeared to be a prerequisite for undertaking sound management and policy decisions. Several lotic (running or fluvial) aquatic ecosystems on earth are named differently such as rivers, streams, rivers, brooks, runs, forks, kills, and creeks, which are characterized by the unidirectional water flows from the upstream (the zone with higher elevation) to the downstream (zone with more volume of water, width and depth having lower elevation) strengthened by the gravitational forces to transport the water. This flowing water carries dissolved substances both inorganic and organic in nature, particulate materials mostly in the form suspended solid materials, towards the downstream by way of a networks of varied forms of drainage channels from relatively simple to highly complicated ones (Allan and Castillo 2007). The riparian zone representing the drainage area bordering the stream has been recognized as a zone of con-
1.3 Historical Background of Rivers in Respect of Human Beings
5
siderable significance in respect of maintaining the ecosystem functioning and also for providing protection by way of eco-management of a river (Naiman et al. 1988, 2005). The rivers and streams function as ecosystems (Fischer and Likens 1972, 1973) with all of the varied and complicated activities and interactions occurring among different structural components (living and nonliving) components, which are characteristic of all ecosystems (Hamilton 1822; Annandale 1922; Armitage 1995; Bayley 1995; Dudgeon 2000, 2000b; Allan and Castillo 2007).
1.3 H istorical Background of Rivers in Respect of Human Beings Rivers and streams, comprising 0.006% of the total fresh water on the Earth (Likens 2009b), are valued by humans far out of proportion to their small size, as these systems supply diverse form of services to human beings as water for drinking, irrigation, waste removal, food, recreation, tourism, transportation, and aesthetic services. The tropical and semitropical regions of the globe are endowed with so many large rivers of the world such as Amazon, Congo, Yangtze, Ganges, Brahmaputra, and Orinoco. The rivers’ margins being the dynamic interfaces between terrestrial and aquatic environments represent the sites for an array of biological interactions and processes involving the steady exchange of materials, mass, energy, etc., which result in higher biological productivity and diversity. The demand for fresh water is met by surface, subsurface, and groundwater sources. While surface water is available through rivers, lakes, ponds, and the like, subsurface fresh water comes to the surface through springs, aquifers, and seepage. The baseline information of the evolution of the uniqueness and multifunctional roles of the physical environment of river ecosystems in a historical perspective have enabled to generate strategies for planning and execution of integrated environmental management of river ecosystem (Haidvogl et al. 2014, 2015; Higgs et al. 2014). Besides, the long-term action-oriented efforts for a prolonged period have not only assisted in the understanding of the dynamics of the functioning of riverine ecosystem but also serving as of the natural and societal drivers in shaping the historical perspectives of changing patterns of the river flows. Therefore, the knowledge based on proper understanding of the historical past of the relationship of rivers with human beings have enabled the human societies to deal with the present state of affairs by identifying trajectories of change. Major rivers of the world such as the Euphrates, the Nile, the Indus, and the Ganges by affording a lot of human benefits have enabled to develop human culture appropriate of the regions and shaped their economy and culture. In Europe, most of the major environmental alterations of the aquatic systems in ancient and medieval periods, especially because of the spreading of strategies, practices, and scientific techniques, have been in use for the eco-management of rivers and their resources to other parts of the present industrialized world. All of those river
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1 Introduction
management strategies did not pay any heed to the well-being of the local and indigenous peoples disobeying their involvement and even by dislodging them from their place of origin and century old settlements (Humphries and Winemiller 2009). In the northern hemisphere of the globe, the major reasons behind the historical river abuses and subsequent ecological consequences have been identified as the shifting of land-use patterns in the human societies with agrarian biasness to an industrialized societies during the period spanning from middle of eighteenth century to the present time. Striking differences exist in respect of overall environmental conditions of rivers in general and ecological functioning in particular because of the increasing anthropogenic activities and their impacts during last one century especially gaining momentum after the 1950s (Downs and Gregory 2004). Such human activities are connected with shifting of the lifestyles of human societies from the preindustrial to the industrial mode of living because of more reliance on fossil fuels than the erstwhile energy sources mainly from wood (Sieferle 2006). Industrialization had disrupted the century-long strong bondages among major strata of societies in respect of their dependences and modes of exploitation of natural resources in different corners of the globe which ultimately resulted in the development of the realization of the sustainable eco-management of resource bases in particular and overall river environment in general. Sudden and steady shifts in industrial and agricultural technologies, cultural developments, and administrative policies in accordance with the changing lifestyles of the modern human civilization during last couple of centuries put their imprints on river management, pushing the river at the brink of eco-degradation. In addition, during this period, research emphasis was also laid on stream hydrodynamics and geomorphology in order to derive information for predicting the changing physical structural components along with geo-ecological processes across the length and breadth of rivers and streams (Leopold and Maddock 1953; Leopold et al. 1964). Since 1960, researchers began both field-based and experimental ecological studies on establishing relationships among environmental variables with biotic and geomorphological factors and biotic factors in the rivers and streams. More recently, the biological and physical concepts pertaining to river and stream organizations have been combined to develop more holistic approach projecting the lotic systems as a blend of two independent landscapes, the terrestrial and aquatic. Out of so many, two primary hypotheses (the river-continuum concept with its corollaries and the flood-pulse concept) explaining the cause of ecological functioning and geomorphological development of lotic systems have received considerable acceptances.
1.4 Classification of Rivers Classification of rivers and streams is essential for establishing characteristics of reference sites on logical basis for developing integral association and relation of rivers with living organisms. Most indicators, especially biota, from a site at the top
1.6 Biogeochemical Pathways: Cyclical Relationship Among Living and Nonliving…
7
of one stream will be unlikely to match those from a site at the bottom of the same stream, or another similar stream. Another approach for other form of classification of natural rivers depends mostly on geomorphology of the physical environment such as channel patterns, slope characteristics, dimension of cross-sectional areas, and proportionate distribution of different sizes of particles as constituting materials for channels (Rosgen 1994, 1996a, b).
1.5 P hysicochemical and Biophysical Parameters in River Ecology Like several other natural ecosystems, rivers display oscillation of abiotic factors (seasonal temperature, precipitation, solar radiation, pH, turbidity, etc.) and biotic components (population fluctuations, outbreaks, dispersal, migrations, etc.) that strongly influence the ecosystem processes (Yang et al. 2008) through an array of ecological interactions. Monitoring and eco-assessment of water quality nowadays have gained momentum across the globe in chalking out and formulating of international, national, and regional environmental policies. In tune with such global perceptions, it has become an increasingly important preoccupation in a developing country like India because of the ongoing consequences out of the mismanagement and overexploitation of freshwater resources leading to the deterioration of both of its surface water quality and groundwater quality mostly because of so many anthropogenic activities (deforestation leading to erosion load, abstraction of water for agriculture and industrial activities, dumping of municipal and industrial wastes, development of dams and hydroelectric power projects, recreational and fishing activities, etc.) in addition to ongoing climate change (Welcomme and Winterbourn 1988; Barbour et al. 1999; Ward and Standford 1983a, b, c; Wetzel 2001).
1.6 B iogeochemical Pathways: Cyclical Relationship Among Living and Nonliving Components The cyclical movement of chemical elements from organism to physical environment ensures the sustenance of the global environment by exchanging essential materials among its different compartments (hydrosphere, lithosphere, atmosphere, and biosphere). This important ecological process is often named as “nutrient cycles” when the elements involved in this cyclical phenomenon are utmost essential for supporting life. Such transfer, transformation, and exchange of materials are possible by several physical processes such as weathering and erosion in the lithosphere, electrification coupled with thunder storming in the atmosphere, etc. and biological processes such as biomagnification, decomposition, biosynthesis of biomolecules, etc. Most of these cycles like nitrogen cycle (N2) are considered as perfect and stable displaying more resilience through more feedback systems in
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1 Introduction
between the different reservoirs of the bio-geo-chemical elements in comparison to imperfect system such as phosphorus cycle (P) which has a sedimentary reservoir accessed by slow-moving physical processes and only with negative biological feedback mechanisms. Most of the organic substances either derived from the human activities (discarded food and other domestic materials,) or natural sources (leaf litter decomposition) ultimately find their ways to faster-moving streams, and thereby ensure continuous addition of dissolved matters providing essential ingredients for the algae to grow, which in turn serve as the food for a diverse herbivorous faunal components (mostly of zooplankton, insects, benthic fauna, and fishes). Besides, some other fauna which are called scavengers (aquatic insects, benthic fauna, and often some bottom-dwelling fish) feed on any tyoe of organic materials they can find without specific choice. All these aquatic organisms have developed morphological excellence and worked out many physiological means to keep themselves from being washed away. Some faunal components glue themselves living on the underside of rocks in the bottom of the flowing water bodies applying different types of sticky traps in order to catch small animals and other organic matters as a means for harvesting their foods (Hamilton 1822; Annandale 1922; Angermeier and Karr 1994; Armitage 1995; Connel 1978; Dudgeon 2000a, b).
1.7 P ulsing of Food Web Dynamics: Roles of Resource Bases and Ecological Factors Rivers experience resource “pulse” for food web dynamics which is produced by an influx of resources followed by an abrupt decrease of the density of consumer populations. All rivers, streams, and estuaries are strongly subjected to hydrology- mediated pulsing as the fundamental driving variable which operate on temporal and spatial scales. In most of the tropical rivers, variable hydrology as being the biophysical factor governs primary dynamics of different biotic components (phytoplankton, zooplankton, fishes, etc.) and thereby facilitates biological production, which in turn influence the top-down and bottom-up processes in trophic networks. Besides, the nutrients, detritus, and other organic components (allochthonous nutrients) imported from riparian biotic assemblages within watersheds and river basins fluctuate in tune with longitudinal fluvial gradients. The scales and structure of freshwater rivers and stream habitats are affected by a good number of physicochemical parameters causing the seasonal and spatial variability in the production and diversity of the riverine environment. Presently, two major forces have been identified and emerged to specify and designate the physical habitat. The first factor is the degree of changes of physical environment in respect of altered flow patterns due to human intervention. This tends to necessitate a prediction of the relationship between altered flows and modified channels to conserve or create adequate habitat for healthy ecosystems. The second factor involves existing disturbance, patches, and refuges which emphasize the adjustment and adaptability of the biological community against the changing major but
1.8 Pulsing of Rivers-Floodplains Hydrology: Top-Down Control of Basal Resources
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relatively conservative and predictable physical variables such as water depth, flow velocity, and substrate size in addition to light and heat, within the broad framework of the whole river continuum (Statzner 1987; Statzner and Higler 1986; Heede and Rinne 1989; Cummins 1992).
1.8 P ulsing of Rivers-Floodplains Hydrology: Top-Down Control of Basal Resources The bottom-up and top-down processes in the trophic interactions of the riverine ecosystem are regulated by the variable hydrology involving the oscillation of biophysical factors in the temporal and spatial scales, which in turn determine the biological productivity. Inter-tropical convergence zone present in the tropical rivers with extensive floodplains experiences precipitation-driven flood pulses which by causing changes in flow patterns contribute to alter concentrations of dissolved nutrients, and thereby the densities of aquatic organisms (per-unit-area) and community interactions. Such scientific proposition helps prediction of the strength of impacts to result in eco-biological consequences of top-down effects (top trophic level to bottom ones) on the aquatic biodiversity. The structure and function of the riverine ecosystem are controlled by the pulsing of an array of abiotic factors (solar radiance, temperature, humidity, precipitation, dissolved oxygen, pH, wind flow, etc.) and biotic factors (autotrophs, heterotrophs, parasites, predators, different form of behavioral manifestations like colonization, migration, etc.) that can strongly influence ecological processes and thereby stability of the ecosystem (Yang et al. 2008; Chakraborty 2017, 2018). The trophic relationships and interactions across the land–water interface, i.e., the lateral dimension, during the rise and fall of flood pulses are supposed to have been determined by the influx of nutrients, detritus, humus, and organic materials as nutrients from the surrounding riparian zones within the river basins and watersheds which display distinct variation along longitudinal fluvial gradients (Woodward and Hildrew 2002). Effective and proper prediction of eco- dynamics of riverine ecosystems depend on the underlying ecological relationships among different geohydrological parameters, physicochemical variables, and the diversity, density, and distribution of biodiversity components. The flood pulses of most of the tropical rivers experiencing seasonal flow patterns primarily caused by seasonal precipitation result in gradual but steady changes in the quantity of dissolved nutrients which impose triggering impacts in establishing the aquatic biotic assemblages. Based on the different research findings, it can be hypothesized that most of the tropical rivers exhibit both transitional and gradual top-down control on aquatic basal biotic components after being determined by the fluctuating water level, hydrological and biological parameters, especially on the faunal components belonging to the higher trophic levels such as fish and other consumers in the aquatic ecosystem (Minshall, 1984; Minshall and Minshall 1977; Minshall et al. 1982, 1983, 1985; Naiman et al. 1988; Tabachi et al 1996; Ward and Stanford 1983a, b, c).
