International Groundwater Law and the US-Mexico Border Region [1 ed.] 9789004385085, 9789004385078

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International Groundwater Law and the US-Mexico Border Region

International Water Law Series Series Editor Stephen C. McCaffrey Editorial Board Laurence Boisson de Chazournes Edith Brown Weiss Lucius Caflisch Joseph Dellapenna Malgosia Fitzmaurice Christina Leb Owen McIntyre Salman M.A. Salman Attila Tanzi Patricia Wouters

volume 7

The titles published in this series are listed at brill.com/iwl

International Groundwater Law and the US-Mexico Border Region By

Maria E. Milanes

LEIDEN | BOSTON

Library of Congress Cataloging-in-Publication Data Names: Milanes, Maria, author. Title: International groundwater law and the US-Mexico border region /  by Maria Milanes. Description: Leiden ; Boston : Brill, [2020] | Series: International water  law series, 2351-9606 ; volume 7 | Based on author’s thesis (J.S.D.—  McGeorge School of Law, 2013) issued under title: A new international  legal and institutional framework to manage fossil aquifers and  groundwater in conjunctive use with surface water along the US-Mexico  border : a water banking perspective. | Includes bibliographical  references and index. Identifiers: LCCN 2020012966 (print) | LCCN 2020012967 (ebook) |  ISBN 9789004385078 (hardback) | ISBN 9789004385085 (ebook) Subjects: LCSH: Water resources development--Law and  legislation—Mexican-American Border Region. | Groundwater—Law and  legislation—Mexican-American Border Region. | Water transfer—Law and  legislation—Mexican-American Border Region. Classification: LCC KDZ639 .M55 2020 (print) | LCC KDZ639 (ebook) |  DDC 341.4—dc23 LC record available at https://lccn.loc.gov/2020012966 LC ebook record available at https://lccn.loc.gov/2020012967

Typeface for the Latin, Greek, and Cyrillic scripts: “Brill”. See and download: brill.com/brill-typeface. ISSN 2351-9606 ISBN 978-90-04-38507-8 (hardback) ISBN 978-90-04-38508-5 (e-book) Copyright 2020 by Koninklijke Brill NV, Leiden, The Netherlands. Koninklijke Brill NV incorporates the imprints Brill, Brill Hes & De Graaf, Brill Nijhoff, Brill Rodopi, Brill Sense, Hotei Publishing, mentis Verlag, Verlag Ferdinand Schöningh and Wilhelm Fink Verlag. All rights reserved. No part of this publication may be reproduced, translated, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission from the publisher. Authorization to photocopy items for internal or personal use is granted by Koninklijke Brill NV provided that the appropriate fees are paid directly to The Copyright Clearance Center, 222 Rosewood Drive, Suite 910, Danvers, MA 01923, USA. Fees are subject to change. This book is printed on acid-free paper and produced in a sustainable manner.

To my parents María Carmen and José Antonio

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Contents Acknowledgements xi 1 Introduction 1 2

Groundwater along the US-Mexico Border 11 1 Introduction 11 2 Defining International Transboundary Groundwater and Aquifers 12 3 Types of Aquifers and Their Implications for International Law 16 4 Case Studies of Groundwater Use along the US-Mexico Border 18 5 Conclusion 34

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Challenges and Issues in the Management of Groundwater: the Case of the US-Mexico Border Region 36 1 Introduction 36 2 Challenges and Problems in the Management of Groundwater 37 3 International Water Disputes along the US-Mexico Border 52 4 Conclusion 58

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The International Legal Regime of International Groundwater and Aquifers 59 1 Introduction 59 2 Customary International Law and International Groundwater 62 3 International Legal Instruments 72 4 State Practice 84 5 Conclusion 105

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History and Current International Water Legal Framework of the United States-Mexico Border 107 1 Introduction 107 2 International Legal Framework in the United States-Mexico Border 108 3 New Perspectives on the International Legal Framework for the United States-Mexico Border 145 4 Conclusion 147

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Domestic Legal and Institutional Framework at the US-Mexico Border 148 1 Introduction 148 2 Domestic Binational Efforts and Agreements 151 3 The United States 154 4 Mexico 182 5 Conclusion 187

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The US-Mexico Transboundary Aquifer Assessment Act, 2006. Cooperation between the US and Mexico, Achievements and Efforts in the Mesilla Aquifer Basin 189 1 Introduction 189 2 Transboundary Groundwater along the US-Mexico Border Region with Special Reference to the Mesilla Aquifer 191 3 Transboundary Groundwater Issues along the US-Mexico Border Region 193 4 United States-Mexico Transboundary Aquifer Assessment Act, 2006 196 5 The Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program 213 6 TAAP Implementation and Achievements on the Mesilla Basin/ Conejos-Médanos 214 7 Efforts and Cooperation 215 8 Further Efforts 218 9 Conclusion 219

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Water Transfer Mechanisms and Regulations: the Role of Water Banking 221 1 Introduction 221 2 Mechanisms to Transfer Water 222 3 Institutional Framework for Water Markets and Banking 227 4 Current Water Transfer Regulations in the US-Mexico Border Region 245 5 Water Banking Trends along the US-Mexico Border 264 6 Conclusion 266

Contents

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A New International Legal and Institutional Framework to Allocate Groundwater in the US-Mexico Border Region 267 1 Introduction 267 2 Reasons for a New International Legal Framework along the US-Mexico Border Region 269 3 Theoretical Basis for a Legal Framework 272 4 New International Legal and Institutional Framework to Allocate Groundwater and Groundwater in Conjunctive Use with Surface Water along the US-Mexico Border 281 5 Legal and Institutional Framework for Minute 2013 296 6 Current Approach to Regulate Groundwater along the US-Mexico Border 297 7 Conclusion 298

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Conclusion and Recommendations 300



Appendix 1: United States-Mexico Transboundary Aquifer Assessment Act 305 Appendix 2: Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program 312 Appendix 3: Proposed Conjunctive Use Regulation 2013 316 Appendix 4: Proposed Fossil Aquifers Regulation 2013 354 Index 363

Acknowledgements This book is based on the author’s JSD Dissertation written at McGeorge School of Law, University of the Pacific. Maria Milanes would like to express her endless gratitude to her advisor, mentor and friend Professor Dr. Stephen C. McCaffrey for his wisdom, guidance, encouragement, and support writing this book. The author would like to acknowledge and thank BRILL USA, Inc, specially Marie Sheldon, Publishing Director, Ms. Johanna M. Lee, Ms. Kelley Baylis Assistant Editors, International Law, and Ms. Christina Sargent, Production Editor. And, she also thanks the comments and corrections done by Ms. Susan Redit. She expresses her gratitude to Professor Gabriel Eckstein, Professor Rachael Salcido and Professor John Sims for their dedication and time. Maria would like to thank Professor Samuel Sandoval Solis and Professor Ariel Dinar for their orientation and comments. Special thanks to Professor Eric McElwain for his help on this work. The author appreciates advice from Professor Gregory Weber, Dr. Margaret Vick and Dr. Bennett Bearden. She expresses gratitude to McGeorge School of Law and the California Victims of Crime Resource Center. She values and really appreciates the support and help offered by Mr. José Antonio Milanés Murcia, Ms. Leire Milanés Campayo, Ms. Nerea Milanés Campayo and Mr. Aitor Milanés Campayo. Maria also thanks Mr. Juan Antonio Guillén Alcazar for his help with all the figures in this book.

chapter 1

Introduction Groundwater is a vital resource that must be managed effectively, especially in areas such as the southwestern United States, where this resource is increasingly scarce.1 This book addresses private and public water management through a multidisciplinary point of view to improve decision-making regarding water allocation. The study area is located along the entire border between the United States (California, Arizona, New Mexico, and Texas) and Mexico (Baja California, Sonora, Chihuahua, Coahuila, Nuevo Leon, and Tamaulipas). It includes the study of the San Diego-Tijuana, Cuenca Baja del Rio Colorado, Sonoyta-Papagos, Nogales, Santa Cruz, San Pedro, Conejos Medanos-Bolson de la Mesilla, Bolson del Hueco-Valle de Juarez, Edwards-Trinity-El Burro, the Mimbres, and Cuenca Baja del Rio Bravo/Grande aquifers.2 The US-Mexico border contains several significant cities, such as San Diego (US), Mexicali (Mexico), Tijuana (Mexico), Matamoros (Mexico), Ciudad Juarez (Mexico), El Paso (US), Las Cruces (US), Laredo (US), Nuevo Laredo (Mexico), Matamoros (Mexico), and Brownsville (US). Each of these cities has a rapidly increasing water demand and extensive agricultural exploitation, all of which places demand on the aquifers in the border region. Both the authorities and the population are concerned about the future of the water supply because of the increasing demand and the effects of climate change.3 Because surface water is scarce in the border region of the United States as well as in other regions around the world, a solution for water allocation will most likely be based on rational groundwater use. How to preserve and allocate groundwater is a question asked by many institutions, such as the Texas

1  United States-Mexico Transboundary Aquifer Assessment Act, 42 USC §§ 1962 (2006), Public Law 109–448 109th Congress (22 December 2006), http://npl.ly.gov.tw/pdf/5672.pdf. The Act uses the term “priority transboundary aquifers.” 2  Internationally Shared Aquifer Resources Management (ISARM) Initiative, International Hydrological Programme, United Nations Educational, Scientific and Cultural Organization (UNESCO), Atlas of Transboundary Aquifers (Paris: UNESCO, 2009), https://isarm.org/sites/ default/files/resources/files/2%20Atlas%20of%20TBA.pdf. See igrac, TAW (2015). 3  C. Brown, ‘Transboundary Water Resources Issues on the US-Mexico Border, Challenges and opportunities in the 21st Century,’ VertigO – la revue électronique en sciences de l’environnement [Online], Hors-série 2 (September 2005), http://journals.openedition.org/vertigo/1883; doi:10.4000/vertigo.1883.

