M&A updates brackish groundwater study for ADWR

Over the past few years, professionals in and around the water industry have shown renewed interest in evaluating the use of desalinated brackish groundwater to augment Arizona’s limited water supplies. In 2023, the Arizona legislature appropriated funding for the Arizona Department of Water Resources (ADWR) to prepare an updated inventory of brackish groundwater in the state to assess the availability of this resource. ADWR contracted with Montgomery & Associates (M&A) to conduct this study, which was completed in June 2024 and culminated with a technical report articulating the hydrogeologic findings.

Two previous investigations identified and characterized brackish groundwater in Arizona. In 1981, ADWR published a map of areas of known brackish or saline groundwater, and in 2008, M&A prepared a brackish groundwater inventory for the Central Arizona Water Conservation District.

For the current study, M&A reviewed public datasets from wells around the state and identified areas where total dissolved solids (TDS) were above 1,000 mg/L. A total of 21 study areas were delineated, and characteristics related to water chemistry, groundwater conditions, and infrastructure were compiled.

From the 21 study areas, ADWR selected 4 focus areas for further evaluation: Gila Bend, Ranegras Plain, West Salt River Valley, and the Little Colorado River Plateau. For each focus area, M&A’s analyses present an overview of the hydrogeologic conditions, maps of water level elevation contours and TDS distribution, estimates of groundwater in storage, and a groundwater budget of the basin.

Download the updated brackish groundwater report here. The information in the report provides a foundation for planning for development of brackish groundwater resources. Any feasibility evaluation or pilot demonstration project should include policy or regulatory considerations, engineering cost estimates of water treatment, and other infrastructure requirements, which was beyond the scope of this study.

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