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1 Introduction
1.9 Geomorphology and Flow Variability of Rivers Natural and managed geomorphological process is concerned with factors (depositional patterns of sediments, catchment conditions, flow regimes, etc.) operating at various scales that affect the functioning of river channels and thereby forming the habitats for the organisms to settle, colonize, and proliferate. Keeping aside the biotic assemblages, dissociation of floodplains followed by the reduction and clearing of vegetation, have been caused due to the reduction of flows and drainage which in turn modify erosion rates and geomorphology along with flow patterns of the catchments. All those changes synergistically structure and restructure the geomorphological units of river channels. Specific hydrologic variability mostly govern natural freshwater ecosystems which undergoes un-intendent eco-degradation due to the paucity of relevant information relating to water flows required for the ecological planners and managers. A river’s flow regime considered as “master variable” drives and governs the variabilities of different structural components (primary producers, fish and benthos, riparian forest-based biotic assemblages, nutrients availability and supply) of river ecosystem (Sparks 1995; Walker et al. 1995; Poff et al. 1997). Traditional water management relies more on the non-judicious usage of water for multifarious requirements of human beings such as floods and droughts. Continuous and steady water supplies for the purposes of domestic and industrial uses, irrigation, navigation, and hydropower lead to disrupt natural rhythms of the river flows with its seasonal variability, and thereby result in moderate to extreme critical water conditions. Too much modification of natural variability in river flows bring forth striking changes in the physical, chemical, and biological conditions and functions of natural fresh water ecosystems by inviting eco-degradation along with the decline of biodiversity and societal demand (Postel and Carpenter 1997; IUCN 2000; WCD 2000).
1.10 D ifferent Dimensions of Hydrogeology and Its Relevance in the River Ecology “Ecohydraulics” being the subject of assessing physical properties of habitats have contributed significantly not only to understand the intricate relationships among different geomorphological and hydrological components within the river tracts, but also to highlight the roles of biotic components in structuring the physical habitats. The subject “hydrogeology,” dealing with the study of the origin, availability, distribution, and movement of subterranean waters and also groundwater, is being considered as one of the important sub-disciplines of the earth-sciences and has experienced wide acceptance in different corners of the globe in recent decades as an integral part of the study of the river ecology, especially in explaining the physical processes by accomplishing the joint undertakings by the hydrogeologists, g eologists, hydrologists, meteorologists,
1.11 Environmental Management of River Basin: Integration and Complementati…
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and engineers. The development of different fields within the subject hydrogeology such as “hydraulic stream ecology” (Statzner et al. 1988), “eco-hydraulics” (Leclerc et al. 1996), or “habitat hydraulics” (Rowntree 1995) have had a long history of different discourses and conflicts and still has been enjoying the status of a relatively new field of science which tend to explain the modes of hydraulic controlling factors (several “geomorphological units” such as riffles and pools) of both flow and sediment transport in a local scale in contrast to the more passive role of purely depositional sediment stores such as bars and shoals. Hydrogeological assessments are important and needed for ensuring water supplies in public and domestic sectors, irrigation schemes, flood protection works, and even to office and industrial buildings. In the agricultural sector, large scale of abstraction of surface water and lifting of groundwater as a part of agricultural activities with the aid of modern agro- technology have not only resulted in the depletion of groundwater but also disrupt the natural environmental flows. Besides, in so many countries of the world, growing urbanization and awareness of personal hygiene have led to develop additional claims on and subsequent exploitation of available groundwater resources. In addition, some other hydraulic variables, such as intensity of currents, turbulence, biogeochemistry, and the spatial velocity gradient, along with fluvial geomorphology of the rivers integrating fluid dynamics, channel morphology, and biogeochemical cycling, play crucial roles in limiting the distribution and migration of aquatic faunal components, like fishes and other nektonic fauna which may generate and act as the repository of baseline information for explaining “hydro-navigation” of biota.
1.11 E nvironmental Management of River Basin: Integration and Complementation of Land and Water Land and water, constituting two most basic resources to sustain the life, have been under tremendous environmental threats with higher intensities because of growing human populations leading to geographical intensification of human activities, in many regions of the world. Several environmental hazards associated with this development are expected to pose alarming consequences towards the depletion of resource base leading to jeopardizing and depriving of the long-term carrying capacity of our environment. Moreover, management of land resources is supposed to become a decisive consideration in the process of water conservation and management due to the complementarity of land and water resources with each other in the exchange of inputs for the eco-management and conservation. Attaching importance on ecosystem approach for sustainable resource utilization, the close interrelationships between water and land, instead of just mere putting stress on assessing the trend of changes of land-use only can become more decisive and effective (Naiman et al. 2012; Schmutz and Senzimir 2018; Walker et al. 1995).
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1 Introduction
1.12 P hysiography of Rivers and Floodplains: Relevant Theories Naturally flowing floodplain rivers are among the more dynamic ecosystems on earth with enormous spatial and temporal complexity. River flows determine the distribution patterns of channels, back swamps, marshes, and tributaries that make up the floodplain (Ward 1998). These floodplain wetlands also include freshwater and saline lakes, anabranches, billabongs, lagoons, overflows, swamps, and waterholes. The flow regime of a river, and its connections to floodplain wetlands, governs biotic responses, channel formation, and sediment transfer (Junk et al. 1989; Walker et al. 1995). Floodplains of rivers, an ecotone between the terrestrial and aquatic ecosystem, support higher biodiversity, mainly because of variable riverine flows caused by the construction of dams, irrigation canals, and other built structures diverting and reducing the intensity of flood-driven water flows to the floodplains, and thereby altering their ecology, causing poor ecological health and resulting in mass mortality of aquatic biota. Landscape measurement of biota in a floodplain wetland involves different eco-hydrological processes facilitating recruitment of biota, which in turn ultimately determine a population’s capacity to respond to the ecological changes (Walker et al. 1995). Hydrological models are developed primarily to derive prediction on the consequences of trophic relationship during flooding and drying spells within riparian vegetation of the floodplain, and contribute profusely to the functioning of river ecosystems, especially by way of promoting rich biodiversity and also facilitating cycling of nutrients. However, without a restoration of a more natural flooding regime, early succession of biotic communities will become increasingly rare. Different floodplain wetlands exhibit successional changes in aquatic vegetation, and cause deterioration of the ecological health of vegetational assemblages. All of these effects in turn result in declining of the numbers of aquatic birds and their nesting abilities, reducing native fish and invertebrate populations. River management planning involves building of dams to divert water from many rivers, mainly for the usage in the domestic, agriculture, fisheries, industrial sectors, etc. and hardly takes into consideration the harmful impacts of succeeding ecological and hydrological changes on floodplain wetlands. Therefore, research-based knowledge pertaining to the floodplain ecology in relation to changing river flows during different period of the year are needed to understand the consequences of such ecological impacts so that further loss of wetlands can be avoided. The river management of the present time emphasizes on the “wasted” water flows to either floodplain wetlands, aquifers, or the sea where river catchments act as “drainage” divisions or basins. Rivers during floods experience “surplus flows” and high water losses take places within floodplain wetlands. The eco-managers of the river basin recognize the significance of productive eco-zones of floodplains and are inclined to utilize eco-dynamics of this eco-zone to mitigate the loss of natural processes, including setting back levees to increase the size of the active fl oodplains, restoring eco-degraded associated limnetic and lotic water systems, and resisting the intrusion of bio-invasive species.
1.14 Geomorphology vs. Biotic Activities: Role of Spatial Heterogeneity
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1.13 Environmental Flows in River Ecosystem A river’s natural flow regime has been considered as the most important determining factor towards ecosystem flow requirements mimicking natural flow characteristics to a considerable extent, which in turn determine the possible flow-biota relationships, other non-flow related variables that affect biota, and the influence by flow on other ecosystem conditions such as water quality or physical habitat (Poff 1997; Poff et al. 1997; Tharme and King 1998). River water management emphasizing on quantified water-related ecological objectives mostly addresses some specified issues such as flood protection, generation of hydropower, flow regimes (wet- and dryseason base flows, normal high flows), ensuring of water supplies during drought, hydrologic variability influencing freshwater biota and ecosystem processes, extreme drought and flood conditions (Rogers and Bestbier 1997; Arthington and Zalucki 1998; King and Louw 1998; Trush and Leopold McBain 2000). Assessment and quantification of ecosystem flow requirements are in need of baseline research information of habitat requirements of native biota (species, communities) in the changing gradients of the hydrologic, geomorphic, and biogeochemical processes which considerably structure those habitats of the biota and support primary productivity and nutrient cycling (Swales and Harris 1995; King and Louw 1998). Establishing ecosystem flow requirements emphasizes more on to the link between flows and the viability of a native species population, which in turn depends upon a number of other ecosystem conditions relating to boarder range of flow variations to conserve healthy river ecosystems (Hill and Platts 1991; Richter and Richter 2000; Trush et al. 2000).
1.14 G eomorphology vs. Biotic Activities: Role of Spatial Heterogeneity Distinct relationship exists in between invertebrate community with the changing scales of diversity in respect of geomorphological units within the rivers (stream runs, riffles and pools, suspended algal mats and submerged vegetation) which strongly influence the species composition and quantum of biological production (Norris and Thoms 1999). Geomorphology of the rivers and streams in conjunction with different environmental processes also determine the formation of varied forms of habitats within the rivers and streams, which in turn impose direct impact on the faunal components at a specific location (Parsons et al. 2003). Besides, natural disturbances lead to develop habitat heterogeneity which triggers more biotic diversity (Vinson and Hawkins 1998). The anthropogenic alterations of the rivers and associated floodplain ecosystems by constructing levees for flood control, developing structures for land drainage, making provisions for river regulation, and also creating hard structures for hydro-power plants, dams and dikes for water diversion, hydro-peaking, etc. which have caused isolation of rivers from their floodplain and have been the major factors behind the riverbed degradation (Petts and Amoros 1996; Jungwirth et al. 2002).
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1 Introduction
All of these disturbances significantly alter the type-specific natural disturbance regimes that normally maintain the structure and complex eco- dynamic of ecotones. The resulting decrease in hydro-morphological dynamics, hydrological connectivity, and habitat turnover degrades habitat diversity and reduces biodiversity to a considerable extent. Occurrence of such changes within the river ecosystems transforms them from their original “shifting mosaic steady-state type” (sensu Bormann and Likens 1967, 1979; Bormann et al. 1968) to an ecologically truncated “static-state system” (Hohensinner et al. 2008). Understanding of these research findings helps undertaking sustainable restoration programs by re-establishing the stabilization process of sediments, reverting the erosion threats, promoting balanced sedimentation processes, and ensuring hydrological connectivity to maintain natural flow patterns, typical for the given natural systems prior to degradation against the human intervention.