© Koninklijke Brill NV, Leiden, 2020 | doi:10.1163/9789004385085_002

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Water Development Board.4 The goal of this book is to answer this question through the examination of the legal framework surrounding groundwater. The objective is to provide the elements to develop an international institutional groundwater framework in conjunctive use with surface water, where an agreement (Minute) is developed using the most efficient mechanism to allocate water among the parties. This book evaluates the benefits of water markets and water banking and other mechanisms to allocate water, to effectively transfer water and prevent negative impacts on any third party, such as the ecosystems in Otero Mesa.5 An appropriate mechanism to allocate groundwater in conjunctive use with surface water would be a water. Thus, the potential effects of a water bank and a water market are studied in this book. The proposed transboundary legal and institutional framework attempts to fill the legal vacuum of international and interstate groundwater management along the US-Mexico border. The proposed legal and institutional framework to manage fossil aquifers and groundwater in conjunctive use with surface water includes specific regulations for water banking, which can improve water allocation and protect the environment. This framework can be adapted to any region around the world. The new legal framework developed here is structured as a new Minute to the Utilization of Waters of the Colorado and Tijuana Rivers and the Rio Grande Treaty between the United States of America and Mexico (1944 Treaty)6 and an amendment (agreement) to the 1906 Treaty.7 The proposed legal and institutional framework (Minute, amendment) respects the surface water distribution scheme established in the 1906 Treaty and the 1944 Treaty, and its main scope is the allocation of groundwater in conjunctive use with surface water while always following the terms in each treaty. The International Boundary and Water Commission (IBWC) manages water along the entire

4  Jarvis, Glenn, “The Developing Law of the Rio Grande From a Texas Perspective,” CLE Inter­ national Texas Water Law Conference, Austin, TX, 13 September 2004. 5  Coalition for Otero Mesa, “History of Otero Mesa,” http://oteromesa.org/otero-mesa/history -of-otero/, “The lands of the Greater Otero Mesa Area have born witness to the presence of Native Americans, the Spanish in the Colonial era, Mexicans, and the sovereignty of the United States. Both prudence and due diligence should be exercised to ensure that our cultural heritage is not jeopardized in a precipitous rush to exploit this fragile landscape.” 6  Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande Treaty between the United States of America and Mexico, 3 February 1944, https://www.ibwc.gov/ Files/1944Treaty.pdf. 7  Convention Between the United States and Mexico Providing for the Equitable Distribution of the Waters of the Rio Grande for Irrigation Purposes, 21 May 1906, https://www.ibwc.gov/ Files/1906Conv.pdf.

Introduction

3

US-Mexico border.8 Under the new regulation, the IBWC would have the authority to allocate groundwater in conjunctive use with surface water along the border. The legislators could also incorporate this new legal framework using another instrument, such as a new treaty. However, the main goal here is to provide the elements to develop a transboundary groundwater treaty in conjunctive management with surface water, which can be adapted to different regions around the world. The ultimate aim is to propose a new legal and institutional framework to allocate groundwater in conjunctive use with surface water rather than to specify how that goal should be accomplished. This book establishes recommendations to manage groundwater in conjunctive use with surface water. The analysis of different water allocation mechanisms such as a water bank and water market determines the best systems for managing this resource along the US-Mexico border and in other regions around the world. These recommendations will be tailored for use by legislators as advice for future modifications. One way to determine if a water allocation mechanism will work is to forecast the future market value of water rights in the area of study. Previous research in the study area shows the importance of projected values of exogenous variables such as the price of one acre of marginal irrigated land, the population, and the total value of crops produced in the agriculture sector.9 Also, the design of water allocation mechanisms and the legal framework should have flexibility built into them to account for the effects of climate change. Moreover, public opinion about mechanisms to allocate water will provide information about chances for success in the allocation process.10 In a previous study focused on a water market in the El Paso area, McGuckin and Gonzalez recommended that a water market is a suitable model for all aquifers at the time to incorporate conjunctive management of surface water and groundwater.11 Water users under this framework would be able to trade rights to surface and groundwater supplies of water. These trades would be 8  See International Boundary and Water Commission (IBWC), “Mission Operations: Diversion Dams and Related Structures,” https://www.ibwc.gov/Mission_Operations/ Diversion_Dams.html, which provides details on the diversion dams and related structures. 9  R. Khoshakhlag, F. Lee Brown and C. Dumars, Forecasting Future Market Values of Water Rights in New Mexico, New Mexico Water Resource Research Institute Project N. 3109209, 163 (1997). 10  Id. See also M. Evans, “Evaluating the Implications of Structural Change: A Multiregional Input-Output Model of the Four Corners States” (1997) (unpublished Ph.D. dissertation, University of New Mexico Albuquerque) (on file with the UNM library). 11  T. McGuckin and M.T. Gonzalez, ‘The Economic Consequences of an International Water Market in the Paso Del Norte Region,’ 20(1) Journal of Borderlands Studies (2005): 45–72.

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done under an international legal, regulatory scheme able to limit effects on third parties.12 This study emphasizes the need to understand and address the enormous political and legal barriers arising from the use of such an international water allocation system framework. International groundwater has been managed through the use of customary international law reflected in few treaties addressing transboundary aquifers.13 The International Law Commission codified international customary rules in the 1997 UN Convention on the Law of the Non-navigational Uses of International Watercourses (UN Watercourses Convention).14 The entry into force of the UN Watercourses Convention is a step forward in providing a legal framework for the conjunctive management of surface water and groundwater.15 The 1992 Convention on the Protection and Use of Transbound­ ary Watercourses and International Lakes (the Water Convention)16 defines transboundary water as “any surface or groundwaters which mark, cross or are located on boundaries between two or more States.”17 The Draft Articles on the Law of Transboundary Aquifers 2008 applies “to the utilization of transboundary aquifers and aquifer systems, other activities that have or are likely to have an impact upon those aquifers and aquifer systems; and measures for the protection, preservation, and management of those aquifers and aquifer systems.”18 The number of aquifers along the US-Mexico border has been estimated to be over 30.19 However, the international regulation is very limited, including 12  I d. 13  S. Burchi, “National Regulations for Groundwater: Options, Issues and Best Practices,” in S.M.A. Salman, ed., Groundwater Legal and Policy Perspectives, Proceedings of a World Bank Seminar, World Bank Technical Paper No. 456 (Washington, DC: World Bank, November 1999), 55–68. 14  United Nation Convention on the Law of the Non-Navigational Uses of International Watercourses, 21 May 1997. 36 ILM 700 (1997), UN Doc. A/RES/51/229.. See also UNGA, “The Law of Transboundary Aquifers,” Resolu­tion 63/124, Report of the Sixth Committee (A/63/439), 63rd session (15 January 2009). 15  U N Watercourses Convention, id., art. 2. 16  Convention on the Protection and Use of Transboundary Watercourses and International Lakes, 17 March 1992. 17  Id., art. 1. 18  See UNGA, “Report of the International Law Commission on the Work of its Sixtieth Session,” UN GAOR, 63rd Sess., Supp. No. 10, UN Doc. A/63/10 (2008), at 19. The documents cited by the International Law Commission are available on the ILC website, http://www.un.org/law/ilc/. 19  R. Sanchez, V. Lopez, G. Eckstein, Identifying and Characterizing Transboundary Aquifers Along the Mexico-US Border: An initial assessment, Journal of Hydrology (2016).

