Transboundary Aquifers between Baja California, Sonora and Chihuahua, Mexico, and California, Arizona and New Mexico, United States: Identification and Categorization

In 2016, research suggested there might be up to 36 transboundary aquifers located along the border between Mexico and the U.S. The main contribution of this study was to put together the available segments already existent in the literature without considering the validity of the criteria used to define the boundaries of those segments. In 2018, updated research reported 33 hydrogeological units (HGUs) crossing the boundaries between Mexico and Texas. This later analysis included the homogenization of geological nomenclatures, standardization of geological and hydrogeological criteria, using a specific methodology to correlate, identify, and delineate each HGU. The purpose of this paper is to use this latter methodology and expand the same analysis to include the transboundary aquifers between Baja California/California, Sonora/Arizona, and Chihuahua/New Mexico. Results of this study indicate that a total of 39 HGUs have been identified in this region which accounts for an approximate shareable land of 135,000 km2 where both countries share half of the area. From the total shareable area, around 40% reports good to moderate aquifer potential and water quality, of which 65% is in the U.S. and 35% on the Mexico side. Border-wide, the total number of HGUs in the border region between Mexico and the United States is 72, covering an approximate area of 315,000 km2 (180,000 km2 on the U.S. side and 135,000 km2 on the Mexico side). The total area that reports good to moderate aquifer potential as well as good to regular water quality ranges between 50 and 55% (of which approximately 60% is in the U.S. and the rest in Mexico).

Modeling as a Tool for Transboundary Aquifer Assessment Prioritization

Transboundary aquifers are critical global water supplies facing unprecedented threats of depletion; existing efforts to assess these resources do not adequately account for the complexities of transboundary human and physical system interactions to the determinant of the impact of assessment outcomes. This study developed a system dynamics model with natural, human, and technical system components for a section of the transboundary Mesilla Basin/Conejos-Médanos aquifer to evaluate the following dynamic hypothesis: how and when information from a transboundary aquifer assessment is reported and perceived, in scenarios where two countries follow identical and different timeframes, dynamically impacts the behaviors of the shared aquifer. Simulation experiments were conducted to quantitatively assess the dynamics of transboundary aquifer assessment information reporting and perception delays. These critical feedbacks have not previously been incorporated practically in simulation and analysis. Simulation results showed that the timing and content of reporting can change the dynamic behavior of natural, human, and technical components of transboundary aquifer systems. This study demonstrates the potential for modeling to assist with prioritization efforts during the data collection and exchange phases to ensure that transboundary aquifer assessments achieve their intended outcomes.

Investigating Management of Transboundary Waters through Cooperation: A Serious Games Case Study of the Hueco Bolson Aquifer in Chihuahua, Mexico and Texas, United States

Management of transboundary aquifers is a vexing water resources challenge, especially when the aquifers are overexploited. The Hueco Bolson aquifer, which is bisected by the United States–Mexico border and where pumping far exceeds recharge, is an apt example. We conducted a binational, multisector, serious games workshop to explore collaborative solutions for extending the life of the shared aquifer. The value of the serious game workshop was building knowledge, interest, understanding, and constituency among critical stakeholders from both sides of the border. Participants also learned about negotiations and group decision-making while building mutual respect and trust. We did not achieve consensus, but a number of major outcomes emerged, including: (1) participants agreed that action is called for and that completely depleting the freshwater in the shared aquifer could be catastrophic to the region; (2) addressing depletion and prolonging the life of the aquifer will require binational action, because actions on only one side of the border is not enough; and (3) informal binational cooperation will be required to be successful. Agreeing that binational action is called for, the serious games intervention was an important next step toward improving management of this crucial binational resource.