1.15 E cological Conditions for Environmental Flows in Rivers Rivers and streams have their own uniqueness that differentiate them from other aquatic ecosystems by a flow of water from upstream to downstream enabling different micro- and macroorganisms belonging to innumerable number of species to enjoy distribution patterns in multidimensional habitats after being affected by the differential spatial and temporal characteristics of environmental flows, such as fast versus slow, deep versus shallow, turbulent versus laminar, and flooding versus low flows (Bayley and Li 1992; Reynolds and Descy 1996; Ward 1989).
1.15.1 Flow Velocity This physical parameter not only governs the deliverance of food and nutrients to organisms, but can also dislodge and prevent them from restricting their distribution at a particular site. The rivers and streams having slow and high flows support the propagation of sluggish and migratory fauna, respectively, as timing of migration and spawning of some fish are coincided with the speed of currents of water.
1.15.2 Temperature Water temperature being a very important factor for cold-blooded aquatic organisms affects many of their physiological and biochemical processes. Different lotic organisms such as insects, algae, and fish have revealed their preference to inhabit in warmer segments of the riverine flows, especially during warmer seasons of the year displaying higher growth rates and development with the increase of water temperature (Sweeney 1992; Ward 1998; Hynes 1970; Reynolds and Descy 1996).
1.15 Ecological Conditions for Environmental Flows in Rivers
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1.15.3 Riparian Vegetation Riparian vegetation tends to control the availability of light and temperature which becomes decreased due to the luxuriant growth of vegetation (Cole 1992; Connell 1978).
1.15.4 Sunlight Penetration of sunlight having required intensity can significantly enhance the water temperature of streams and rivers having slow-moving water especially in the summer. Sweeney (1992) found that temperature changes of 2 °C–6 °C usually altered key life-history characteristics of some species. It has been observed that buffering effect of riparian forest helps prevent changes in natural temperature patterns even after deforestation which tend to increase the temperature due to the lack of covering over the surface.
1.15.5 Oxygen Dissolved in Water (D.O) Oxygen on entering the water directly by absorption from the atmosphere and also after being produced by photosynthesis of plants are dependent for their saturation on the depth, intensity of water currents, flow patterns, motion, and the extent of surface area exposed to the air. Aquatic organisms survive getting appropriate concentrations of dissolved oxygen (3 mg/L), which enables them to reproduce and survive maintaining the needed metabolic activities (Mackenthun 1969). Dissolved oxygen concentration more than 5 mg/L in water is required by the aquatic organisms for their normal activities (Walburg et al. 1981). The increasing demands of oxygen needed for chemical and biological processes exceeding the availability of oxygen provided by re-aeration and photosynthesis, cause mass mortality of living faunal components. Besides, slow currents, with high temperatures, profuse growth of macrophytes, algal blooms, higher nutrients loads, all together deplete the dissolved oxygen concentrations. Major ecological factors determining the supply and retention of D.O. in water are temperature, pressure, salinity, abundance of aquatic plants, and the water-atmosphere interphasic exchange of oxygen (Needham and Lloyd 1930).
1.15.6 pH Value of Water Aquatic biota survive best in the water with a pH of 7, i.e., nearly neutral hydrogen ion activity. Stresses due to the changes of pH towards more acidic or more alkaline ranges are increased and result in the decline in the diversity and abundance of spe-
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1 Introduction
cies. One of the main causes for changes in the pH of aquatic environments is the increase in the acidity of rainfall (Schreiber et al. 1995). Some soils have the ability to buffer pH changes; however, those which cannot neutralize acid inputs cause environmental concerns.
1.15.7 Substrates and Their Roles Differential patterns of species assemblages, mostly the benthic micro- and macroinvertebrates in the different stretches of the riverine flows, are determined by the texture and nutrient contents of the substrates within and also of river basins. Several studies have depicted such interpretation where one reach of a stream harbors species having different abundances and diversities than others due to the changing substrate conditions developed by the aggregations of different textural components of the sediment (silts, clays, snags, sand, bedrock, cobbles, etc.) (Benke et al. 1984; Smock et al. 1985; Huryn and Wallace 1986). The hyporheic zone representing the substrate-water boundary forms the main habitat for most of the benthic invertebrate species to settle, grow, colonize, and breeding. The strength and constitution of substrates being solid structures due to different combination of textural components influence and modify surface and interstitial flow patterns, which in turn control the accumulation of organic materials, biological production processes, decomposition, and other trophic interactions. The substrates of rivers formed by sand and silt are considered to be the least suitable habitats for the aquatic organisms supporting the presence of fewest species and individuals which are in contrast to rubble substrates enabling aquatic organisms to reach highest densities and diversities (Odum 1971; Chakraborty 2017).
1.15.8 Nutrients and Eutrophication of Water Several macronutrients such as nitrogen (N), phosphorus (P), carbon (C), potassium (K), and sodium (Na) and micronutrients like selenium (Se), boron (Br), and silica (S) are needed for growth and biomass production of plants. However, excessive supply of major nutrients (nitrogen and phosphorus), surplusing their optimum requirements, may cause an increase in the rate of growth of aquatic plants in a stream. This process of transformation of a oligotrophic water body (nutrient poor) to an eutrophic (nutrient rich) one is known as eutrophication which cause several environmental and ecological problems such as excessive growth of plant biomass, inhibition of the penetration of solar rays, depletion of dissolved oxygen, changes in the diversity and species composition, increased rates of decomposition, of the affected water body, etc. reaching to a terrible aesthetic state with the worst consequences of death of fish.
1.16 River Continuum Concept (RCC): A Means of Orderly Arrangement…
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1.16 R iver Continuum Concept (RCC): A Means of Orderly Arrangement of Ecological Processes Comprehensive ecological studies on large rivers are very meager in comparisons with such studies for small streams and very drastic but predictable ecological changes are seen to occur in the sixth-order rivers in contrast to small streams because in the course of more than thousand kilometer journey, the large rivers experience excessive biological production and development of fisheries resources but with little predictable change (Welcomme 1985). Moreover, viewing of large rivers as separate systems with a different set of ecological characteristics and management problems than upstream rivers of their valleys, poses more difficulty to extrapolate concepts of riverine ecosystem function which are more suited to upper river stretches to downstream areas. Besides, dams, tributaries, floodplain wetlands, oxbow lakes, etc. create blockages in the continuity of flows, resulting in “discontinuities” directing the flows of water of main rivers into more or less independent reaches (Ward and Stanford 1983a, b, c; Decamps 1984). River floodplains with their riparian vegetation enjoying variable extended horizontal and transverse interactions with the rivers influence the structuring of longitudinal characteristics of riverine ecosystem. Variation in the extent of large rivers floodplains and transverse interactions between river and floodplain forests often influence the functioning of the riverine ecosystem (Hynes 1975; Welcomme 1979; Junk et al. 1989; Pautou and Decamps 1985; Bravard et al.1986; Amoros et al. 1987). Large river systems are contemplated as continuous physical and biological gradients (meager riparian vegetation, changes of the sediment textures from the rocky to sandy to silty clay state, chronological replacement of feeding groups from shredders to grazers to scrapers to filter feeders, shifting of dependencies from the allochthonous supply of nutrients to autochthonous ones, etc.) in course of the entire stretch of rivers starting from the head water to the confluence with the sea (Ward and Stanford 1983a, b). However, biotic assemblages do not match the functionally defined progression in responses to stream order (Balon and Stewart 1983; Benke et al. 1984; Richter et al. 1996). The river continuum concept (RCC) was proposed by Vannote et al. (1980). They tried to highlight the river network as a continuously integrated series of physical adjustments where the basin and ecosystem processes determine resource gradient in which the biotic assemblages in such longitudinally linked systems are orderly arranged and developed due to the linkage of ecosystem level processes in downstream reaches to those of upstream parts of the riverine networks. Subsequently, this concept was subjected to a lot of debates that have triggered the initiation of new studies to evaluate its usefulness as a uniformly acceptable concept. The river systems are considered as being composed of a firmly integrated series of biotic and ecosystem changes from the upstream down to the confluence with the sea on a set of geomorphically and biologically independent reaches. Analyzing of the eco-dynamics of a river therefore needs to incorporate both concepts pertaining
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1 Introduction
to physical and biological processes. This has necessitated to link up ecologically important processes at the reach levels to large river systems at different spatial and temporal scales by integrating various scientific disciplines.
1.17 Concluding Remark In view of the above, to justify the study of river ecology in association with a broad spectrum of different related subcomponents of major subjects such as geohydrology, geomorphology, physiography, biodiversity studies, limnological parameters (water and soil), land uses, and other river-associated ecosystems/landscapes, the present book elaborately discussed and has highlighted basic facts, and concepts relevant to scientific principles, hypotheses, and theories which have been put forward by different researchers from different corners of the globe alongside citing research outcomes from different research efforts from the riverine networks of South West Bengal, India. The book has also attempted to integrate and correlate apparently diverse fields of research on river ecosystem with a holistic approach for integrating the continuous flow of information emerging out of different case studies, by citing and utilizing different scientific principles, hypotheses, and theories pertaining to aquatic ecology dealing with different dimensions of the natural world from the qualitative and quantitative approaches.
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Higgs, E., D.A. Falk, A. Guerrini, M. Hall, J. Harris, R.J. Hobbs, S.T. Jackson, J.M. Rhemtulla, and W. Throop. 2014. The changing role of history in restoration ecology. Frontiers in Ecology and the Environment 12: 499–506. Hill, M., and W.S. Platts. 1991. Ecological and geomorphological concepts for instream and outof-channel flow requirements. Rivers 2: 319–343. Hohensinner, S., M. Herrnegger, A.P. Blaschke, C. Habereder, G. Haidvogl, T. Hein, M. Jungwirth, and M. Weib. 2008. Type specific reference conditions of fluvial landscapes: a search in the past by 3D-reconstruction. Catena 75: 200–215. Humphries, P., and K. Winemiller. 2009. Historical impacts on river fauna, shifting baselines, and challenges for restoration. BioScience 59: 673–684. Huryn, A.D., and J.B. Wallace. 1986. A method for obtaining in situ growth rates of larval Chironomidae (Diptera) and its application to studies of secondary production. Limnology and Oceanography 31: 216–222. Hynes, H.B.N. 1970. The ecology of running waters, 555. Liverpool: Liverpool Univ. Press. ———. 1975. The stream and its valley. Verhandlungen - Internationale Vereinigung fur Theoretische und Angewandte Limnologie 19: 1–15. IUCN 2000. Guidelines for the prevention of biodiversity loss caused by alien invasive species approved by the 51st meeting of the IUCN council, Gland Switzerland. Jungwirth, M., S. Muhar, and S. Schmutz. 2002. Re-establishing and assessing ecological integrity in riverine landscapes. Freshwater Biology 47: 867–887. Junk, W.J., Bayley, P.B., and Sparks, R.E. 1989. The flood pulse concept in river-floodplain systems. Proceedings of the International Large River Symposium, Journal of Fisheries and Aquatic Sciences. DP Dodge, 106:110–27. King, J.M., and M.D. Louw. 1998. Instream flow assessments for regulated rivers in South Africa using the Building Block Methodology. Aquatic Ecosystem Health and Management 1: 109–124. Leclerc, M., Y. Secretan, M. Heniche, and Y. Roy. 1996. Project Metrique: Bilan scientifique, Rapport d’ etape# 3 au Fonds de recherche et de de’ve’lopment technologique en environment (MEF), Rep.INRS-Eau R 482, 237 pp., INRS -Eau, Quebec, Canada. Leopold, L.B., and T. Maddock, Jr. 1953. The hydraulic geometry of stream channels and some physiographic implications. U.S. Geological Survey Professional Paper 252. Washington, DC: United States Goverment Printing Officep. 57 Leopold, L.B., M.G. Wolman, and J.P. Miller. 1964. Fluvial processes in geomorphology, 522. San Francisco, CA: W.H. Freeman. Mackenthun, K.M. 1969. The practice of water pollution biology, 1–281. Washungton, D.C.: U.S. Dept. Interior, Fed. Water Pollution Control Administration. Minshall, G.W. 1984. Aquatic insect-substratum relationships. In The ecology of aquatic insects, ed. V.H. Resh and D.M. Rosenberg, 358–400. New York: Praeger Publishers. Minshall, G.W., and J.N. Minshall. 1977. Microdistribution of benthic invertebrates in a Rocky Mountain (U.S.A.) stream. Hydrobiologia 55: 231–249. Minshall, G.W., J.T. Brock, and T.W. LaPoint. 1982. Characterization and dynamics of benthic organic matter and invertebrate functional feeding group relationships in the upper Salmon River, Idaho (USA). Internationale Revue der Gesamten Hydrobiologie 67: 793–820. Minshall, G.W., R.C. Peterson, K.W. Cummins, T.L. Bott, J.R. Sedell, C.E. Cushing, and R.L. Vannote. 1983. Interbiome comparison of stream ecosystem dynamics. Ecological Monographs 53: 1–25. Minshall, G.W., K.W. Cummins, R.C. Peterson, C.E. Cushing, D.A. Bruns, J.R. Sedell, and R.L. Vannote. 1985. Developments in stream ecosystem theory. Canadian Journal of Fisheries and Aquatic Sciences 42: 1045–1055. Naiman, R., and R. Bilby, eds. 1998. River ecology and management: lessons from the pacific coastal ecoregion, 1–73. New York: Springer. Naiman, R.J., H. Decamps, J. Pastor, and C.A. Johnston. 1988. The potential importance of boundaries to fluvial ecosystems. Journal of the North American Benthological Society 7: 289–306.