Introduction

5

Minute 242 to the 1944 Treaty, which shows the intention of both countries to develop a future “comprehensive agreement on groundwater in the border areas.”20 The US-Mexico Transboundary Aquifer Assessment Act21 was signed into law by the President of the United States on December 22, 2006.22 It promoted cooperation between both countries on scientific research efforts to assess the transboundary aquifers designated as a priority by the aquifers prioritized by the Act, including Santa Cruz and San Pedro aquifers in Arizona, the Mesilla aquifer located in the border with New Mexico23and the Hueco Bolson along New Mexico and Texas.24,25 This Act authorized the Secretary of the Interior, through the US Geological Survey (USGS), to collaborate with the States of Arizona, New Mexico, and Texas through their Water Resources Research Institutes (WRRIs) and with the IBWC, stakeholders, and Mexican counterparts to develop mapping, modeling of priority transboundary aquifers and hydro-geologic characterization. The Act addressed the multi-disciplinary, binational, scientific approaches to provide answers to all complex, interrelated transboundary issues. These efforts are reflected in the current work developed through the Transboundary Aquifer Assessment Program,26 which is a unique Federal

20  I BWC, Minute N. 242. International Boundary and Water Commission United States and Mexico. August 30, 1973. 21  Pub. L. No. 109–448, supra note 1. 22  Id. 23  Id. s. 4. 24  Id. ss. 2 and 4. 25  Mexico does not have an Act similar to the Pub. L. No. 109-448, establishing direct cooperation with the US on transboundary aquifers. Mexico, however, manages groundwater under the National Water Law, which is administrated by the National Water Commission (CONAGUA) and it designated 3.9 million pesos in 2018 to continue the study of aquifers along the border in direct cooperation with the IBWC Mexican and US sections. The development of the US Law Pub. L. No. 109-448 did not include opinions or perspective from Mexico. It is exclusively US Law, although it aims to establish cooperation among both countries and allowed the allocation of funds to Mexico, see Willian M. Alley, infra note 27. 26  “The program was authorized for a total of $50 million for FY 2007 through 2016. Appropriations were $500,000 for FY 2008 and 2009, and $1 million for FY 2010. No funding was provided in FY 2011 and 2012. The USGS received 50 percent of all funds, and the three State WWRIs (Arizona, New Mexico, and Texas) shared the other 50 percent equally. Part of the WRRI funding was matched with contributions from Mexico to support the binational research”.   see Willian M. Alley, infra note 27, p. 2. 

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agency-universities-binational partnership27 that carries out the activities in support of the Act in the US and Mexico.28 As a result of the cooperative efforts reflected in the Act and the interest of both countries in establishing a joint cooperative process to implement an assessment program for the shared transboundary aquifers,29 the IBWC (US and Mexican sections)30 signed the Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program in 2009.31 This book also addresses the practices and trends of countries around the world. Besides, it presents a summary of certain international groundwater agreements. A comparative analysis of existing international groundwater agreements is an essential tool to develop a new agreement and determine the most effective mechanism to allocate groundwater among nations.32 The implementation of the new legal framework developed in this book would improve the management of water resources, support agricultural production and enhance the environment around the world, especially along the US-Mexico border. Without such a model, the increasing population33 of cities like San Diego, Las Cruces, El Paso, Ciudad Juarez, and Nuevo Laredo, together with an inappropriate selection of crops, may seriously jeopardize the 27  W  illiam M. Alley, Five-Year Interim Report of the United States-Mexico Transboundary Aquifer Assessment Program: 2007–2012, US Geological Survey, Open-File Report 2013-1059 at 3 (2013). 28  Pub. L. No. 109-448, supra note 1. The sunset of the Act Pub. L. No. 109-448 was established for ten years since the Act was enacted and that expired in 2016. The USGS allocated an additional $1 million between Arizona, New Mexico, and Texas Water Resources Research Institutes for the fiscal year 2016. See chapter 7 of this book. 29  International Boundary and Water Commission United States and Mexico, Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program. El Paso, Texas, August 19, 2009. 30  The IBWC Mexican Section is named in Spanish Comisión Internacional de Límites y Aguas (CILA). See Secretaría de Relaciones Exteriores, La Comisión Internacional de Límites y Aguas entre México y Estados Unidos (International Boundary and Water Commission), es un Organismo Internacional creado en 1889 entre ambos países para resolver las diferencias en materia de límites, http://www.gob.mx/sre/ acciones-y-programas/c-i-l-a-mex-eua. 31  I BWC 2009, supra note 29. 32  See generally, “Organisation for Economic Co-operation and Development (OECD), Water Resources Allocation, Sharing Risks and Opportunities,” Policy Highlights (2015), https://www.oecd.org/environment/resources/Water-Resources-Allocation-Policy -Highlights-web.pdf. 33   Migration Policy Institute, “The US-Mexico Border,” Migration Information Source (1 June 2006), http://www.migrationinformation.org/USfocus/display.cfm?ID=407. 

Introduction

7

future of both agricultural and domestic supplies of water. In order to protect its national interest in food production, the United States must efficiently manage its natural resources.34 Water is essential to achieve a high level of production. The US-Mexico border area is capable of producing high crop yields if the water is properly administered and its future supply guaranteed.35 Previous research shows the existence of extensive groundwater aquifers in the El Paso area that have not yet been fully exploited. For example, the cities of El Paso and Ciudad Juarez cannot access the Jornada aquifer.36 The entire Jornada aquifer is located in New Mexico, which precludes access by either Mexico or Texas, although the connection between the Jornada and the other aquifers along the border region is not clear. The management of such aquifers could be through an international institutional framework that provided an effective water allocation mechanism for groundwater in conjunctive use with surface water and specific regulations for fossil aquifers, while also addressing political issues and guaranteeing third-party interests, such as protection of the environment.37 In Sporhase v. Nebraska,38 the United States Supreme Court ruled that groundwater must be considered an item of commerce and that states may not interfere with the interstate transfer of groundwater unless it is demonstrated to be detrimental to public welfare or contrary to state water conservation plans. The Court ruling does not apply to international trade, but the underlying assumption of the Court and microeconomics still applies, that is, allow the market exchange of groundwater in a manner that does not impair third parties and increases public welfare.39 The analysis of alternative institutional mechanisms facilitates planned international development of all groundwater resources shared by the United States and Mexico. An institutional framework can either improve or impair water allocation. If the institutional framework defines clear water rights and laws, the water allocations will be efficient. When water rights are adjudicated and identified, the transaction cost of water transfers is reduced because the water rights

34  S ee generally, Environmental Protection Agency (EPA), “Major Crops Grown in the United States,” in Ag101 (EPA, 9 July 2015), at 62, https://www.epa.gov/sites/production/files/2015 -07/documents/ag_101_agriculture_us_epa_0.pdf. 35  McGuckin and Gonzalez, supra note 11 at 60. 36  Id. at 56. 37  Id. at 46. 38  Sporhase v. Nebraska, 458 US 102, 963 (1982). 39  Id.

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holders feel secure.40 The US-Mexico border area has five different jurisdictions: California, Arizona, New Mexico, Texas, and Mexico; a legal solution that combines the water rights of these jurisdictions and guarantees ownership of them in an international groundwater market would reduce transactions cost and establish efficient water trade. An inefficient institutional framework could worsen the water allocation among users, if there are legal restrictions that do not allow water trades between users.41 Also, if statutory regulations are weak, insecurity in water transactions will result. This situation may lead to farmers preferring to sell their water rights quickly at a meager price rather than going to court.42 An effective allocation mechanism requires a clear and strong legal framework. The US-Mexico border needs an institutional framework for groundwater that can protect farmers, agricultural, residential, industrial, and environmental interests. Resistance by public agencies to losing control over water rights severely limits the creation of mechanisms to allocate water.43 The ownership of groundwater rights is a problem that was addressed at the Continuing Legal Education (CLE) Texas International Water Law conference.44 In 1999, the questions “Who owns the groundwater in Texas? Is it the landowner? Is it the state? Does anyone really own it?”45 describe what was, and remains today, a hot topic. Groundwater in the southwest part of North America has been withdrawn at high rates. The United Nations Educational, Scientific and Cultural Organization (UNESCO) studied 11 shared aquifers along the US-Mexico border.46 Other research shows that the lack of a coordinated program and a

40  B.G. Colby, K. Crandali and D. Bush, “Water Right Transactions: Markets Values and Price Dispersion,” 29 (6) Water Resources Research (1993): 1565–1572. 41  See C.W. Howe, “Increasing Efficiency in Water Markets: Examples from the Western United States,” in T.L. Anderson and P.J. Hill, eds., Water Marketing: The Next Generation (New York: Rowman and Littlefield, 1997), at 79–100. 42  V. Ostrom, “Western Water Institutions in a Contemporary Perspective,” in Proceedings: Western Inter-State Water Conference (Los Angeles: University of California, Water Resources Center, 1964). 43  K.W. Easter, M.W. Rosegrant and A. Dinar, “Formal and Informal Markets for Water: Institutions, Performance, and Constraints,” 14(1) World Bank Research Observer (1999): 99–116. 44  Jarvis, Glenn, “Legislative and Regulatory Update,” Continuing Legal Education (CLE), International/Texas Water Law, 9th Annual Conference, Presenter, (21 October 1999). 45  Id. 46  I SARM, supra note 2.

