Extracting and desalting groundwater that has been impacted by seawater intrusion could create a new source of water supply, reducing the region’s dependence on groundwater. SVBGSA is preparing a feasibility study to evaluate whether this type of program would slow or reverse the eastward inland migration of seawater intrusion and provide a new drought-proof water supply to the region. The Brackish Groundwater Restoration Project Draft Summary Memo is available here. An initial feasibility study will be completed in early 2025.
The concept for this project is to establish a string of extraction wells across the mouth of the Salinas Valley, near the coast, to capture seawater on the coastal side of the wells and to start pulling back intruded seawater from the inland side of the wells. This extracted brackish groundwater would then be treated through reverse osmosis to remove salts and create a supply that meets potable water standards. The treated water would be distributed inland to offset groundwater users for both domestic and agricultural customers.
The extraction wells and treatment would be run at a fairly steady flow rate to prevent seawater intrusion from leaking past the wells. This would result in times (particularly winter months) where more treated water is available than users demand. This excess treated water would be injected back into the groundwater basin inland along the edge of the seawater intrusion front to assist in raising groundwater levels to push the intruded zone back to the coast. Injection of this high-quality water would also improve groundwater quality. Graphic illustrations of the project concept and its components are shown in the figure and an Overview and Modeling Results are available here.