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Naiman, R.J., R. Alldredge, D.A. Beauchamp, P.A. Bisson, J. Congleton, C.J. Henny, N. Huntly, R. Lamberson, C. Levings, E.N. Merrill, W.G. Pearcy, B.E. Rieman, G.T. Ruggerone, D. Scarnecchia, P.E. Smouse, and C.C. Wood. 2012. Developing a broader scientific foundation for river restoration: Columbia River food webs. Proceedings of the National Academy of Sciences of the United States of America 109 (52): 21201–21207. (Published by: National Academy of Sciences). Needham, J.G., and J.T. Lloyd. 1930. The life of inland waters, 1–438. Baltimore, MD: C.C. Thomas Publishers. Norris, R.H., and M.C. Thomas. 1999. Development and testing of an index of stream condition for waterway Management in Australia. Freshwater Biology 41: 453–468. Odum. 1971. Fundamentals of ecology. Philadelphia: Saunders. Parsons, M., M.C. Thoms, and R.H. Norris. 2003. Scales of macroinvertebrate distribution in relation to the hierarchical organization of river systems. Journal of the North American Benthological Society 22: 105–122. Pautou, G., and H. Decamps. 1985. Ecological interactions between the alluvial forests and hydrology of the Upper Rhone. Archiv für Hydrobiologie 104: 13–37. Petts, G.E., and C. Amoros. 1996. Fluvial Hydrosystems. Chapman and Hall: London Petts G.E. (1996) Water allocation to protect river ecosystems. Regulated Rivers: Research and Management, 12, 353–365. Poff, N.L. 1997. Landscape filters and species traits: toward mechanistic understanding and prediction in stream ecology. Journal of the North American Benthological Society 16: 391–409. Poff, N.L., J.D. Allan, M.B. Bain, J.R. Karr, K.L. Prestegaard, B.D. Richter, R.E. Sparks, and J.C. Stromberg. 1997. The natural flow regime: a paradigm for river conservation and restoration. BioScience 47: 769–784. Postel, Sandra, and Stephen Carpenter. 1997. Freshwater ecosystem services. In Nature’s services: societal dependence on natural ecosystems, ed. Gretchen C. Daily, 195–214. Washington, D.C.: Island Press. Reynolds, C.S., and J.-P. Descy. 1996. The production, biomass and structure of phytoplankton in large rivers. Archiv für Hydrobiologie, Supplement (113): 161–187. Richter, B.D., and B.D. Richter. 2000. Prescribing flood regimes to sustain riparian ecosystems along meandering rivers. Conservation Biology 14: 1467–1478. Richter, B.D., J.V. Baumgartner, J. Powell, and D.P. Braun. 1996. A method for assessing hydrologic alteration within ecosystems. Conservation Biology 10: 1163–1174. Rogers, K.H., and R. Bestbier. 1997. Development of a protocol for the definition of the desired state of riverine systems in South Africa. (Report on the project of the Department of Environmental Affairs: Centre for Water in the Environment, University of the Witwatersrand), pp 1–97 Rosgen, D. 1994. A classification of natural rivers. Catena 22: 169–199. Rosgen, D.L. 1996a. A classification of natural rivers: reply to the comments by J.R. Miller & J.B. Ritter. Catena 27: 301–307. ———. 1996b. Applied river morphology, wildland hydrology. Pagosa Springs, CO. Rowntree, K.M. eds. 1995. The hydraulics of physical biotopes: Terminology, inventory and calibration. Report of a workshop held at Citrusdal (4–7 February, 1995): 1–57. Schmutz, S., and J. Sendzimir. 2018. Riverine ecosystem management: science for governing towards a sustainable future (Aquatic Ecology Series, Volume 8; Published by Springer), pp 1–562. Schreiber, U., H. Horman, C. Neubauer, and C. Klughammer. 1995. Assessment of photosystem II Photochemical quantum yield by chlorophyll fluorescence quenching analysis. Australian Journal of Plant Physiology 22: 209–220. Smock, L.A., E. Gilinsky and D.L. Stoneburner. 1985. Macroinvertebrate production in a southeastern United States blackwater stream. Ecology 66: 1491–1503. Smock, L.A., A.B. Wright, and A.C. Benke. 2005. Atlantic coast rivers of the Southeastern United States. In Rivers of North America, ed. A.C. Benke and C.E. Cushing, 73–122. Burlington, MA: Academic Press/Elsevier. Sparks, R.E. 1995. Need for ecosystem management of large rivers and their floodplains. BioScience 45: 168–182.
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Statzner, B. 1987. Characteristics of lotic ecosystems and consequences for future research directions. In Potentials and limitations of ecosystem analysis, ed. E.-D. Schulze and H. Zwolfer, 365–390. New York: Springer-Verlag. Statzner, B., and B. Higler. 1986. Stream hydraulics as a major determinant of benthic invertebrate zonation patterns. Freshwater Biology 16: 127–139. Statzner, B., J.A. Gore, and V.H. Resh. 1988. Hydraulic stream ecology: Observed patterns and potential applications. Journal of the North American Benthological Society 8: 36–50. Swales, S., and J.H. Harris. 1995. The expert panel assessment method (EPAM) : a new tool for determining environmental flows in regulated rivers. In The ecological basis for river management, ed. D.M. Harper and A.J.D. Ferguson, 125–134. Chichester: Wiley. Sweeney, B.W. 1992. Streamside forests and the physical, chemical and trophic characteristics of Piedmont streams in Eastern North America. Water Science and Technology 26 (12): 2653–2673. Tabacchi, E., A.-M. Planty-Tabacchi, M.J. Salinas, and H. De’camps. 1996. Landscape structure and diversity in riparian plant communities: a longitudinal comparative study. Regulated Rivers 12: 367–390. Tharme, R., and J.M. King. 1998. Development of the building block assessments and supporting research on the effects of different magnitude flows on riverine ecosystem. WRC report no. 576/1/98, 1–432. Pretoriae: Water Research Commission. Trush, W., and L.B. Leopold McBain. 2000. Attributes of an alluvial river and their relation to water policy and management. Proceedings of the National Academy of Science 97 (22): 11858–11863. Vannote, R.L., G.W. Minshall, K.W. Cummins, J.R. Sedell, and C.E. Cushing. 1980. The river continuum concept. Canadian Journal of Fisheries and Aquatic Sciences 37: 130–137. Vinson, M.R., and C.P. Hawkins. 1998. Biodiversity of stream insects: variation at local, basin and regional scales. Annual Review of Entomology 43: 271–293. Walburg, C.H., J.F. Novotny, K.E. Jacobs, W.D. Swink, T.M. Campbell, J. Nestler, and G.E. Saul. 1981. Effects of reservoir releases on tailwater ecology: A literature review. Vicksburg, MS: U.S. Army Corps of Engineers, Waterways Experimental Station. Technical Report E-81-12. Walker, K.F., F. Sheldon, and J.T. Puckridge. 1995. A perspective on dryland river ecosystems. Regulated Rivers 11: 85–104. Ward, J.V. 1989. The four-dimensional nature of lotic ecosystems. Journal of American Benthological Society 8: 2–8. ———. 1998. Riverine landscapes: biodiversity patterns, disturbance regimes and aquatic conservation. Biological Conservation 83: 267–278. Ward, J.V., and J.A. Stanford. 1983a. The serial discontinuity concept of lotic ecosystems. In Dynamics of lotic ecosystems, ed. T.D. Fontaine and S.M. Bartell, 29–42. Ann Arbor, MI: Ann Arbor Science. ———. 1983b. The ecology of regulated streams, 398. New York: Plenum Press. ———. 1983c. The intermediate disturbance hypothesis: an explanation for biotic diversity patterns in lotic ecosystems. In Dynamics of lotic ecosystems, ed. T.D. Fontaine and S.M. Bartell, 347–356. Ann Arbor, MI: Ann Arbor Science Publishers. Welcomme, R.L. 1979. Fisheries ecology of floodplain rivers, 317. London: Longman. ———. 1985. River fisheries. FAO Fisheries Technical Paper 262: 1–330. Welcomme, R.L., and M.J. Winterbourn. 1988. Patch dynamics in lotic systems: the stream as a mosaic. Journal of the North American Benthological Society 7: 503–524. Wetzel, R.G. 2001. Lymnology: lake and river ecosystems. London: Academic Press. Woodward, G., and A.G. Hildrew. 2002. Food web structure in riverine landscapes. Freshwater Biology 47: 777–798. World commission on Dams (W.C.D.) 2000. Dams and Development: A new framework for decision -making. Report of the World Commission on Dams. WCD, Cape Town, South Africa. Yang, T., Q. Zhang, Y.D. Chen, X. Tao, Chong-yu Xu, and X. Chen. 2008. A spatial assessment of hydrologic alteration caused by dam construction in the middle and lower Yellow River, China. Hydrological Processes 22: 3829–3843.