Introduction

9

management framework for transboundary groundwater47 are the main issues that need to be addressed. The lack of groundwater quality data48 is a barrier to designing water quality standards in the international legal framework. Data from both countries provide information to develop effective water quality standards. However, “the lack of consensus for approaches to investigations; a lack of agreement on data collection protocols; variability in laboratory methodologies, lack of data base management documentation and reporting systems; and a lack of agreement of data interpretation methods all can cause problems.”49 Establishing a mechanism to collaborate with all levels of government and the private sector in conducting water information activities is the key element to ensuring the sustainability of transboundary water resources. Hydrologic and geologic data are essential tools to manage water resources.50 Information is required on the “river characteristics, interaction between groundwater and surface water, the amount of ground water in storage, the direction, and rate of movement, and the quality of the data.”51 These data are required to make policy decisions. For example, scientific data may reveal that the water in a particular area is either salty or too deep. Therefore, the extraction of water from that site will be too expensive. Even if the data have been collected, it may not be easy to have access to it.52 Scarcity of water resources is the main reason to hold such data confidential. “Different water user sectors such as industry and residential may be reluctant to share data across the border for fear of losing their current water shares to

47  Environmental Protection Agency (EPA), Good Neighbor Environmental Board (GNEB), Water Resources Management on the US-Mexico Border. Eighth Report to the President and the Congress of the United States (EPA, February 2005), https://nepis.epa.gov/Exe/ZyPDF. cgi/30006HEH.PDF?Dockey=30006HEH.PDF; see also EPA, GNEB, Environmental Quality and Border Security: A 10-Year Retrospective. Eighteenth Report to the President and the Congress of the United States (EPA, September 2017), https://nepis.epa.gov/Exe/ZyPDF. cgi/P100STQO.PDF?Dockey=P100STQO.PDF. Both reports discuss the same issues regarding water quality and management. 48  See EPA 2005, id., at 24; see also EPA 2017, id., at 47. 49  E PA 2005, id., at 25. Although this document was written in 2005, the current situation is similar. See EPA, GNEB, Climate Change and Resilient Communities Along the US-Mexico Border: The Role of the Federal Agencies. Seventeenth Report of the GNEB to the President and Congress of the United States (EPA, December 2016), https://nepis.epa.gov/Exe/ ZyPDF.cgi/P100QFGF.PDF?Dockey=P100QFGF.PDF, at Chapter 4, “Water-related Issues and Climate Change.” 50  See EPA 2005, id., at 26. 51  Id. 52  Id.

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water users in the other portion of the bi-national watershed due to different national or local water priorities.”53 This volume intends to set out the benefits of an international institutional framework where an agreement can regulate water allocation through a water bank. The analysis also attempts to understand and address the main issues among stakeholders during the implementation of a water allocation system. It is important to understand these problems and educate the public before establishing an institutional framework that can manage water allocation. This book’s structure is as follows: Chapter 2 examines groundwater resources and the classification of this natural resource. Chapter 3 analyses challenges and issues in the management of groundwater along the US-Mexico border and the current approaches to groundwater allocation along the border. Chapter 4 provides an overview of the existing international legal regime of transboundary groundwater and aquifers. Chapter 5 discusses the history of the current international legal framework for the US-Mexico border and analyses existing border agreements. Chapter 6 provides an analysis of the domestic law of surface water, groundwater, and conjunctive use of each border state in the United States and in Mexico. Chapter 7 addresses a detailed study of the United States-Mexico Transboundary Aquifer Assessment Act, 2006, and looks at the implementation of this Act in the Mesilla Aquifer Basin. Chapter 8 gives an overview of existing water transfer mechanisms, as well as how water banking and water markets have been implemented in other countries. Chapter 9 proposes a new legal and institutional framework to allocate groundwater at the US-Mexico border region in conjunctive use with surface water and includes a specific regulation for fossil aquifers. Finally, Chapter 10 provides conclusions and recommendations. 53  Id.

chapter 2

Groundwater along the US-Mexico Border 1

Introduction

Many different scholars and professionals have studied aquifers and transboundary groundwater. Still, this water source remains a mystery for the scientific community.1 The literature shows a variety of definitions and terms relating to aquifers and groundwater. The interpretation of these definitions and terms creates differing theories and models to manage groundwater.2 Aquifers are classified according to the material that forms the aquifer: fossil, confined, and unconfined.3 The 1997 UN Convention on the Law of the Non-navigational Uses of International Watercourses (UN Watercourses Convention) includes groundwater in the definition of “international watercourses,” namely, as water that is part of a connecting system with surface water, where there is a “physical relationship” as “a unitary whole and normally flowing into a common terminus.”4 The International Law Commission (ILC) did not include confined aquifers in the purposes of the Convention but defined “confined” as groundwater no hydrological relationship to surface water.5 The 2008 ILC Draft Articles on the Law of Transboundary Aquifers, however, took a different approach and do not distinguish between groundwater hydrologically connected with surface water and that which is not connected.6 The Draft Articles overlap with the UN Watercourses Convention regarding the subject matter and can create confusion between countries seeking to regulate the use of transboundary aquifers.7 1  See generally T.N. Narasimhan, “Groundwater: From Mystery to Management,” 4(3) Environmental Researc Letters (2009), doi:10.1088/1748–9326/4/3/035002. 2  J.E. Moore, A. Zaporožec and J.W. Mercer, Groundwater: A Primer (Alexandria, VA: American Geological Institute 1995), at 1. 3  Id. 4  United Nations Convention on the Law of the Non-navigational Uses of International Watercourses 21 May 1997, art. 2. 36 ILM 700 (1997), UN Doc. A/RES/51/229. 5  International Law Commission (ILC), “Report of the International Law Commission on the work of its forty-sixth session, 2 May–22 July 1994,” Official Records of the General Assembly, Forty-ninth session, Supplement 10, UN Doc. A/49/10, Commentary to Article 2, para. 4, p. 90. 6  See S.C. McCaffrey, “Current Developments The International Law Commission Adopts Draft Articles on Transboundary Aquifers,” 103(2) American Journal of International Law (2009): 272, 273–274. 7  Id.

© Koninklijke Brill NV, Leiden, 2020 | doi:10.1163/9789004385085_003

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Groundwater along the US-Mexico border has been withdrawn at high rates.8 This situation has brought the attention of the United Nations Edu­ cational, Scientific and Cultural Organization (UNESCO), Internationally Shared Aquifer Resources Management (ISARM) Initiative, and International Groundwater Resources Assessment Centre (IGRAC),9 which have studied and assessed 11 shared aquifers on the US-Mexico border.10 The aquifers studied in this chapter are the following – San Diego-Tijuana (8N) – Cuenca Baja del Rio Colorado (9N) – Sonoyta-Pápagos (10N) – Nogales (11N) – Santa Cruz (12N) – San Pedro (13N) – Conejos Medanos-Bolson de la Mesilla (14N) – Bolson del Hueco-Valle de Juarez (15N) – Edwards-Trinity-El Burro (16N) – Cuenca Baja del Rio Bravo/Grande (17N) – Los Mimbres-Las Palmas (18N) The first part of this chapter contains a selected review of the literature of international transboundary groundwater, including the different terms used to identify aquifers and transboundary groundwater. Second, it discusses types of aquifers and their implications in international law. Third, it presents the list of case studies of international aquifers studies by UNESCO. 2

Defining International Transboundary Groundwater and Aquifers

Numerous international transboundary groundwater studies examine the best way to manage this resource. Scholars and professionals from different 8  Environmental Protection Agency (EPA), Good Neighbor Environmental Board (GNEB), Water Resources Management on the US-Mexico Border. Eighth Report to the President and the Congress of the United States (EPA, February 2005), https://nepis.epa.gov/Exe/ZyPDF. cgi/30006HEH.PDF?Dockey=30006HEH.PDF. 9  See “Country and aquifer briefs,” International Groundwater Resources Assessment Centre (IGRAC) (2017), https://apps.geodan.nl/igrac/ggis-viewer/region_information. 10  Internationally Shared Aquifer Resources Management (ISARM) Initiative, International Hydrological Programme, United Nations Educational, Scientific and Cultural Organiza­ tion (UNESCO), Atlas of Transboundary Aquifers (Paris: UNESCO, 2009), https://isarm.org/ sites/default/files/resources/files/2%20Atlas%20of%20TBA.

