Gilroy-Hollister Valley – North San Benito

Gilroy-Hollister Valley – North San Benito


  • Basin Name
  • Gilroy-Hollister Valley – North San Benito
  • Basin Number
  • 3-003.05
  • SGMA Basin Priority
  • Medium
  • Critically Overdrafted
  • No
  • Hydrologic Region Name
  • Central Coast Hydrologic Region
  • Counties
  • San Benito, Santa Clara


Located in California’s hydrologic region, the Gilroy-Hollister Valley – North San Benito is 131,030.03 acres in size. This Medium priority basin is home to an estimated 51,081 people (2010 value), which have been at a rate of .

Gilroy-Hollister Valley – North San Benito is a(n) basin with approximately 938 wells, of which approximately 84 are water supply wells. Groundwater accounts for approximately percent of the basin’s water supply.

Basin Notes

1972: Ground-water Hydrology of the Hollister and San Juan Valleys, San Benito County, California, 1913-68, U.S. Geological Survey, 1972

2004: Bulletin 118 basin description

2014: Distribution of Groundwater Nitrate Concentrations Gilroy-Hollister Valley Groundwater Basin, California, Central Coast Groundwater Coalition

2019: Formed by boundary modification consolidation of Bolsa Area, Hollister Area, and San Juan Bautista Area subbasins of Gilroy-Hollister Valley basin.

Prioritization comments: 1) Hydrographs show groundwater level decline. Source: 3-003.05_7a_Hydrographs_NorthSanBenito.pdf 2) GWLs continued to decline in areas of basin that rely on GW, specifically in the former 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: 3-003.05_SanBenitoAnnualGWReport_NorthSanBenito.pdf

GSA Information