Chapter 2
Water: Its Properties, Distribution, and Significance
Abstract Water, a chemical compound, exists in nature in three physical states: liquid, gas, and solids, and all these forms are useful to human beings. Water has become a widespread life-sustaining substance, comprising 50–90% of living materials and covering nearly three-fourths of the Earth’s surface. All living organisms are composed mainly of water, the prime medium of life on earth and those of rivers are partly or wholly immersed in water. Life evolved in water, with water, and with the physical and chemical characters of natural water, and this balance is necessary. The global distribution of water is irregular. Some regions have plenty and others have shortages. The availability of liquid water depends on a reserve of inland waters, characterized by waters in lakes, rivers, reservoirs, wetlands, and groundwater. Water like other substances, expands when frozen, and help ice to float on the surfaces of the freshwater bodies. Cohesion of internal molecular constituents gives rise to another physical property of water, surface tension, which allows water organisms to traverse on the surface of the water. Water being the most essential and integral part of the lives and livelihoods of human beings for food, health, energy, and environment needs proper management in order to achieve sustainable eco-development. The water being a renewable natural resource will never “run out” the availability and variability of water impose the greatest impact on all-round development of a nation. Almost all rivers from a large country like India along with several other regions of the world have been identified as water-stressed rivers because of cumulative impacts of water abstractions, and environmental perturbations out of deforestation, global climatic changes, etc. Although life originated in water, it is really challenging for the aquatic organisms to adjust and survive in the ever-changing aquatic realm which appears to be not only unstable but hostile too as this aquatic environment is governed by unfamiliar rules of cold, wave-swept seacoasts, torrential mountain streams, and rivers, also by the very turbulent waters at the confluence of rivers with the sea. The living organisms of aquatic environments and their bioecological activities are very dependent on the prevailing ecological factors, both living and nonliving in the temporal and spatial scales. The unique physical and chemical characteristics of water and their interaction define the different aquatic environments and constrain the evolution of organisms that inhabit them. In view of the above, this chapter mostly highlights different properties of water which have made water as the most unique chemical entity of the world. Besides, the mutual interactions among varied properties of water with the physical processes of © Springer Nature Switzerland AG 2021 S. K. Chakraborty, Riverine Ecology Volume 1, https://doi.org/10.1007/978-3-030-53897-2_2
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river ecosystem and vice versa have been taken care of. In view of the problems of nonavailability of water, comments have been put forward to point out basic guidelines for water management. Keywords Molecular structure of water · Hydrological cycles · Distribution of water · Water balance within living organisms · Dissolved substances of water · Physical–chemical properties of water · The Reynolds Number · Movement of water · Colligative properties · Past and present trend of water utilization
2.1 Water: A Unique Creation of Nature Water being the dynamic substance and universal solvent with varied form of substances (dissolved gases, different solid elements, and organic compounds) forms the basis of all plants and animals life on the planet. Besides, all life processes of living organisms depend on water and thereby making it an indispensable and remarkable substance that makes all forms of life possible. Even, the possibilities of the presence of any life forms on other planets are directly evidenced by the availabilities of water (Fig. 2.1; Tables 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, and 2.7). Water’s unique properties are related to its atomic structure, intermolecular hydrogen bonds, and the molecular associations in the solid, liquid, and gas phases. Oxygen Fig. 2.1 Molecular structure of water molecule
2.1 Water: A Unique Creation of Nature
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Table 2.1 Some properties of water Property Density Melting and boiling points Heat capacity Heat of vaporization Surface tension Absorption of radiation Solvent properties
Comparison with other substances Maximum near 4 °C, not at freezing point, expands upon freezing Very high Only liquid ammonia is higher Highest among all liquids High Minimum in visible regions; higher in red, infrared, and ultraviolet Excellent solvent for ions and polar molecules, increases for ions with increasing temperature, decreases for gases with increasing temperature
Adapted from Berner and Berner (1987) Table 2.2 Different processes involved in hydrological cycle Process Description Condensation From vapor to liquid water droplets in the air (clouds and fog) Precipitation Condensed water vapor falls onto the planet’s surface (rain, snow, hailstorm, fog drop, drizzle, and sleet) Runoff Water moving across the land including both surface runoff (overland flow) and channel runoff. While flowing, water may leach into the ground, evaporate into the air, remain stored in lakes or reservoirs, or extracted for agricultural or other human uses Snowmelt Contribution to runoff by melting snow Infiltration Water flowing from the surface into the ground (soil moisture, groundwater) Subsurface Water flowing underground, in the vadose zonea and the aquifer. Subsurface flow water may emerge to the surface (springs or wells) or eventually flow into the oceans. Gravity or gravity-induced pressures push water to the surface at lower elevation than where it has been infiltrated. Generally, groundwater moves slowly and its residence time in aquifers may be of thousands of years Evaporation Phase transition from liquid to gas resulting in water moving from the ground or water bodies into the atmosphere. Energy for evaporation comes primarily from solar radiation Transpiration The release of water vapor from soil and plants into air Sublimation Phase transition from solid water (snow or ice) directly to vapor The vadose zone is the underground portion of land between the surface and the top of the groundwater table
a
remains as highly electronegative element in water, and its atoms bind with two hydrogen atoms that retain positive charge. The asymmetric charge in water molecules enables the oxygen in a molecule to form a weak bond with the hydrogen of two adjacent molecules. Such covalent O–H bonds result in strong intermolecular attraction. Water remains as monomeric, component (a basic unit of polymers) without structure in its gaseous phase. In solid state of water (ice form), each atom of oxygen in the molecular structure is connected, through hydrogen, to four more oxygen atoms, forming a tetrahedron, a network of hexagonal rings with spaces between the mole-
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Table 2.3 The distribution of water in the Biosphere (compiled information from varied sources)
Oceans Polar ice, glaciers Groundwater (actively exchanged) Freshwater lakes Saline lakes Soil and subsoil moisture Rivers Atmospheric water vapor
Volume (thousand of km3) 1,370,000 29,000 4067 126 104 67 1.2 14
Percentage of total 97.61 2.08 0.295 0.009 0.008 0.005 0.00009 0.0009
Renewal time 3100 years 16,000 years 300 years 1–100 years 10–1000 years 280 days 12–20 days 9 days
cules, and such configuration has enabled the ice to float on liquid water. It is the hydrogen bridges that hold the water molecules together. Hydrogen bonding of water also contributes to maintain other properties of water, including high heat fusion, heat of vaporization, heat capacity, and surface tension, which are very important for several biological functions. Unlike most other common gaseous and solid compounds in the biosphere, water exists in liquid form at the normal atmospheric temperatures and pressures on the surface of Earth. Polarity due to unequal distribution of charge and hydrogen bonding of the water molecule demonstrates the range of temperatures and pressures when water remains in a liquid state. The molecules of water are formed with two hydrogen and one oxygen atoms, where two smaller hydrogen atoms are attached on opposite sides (105° angles) to the larger oxygen atom. The negatively charged oxygen atoms remain bonded with the two positively charged hydrogen atoms due to the pulling forces between two opposite charges that draw the elements together. Each molecule of water has two hydrogen nuclei, and these are held to a central oxygen molecule with two charged electrons. This very durable molecular structure, also called a covalent chemical bond, can absorb large amounts of energy with little change in temperature because of the unique orientation of hydrogen atoms and their attachment with oxygen atoms. The angle of attachment (104.5°) between the two covalent bonds, one for each of the hydrogen atoms attached to the oxygen, means a slight positive charge near the hydrogen atoms, to one side of the molecule. The negative region near the oxygen attracts positive regions near the hydrogen atoms of nearby water molecules resulting in hydrogen bonding (Fig. 2.1). This molecular structure enables other chemicals to adhere to water; thus, water often is referred to as a “universal solvent (Weast and Astle 1979; Goldman and Horne 1983; Voet et al. 1992; Pinet 1992; Morgan and Stumm 1998).
2.1 Water: A Unique Creation of Nature
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Table 2.4 Some unique physical features of liquid water Comparison with other Property substances Fusion point and latent heat High, with exception of NH3 of fusion Specific heat (amount of heat in calories needed to raise the unit weight of substance by 1 °C) Evaporation point and latent heat of evaporation Thermal expansion
Surface tension
Power of solution
Electrolytic dissociation Transparency
Conduction of heat
Dielectric constant
Physical and biological significance Thermostatic effect at the freezing point due to absorption or release of latent heat Highest of the solids and Impedes extreme changes in liquids (except NH3) temperature. Transfer of very high heat due to movements of water. Maintains uniform body temperature Highest of all substances Extremely important in the transfer of heat and water in the atmosphere The temperature of maximum Maximum density of freshwater density for pure water is 4 °C and diluted seawater is above the freezing point This temperature decreases with increased salinity The highest of all liquids Important in cellular physiology controls surface phenomena. Decreases with increasing temperature. There are organisms adapted to this layer of surface tension. Organic compounds reduce surface tension High (universal solvent) Highly important due to the dissociation capacity of dissolved organic substances Very low A neutral substance that contains H+ and OH− ions Relatively high Absorbs infrared and ultraviolet rays of solar radiation. Low selective absorption in visible spectrum Highest of all liquids Important in live cells, the molecular processes can be affected by the condition for diffusion Pure water has the highest of Results in high dissociation of all liquids dissolved inorganic substances
Source: Modified from Sverdrup et al. (1942)
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Table 2.5 Physical properties of water Density Maximum density Temperature of maximum density Viscosity (Pa/s) Kinetic viscosity (m2/s) Freezing point (°C) Boiling point (°C) Latent heat of ice Latent heat of evaporation Specific heat Thermal conductivity Surface tension Dielectric constant
(25 °C) kg/m3 kg/m3 °C 25 °C 25 °C (101,325 Pa) Pat n (101,325 Pa) Pat n (kg/mol) (kg/mol) (15 °C in J/kg °C) (25 °C) J/cm °C) W/m 25 °C
997.075 1000.000 3.840 0.890 × 10−3 0.89 × 10−6 0.0000 100.00 6.0104 40.66 4.186 0.00569 71.97 × 10−3 78.54
Source: Schwoerbel (1987) and Wetzel (2001)
Table 2.6 Total relative areas and volumes of water in the world’s main bodies of water Reserve of water Oceans Groundwater Freshwater Humidity in soil Polar caps Antartic Greenland Arctic Glaciers Frozen ground Lakes Freshwater Salt water Swamps Flow of rivers Water in the biomass Water in the atmosphere Total Total reserve of freshwater
Area (103 km2) 361,300 134,800 – – 16,227 13,980 1802 226 224 21,000 2058.7 1236.4 822.3 2682.6 148,800 510,000 510,000
Volume (103 km3) 1338.000 23.400 10.530 16.5 24.064 21.600 2.340 83.5 40.6 300 176.4 91 85.4 11.47 2.12 1.12 12.9
% of total volume 96.5 1.7 0.76 0.001 1.74 1.56 0.17 0.006 0.003 0.022 0.013 0.007 0.006 0.0008 0.0002 0.0001 0.001
% of volume of freshwater – – 30.1 0.05 68.7 61.7 6.68 0.24 0.12 0.86 – 0.26 – 0.03 0.006 0.003 0.04
510,000 148,800
1358.984 35.029
100 2.53
– 100
Source: Shiklomanov (1998, 2000)
2.2 Water Balance Within Living Organisms: A Prerequisite for Survivality…
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Table 2.7 Water resources and annual water balance of the continents of the world
Area (106 km2) Precipitation (km3) River runoff (km3) Total Underground Surface Total soil moistening (infiltration and renewal of soil moisture) Evaporation Underground runoff (% of total)
North Europe Asia Africa America 9.8 45.0 30.0 20.7 7165 32,690 20,780 13,910
South America 17.8 29,355
Australia Total 8.7 s132.0 6405 110,305
3110 1065 2045 5120
13,190 4225 3410 1465 9780 2760 22,910 18,020
5960 1740 4220 9690
10,380 3740 6640 22,715
1965 465 1500 4905
38,830 11,885 26,945 83,360
4055 34
19,500 16,555 26 35
7950 32
18,975 36
4440 24
71,475 31
Source: Lvovitch (1973)
2.1.1 Some Facts of Water Maximum Density: At 4 °C Melting and boiling points: Very high Heat storing capacity: Higher than most of the chemical compounds Surface tension: Moderately High Absorption of radiation: Minimum in visible range; higher in infrared and ultraviolet spectrum of light Solvent properties: Excellent
2.2 W ater Balance Within Living Organisms: A Prerequisite for Survivality of Organisms Cells of all living organisms contain about 75–95% water, making this unique chemical substance as most essential constituent of life, and thereby water is involved in all biochemical reactions within the body. The functioning of excretory system is entirely dependent on water through which metabolic wastes are removed from the body which helps dissipating excess heat through body surface evaporation. In order to compensat such loss of water and maintaining the water balance within the body, water balance of the organisms is maintained. Two major ways that exist for meeting demands for water along with solutes in terrestrial animals are: (1) directly drinking water and indirectly producing metabolic water in the process of excretion and (2) losing water and solutes through urine, feces, evaporation from the skin, and from the moist air they exhale.
