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Introduction

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Many of the 15 million inhabitants along the United States-Mexico border derive fresh water from transboundary aquifers straddling and extending far beyond the political boundary separating the two countries. The previous lack of a large-scale cooperative and structured data collection effort and groundwater management strategy for the region has left border communities with little information on current and future groundwater supplies. In 2006, the U.S. Federal Government enacted the United States � Mexico Transboundary Aquifer Assessment Act (Public Law 109�448) to address this issue.

The International Boundary and Water Commission (IBWC) played a key role in the development and administration of a joint program as part of the Transboundary Assessment Act by publishing a framework for cooperation to guide the multidimensional collaborative assessment and established a Transboundary Aquifer Assessment Program (TAAP). TAAP has identified and continues to assess priority transboundary aquifers and addresses the region’s water information needs by facilitating data exchange or developing new datasets where there are data gaps. The assessments inform border communities, participating agencies, and water authorities in the United States and Mexico of where the possible expansion or modification of existing programs or agreements are most beneficial.

Priority aquifers are identified by TAAP according to proximity to areas of high population density, the extent to which aquifers are used, and their susceptibility to contamination. Priority aquifers chosen for further assessment by TAAP include the Hueco Bolson and Mesilla Basin/Conejos- Médanos aquifers underlying parts of Texas, New Mexico, and Mexico, and the San Pedro and Santa Cruz aquifers underlying parts of Arizona and Mexico.

Individual study plans were developed for each aquifer to help ensure the TAAP produces the types of assessments that Federal, state and local water authorities in both countries need. Study plans were constructed by evaluating all available data and publications before identifying gaps in knowledge. These gaps represented opportunities to create new, or update existing, geographic information databases, numerical groundwater models, three-dimensional hydrogeologic frameworks, and binational socio-economic evaluations pertaining to future water use and water availability.

Key Issues Addressed

International borders can create political boundaries separating societies that share the same challenges. The United States–Mexico border region has experienced declining groundwater levels due to increased withdrawals of groundwater supply and deteriorating water quality due to hazardous industrial and agricultural waste. These issues have been exacerbated by a lack of binational collaboration in aquifer assessments and no formal mechanism for binational resource policy development.

Aquifers ignore political boundaries. Groundwater withdrawals in one country may derive from precipitation and recharge in the other. A contaminant introduced on one side of the border may migrate through the aquifer and affect the public water supply of the other. TAAP was established to provide a framework for cooperation to address water resource issues through non-biased binational research.

Project Goals

• Develop and implement strategies for non-biased binational research
• Identify and prioritize transboundary aquifers for assessment
• Improve the understanding of regional groundwater conditions by compiling available information
• Provide integrative, multidimensional assessments of priority aquifers

Project Highlights

Breaking Through Barriers: TAAP developed, documented, and published the cooperative framework between the United States and Mexico that made the program so successful in conquering language and funding barriers.

• A Milestone Publication: TAAP resulted in the first-ever binationally prepared and peer-reviewed aquifer assessment published between the United States and Mexico, in English and Spanish ().
• Current (2020) Management Strategies and Pitfalls: By documenting successful and missed coordination efforts between Federal, state and local authorities, TAAP highlighted the challenges in developing homogenous management principles, suggesting a need for binationally-coordinated localized strategies.
• Integrating Social Science: The program used a two-phase approach to examine the historical social elements critical to engagement on both sides of the border and the resulting scientific collaboration it produced.
• Multidimensional Approach: Using different geoscience techniques, TAAP produced models of groundwater flow and quality, a detailed characterization to the region’s geology, and provided assessments of groundwater pumping and climate change climate change
  Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
  
  Learn more about climate change impacts on future precipitation projections in the region.

Lessons Learned

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Building a mutual understanding in the initial planning phase is essential to cooperative transboundary scientific studies. Binational meetings with key agencies, stakeholders, and individuals provide adequate representation and an integration of skills between teams.

Transparency is crucial through the entire lifecycle of the project. Successful collaboration is driven by open communication. TAAP researchers found that a willingness to be forthcoming about errors made along the way was a pillar of the project’s success. 

The inclusion of a social science perspective early in research development is critical for proper planning and implementation of a transboundary study. Recognition of various physical, institutional, historical, and socio-political contexts surrounding the study creates an agreement on the necessary processes and accuracy of the assessment, and what parameters will define success.

Next Steps

• Maintain inclusion and communication through binational data exchange, stakeholder meetings, and bilingual peer review
• Share and combine geographic data to create seamless datasets for mapping across political boundaries
• Complete prioritized research on groundwater flow, water quality, and surface-water/groundwater interactions in priority aquifers
• Develop a transboundary groundwater-flow model for the Hueco-Bolson Aquifer near El Paso, Texas, and Ciudad Juarez, Chihuahua
• Expand water quality sampling to additional wells, and collect geophysical data on surface-water/groundwater interactions in the Mesilla Aquifer, immediately west of the Hueco-Bolson

Resources

Contacts

• Gilbert Anaya, International Boundary and Water Commission, United States Section: [email protected]

• Hueco Bolson Aquifer

  • Andrew Teeple, USGS Texas Water Science Center: [email protected]
  • John Tracy, Ph.D., Texas Water Resources Institute: [email protected]

• Mesilla Conejos-Medanos Aquifer

  • Anne-Marie Matherne, Ph.D., USGS New Mexico Water Science Center: [email protected]
  • Andrew Robertson, New Mexico Water Science Center: [email protected]
  • Sam Fernald, Ph.D., New Mexico Water Resources Research Institute: [email protected]

• San Pedro and Santa Cruz Aquifers

  • James Callegary, Ph.D., USGS Arizona Water Science Center: [email protected]
  • Sharon B. Megdal, Ph.D., University of Arizona Water Resources Research Center: [email protected]

Case Study Lead Author

• Nathan Pasley, Student Geographer, USGS OK-TX Water Science Center: [email protected]

Suggested Citation

Pasley, N., K., (2020). “Identifying and Assessing Priority Transboundary Aquifers Along the United States-Mexico Border.â€� CART. Retrieved from /project/priority-transboundary-aquifers-along-us-mexico-border.