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disciplines have developed complex and fascinating literature. Hydrologists, geologists, politicians, and lawyers provide different points of view in interpreting and defining aquifers and international transboundary groundwater.11 Freeze and Cherry define an aquifer as “a saturated permeable geologic unit that can transmit significant quantities of water under ordinary hydraulic gradients.”12 They also define aquitards, “the less-permeable beds in a stratigraphic sequence,”13 and aquicludes, “a saturated geologic unit that is incapable of transmitting significant quantities of water under ordinary hydraulic gradients.”14 A confined aquifer is an aquifer situated between two aquitards. This type of aquifer occurs at great depths. An unconfined area near the ground surface and the water table forms the upper boundary. A different kind of unconfined aquifer, a perched aquifer, is a saturated lense bounded by a perched water table.15 According to Moore, Zaporozec, and Mercer, an aquifer “is defined as a formation, or part of a formation, containing sufficient saturated permeable material to yield significant quantities of water to wells and springs.”16 These authors also define groundwater as “all subsurface water, as distinct from surface water; that part of the subsurface water in the saturated zone.”17 The real world is complex and has a large variety of hydrological cases that are difficult to classify under one or another type of aquifer. This situation brings uncertainty when trying to establish specific jurisdiction for groundwater resources. Groundwater has been included in the definition of “international watercourses” in the UN Watercourses Convention. Article 2(a) defines “watercourse” to mean “a system of surface waters and groundwaters constituting, by virtue of their physical relationship, a unitary whole and normally flowing into a common terminus.”18 According to McCaffrey, “international watercourse system” is a term which emphasizes the location of a watercourse system in different States and

11  S ee generally, “Focal Areas,” IGRAC, https://www.un-igrac.org/focal-areas. 12  R.A. Freeze and J.A. Cherry, Groundwater (Englewood, NJ: Prentice-Hall, 1979), at 47. The authors show how important it is to understand the hydrologic cycle to fully study groundwater. 13  Id. 14  Id. 15  Id., at 48. 16  Moore et al., supra note 2, at 7. 17  Id., at 12. 18  U N Watercourses Convention, supra note 4.

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keeps before the reader the fact that the waters of an international watercourse form a system. This will help to reinforce appreciation of the fact that all components of watercourses are interrelated; and thus, by implication, that it is important to take into account the impact of actions in one watercourse State upon the system-wide condition of the watercourse.19 Eckstein states that the term “system” has not been explicitly defined in the Convention. However, he assumes that “system” implies an interrelationship between groundwater and surface water, where water flows from one to the other resource consistently and in a defined pattern. According to Eckstein, this supposition is supported by the definition of watercourses in the UN Water­ courses Convention, which includes the phrase “constituting by virtue of their physical relationship a unitary whole.”20 He emphasizes that the relationship must also be of a “physical nature,” following on the ILC’s work “that a hydraulic relationship between two surface bodies of water, such as a lake and a connected river, but with no hydraulic connection to any groundwater, also would fulfill the ‘system’ criterion.”21 As noted above, the ILC excluded confined aquifers from the purposes of the UN Watercourses Convention. The ILC defined “confined” as groundwater that has no hydrological relationship to surface water.22 This definition resulted in discussion among different disciplines; hydrologists manifest their perspective of the term “confined” as “groundwater relates to groundwater contained and flowing through an aquifer that is under pressure between overlaying and underlain impermeable strata.”23 “The distinction between confined water, semiconfined water, unconfined water, and perched water is generally a very difficult distinction to make.”24 “Groundwater flow is confined when the boundaries or bounding surfaces of the medium (that is, the space made up by the water-filled pores) through which the water percolates are fixed in space for different states of flow.”25 Eckstein also states that “hydrogeologists know 19  S .C. McCaffrey, Seventh Report on the Law of the Non-navigational Uses of International Watercourses, Special Rapporteur, Yearbook of the International Law Commission 1991, vol. II (1) (UN Doc. A/CN.4/436 and Corr. 1–3), p. 64, comment 1, para. 1 (emphasis in the original). 20  G. Eckstein, “Hydrogeological Perspective of the Status of Ground Water Resources Under the UN Watercourse Convention,” 30 Columbia Journal of Environmental Law (2005): 525– 564, at 547–548. 21  Id., at footnote 97. 22  See ILC, supra note 5. 23  Eckstein, supra note 20, at 550. 24  See S.N. Davis and J.M. DeWiest, Hydrogeology (New York: John Wiley & Sons, 1966). 25  Id., at 159.

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that confined aquifers often are hydraulically connected to and recharged from surface waters in portions of the aquifer that are unconfined, or through lateral flow from higher elevations where the aquifer crops out on the land surface.”26 Accordingly, “hydraulically connected to and recharged from surface waters” implies connectivity with surface water and, therefore, these aquifers fall under the scope of the UN Watercourses Convention, which establishes explicitly the term “system” as a physical relationship among surface and groundwater. Only those fossil aquifers without a connection with surface water and groundwater are outside of the scope of the Convention. Fossil aquifers, also known as non-renewable waters,27 were formed by recharged water from other geological eras thousands of years ago, and have no hydrological connection between surface water and other aquifers.28 Nonetheless, the 1994 ILC Resolution on Confined Transboundary Groundwater 1994 states: “the principles contained in its draft articles on the law of the non-navigational uses of international watercourses may be applied to transboundary confined groundwater.” This means that the principles reflected in the 1997 UN Watercourses Convention apply to fossil aquifers. The UN Watercourses Convention entered into force in 2014 and is applicable to non-parties under the interpretation of agreements in international law and customary law.29 In this regard, the Convention has a significant bearing upon controversies between states, one or more of which is not a party to the Convention. In addition, the Convention may be of value in interpreting other general or specific agreements … that are binding on the parties to a controversy, whether or not the Convention is itself binding on those parties.30

26  Eckstein, supra note 20, at 205. 27  R. Krishma and S.M.A. Salman, “International Groundwater Law and the World Bank Policy for Projects on Transboundary Groundwater,” in S.M.A. Salman, ed., Groundwater Legal and Policy Perspectives: Proceeding of a World Bank Seminar, World Bank Technical Paper No. 456 (Washington, DC: World Bank, 1999), 163–190 at 164. 28  S. Sandoval-Solis, D.C. McKinney, R.L. Teasley and C. Patino-Gomez, “Groundwater Banking in the Rio Grande Basin,” 137(1) Journal of Water Resources Planning and Management (2011): 62–71. 29  F. Rocha Loures, A. Rieu-Clarke, J.W. Dellapenna and J. Lammers, “The Authority and Function of the UN Watercourses Convention,” in F. Rocha Loures and A. Rieu-Clarke, eds., The UN Watercourses Convention in Force: Strengthening International Law for Transboundary Water Management (London and New York: Routledge2013), at 65. 30  S.C. McCaffrey, “International Water Law for the 21st Century: The Contribution of the UN Convention,” 118(1) Journal of Contemporary Water Research and Education (2001): 11–19, at 17.

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Scholars and professionals from different disciplines are concerned about the implementation of the 1997 UN Watercourses Convention, as the instrument able to bind countries to manage surface and groundwater. International organizations such as the World Wildlife Fund (WWF) are working on the application of the UN Watercourses Convention to the management of transboundary groundwater in conjunctive use with surface water.31 3

Types of Aquifers and Their Implications for International Law

The term aquifer “means different things to different people, and perhaps different things to the same person at different times.”32 It is used to refer to complete geologic formations, to individual geologic layers, and even to groups of geologic formations. Aquifers are classified by the type of material forming the aquifer. Moore et al. identify the most common types of aquifers around the world as follows: (1) Geologically recent unconsolidated sand and gravel aquifers are the sources of most of the water pumped in many parts of the world, including North America, the Netherlands, France, Spain, and China. Sand and gravel aquifers are common near large to moderately-sized streams; these aquifers were formed by rivers or the meltwater from glaciers. (2) Older sedimentary rocks [which] are usually consolidated by mineralization and the pressure of overlying formations. The consolidation and cementation of sand forms sandstone aquifers. Their porosity ranges from five to 30 percent. Their permeability is mostly a function of the amount of cement (clay, calcite, and quartz). Sandstone aquifers are an important source of groundwater in Libya, Egypt (Nubian Sandstone), the United Kingdom (Permo-Triassic sandstones), north-central United States (St. Peter-Mount Simon Sandstone), and west-central United States (Dakota Sandstone). (3) Limestone aquifers, formed by the consolidation of ocean-bottom calcareous deposits, are the source of some of the world’s largest well and spring yields. Openings that existed when the rocks were formed are frequently enlarged by solution, providing highly permeable flow paths for

31  S ee “UN Watercourses Convention,” WWF Global. http://wwf.panda.org/our_work/ governance/policy/conventions/water_conventions/un_watercourses_convention/. 32  See Freeze and Cherry, supra note 12, at 47.

