Lower Rio Grande Basin Study Identifies Brackish Groundwater Desalination
As Best Option for Meeting Region’s Long-Term Water Needs
A two-year study by the RGRWA and the U.S. Bureau of Reclamation has determined that a regional system of three brackish groundwater desalination (BGD) facilities in the Lower Rio Grande Valley is the best option for meeting water needs of a soaring population and addressing a mounting water deficit projected to reach 678,522 acre-feet of water per year (AF/yr) by 2060.
The RGRWA and Reclamation have identified and are pursuing potential funding opportunities to help develop these facilities.
Action is needed, says the study report, because surface water supplies will continue to be impacted by drought, long-term climatic changes, and competition from Mexico. Brackish groundwater supplies, on the other hand, abound in the region – four times more plentiful than fresh groundwater supplies – and have much fewer competing demands. Several BGD facilities already are in operation in the region and conditions are ripe for regional systems that would serve several communities.
Brackish groundwater desalination is one of the long-term “Water Management Strategies” developed by the Rio Grande Regional Water Planning Group and included in the 2012 Texas State Water Plan.
RGRWA funded 52% of the total study cost of $412,798 and Reclamation the remaining 48% through its WaterSMART program. Other collaborators on the project included the Rio Grande Regional Water Planning Group (RGRWPG), Texas Water Development Board, Texas Commission on Environmental Quality, and International Boundary and Water Commission. The study report was released in December 2013.
Major Findings of the Study:
Climate change is likely to result in increased temperatures, decreased precipitation, and increased evapotranspiration in the study area. These factors will exacerbate the considerable water supply deficit of 592,084 AF/yr by 2060 projected in the 2011 Regional Water Plan. The basin study projects that the impacts of climate change will create an additional supply shortfall of 86,438 AF/yr higher, for a total deficit of 678,522 AF/yr.
The supply imbalances exacerbated by climate change will greatly reduce the reliability of deliveries to all users dependent on deliveries of Rio Grande water via irrigation systems, including many municipal and industrial (M&I) users. Extreme drought conditions in 2013 have shown that reductions in agricultural water deliveries can negatively affect the push water needed to supply M&I users.
Competing use from Mexico also severely compromises the reliability of the Rio Grande to meet future needs in the region. Some 78 percent of the watershed that feeds the Falcon and Amistad reservoir system – the water supply for the study area – is located in Mexico. Historically, Mexico has not always been able to meet its treaty obligations to deliver water to the Rio Grande due to drought and its own competing uses for tributary waters.
The largest municipal, manufacturing, and mining users within the RGRWA’s jurisdiction are located in Cameron, Willacy, and Hidalgo counties. Demand from these users is expected to grow rapidly during the planning horizon, while demand from agricultural is expected to decline due to projected urbanization.
Regional BGD systems designed to satisfy a portion of the municipal demands of area cities by 2060 best met the study objectives.
Recommended Locations for Regional BGD Systems
The study examined various options for regional BGD systems. Criteria included population served; short- and long-term needs and vulnerability to drought; potential for regionalization through existing infrastructure; accessibility to a productive aquifer; opportunity for co-location with a power plant; legal and regulatory considerations, including brine disposal; and cost of service.
Based on these criteria, the study recommended three regional systems:
Group 1 would serve 10 communities in Hidalgo County, stretching from Palmview to Alamo and Hidalgo to Edinburg. Components would include two BGD facilities, each with a capacity of 31.4 million gallons per day (MGD), plus associated transmission pipelines and pumps. The project would cost an estimated $308 million and provide 70,400 AF/yr.
Group 2 would serve 10 communities along the borders of Hidalgo, Cameron, and Willacy counties, from Progreso to Weslaco through Elsa/Edcouch to Santa Rosa and northward to Lyford and Raymondville. Components would include one desal facility with a capacity of 9.2 MGD plus pipelines and pumps. The project would cost an estimated $86.5 million and provide 10,300 AF/yr.
Group 3 would serve 8 communities in Cameron County, from Rio Hondo through Harlingen to La Feria as well as San Benito and La Feria. Components would include an 11.8 MGD desal facility, plus pipelines and pumps. The project would cost an estimated $99.6 million and would provide 12,300 AF/yr.
The specific recommendations were developed based on:
Hydrologic projections of water supply and demand in the face of changing climatic conditions;
Evaluations of how existing water and power infrastructure would perform under changing water realities;
Development of a range of alternatives to meet short, mid, and long-term planning objectives, particularly during times of drought; and
Evaluation and screening of alternatives based on several factors, including cost/benefits, public acceptance, and various political, institutional, regulatory, and environmental constraints.
Access all plan documents of the Lower Rio Grande Basin Study by clicking on the links below.
- Chapter 1: Problems, Needs, and Opportunities
- Chapter 2: Regional Demands and Supplies and Future System Reliability
- Chapter 3: Planning Objective and Water Management Strategies
- Chapter 4: Alternatives Formulation Report
- Chapter 5: Alternatives Evaluation
- Chapter 6: Affordability Report
- Appendix A: Technical Sufficiency Memo
- Appendix B: Existing Desalination Plant Data
- Appendix C: Site Selection Criteria Table
- Appendix D: Unified Cost Model Methodology and Assumptions
- MAY 2012 STUDY UPDATE
- BASIN STUDY FACT SHEET
- PLAN OF STUDY
- INITIAL PROPOSAL
US Bureau of Reclamation – Jeff Gerber, Environmental Protection Specialist, Oklahoma-Texas Area Office, 512-899-4157
Rio Grande Regional Water Authority – Marcie Oviedo, Director of Regional Planning, Lower Rio Grande Valley Development Council, 956-682-3481