Gilroy-Hollister Valley – Bolsa Area

Source: CA DWR

Gilroy-Hollister Valley – Bolsa Area


  • Basin Name
  • Gilroy-Hollister Valley – Bolsa Area
  • Basin Number
  • 3-003.02
  • SGMA Basin Priority
  • Medium
  • Critically Overdrafted
  • No
  • Status
  • Subject to SGMA
  • DWR Region & POC
  • South Central Regional Office
    Mike McKenzie
    (559) 230-3308

  • Number of Wells
  • 132
  • Hydrologic Region Name
  • Central Coast Hydrologic Region
  • Counties
  • San Benito


Located in California’s Central Coast hydrologic region, the Gilroy-Hollister Valley – Bolsa Area is 20,777 acres in size. This Medium priority basin is home to an estimated 2,908 people (2010 value), which have been at a rate of 7.11. Gilroy-Hollister Valley – Bolsa Area is a(n) basin with approximately 132 wells, of which approximately 2 are water supply wells. Groundwater accounts for approximately 91.87 percent of the basin’s water supply.

Source: CA DWR
Source: CA DWR

Basin Notes

2003: Bulletin 118 basin description

2018: Basin prioritization groundwater level comment – 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR 2) GWLs continued to decline in areas of basin that rely on GW, specifically in the Bolsa, San Juan, Hollister West, Bolsa SE, and Tres Pinos subbasins. While some subbasins showed groundwater level increases, overall groundwater in storage decreased. Groundwater elevation declines and storage decreases during drought do not constitute overdraft; nevertheless, the continued reduced supplies of imported water in tandem with increased groundwater demands are a warning of potential overdraft. Source: San Benito County Water District

Basin boundary modification request pending

GSA Information

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