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groundwater. Chalk (a type of limestone) is an important water source in France and the United Kingdom. (4) Basalt and other volcanic rocks also make up some of Earth’s most productive aquifers. Basalt aquifers contain water-bearing spaces in the form of shrinkage cracks, joints, and lava caves. Lava tubes are formed when tunneling lava ceases to flow and drain out, leaving a long, cavernous formation. The well yields from volcanic aquifers range from very poor in some regions to some of the most productive aquifers in the world. Recent lavas form the major aquifers in the Hawaiian Islands and the Columbia River Plateau in the northwestern United States. (5) Fractured igneous and metamorphic rock aquifers are the principal sources of groundwater for people living in mountainous areas. Where fractures are numerous and interconnected, rocks can supply water to wells and can be classified as aquifers. Wells are commonly 15 to 30 meters (50 to 100 feet) deep. Granite and metamorphic rocks have not been extensively developed as aquifers. Groundwater movement in these rocks is irregular, making exploration for a water supply difficult.33 Aquifers can also be distinguished as confined or unconfined. Confined aquifers are also known as artesian aquifers. This type of aquifer is “contained between two impermeable layers – the base, or ‘floor,’ and the ‘ceiling’ strata – that subject the stored water to pressure exceeding atmospheric pressure.”34 A confined aquifer is overlain by a layer (confining bed) of rocks of lower permeability than the aquifer.35 The low permeability of the confining bed restricts groundwater movement either into or out of the aquifer. In some cases, a spring will result when a fault allows the passage of water from a confined aquifer to the surface.36 An unconfined aquifer also called a water-table aquifer, “is bounded by an impermeable base layer of rock or sediments, and overlain by layers of permeable materials extending from the land surface to the impermeable base of the aquifer.”37 The recharge to unconfined aquifers is basically by downward seepage through the unsaturated zone. “The water table in an unconfined

33  Moore et al., supra note 2, at 11. 34  G. Eckstein and Y. Eckstein, “A Hydrogeological Approach to Transboundary Ground Water Resources and International Law,” 19(2) American University International Law Review (2003): 201–258, at 212. 35  Moore et al., supra note 2, at 10. 36  Id. 37  Eckstein and Eckstein, supra note 34, at 211.

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aquifer rises or declines in response to [the] infiltration of rainfall, pumpage, and changes in stream stage.”38 These physical characteristics bring about different political, geographical situations, which have been classified into different international groundwater resources law models. Barberis sets out legal guidelines to identify the transboundary implications of aquifers among countries. Barberis identifies four models: (1) Confined aquifer (fossil aquifer) without connection to other groundwater or surface water, intersected by an international boundary. (2) Aquifer connected with an international river, but the aquifer is totally in the territory of one state. (3) Two aquifers connected, one is in state A and the other in the neighboring state B. (4) The aquifer recharge source is in state B, but the aquifer is located in state A.39 The only type of aquifer excluded from the UN Watercourses Convention is the first model, which does not have any connection to other waters. Chapter 4 provides a detailed explanation of the aquifers covered by the UN Watercourses Convention. All of these aquifer models are present along the US-Mexico border. An analysis of the physical characteristics of each aquifer identified as a case study by the International Shared Aquifer Resources Management (ISARM) of UNESCO is presented below. 4

Case Studies of Groundwater Use along the US-Mexico Border

As noted above, there is a high withdrawal rate from groundwater sources along the US-Mexico border.40 It has been estimated that some 18 to 20 shared aquifers exist along the US-Mexico border. Following the research of ISARM and IGRAC,41 the environmental and governance issues and challenges facing 11 shared aquifers on the US-Mexico border are identified in the case studies discussed below (Figure 2.1).42 The main problems in all of these aquifers are contamination and the high level of water decline. 38  Moore et al., supra note 2, at 10. 39  See J.A. Barberis, International Groundwater Resources Law, FAO Legislative Study No. 40 (Rome: Food and Agricultural Organization of the United Nations, 1986). 40  EPA 2005, supra note 8. 41  See IGRAC, supra note 9. 42  I SARM, supra note 10.

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figure 2.1 Map groundwater aquifers in the US-Mexico border Source: IGRAC (International Groundwater Resources Assessment Centre), UNESCO-IHP (UNESCO International Hydrological Programme), Transboundary Aquifers of the World [map]. Edition 2015. Scale 1: 50 000 000 (Delft, Netherlands: IGRAC, 2015). https://www.un-igrac.org/es/resource/transboundary-aquifers -world-map-2015

1. San Diego-Tijuana (8N) 2. Cuenca Baja del Rio Colorado (9N) 3. Sonoyta-Pápagos (10N) 4. Nogales (11N) 5. Santa Cruz (12N) 6. San Pedro (13N) 7. Conejos Medanos-Bolson de la Mesilla (14N) 8. Bolson del Hueco-Valle de Juarez (15N) 9. Edwards-Trinity-El Burro (16N) 10. Cuenca Baja del Rio Bravo/Grande (17N) 11. Los Mimbres-Las Palmas (18N) 4.1 San Diego-Tijuana The Tijuana Groundwater Basin underlies a portion of the Tijuana River Valley. The Basin’s southern boundary is the international border between the United States and Mexico. The eastern and northern boundaries are in contact with semi-permeable Pleistocene and Pliocene marine deposits. The western

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boundary is the Pacific Ocean. The intermittent Tijuana River and several ponds are hydrologic surface features in the Basin.43 This is a small extent aquifer. The elevation of this aquifer ranges between 0 and 200 meters above the mean sea level. The US area of the aquifer is a geological formation while the Mexican side is a hydrological basin. The aquifer is subject to high water demand in both countries, with especially high exploitation in Mexico. The climate in the area is semiarid. The main problems are contamination and seawater intrusion.44 Recharge to the Basin is mainly from the Tijuana River and controlled releases from the Barrett and Morena Reservoirs in San Diego County in the United States and Rodriguez Reservoir in Mexico. Some applied irrigation waters recharge the Basin by deep percolation, and discharges from septic tanks also contribute to recharging the aquifer. Irrigation water accounts for more than one-third of the recharge in the Basin.45 Groundwater storage capacity is about 50,000 to 80,000 af (acre-foot) (61.674.000 m³ to 98.678.400 m³). The level of groundwater dropped throughout the 1950s and 1970s. This decline “allowed seawater to infiltrate the alluvial aquifer and move eastward, degrading the groundwater quality and the productivity of agriculture in the western part of the valley.”46 4.2 Cuenca Baja del Rio Colorado The Cuenca Baja del Rio Colorado is in an arid climate. The aquifer extends 16,000 km² along both countries, with a 710,000 population depending on it. The rainfall level is very low in the region, an average 70 mm/year.47 It is an unconfined hydraulically connected system. The total groundwater volume is estimated at 100 km³. The distance to reach groundwater is 22 m, and the vertical thickness is 600 m. The transmissivity of this aquifer is estimated at 6,400 m²/d. The recharge to the aquifer system is rated at 240 Mm³/ annum from precipitation over an area of 860 km². The discharge from the

43  C  alifornia Department of Water Resources, Hydrologic Region South Coast, Tijuana Groundwater Basin, California’s Groundwater Bulletin 118 (2006), http://www.water .ca.gov/pubs/groundwater/bulletin_118/basindescriptions/9-19.pdf. 44  I SARM, supra note 10. 45  Tijuana Groundwater Basin, supra note 43. 46  Id. 47  Transboundary Water Assessment Programe (TWAP), “9N Cuenca Baja del Rio Colorado,” Transboundary Aquifer Information Sheet (October 2015), https://services.geodan.nl/ public/document/AGRC0001XXXX/api/data/AGRC0001XXXX/mim/9N_20151028.pdf _ueu6flfyf, at 1. 



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system is through submarine outflow.48 It has been estimated that 64% of the aquifer is not appropriate for human consumption. The aquifer has spread contamination (salinization) due to agricultural practices. The total abstraction of groundwater has been estimated at 260 Mm³/annum.49 The aquifer is studied in both countries, and the International Boundary and Water Commission (IBWC) is involved in negotiations concerning this aquifer.50 The direct relation between surface water (Colorado River) and groundwater is reflected in Minute 242, which addresses the “permanent and definitive solution to the international problem of the salinity of the Colorado River.”51 Specifically, Minute 242.6 established that “[w]ith the objective of avoiding future problems, the United States and Mexico shall consult with each other prior to undertaking any new development of either the surface or the groundwater resources, or undertaking substantial modifications of present developments, in its own territory in the border area that might adversely affect the other country.”52 This cooperation is also reflected in Minute 317, “Conceptual Framework for US-Mexico Discussions on Colorado River Cooperative Actions,”53 dated 17 June 2010, which stipulates that the Commission shall in particular explore opportunities for binational cooperative projects that: minimize the impacts of potential Colorado River shortage conditions; generate additional volumes of water using new water sources by investing in infrastructure such as desalinization facilities; conserve water through investments in a variety of current and potential uses, including agriculture, among others; and envision the possibility of permitting Mexico to use United States infrastructure to store water.54 Such measures apply to Minute 318, which calls for “[a]djustment of delivery schedules for water allotted to Mexico for the year 2010 through 2013 as a result of infrastructure damage in irrigation district 014, Rio Colorado, caused 48  Id., at 3. 49  Id. 50  International Boundary Water Commission (IBWC), Minute 317: Conceptual Framework for US–Mexico Discussions on Colorado River Cooperative Actions, 17 June 2010, https:// www.ibwc.gov/Files/Minutes/Minute_317.pdf. 51  I BWC, Minute 242: Permanent and Definitive Solution to the International Problem of the Salinity of the Colorado River, 30 August 1973, https://www.ibwc.gov/Files/Minutes/ Min242.pdf. 52  Id. 53  I BWC Minute 317, supra note 50. 54  Id. 