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Salt glands of some birds and reptiles and cloaca, a common receptacle for the digestive, urinary, and reproductive tracts, of all birds and reptiles reabsorb water from the terminal portion of the digestive tract back into the body properly. Kidneys of mammals, the prime excretory organs, produce and excrete urine with high ion concentrations and thereby maintain water balance. These organs in several aquatic animals, especially in migratory fishes, undergo structural and physiological changes for the osmoregulation (maintaining of constant internal osmotic environment in spite of changes in the external environment) in water having different solute concentrations (Hutchinson 1957; Kozhov 1963; Wallace et al. 1991; Klaff 2002) (Tables 2.1–2.8).
2.3 Hydrological Cycles Moving from one area of the planet to another, water repeatedly circulates through a series of states commonly known as the hydrologic cycle. The hydrologic cycle on the planet includes three components of evaporation, transport by wind, precipitation, and drainage. Driven by solar radiation and wind energy, the cycle depends on the perpetual transition from the liquid phase in the oceans to the gaseous phase in the atmosphere to precipitation over the continents (Fig. 2.2). Although today’s oceans cover 71% of the planet, the distribution and volume of freshwater vary from place to place, depending on weather patterns. In addition, all unfrozen water is in constant motion. Sometimes, the pattern of water movement is predictable, but it also may be random. For example, rain falls on the Earth’s surface, and this precipitation trickles above and below land to arrive in rivers. Once
Fig. 2.2 Hydrological cycle depicting the operation of different of its constituents within varied environmental processes
2.3 Hydrological Cycles
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there, the water is transported to the oceans. Along the way, some water evaporates back into the atmosphere. As water moves, air pressure and temperature variations cause its molecules to shrink, expand, accelerate, or slow down. Hydrologic cycle includes five major processes: (1) evaporation; (2) condensation; (3) transpiration; (4) percolation; and (5) precipitation (Tables 2.2 and 2.3).
2.3.1 Evaporation Evaporation occurs when water from the surface of different water bodies such as oceans, rivers, lakes, and other wetlands changes from a liquid to a gas after being heated by the sun or another energy source, such as underground magma. As water turns to a gas, the molecules speed up their molecular movement, eventually breaking apart from one another. The vapor that forms often is carried away to another location by thermal currents or wind. Rates of evaporation, in turn, are controlled by a number of factors, such as the types of water (fresh or saline), the surface area of the water, the atmosphere water surface interactions, changing profiles of the temperatures of the air and water, and the intensity of sunlight to heat the water. The higher salt concentration of the water in ocean makes its evaporation rate slower than that of freshwater.
2.3.2 Condensation The reverse process of evaporation is known as condensation. It occurs when evaporated water becomes cool or come in contact with a cooler substance, transforming the water vapor to form into water droplets and fall down in the form of precipitation. The dews are formed on the ground by the process of condensation when cool night air comes in contact with rising warm water vapor.
2.3.3 Transpiration Transpiration occurs because of the evaporation of water from the leaves, stems, and roots of plants. The movement of water occurs in this process through roots and vascular system of plants. As vegetation takes in carbon dioxide (CO2) and releases oxygen (O2), the expenditure of energy is tremendous. As part of the cooling process, a large amount of water evaporates from the vegetation’s roots, stems, and leaves.
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2.3.4 Percolation Percolation occurs when water soaks downward through the surface of the ground. This process, which also is called infiltration, occurs when water moves through rocks and soil to become groundwater. It may take hours or even years to complete. As the water travels through cracks of bedrock and layers of sand and soils, gravity directs the percolation in a downward direction. Depending on the height of the water table, groundwater supplies may be near the surface or deeper in the ground. In more arid communities, the water table occurs about hundreds of feet below ground.
2.3.5 Precipitation The moisture that falls by the deposition of storm mediated rain or snow is called precipitation. This is the culmination of several distinct events. First, condensation increases the size of tiny water droplets floating in the atmosphere. Second, these larger molecules then cluster with others to form larger clouds containing more water. This subsurface water is typically fresh with the exceptions of coastal areas, where saltwater has crept into bedrock. In all cases, the water contains dissolved elements, derived from the surrounding rocks. Some water may include radioactive isotopes, naturally occurring in rock formations. Other water sources contain iron, manganese, and sulfur. The underground environment is difficult to understand, because it cannot be seen from the surface. Groundwater is primarily replenished through rain and snowmelt. Sometimes, a large fracture in rock such as limestone or basalt fills with water. Over time, a small opening is widened by the dissolving action of water running across the rock surface. Eventually, a series of connected channels or caves may hold hundreds of millions of gallons of water.
2.4 Water Cycles Between Earth and the Atmosphere All types of water bodies (marine and freshwater) are linked, directly or indirectly, through an important ecological process, known as water cycle (hydrologic cycle) which is the cyclical pathways for the movement of water from the air to Earth and returns to the atmosphere in a sequential manner. Solar radiation acts as main driving force of this Earth’s cyclical phenomenon by heating Earth’s atmosphere and providing energy for the evaporation of water. Water vapours in the atmosphere after being condensed form the rain droplets which after falling on the earth as precipitation triggers the motion of the hydrological cycle. Water vapor, circulating in the atmosphere, after reaching to the soils of earth surface as precipitation moves into the ground by infiltration and some amount of water before reaching to the soil surface is intercepted by green coverage of plants, hard structures of rocks and mountains, decomposed organic matters, and built structures in urban
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areas. Such interception and resistance do not allow a considerable amount of water to infiltrate into the surface and subsurface of the ground and undergoes evaporation directly back to the atmosphere. The rate of evaporation is governed by the amount of water vapor in the air relative to the saturation vapor pressure, i.e., relative humidity. The rate and intensity of infiltration depend on the type of soil, slope, vegetation, and intensity of the precipitation. Excessive rainwater falling on the saturated soil, instead of making vertical percolation, experience horizontal flows across the surface of the ground as surface runoff or overland flow. At some places, these water flows get accumulated into d epressions and gullies, where the flow changes from sheet to channelized flow by a process that can be observed on city streets as water moves across the pavement. Some amount of surface water seeps down to an impervious layer of soils (clay or rock) as groundwater and the rest larger amount of water finally moves and reaches into springs and streams. Several streams join together to form rivers, which ultimately ends to sea by forming a transition zone, in between freshwater to marine environments. Certain amount of water that never infiltrate the ground evaporate directly back to the atmosphere because of interception and resistance imparted by the plants, hard earthen and man-built structures and even the accumulated organic matter on earth’s surface. Precipitation that reaches the soil moves into the ground by infiltration, the rate of which depends on the type of soil, slope, vegetation, and intensity of the precipitation. Plants cause additional water loss from the soil. Through their roots, they take in water from the soil and lose it through the leaves and other organs in a process called transpiration which is a plant’s physiological process for transmitting water from internal surfaces of leaves, stems, and other living parts. The sum total of evaporating water from the surfaces of the ground and vegetation (surface evaporation plus transpiration) is called evapotranspiration. Figure 2.2 is a diagram of the global water cycle showing the various reservoirs (bodies of water) and fluxes (exchanges between reservoirs) (Pinet 1992; Voet et al. 1999; Mortimer 2004).
2.5 Properties of Water 2.5.1 Physical Properties of Water Unlike most substances that contract when frozen, water expands, allowing ice to float on the surfaces of the lakes and streams. It is found as a liquid at temperatures common to most places on Earth. With its great capacity, it can absorb or lose a large amount of energy before showing a change in temperature. As a universal solvent, it dissolves gases, nutrients, and minerals. Its internal cohesion gives rise to surface tension, which allows aquatic fauna like water striders to traverse a pool’s surface or even run upstream. Water being endowed with two unique physical properties such as ideal solvent and liquid with specific density, is very much responsive towards change of tem-
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perature. Moreover, such uniqueness of physical properties have made water very much essential for all living organisms, and thereby constitute not only strong foundation for aquatic science but also to become central or focal points of that science which are used to define several units of measurement, including mass, heat, viscosity, temperature, and conductivity. The physical properties of water, in particular of its anomalies in density, surface tension, and thermal features, are important to aquatic organisms inhabiting the liquid medium. Another significant biological property is that surface tension enables the existence of special forms of aquatic life. Viscosity is another important property, as the mobility of aquatic organisms in the liquid medium depends on it. Properties of water actually determine its power of controls over geomorphology and aquatic habitats for different aquatic organisms which maintain the links among themselves and also with nonliving components of aquatic ecosystem (Fig. 2.2; Tables 2.3, 2.4, 2.5 and 2.6). 2.5.1.1 Role of Temperature in the Transformation of Water Molecules Intermolecular distances within the water molecules are controlled by temperature variation. At the time of melting of ice, the empty spaces in the molecular structure of water disappear, increasing the density of water, which ultimately reaches its maximum at 4 °C. Similarly on receiving higher temperature, the intermolecular distance of the water is increased at lower density causing the liquid to expand. Besides, the water molecule is characterized in having a strong dipole with two hydrogen atoms (positive) and one oxygen atom (negative), and distance (as charge distance) between them act significantly in determining effects on water’s physical properties. Without this strong dipolar feature, the water remains as liquid because of its strong dipolar feature that enables the water molecules to remain strongly attracted to each other, forming spherical or linear aggregates. Owing to a very unique relationship that exists in between water molecules with temperature and density (maximum density at 4 °C), the deepest parts of water in the freshwater bodies cannot be colder than water at its maximum density at 4 °C. Water tends to freeze from the surface towards the bottom, leaving a layer of ice that protects the deeper water from freezing leading to develop a phenomenon, thermal stratification which enables the distribution and survival of aquatic organisms. Such anomalies of density of water are important in the process of circulation of water and distribution of temperature especially during the winter period in temperate water bodies, but this phenomenon offers the stability by ensuring mixing through circulation of water in the inland water bodies of lakes in the tropics too. The density of liquid water, after being determined by temperature and dissolved ions, influences water flow and viscosity of water in wetlands, groundwater, lakes, reservoirs, rivers, and oceans. Less dense water having less density floats on the surface of water causing thermal stratification, which in turn govern the movement and distribution of chemicals and organisms in the inland water bodies, characterized to adapt with feeble water currents.
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Water being one of the best solvents can dissolve both gases and ions. An increase of temperature accelerates the dissolving process of most solids in water, which is in contrast to the solubility of gases in water that tends to decrease when temperature increases. Influence of temperature on the solubility of gas causes significant biological effects as evidenced by the mortality of aquatic animals such as fishes in low dissolved oxygen (O2) as less dissolved oxygen occurs in less amount in elevated temperature and the animal’s metabolic requirements for O2 increase as temperature increases. Four other physical properties of water include high heat capacity, heat of fusion (freezing), heat of vaporization, and surface tension. Water is characterized by having high heat capacity, which requires a relatively large amount of energy to increase the temperature of liquid water. Water is also endowed with high heat of fusion and vaporization in comparison to other liquids. Such properties have enhanced the requirement of water for a considerable amount of solar energy, which imparts heating to inland water bodies in the summer, and need a long period to freeze the surface of the same water bodies. High heat capacity also buffers water against rapid changes in temperature. Thus, aquatic organisms generally do not experience the rapid oscillation of temperatures in comparison to their terrestrial counterparts who are subjected to a range of temperature from 0 °C to 100 °C. Many aquatic organisms after having their origin in the thermally buffered environments, have evolved as very sensitive biotic components through ages to react against slight fluctuation of temperature. These adaptive features of such temperature-sensitive aquatic faunal components, being the bioindicators for temperature changes, can even be used for predicting climate changes (Firth and Fisher 1992). The evaporation of the water cools the body surfaces of animals by taking away energy. Surface waters representing the junction between hydrosphere and atmosphere can become an important determinant of local, regional, and global climate mainly because of having high heat capacity and heat of vaporization. 2.5.1.2 Surface Tension Another important physical property of water is surface tension. The high surface tension of water results from hydrogen bonding, which pulls water into a tight surface at a gas–water interface. Several organisms, such as water striders, efficiently utilize the unique physical property of water, of the surface tension, and can walk on the surface of water. Surface tension also limits the distribution of aquatic organisms by restricting the movement of the organisms inhabiting in the subsurface or deep water to the water surface. The respiratory siphons possessed by many aquatic insect larvae are used to breathe atmospheric air and the functioning of air bubbles carried by many aquatic beetles and bugs are facilitated by the surface tension of water. These structures function because of the tendency of water molecules to stick together (cohesion) and to other surfaces (adhesion). Surface tension promotes capillary action, which represents the ability of water to move up narrow tubes.