Pilot Study of Methods to Support Stakeholder Prioritization of Transboundary Aquifers for Investigation along the US-Mexico Border

<p>Four US and six Mexican border states share significant interconnections in terms of trade, jobs, energy production, manufacturing, and natural resources such as water. The border states have a mutual interest in characterizing groundwater resources shared between the US and Mexico, a task made difficult by scarcity of information. To address this challenge, a number of US and Mexican federal agencies and universities via the Transboundary Aquifer Assessment Program (TAAP) have come together to jointly study the shared groundwater resources of the border region, and to develop the information needed by cities, states, industries and local communities to support decision making and land management.</p><p>Investigations of four binational aquifers selected in the first phase of TAAP are in progress. Carrying out these investigations has created a cohesive binational multi-institutional team of social and physical scientists and established relationships with a broad network of stakeholders. Completed products relevant to the present work include: (1) analysis of the availability and integration potential of binational data sets, (2) aquifer assessments including a review of US-Mexico aquifer classifications (3) development of water-balance models, (4) analysis of aquifer vulnerability to contamination, and (5) a set of protocols and agreements that address the specific physical, legal, cultural, and institutional setting of the US-Mexico border.</p><p>Additional aquifers along the border (estimates of the total range from of 8 to 38) could be investigated, but there are questions as to how to define them, which to choose, and what types of studies are needed. To help answer these questions, we developed a pilot project to investigate and develop methods and tools to assist decision makers and land managers in prioritizing additional aquifers for investigation along the US-Mexico border. First is an approach for rapid assessment of additional aquifers using existing data, published literature, and simple analytical tools including conceptual hydrogeologic model development and precipitation-groundwater lag-correlation analysis. Second, a groundwater modeling platform was developed for use by stakeholders for both learning and planning. Third, in preparation for stakeholder ranking of aquifers for investigation, we conducted a review of multicriteria decision analysis (MCDA) as applied to coupled human-natural resource systems and a review of real-world examples of aquifer prioritization schemes used by governmental entities. Finally, an assessment of uncertainty with respect to knowledge about and trajectory of the coupled human-biophysical system was carried out to aid in stakeholder discussions of prioritization criteria and weighting schemes. These results and tools can be used to support prioritization of any set of aquifers. However, some are specifically designed to address transboundary aquifers and will be used to inform binational discussions regarding prioritization of future aquifer investigations along the US-Mexico border.</p>

The U.S.-Mexico Transboundary Aquifer Assessment Program as a Model for Transborder Groundwater Collaboration

The assessment of transboundary aquifers is essential for the development of groundwater management strategies and the sustainable use of groundwater resources. The Transboundary Aquifer Assessment Program (TAAP) is a joint effort by the United States and Mexico to evaluate shared aquifers. This study examines the TAAP Cooperative Framework as a guide for further transboundary groundwater collaboration. We compared lessons learned from six transboundary aquifers that currently have mechanisms for groundwater collaboration to identify common elements of collaboration. Though the TAAP Cooperative Framework governs an assessment-only program, the elements of collaboration included are consistent with the principles of other institutional agreements around the world. Importantly, all the analyzed agreements included a knowledge-improvement phase, which is the main objective of the TAAP Cooperative Framework. The present study finds evidence of successful outcomes within the TAAP Cooperative Framework consistent with available transboundary groundwater management agreements, demonstrating that this approach is suited to serve as a model for those wishing to engage in transborder aquifer assessments. Furthermore, the TAAP elements of collaboration can help to establish the meaningful and robust binational cooperation necessary for the development of U.S.-Mexico groundwater management agreements at the aquifer level.

Contribution of General Principles of International Law in Progressive Development of Transboundary Aquifers

Man’s ruthless exploitation of natural resources means that we are housed in a resource-deprived world. The tug of war for meager resources has led to many conflicts between States that we witness today. At the heart of the whole debate on resource crunch is the issue of shared natural resources between States. International law has formulated several legal instruments to govern the shared transboundary resources, laws on transboundary aquifers being one. The objective of this paper is to unlock the general principles of international law that regulate the transboundary aquifers. In this regard, the paper has been apportioned into three sections. The first section sets the tone by detailing the provisions of the 2008 Draft Articles on the Transboundary Aquifers dealing with general principles. The second segment of the paper lays down the cardinal principles regulating transboundary aquifers, which range from sustainable development to the principle of good faith. The final portion delves into the Israel-Palestine dispute and the India-Pakistan Indus Waters Treaty in the context of transboundary aquifers.