Olivenhain Municipal Water District, Groundwater Supply and Brine Management Program

San Diego County, CA

Olivenhain Municipal Water District (OMWD) serves approximately 84,000 customers in the communities of Encinitas, Carlsbad, portions of San Diego, San Marcos, and Solana Beach. Because OMWD relies almost entirely on imported water from the California and Colorado aqueducts, the district is investigating ways to develop local water supplies. Currently, OMWD is not pumping from the San Dieguito basin because it contains mostly brackish water caused by sea water intrusion and recharge with marine sediments— degrading the water quality. The basin was mapped by the state Department of Water Resources in 2016 as part of the Sustainable Groundwater Management Act, however it did not consider the relationship between the mapped geology and the extent of water bearing materials within the basin. 

Geoscience is working with OMWD staff to determine the safe yield increment of water available in the San Dieguito basin without impacting other users. We are also helping to determine locations for well fields, treatment facilities, pipelines, and brine discharge facilities to produce 1,600 acre-fee (AF) per year. Our team is assessing the current basin conditions and helping to plan for water treatment facilities to provide the district with an additional source of water. To support a future GSP, we are:

  • Collecting data
  • Completing a hydrological investigation
  • Updating the current groundwater model
  • Calculating sustainable yield 
  • Developing preliminary well designs
  • Recommending brine management activities
  • Supporting community outreach
  • Completing desk-top environmental reviews

To develop a more accurate model, we modified the basin boundaries based on the local lithology and bedrock geology. The refined boundary allowed OMWD to get a clearer picture of the basin’s sustainable yield and more accurate data to plan for the future. Currently our team is designing production wells to supply a brackish water desalter.

Details at a Glance:
  • Client: Olivenhain Municipal Water District
  • Date: Ongoing