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2.5.1.3 Water Movement Water movement can be of three types: molecular, laminar, or turbulent. Molecular movement is also referred to as Brownian motion. Laminar flow is caused by physical processes that predominate at smaller Reynolds numbers and is more commonly close to solid surfaces or in the pores of sediments. Turbulent flow commonly occurs in open water at greater Reynolds numbers.
2.5.2 Chemical Properties 2.5.2.1 Chemical Composition and the Hydrophobic Effect The chemical composition of natural inland waters is complex because of the large number of dissolved ions and organic substances resulting from the natural conditions of drainage basins and human activities. The hydrophobic effect, extremely important in materials science with obvious biological importance because of the inability of some molecules to dissolve in water. It is also a function of the small size of the molecule which helps partial understanding of the methods of interaction of solutes with the hydrogen bonding (Granick and Bae 2008).
2.6 F lows and Exchange of Materials from Water to Other Environmental Compartments Different compartments of the ecosphere viz hydrosphere, atmosphere, lithosphere, and biosphere not remain interconnected but also exchange continuously materials aaand energy among them. One of the major sources of chemical components in water is from the substances and elements in the atmosphere. The chemistry of natural waters varies greatly due to the geochemistry of soil and rocks that constitute the substratum of water basins. Activities of organisms (excretion, respiration, bio- perturbation) also play a role in the balance of materials in aquatic systems (Table 2.3). Dissolved ions and organic substances play diverse biological roles such as regulation of the physiological processes in organisms, including activities of membranes and activation of enzyme systems. Out of gases dissolved in water, oxygen and carbon dioxide are the key representative gases because they are involved several in the processes of production of organic matter by primary producers (photosynthesis) and respiration by all organisms. Diurnal variations in the levels of these gases are caused by changes in the processes of photosynthesis, respiration, and circulation of water masses. The vertical distribution of dissolved ions, organic substances, and gases depends on horizontal and vertical circulation processes, stratification mechanisms, and interactions of tributaries with aquatic ecosystems.
2.6 Flows and Exchange of Materials from Water to Other Environmental…
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Air pollution affects the chemical composition of rainwater, contributing various ions, including H2SO4 and oxides of nitrogen (NOx). The pH of rainwater sometimes drops to below 5.4 to become acidic rain which affects the chemical composition of the water flowing through drainage basins into rivers and lakes, experiencing complex chemical interactions which also vary in turn with the changes of soils, rocks, etc., of the river basins and subbasins. Human interferences also influence the chemical composition of water by the removal of plant cover, by undertaking different treatments of soil, and releasing of domestic, industrial, and agricultural effluents, etc. Emissions of ammonia (NH3), nitrogen (N), and sulfur (S) chemically modify the atmospheric composition, and in turn oxidation of all those chemical substances alters the quality of rainwater which impart negative influences on surface waters and groundwater (Pinet 1992; Voet et al. 1999; Mortimer 2004).
2.6.1 Dissolved Substances in Water The most common ions are called “conservative ions” because their concentrations vary a little because of functional activities of organisms. The sources of all those constituents of water are: 1. Recycling of biogenic materials 2. Sedimentation and processes of exchange at sediment–water interface 3. Exchange between water and atmosphere 4. Influx from precipitation 5. Adsorption and desorption of dissolved substances on the surface of particulates in suspension 6. Inflows and outflows 7. Lateral transportation The main nutrient ions are not conservative, i.e., their concentrations, which are less than those of the most common ions, vary considerably depending on activities of organisms. N2, a dissolved gas, is essential in the nitrogen cycle and important for a group of organisms that can fix it from the atmosphere. O2 is essential in respiratory processes and CO2 can be a limiting factor for primary producers under certain conditions. Many organisms require trace ions. The processes of reduction and oxygenation are important for some elements, such as Fe and Mn. Some of these elements are toxic to aquatic organisms when the levels rise due to industrial discharges, human activities, or natural processes such as that occur in volcanic areas or natural waters draining through soils where high levels of these elements occur naturally. Such is the case with mercury and arsenic in certain areas. Organic substances occurring in natural waters have a complex origin and countless and varied reactions in the water, depending on photo-reductive and photo-oxidative processes. These dissolved organic substances include various stages of decomposition of natural vegetation and they play an essential role in inland aquatic systems. In general, dissolved organic matter (DOM) in water is classified into two groups:
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1. Humic substances: They are defined as a general category of naturally occurring highly heterogeneous biogenic organic substances, characteristically yellow and black in color, with high molecular weight and with refractory properties (Aiken et al. 1985). “Humic acids,” prime constituent of humic substances, are defined as those decomposing materials which are not soluble in water with acidic pH (>2), but maybe soluble at higher pH levels. 2. Non-humic substances: The organic substances other than humic substances include amino acids, carbohydrates, oils, and resins. Besides, fulvic acids represent that portion of humic substances which are soluble in all pH conditions whereas humic acids are that portion of humus which remain insoluble in water under any pH condition (Aiken et al. 1985).
2.6.2 Humic Substances and Other Organics in Water These substances constitute an essential component of dissolved organic matter in natural waters. In many natural bodies of water, humic substances account for about 50% of the dissolved organic carbon. Important elements in humic substances include oxygen (35–40% by weight), hydrogen (4–5% by weight), and nitrogen (2%). The terms total organic material (TOM), dissolved organic material (DOM), and particulate organic material (POM) are similar to carbon-based TOC, DOC, and (POC). However, these terms (TOM, DOM, and POM) refer to all materials present, including oxygen, hydrogen, and nitrogen. In general, the values are twice as high as TOC, DOC, and POC alone. The variability of dissolved organic carbon in natural waters is large and depends on internal (autochthonous) and external (allochthonous) inputs, periods of drought and precipitation, and internal processes in both lentic and lotic aquatic bodies (decomposition, bacterial action, water temperature, turbulence, and stratification). Dissolved organic substances, especially humic substances, play an important role in the availability of organic and inorganic nutrients for bacteria, fungi, phytoplankton, and aquatic macrophytes. Dissolved organic matters play an important role in the complexation, absorption, and immobilization of many contaminating organic substances and heavy metals too.
2.7 Hydrologic Cycle It is important to know how the hydrologic cycle is completed and how its various components are correlated in nature. The hydrologic cycle and its components are illustrated in Fig. 2.2 which shows that water, in its three phases (gas, liquid, and solid), starting from the ocean, land, or living matters, moves into the atmosphere by evaporation and transpiration. It passes through complicated atmospheric phenomena, generalized as the precipitation process, back to the earth’s surface, upon and within which it moves in a variety of ways and is incorporated into nearly all
2.8 Relationships Among Water Viscosity, Inertia, and Physical Parameters
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compounds and organisms. One can conclude that the oceans are immense reservoirs from which all water originates and to which all water returns. This simple statement may be further explained as follows: water evaporates from the ocean, forms clouds that move inland, condenses, and falls to the earth as precipitation. From the earth, through rivers and underground, water runs off into the ocean. However, total amount of water across the world did not experience that much of decrease mainly because of the proper functioning of the hydrological cycle involving different eco-hydrological factors and processes. It is an established proposition that no water can be depleted, or can be generated either, according to the law of conservation of matter. For human usage, however, the physical state of water is important, and so is its quality. Although the available quantity is limited, the need for water is ever-increasing, and consumption is bound to exceed the ceiling of supply.
2.8 Relationships Among Water Viscosity, Inertia, and Physical Parameters 2.8.1 V iscosity Is the Resistance to Change in Form, or a Sort of Internal Friction A change in the state of motion in a moving body withstanding resistance is referred to as inertia. Viscosity of water exhibits an increasing trend with smaller spatial scale, greater water movement, and lower temperature. Inertia increases with size, density, and velocity. However, these facts so far have received underappreciation but reveal biological and physical relevance to aquatic ecology. Consequences of these physical properties have raised a number of queries, which are: 1. Why fish are streamlined, but microscopic swimming organisms are not? 2. Why the sizes of suspended particles captured by filter feeding animals are with a lower limit? 3. Why the organisms of flowing water can find refuge near solid surfaces? Many aspects of these untold features of life in aquatic environments can be discussed conveniently using the Reynolds number (Re).
2.8.2 The Reynolds Number (Re) The Reynolds number (Re) as the ratio of inertia to viscous force explains the variability of the properties of water with spatial scale and water movement. Small organisms having low values of Re coupled with little inertia relative to the viscous forces are experienced by small animals which are just opposite to larger organisms. Reynolds numbers highlights different properties of water which put constrains to different biological activities, of aquatic organisms such as swimming, filter and
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suspension feeding, and sinking and many other aspects of aquatic ecology. This number can quantify spatial- and velocity-related effects on viscosity and inertia.
2.8.3 R elative and Dynamic Viscosities and Their Effects on Aquatic Organisms The physical properties of water like viscosity and inertia on the biology of living organisms have been studied in detail and profusely during the last few decades from the different parts of the world (Purcell 1977; Denny 1993; Vogel 1994, 1996). Relative viscosity increases and inertia decreases as the spatial scale becomes smaller. Viscosity increases because the attractive forces between individual water molecules become more important relative to the organism. Variation in dynamic viscosity in conjunction with other changing environmental parameters can have major effects on aquatic organisms. Dynamic viscosity has been observed to be greater in cold temperature and fishes are compelled to spend more energy to swim in cold than warm water, and cold viscous water also poses difficulty for the animals to filter out small particles at lower temperatures (Podolsky 1994; Vogel 1996). Effects of dynamic viscosity and viscous force are diverse and explain the following: 1. How do aquatic organisms collect food? 2. How do fast organisms swim? 3. When does natural selection favor streamlined organisms? 4. How quickly do particles settle in water? 5. How does fast groundwater flow?
2.8.4 Movement of Water (Brownian Motion) Molecules of water tend to move independently at the smallest scale through a process called Brownian motion. The warmer the water, the more rapidly the molecules move. Such flow of water can either be laminar or turbulent. Laminar flow is characterized by flow paths in the water that are primarily unidirectional (parallel to each other). Turbulent flow is characterized by eddies, where the flow is not unidirectional. Turbulent flow (mixing) decreases at small scales because viscosity dampens out turbulence as the Reynolds number decreases. Water flows more slowly near the surface of water bodies whereas flow becomes more laminar at the bottom and sides of water channels. The outer edge of the region where water changes from laminar to turbulent flow is called the flow boundary layer, the thickness of which increases with decreased water velocity, increased roughness of the surface, increased distance from the upstream edge of an object, and increased size of the object. Aquatic invertebrates found in fast-flowing waters often have characteristic flattened body forms
2.9 Movement of Light, Heat, and Chemicals in Water
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that allow them to take advantage of the slower velocity microhabitats of the boundary layers. Very small objects experience laminar flow, and larger ones experience turbulent flow. Large organisms that swim through the water benefit from being streamlined (shaped to avoid turbulence) as turbulent flow acts opposite to the moving large organism by exerting a force to slow down the speed of the organism. Small organisms (bacteria sized) do not need to be streamlined because turbulence increases the force of drag. Greater water velocities also increase turbulence (Goldman and Horne 1983; Voet et al. 1999; Klaff 2002).