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by the April 2010 Earthquake in the Mexicali Valley, Baja California,”55 and to Minute 319, which calls for “international cooperative measures in the Colorado River Basin through 2017 and extension of Minute 318 cooperative measures to address the continued effects of the April 2010 Earthquake in the Mexicali Valley, Baja California.”56 Minute 319 also provides for measures to manage the Colorado River system through the creation of an “Intentionally Created Mexican Allocation,” which would engage in “coopertive measures to reduce the likelihood of unprecedented drought-related reductions in water deliveries to water users in both countries.”57 Minute 323 extends Minute 318, addressing cooperative measures and the adoption of a binational water scarcity contingency plan in the Colorado River Basin.58 Although these Minutes do not directly call for conjunctive management of surface water and groundwater, they establish the idea of a comprehensive management approach for the Colorado River system. This extends the expectation of a new Minute that would manage conjunctive use along the Colorado system in both the United States and Mexico. 4.3 Sonoyta-Pápagos The Sonoyta-Pápagos aquifer extends 16,000 km² and provides water to 47,000 people. An unconfined alluvial aquifer, the whole aquifer is a hydrological formation with an elevation of 200 to 400 meters above mean sea level.59 The average distance to groundwater level is 58 m and total vertical thickness of the aquifer system is 600 m with a maximum depth of 1,600 m.60 The estimated groundwater volume is 36 km³, and the average annual aquifer recharge is estimated at 41 Mm³/annum, where the recharge area is 3,022 km².61 55  I BWC, Minute 318: Adjustment of Delivery Schedules for Water Allotted to Mexico for the years 2010 through 2013 as a result of Infrastructure Damage in Irrigation District 014, Rio Colorado, caused by the April 2010 Earthquake in the Mexicali Valley, Baja California, 17 December 2010, https://www.ibwc.gov/Files/Minutes/Min_318.pdf. 56  I BWC, Minute 319: Interim International Cooperative Measures in the Colorado River Basin Through 2017 and Extension of Minute 318 Cooperative Measures to Address the Continued Effects of the April 2010 Earthquake in the Mexicali Valley, Baja California, 20 November 2012, https://www.ibwc.gov/Files/Minutes/Minute_319.pdf. 57  Id. 58  I BWC, Minute 323: Extension of Cooperative Measures and Adoption of a Binational Water Scarcity Contingency Plan in the Colorado River Basin, 21 September 2017, https:// www.ibwc.gov/Files/Minutes/Min323.pdf. 59  I SARM, supra note 10, at 105. 60  T WAP, “10N Sonoyta-Papagos,” Transboundary Aquifer Information Sheet (October 2015), https://services.geodan.nl/public/document/AGRC0001XXXX/api/data/AGRC0001 XXXX/mim/10N_20151028.pdf_mxkunp96g, at 3. 61  Id. 





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The climate in this region is arid to semiarid, which, along with abundant brackish groundwater, provides favorable conditions for irrigated agriculture.62 Annual precipitation averages 5 to 8 inches per year on the desert floor. Runoff, which occurs as intermittent streamflow and sheetflow, is too short-lived and too laden with suspended sediment to be a reliable source for irrigation or public water supply. It has been estimated that approximately 33% of the aquifer is unsuitable for human consumption due to high salinity levels.63 The water in the aquifer is moderate to poor in chemical quality for irrigation and public-supply use. Groundwater is mainly a sodium bicarbonate type with dissolved-solids concentrations that range from about 250 to 5,000 milligrams per liter and an average about 530 milligrams per liter. The poorest quality water is associated with the basin-center lakebed-clay deposits. In most of the basin, the water contains fluoride concentrations that exceed the maximum contaminant levels acceptable for drinking water. High concentrations of sodium and bicarbonate in the groundwater of the study area present potential hazards to most crops, and the use of this type of water requires careful farm management practices.64 4.4 Nogales The Nogales Transboundary Aquifer System extends 1,700 km² across the northern portion of the State of Sonora, Mexico, and the southern portion of the State of Arizona in the United States with an elevation of between 1,000 and 1,500 meters above mean sea level. It encompasses a population of approximately 74,000 that is concentrated in the twin cities of Nogales. The main economic activities are agriculture and industry. The climate is semiarid, with rainfall averaging 460 mm/year and evaporation higher than 2,000 mm/year. The aquifer consists of alluvial materials and fissured rocks, is of small size, and has thin medium permeability. The distance to the groundwater level is estimated at 34 m. Recharge is poor due to the aridity of the region. The average annual groundwater recharge is 5.2 Mm³/annum, where the recharge area extends 120 km². Transmissivity is estimated at 240 m²/day, and the total groundwater volume as 0.54 km³.65 62  I SARM, supra note 10, at 105. 63  T WAP 10N Sonoyta-Papagos, supra note 60, at 3. 64  K.J. Hollet, Geohydrology and Water Resources of the Papago Farms – Great Plain Area, Papago Indian Reservation, Arizona, and the Upper Rio Sonoyta Area, Sonora, Mexico, USGS Water Supply Paper no. 2258 (1983), http://pubs.er.usgs.gov/publication/wsp2258. There is not very much up-to-date information about this aquifer. 65  T WAP, “11N Nogales,” Transboundary Aquifer Information Sheet (October 2015), https:// services.geodan.nl/public/document/AGRC0001XXXX/api/data/AGRC0001XXXX/ mim/11N_20151028.pdf_j87hyw9ly, at 1 and 3.

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Groundwater flows from Mexico to the United States through the narrow band of the Nogales Wash with an estimated flow rate of 2 Mm3/year. The natural water quality is acceptable, although in Mexico, it is contaminated by industrial pollutants. The system is important for urban and industrial development. The transboundary management issues are more related to quality than quantity; the aquifer pollution generated in Mexico may spread to the United States and affect the quality of the water collected by municipal wells in Nogales, Arizona. However, only one percent of water from the aquifer is unsuitable for human consumption. Further, extraction increases the flow of the Mexican portion and can intercept the flow rate passing underground across the international border from Mexico to the United States.66 The lack of an adequate waste system has contributed to contamination and degradation of the groundwater. Placido Dos Santos, border environmental manager for the Arizona Department of Environmental Quality, commented that when it rains, garbage and debris-laden water courses into the sewers, clogging pipes and overloading the city’s binational treatment plant that lies nine miles downstream on the US side of the border. If the two sides fail to work together, their shared underground aquifer could be sucked dry or contaminated, and their shared treatment plant could be damaged or overwhelmed. The futures of both communities are totally dependent on one another.67 4.5 Santa Cruz The northern State of Sonora, Mexico, and the southern State of Arizona, the United States, share the Santa Cruz Transboundary Aquifer System.68 It extends 9,300 km², and the whole aquifer is unconfined. The composition includes alluvial materials, conglomerates, and fissured volcanic rocks. The climate is semi-arid in the region, with rainfall of 450 mm annually and potential evaporation of 2,000 mm/year. The distance to the groundwater table is 20 m, and the vertical thickness of the aquifer is 300 m. The estimated mean transmissivity is 1,900 m²/d. The elevation is 1,000 to 2,000 meters above mean sea level.69 66  I SARM, supra note 10, at 106. 67  M. Davidson, “Bridging Troubled Waters in Ambos Nogales,” The Alicia Patterson Founda­ tion (2011), http://aliciapatterson.org/stories/bridging-troubled-waters-ambos-nogales. 68  I SARM, supra note 10, at 107. 69  T WAP, “12N Santa Cruz,” Transboundary Aquifer Information Sheet, https://services .geodan.nl/public/document/AGRC0001XXXX/api/data/AGRC0001XXXX/mim/ 12N_20151028.pdf_2kk0x3hx0, at 1 and 3.

