Building shared vision: assessment of transboundary aquifers along the United States – Mexico border. Presented at International Conference on Water Scarcity, Global Changes, and Groundwater: Management Responses, University of California – Irvine, UNESCO, USGS, 1-5 December

Building Shared Vision Assessment of Transboundary Aquifers along the United States – Mexico Border Christopher Scott Udall Center for Studies in Public Policy, and Dept. Geography & Regional Development, University of Arizona

Co-Authors Sharon Megdal Water Resources Research Center, University of Arizona Lucas Antonio Oroz Comisión Nacional del Agua Martín Mexía Comisión Estatal del Agua de Sonora Hildebrando Ramos Comisión Estatal del Agua de Sonora Special Thanks James Callegary US Geological Survey Prescott Vandervoet Udall Center for Studies in Public Policy, University of Arizona

4 U.S.-Mexico Transboundary Aquifer Assessment Act U.S. Public Law (Dec. 22, 2006) legislated objectives Integrated scientific approach to assess priority transboundary aquifers Produce scientific products…that: – are capable of being broadly distributed; and – provide scientific info. needed by water managers and natural resource agencies on both sides of the border Currently designated priority transboundary aquifers Secretary of Interior (through USGS) directed to collaborate with: State water resource agencies Any affected Indian tribes Others monitoring/ metering water International Boundary and Water Commission “as appropriate” México

5 Congress authorized $50M over 10 years (FY07 – FY16) Funds to be divided 50-50% USGS - State Water Resources Research Institutes Funds appropriated for FY08 only ($0.5M) Arizona - 1/6 for USGS, 1/6 for Water Resources Research Center at Univ. Az) Background California Congressional Delegation opted out of participation WRRIs’ funds can be spent in Mexico, but there must be a 50% match (may be in-kind) Aquifers to be investigated initially: – Hueco Bolson, Mesilla, potentially others (in NM/TX - Chihuahua) – Santa Cruz, San Pedro only (AZ - Sonora)

6 San Pedro Aquifer Population ~ 150,000 San Pedro National Riparian Conservation Area: > 300 bird species, endangered Sonoran pronghorn Fort Huachuca Army Garrison Congressionally mandated maintenance of sustainable yield 3rd largest copper deposit in the world at Cananea Number of modeling efforts. Some consider aquifer on both sides of border.

7 Santa Cruz Aquifer River begins and ends in US Combined population of Ambos Nogales between 300,000 and 400,000 Intensive mining both historic and current; source of contamination Aquifers not extensive AZ water law encourages maximal pumping until water rights are legally established Number of modeling efforts, none binational

8 Rapid economic growth Border current population over 12 million; projected to be 13 million to 15 million by 2010 Arid environment, declining water tables, and contamination (lack of even basic sewage treatment in some Mexican cities) Challenges Aquifers are sole or next available water source High water demand:e.g. U.S. side of the Santa Cruz aquifer:

9 Progress - Santa Cruz

10 Update water balances Assess movement and interaction of surface and groundwater; develop hydrogeologic maps of surficial and bedrock geology Analyze trends in groundwater quality (salinity, toxins, and pathogens) Characterize institutions, assess possibilities and limits of shared aquifer management Apply new data and models to evaluate strategies to protect water quality and enhance supplies Compile, develop info. on land-use, population, and economic growth; monitor changes through time Scientific Plans - Santa Cruz

11 Priority Studies Create a physically-based hydrologic model of each binational basin that integrates surface-, ground-, and unsaturated-zone water. – Summary of Approach: Compile extant data Examine existing models Identify data gaps Develop unified hydrologic framework Model Applications Synthesize model inputs and outputs for each complete binational basin Provide aquifer-based decision support for policy makers to address: – aquifer and basin water budgets – scenarios of demographic and economic growth – climate change impacts – water management plans

Improve Binational Data Exchange (e.g. Location of wells sampled In Mexico’s San Pedro)

13 Institutional Asymmetries Contrasting organizations, responsibilities IBWC/ CILA groundwater mandate unclear Border ‘security climate’ Stakeholder interest in collaboration, info exchange Shared aquifers, shared futures

UNESCO’s Internationally Shared Aquifer Resources Management (ISARM) Program now includes as case studies TAAP Arizona-Sonora. (Note: San Pedro already a UNESCO HELP basin.) This will facilitate international exchange of approaches to transboundary aquifer assessment

15 For further information, see Christopher Scott Thank you