2.8.5 Solar Heating and Evaporation of Water This solar energy being central to water movement provides energy which by driving and accelerating the evaporation of water control the hydrological cycle and the evaporated water is deposited subsequently as precipitation on land. Similarly, flowing down of water from the hills in rivers or groundwater triggers the release of the potential energy it gained against gravity during the process of evaporation.
2.9 Movement of Light, Heat, and Chemicals in Water An array of chemical substances and their movements in water is established as a key factor for the survival and growth of most of the aquatic organisms alongside throwing light on the understanding of water pollution and material transport. Light being the ultimate energy source for most life on our planet determines most of the biogeochemical cycles of the earth. Light heats water and thereby results in stratification of the water bodies, especially the lentic ones. The fluctuation of temperature also controls the movement of water and thereby regulate rate of movements of chemicals through water.
2.9.1 Diffusion of Chemicals in Water An insect detecting prey, algal cells acquiring nutrients, a microbe sensing its environment, fishes breathing, and a contaminant moving through an aquifer are all subject to the effects of diffusion of substances through water. Diffusion of heat and dissolved materials can be described as similar to that of movement of heat. Diffusion of chemicals is affected by many factors, including the concentration gradient between two points (distance and concentration difference), advective transport of water (water currents that move the chemicals), temperature, size of molecules, the presence and structure of sediments or polymers excreted by organisms,
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and any direct movement of the chemicals by organisms. Cooling and convection currents are created as water cools at the surface from evaporation and drops to the bottom of the glass. These density currents cause the sugar to dissolve much more quickly in normal circumstances because the temperature of the glass is not controlled precisely. Water currents often occur at spatial scales exceeding those of individual molecules, and such currents can dominate material transport. Molecular diffusions with many orders of magnitude tend to become slower than diffusion with water movement and are differently referred to as transport diffusion, advective transport, or eddy diffusion. Turbulent flow causes transport diffusion and relatively high diffusion coefficients. Thus, if there is any appreciable movement of water, transport diffusion will dominate over molecular diffusion. With very small spatial scales, Reynolds number is found to be small, where viscosity is large with the virtual absence of turbulence, and molecular diffusion assumes more importance. Transport diffusion overrides molecular diffusion in the water column of several freshwater bodies such as lakes and other wetlands, groundwaters, streams, and rivers. In sediments, such as in groundwater or on bottoms of freshwater bodies, the rate of chemical diffusion is also influenced by the mean path length and size of the pores and channels within the sediment. Short path length and large channels lead to high permeability. When the channels are long, diffusion rates are observed to become slowed down in the long channels or in many existing dead-end channels because molecules must take a longer path to diffuse between two points, and transport diffusion is limited due to slow water velocity.
2.10 Some Unusual Properties of Water Some of the unusual properties of water which are very relevant to understand the world of inland waters are mentioned below. Liquid water can be formed through some hydrogen bonding and electrostatic attraction of two slightly positively charged atoms of the gaseous hydrogen (H) and one slightly negatively charged atom of the gaseous oxygen (O) to form one molecule of water (H2O). The relative elemental simplicity of water is somewhat deceptive because of the great influence that some of the unusual properties of water have on the physics, chemistry, and biology of the world generally, and on the distribution of life specifically.
2.10.1 Density Density may be simply defined as the amount of weight or mass contained in a specific volume. If the volumes of all substances could be standardized to one size, e.g., one cubic centimeter (cm3), then a measure of the weight or mass in that fixed volume gives the density.
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2.10.2 Heat Capacity and Specific Heat Heat is a form of energy and, as such, can be measured by the changes in the temperature of a given volume of a substance and determine its heat capacity. The higher heat capacity of water is due to the taking away of more energy to raise the temperature of water in comparison to other substances. Water as the common standard is used and its heat capacity (arbitrarily defined as the heat needed to increase the temperature of 1 g of water by 1 °C) is comparatively large. When the mass is also considered, then the number of calories needed to raise 1 g of a substance by 1 °C is termed its specific heat, which represents an important property of water and is related to the amount of heat taken to make the water hot. The specific heat in other way is the amount of heat required to increase the temperature of 1 g of substance to 1 °C.
2.10.3 Heat of Fusion/Melting This is just the amount of heat exchanged during a phase shift from either liquid water to solid ice or from solid ice to liquid water. One gram of water at 0.0 °C can be converted to ice at 0.0 °C if 80 cal (79.72 cal g/l to be precise) are released in the process. The same quantity, i.e., 80 cal, is required to melt that 1 g of ice back to 1 g of water. No further caloric additions or subtractions are needed to effect the phase shift.
2.10.4 Heat of Vaporization/Condensation As was the case for “Heat of Fusion/Melting,” the Heat of Vaporization and Condensation also represents the amount of heat exchanged during a phase shift. For vaporization, it is the quantity of heat (540 cal g_1) needed to convert 1 g of water to 1 g of water vapor. The same amount of heat is exchanged or released in the phase shift during the condensation of 1 g of water vapor to 1 g of water. On a very narrow scale for life, water after being evaporated from the perspiring warm-blooded animals, including humans, helps maintain body temperatures. On a global scale, the alternative shifting of liquid water into water vapor in the atmosphere and vice versa have proved to be the key determinants in the redistribution of water and heat within the hydrological cycle around the world.
2.10.5 Isotopes An isotope is one of two or more forms of the same chemical element. Different isotopes of an element have the same number of protons in the nucleus giving them the same atomic number, but a different number of neutrons giving each elemental
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isotope a different atomic weight. Isotopes of the same element have different physical properties (melting points, boiling points) and the nuclei of some isotopes are unstable and radioactive. For water (H20), each of the elements of hydrogen (atomic number 1) and of oxygen (atomic number 16) is having three isotopes: 1H, 2H, and 3H for hydrogen; 16O, 17O, and 18O for oxygen. Isotopes of hydrogen and oxygen have gained special interest because of the occurrence of fractionation in vapor–liquid–solid phase changes. Some isotopes (heavier molecular “species” enriched in the condensation phase and lighter molecular “species” in the vapor phase) are being used to understand water movements and exchanges within atmospheric, oceanic, lake, stream, and groundwater systems.
2.10.6 Sublimation The sublimation of water refers to a process of transformation of water directly from a solid (ice) stage without experiencing any liquidation in between the solid and liquid stages. Such conversion of solid to liquid phase involves the requirement of heat energy (679 cal/g).
2.10.7 Surface Tension and Cohesiveness: Roles of surfactants Resistance force is offered by liquid water at the time of its deformation through the surface film of water. The surface tension of water measured in Newton’s per meter which exhibits slight increase as the temperature falls from 100 °C (0.0589 N/m) to (0.0765 N/m) at 0 °C. The molecules of water are strongly attracted to each other through their cohesiveness (attraction of like substances). The primary force for restoring larger wind-generated surface and internal waves of lakes is gravity, but the primary force for restoring the much smaller capillary waves or ripples on the surface of rivers or other water bodies’ surface seems to be surface tension of the water itself. There is a specialized community of organisms, sometimes called neuston, associated with the surface film. For many observers of nature, it is always fascinating to see small insects, such as pond skaters or water striders (Gerris sp.), within the insect Order Hemiptera, and whirligig beetles (Gyrinus sp. and Dineutes sp.), within the insect Order Coleoptera, running around on the surface of ponds, sheltered lakes, and some streams. Owing to the presence of padded ends to the long middle and hind feet of water striders, and the much shortened but paddle-like feet of the whirligig beetles, the high surface tension of the water is such that the insects may dimple, but not break through the surface film.
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2.10.8 Viscosity This property may be thought of as the internal friction or resistance exerted on one substance (gas, liquid, or solid) as that substance tries to flow or move through the same or another liquid. Viscosity is usually measured in poises (N/m2) or centipoises (¼ 0.01 P). The rate of passive descent through a liquid reflects the density of the liquid itself as well as the surface area and density of the substance moving through it. Viscosity changes with water temperature in that viscosities decrease as water temperatures rise and increase as water temperatures fall. Many fish are powerful enough, slippery from mucous on their skin, and shaped so they can “slip through” water relatively easily. In contrast, tiny zooplankton, with multiple projections on their body, are ordinarily challenged as they attempt to move in any direction and particularly so when moving in cool waters.
2.10.9 Colligative Properties These are the four special properties of water that are significantly altered or modified when solutes are added to and dissolve in water. The alterations or modifications of a colligative property (regarded as a binding property) may be predictable in dilute solutions when the number of solute particles is known. It is the number of solute particles, not their chemical nature, that determines the extent to which a property is modified. The four colligative properties of water are vapor pressure (when water is in equilibrium with its own vapor), osmotic pressure (the pressure controlling the diffusion of a solvent across a semi-permeable membrane), boiling point (the temperature at which water undergoes a phase shift to a gas), and freezing point (the temperature at which water undergoes a phase shift to a solid). Even at standardized pressures and temperatures, the extent to which a property is modified depends on the number of solute particles added.
2.11 C irculation of Water: Influence on Chemical and Biological Processes The perpetual mobility of water masses has considerable influence on chemical and biological processes. All vertical or horizontal transport is performed by these movements, which depend on kinetic energy from wind action or factors of diffusion caused by turbulence. Scales of mobility vary diurnally and seasonally. There are diel movements associated with climatic variations in short time periods, and movement with seasonal scale, related to periodic effects of wind and formation of a thermocline. Seasonal
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interactions between energy flows, thermal heating, and wind action produce seasonal patterns of circulation and horizontal and vertical dislocation of water masses. The prognosis of thermal structures of inland water bodies is dependent on solar radiation and wind-produced kinetic energy, and plays an important role in the management of these inland systems. Owing to the prevailing close interrelationships of the atmosphere and water ecosystems, it is of value which can monitor the relationship between climatic factors (such as solar radiation, winds, and precipitation) and events in the lake (thermal structure, vertical, and horizontal circulation). The use of climate data derived from the studies of climatic and hydrological interactions is essential for understanding many of the chemical and biological processes in freshwater lentic and lotic bodies.
2.11.1 C irculation of Water in Freshwater Bodies (Lentic and Lotic) There are several differences in the circulation in lakes, reservoirs, and rivers. For example, the selective removal of water from different depths in the reservoir produces some specific circulation mechanisms, mainly advection currents. The very characteristic of the use of the dam with through-flow to produce electricity can cause short-term differences in horizontal and vertical circulation. Pollutants can be distributed horizontally by advection or accumulate in the hypolimnion, in sediments and their interstitial water. Circulation (both horizontal and vertical) in both lentic and lotic water bodies contributes greatly to the dispersion and concentration of heavy metals and toxic substances in the system’s various spatial compartments (horizontal and vertical). In the case of stratified lakes, accumulation of pollutants or toxic substances can occur in the metalimnion along with the accumulation of suspended material. Horizontal movements or vertical instabilities of water masses in certain periods can increase the dispersion in this layer and in the deep part of the epilimnion.
2.11.2 Diffusion in Water The processes of diffusion correspond to chaotic and random movements. These processes are related to concentration gradients between a particular substance and that concentration which already exists in the surrounding water. Diffusion is the inliquid movement of an element or substance, down a gradient of its concentration. Molecular diffusion of ionic solutions in porous media (sediments) refers to the diffusion, within a single phase of atomic constituents, i.e., atoms, ions, or molecules. Molecular diffusion is an important process, for example, in the sediment/ water interaction.
2.13 Characteristic of Freshwater Systems
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Vertical and horizontal turbulent diffusions occur on the surface and in the thermocline of freshwater water bodies. In general, the horizontal turbulent diffusion on the surface accompanies the advection process, which involves distances greater than 1000 m. Small-scale diffusion or turbulence occurs at distances of