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Recharging of the aquifer is not substantial, and partly originates in Mexico to the rightful “upstream” system. “The average annual aquifer recharge is estimated at 38 Mm³/annum coming from a recharge area of 310 km². The total groundwater volume is 7.8 km³.”70 The main direction of groundwater flow is from south to north, that is, from Mexico to the United States, with a flow rate estimated at 1.7 Mm3/year. The natural quality of the groundwater is good and no major pollution sources have been identified. The system is important for agricultural development in the United States and for urban development in Mexico.71 The aquifer supports a population estimated at 970,000, which is concentrated in the United States, with Mexico mostly using the aquifer for agricultural. The population density is low. Groundwater is exported from Santa Cruz Valley in Mexico to supply the population of Nogales, Arizona, through a well field. An increase of groundwater extraction on the Mexican side can reduce or even nullify the flow rate passing from Mexico to the United States.72 The Santa Cruz aquifer is characterized as a priority under the United States-Mexico Transboundary Aquifer Assessment Act (Public Law 109-448).73 This Act represents the main cooperative effort on the assessment of transboundary aquifers (see Chapter 7 below for detailed analysis of this Act). The Act establishes the US-Mexico Transboundary Aquifer Assessment Program to compile and synthesis scientific and other materials from university, governmental, and non-governmental agencies in both the United States and Mexico and to establish guidelines to implement the Act for each aquifer.74 4.6 San Pedro The San Pedro Transboundary Aquifer System is located in northern Sonora, Mexico, and southern Arizona in the United States. It is an unconfined aquifer, which extends 10,000 km² with a total groundwater volume of 31 km³. The region is arid and contains alluvial materials in valleys and conglomerates in adjacent hills. The rainfall is estimated at 420 mm/year, and evaporation is higher than 2,000 mm/year. The distance to groundwater level is 32 m, and the total vertical thickness of the aquifer system is 350 m to a maximum of 1,000 m.75 The recharge is from precipitation, and it is not substantial due to the aridity 70  71  72  73  74  75 

I d., at 3. Id.; see also ISARM, supra note 10, at 107. T WAP 10N Sonoyta-Papagos, supra note 60. United States-Mexico Transboundary Aquifer Assessment Act, 42 USC. § 1962 (2006). Id., at §. 4(c)(2). I SARM, supra note 10, at 108. See also TWAP, “13N San Pedro,” Transboundary Aquifer Information Sheet, https://services.geodan.nl/public/document/AGRC0001XXXX/api/ data/AGRC0001XXXX/mim/13N_20151028.pdf_vwvi32bf4, at 1 and 3.

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of the region. The portion “upstream” refers to Mexico. Extraction of groundwater is widely distributed in both countries. Groundwater is abstracted at an annual rate of 31 Mm³/annum. The main direction of groundwater flow is from Mexico to the United States, with the flow rate passing through the international border at an estimated 2 Mm3/year. The average aquifer transmissivity is estimated as 515 m²/d.76 The natural groundwater quality is acceptable, although there has been a contamination risk resulting from the discharge of wastewater from a mining company based in the system header. It is estimated that 5% of groundwater is not suitable for human consumption because of high natural salinity concentrations. The aquifer also supports ecosystems, with an estimated 2% of the aquifer considered essential for protecting them. The major use of the aquifer is for agricultural development in both countries.77 The San Pedro Aquifer was also designated as a priority aquifer under the United States-Mexico Transboundary Aquifer Assessment Act (Public Law No. 109-448).78 4.7 Los Mimbres-Las Palmas The Los Mimbres-Las Palmas aquifer is shared between New Mexico, United States, and Chihuahua, Mexico. The aquifer covers 5,100 km², and the area is arid with an annual rainfall average of 230 mm/year. The whole aquifer is considered unconfined,79 and the distance to reach groundwater is estimated at 60 m, with the average total vertical thickness of the aquifer system at 400 m.80 The recharge of this aquifer is from precipitation, and the average is very low (4 Mm³/annum) over an area of 1,000 km² where the total volume is 21 km³. The discharge of the aquifer is through groundwater flow into another aquifer. The aquifer transmissivity is considered as 190 m²/d.81 The whole aquifer is in good condition for human consumption, and no pollution is identified. Groundwater abstraction has been estimated at 1.2 Mm³/ annum. Thus, there is no groundwater depletion.82

76  77  78  79 

I d. Id. United States-Mexico Transboundary Aquifer Assessment Act, supra note 73. T WAP, “18N Los Mimbres-Las Palmas,” Transboundary Aquifer Information Sheet, https:// services.geodan.nl/public/document/AGRC0001XXXX/api/data/AGRC0001XXXX/ mim/18N_20151028.pdf_qy5wjn70j, at 1. 80  Id., at 3. 81  Id. 82  Id.

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4.8 El Paso del Norte Region Aquifers El Paso del Norte Region aquifer is composed of Tertiary and Quaternary basin-fill deposits of silt, sand, gravel, and clay in two basins, or bolsons: the Hueco Bolson and the Mesilla Bolson. The Hueco and Mesilla Bolson transboundary aquifers are shared between New Mexico, Texas, and Mexico (Figure 2.2). The aquifers extend northward into New Mexico and westward into Mexico. The Hueco Bolson, east of the Franklin Mountains, is the principal aquifer in the El Paso area; to the west is the Mesilla Bolson. Eighty-seven percent of the water pumped from the aquifers is used for municipal water supply, primarily for the City of El Paso.83 The upper portion of the Hueco Bolson contains fresh to slightly saline water. The Hueco Bolson, approximately 9,000 ft in total thickness, consists of silt, sand, and gravel in the upper part, and clay and silt in the lower part.84

figure 2.2 El Paso del Norte Region Aquifers Source: Schmandt, Jurgen. Bi-national water issues in the Rio Grande/Río Bravo basin. Water Policy, Volume 4, Issue 2, 2002, Pages 137–155

83  “Hueco-Mesilla Bolsons Aquifer,” Texas Water Development Board, http://www.twdb .texas.gov/groundwater/aquifer/majors/hueco-mesilla-bolsons.asp. 84  Id.

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Water level declines have contributed to higher salinity in both aquifers. The Hueco Bolson is the principal aquifer for the El Paso, Texas area and for Ciudad Juarez, Mexico – nearly 90 percent of the water pumped from the Mesilla and the Hueco Bolsons in Texas is used for public water supply. Several hundred feet of water level decline has occurred, primarily due to municipal pumping in the Hueco Bolson, from which water for Ciudad Juarez is supplied.85 Only the upper several hundred feet of the Bolson contain fresh to slightly saline water. The majority of the Hueco water in Texas occurs in the El Paso metropolitan area; very little occurs in Hudspeth County. The Mesilla Bolson consists of approximately 2,000 ft of clay, silt, sand, and gravel. Three water-bearing zones in the Mesilla (shallow, intermediate, and deep) have been identified based on water levels and quality. Water in the Mesilla Bolson ranges from fresh to saline, with salinity typically increasing to the south and in the shallower parts of the aquifer.86 The shallow waterbearing zone includes the overlying Rio Grande Alluvium. The chemical quality of the groundwater in the Hueco Bolson differs according to its location and depth. Dissolved-solids concentrations in the upper, fresher part of the aquifer range from less than 500 mg/L to more than 1,500 mg/L and an average of about 640 mg/L. The quality of Hueco Bolson water in Mexico is slightly weaker. The chemical quality of groundwater in the Mesilla Bolson ranges from fresh to saline, with salinity generally increasing to the south along the valley. The water is commonly freshest in the aquifer’s deep zone and contains progressively higher concentrations of dissolved solids in the shallower zones. The increasing deterioration in the quality of these aquifers is the result of large-scale groundwater withdrawals, which are depleting the aquifers of the freshest water. Historical large-scale groundwater withdrawals, especially from municipal wells fields in the downtown areas of El Paso and Ciudad Juarez, have caused major water-level declines. These declines, in turn, have significantly changed the direction of flow, rate of flow, and chemical quality of groundwater in the aquifers. Declining water levels have also resulted in a minor amount of landsurface subsidence.87 The Far West Texas Regional Water Planning Group recommends the conjunctive use of water from the Rio Grande with groundwater from the Hueco-Mesilla Bolsons Aquifer as a water management strategy. In addition, El Paso has the world’s largest inland desalination plant, the Kay Bailey Hutchison 85  I d. 86  Id. 87  Id.

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Desalination Plant, with a capacity of 27.5 million gallons of water every day.88 This desalination plant has provided 4 percent of the city’s total water supply, and the level of desalination is expected to increase over the next decade.89 There are additional aquifers in this region (Figure 2.2). The Jornada del Muerto Bolson and Tularosa aquifer are totally located in New Mexico, and the Diablo Plateau Aquifer is located between New Mexico and Texas. Connectivity among these four aquifers and the Rio Grande would create an entire hydrological system between the different aquifers in the region. The uncertainty of connectivity among all the aquifers makes it challenging to develop an integrated legal and institutional framework for the management of these aquifers. 4.9 Conejos Medanos-Bolson de la Mesilla The Conejos Medanos-Bolson de la Mesilla aquifer is vast, with a total area of 13,000 km². It is shared by New Mexico and Texas in the United States and Mexico. It is directly connected with the Rio Grande and is located in a very arid region. The elevation ranges between 1,000 to 2,000 meters above sea level. Most parts of the aquifer are unconfined, although some parts are confined. The average rainfall is 230 mm/year, and the potential evaporation is greater than 2,000 mm/year.90 The Mesilla aquifer is part of the closed basins of the western portion of Texas and the northern portion of Mexico. The material consists of pocket alluvial deposits whose thickness ranges from several hundred meters to greater than 1,000 meters in both countries, and its surface area is about 10,000 km2. This is a type of “free” material with medium to low permeability and high storage capacity. The water is sweet (