Inland Brackish Desalination to Address Groundwater Overdraft
El Paso, Texas
Industry: Water Supply
Organization: El Paso Water Utility
SUMMARY: The Kay Bailey Hutchison desalination plant is the world’s largest non-coastal water desalination plant. It provides water to El Paso, Texas, which opened the plant in 2007 in conjunction with the U.S. Army Corps of Engineers in order to diversify and augment the city’s water supply.
The Kay Bailey Hutchison plant draws brackish water from an aquifer called the Hueco Bolson, which contains both fresh and brackish water. In the early 2000s El Paso’s rapidly expanding population pushed the Hueco Bolson to the point of freshwater being overdrawn, which risked brackish water intrusion into the freshwater portion of the aquifer.
Construction of the desalination plant was part of a broader effort to increase water supply and decrease demand that included a public education and conservation initiative, more balanced management of surface water from the Rio Grande, and wastewater reclamation.
- Excessive groundwater pumping was leading to brackish water intrusion along the eastern margin of the Hueco Bolson aquifer, compromising the remaining freshwater within the aquifer.
- The Hueco Bolson aquifer transcends a state border with New Mexico and an international border with Mexico, complicating the issue of water rights and legal appropriation amounts in the area.
- Disposal of brine waste from inland brackish water desalination is an economic and environmental concern. Inland sites do not have the option to discharge brine waste back to the ocean, so careful consideration was required for that aspect of the process.
- Extensive planning and testing through pilot projects was an initial step in the construction of the Kay Bailey Hutchinson (KBH) desalination plant. A small pilot desalination plant was constructed in 1993 to determine the feasibility of inland brackish water desalination.
- Thorough mapping of the Hueco Bolson aquifer was required to ensure that brackish water pumping would not contaminate adjacent freshwater supplies.
- Surface water disposal, sewer disposal, evaporation ponds and injection wells were all considered as options for brine waste disposal. Injection wells were deemed the most cost-effective and environmentally sound method of disposal.
- Brine injection wells extend 3,500-4,000 feet below the surface into beds of fractured and permeable carbonate rocks. The strata overlying these rocks are impermeable, and as such sufficient to confine the wastewater in the carbonate rocks.
- The El Paso Water Utility -- in conjunction with the U.S. Geological Survey, Fort Bliss, the International Boundary and Water Commission, and the Water Utility of Juarez, Mexico -- developed a model to determine what rate of brackish groundwater withdrawal would be environmentally sound, sustainable, and not impede the groundwater supply rights of Juarez, Mexico.
- The water utility coordinated with the State of New Mexico to develop a plan where during droughts, the Elephant Butte Reservoir (a large source of water for El Paso, located in New Mexico) reduces surface water use and relies on groundwater instead. In years without drought, groundwater pumping is reduced to reduce stress on the aquifer and El Paso relies on surface water and wastewater reclamation plants.
- One wastewater reclamation plant within El Paso directly pumps treated wastewater to the Hueco Bolson aquifer for recharge.
- Freshwater stores in the Hueco Bolson have begun to stabilize and the intrusion of brackish water has been reduced in some areas and eliminated in other areas.
- The Center for Inland Desalination Studies (CIDS) was founded at the KBH desalination plant. Current research efforts at CIDS have investigated re-concentrating brine resulting from reverse osmosis, allowing for increased water yield from the plant and a decreased cost to dispose of brine waste.
- In a further effort to reduce dependence on groundwater, the City of El Paso undertook an extensive public conservation campaign. As a result, per capita water use has dropped in the city by more than 40 percent since the campaign began in 1977.
- $26 million of the $90 million construction cost of the KBH plant was funded in part through the Department of Defense.
This case study was drafted in collaboration with the American Geosciences Institute - Critical Issues Program.