- Basin Name
- San Jacinto
- Basin Number
- SGMA Basin Priority
- Critically Overdrafted
- Adjudicated Basin
- DWR Region & POC
DWR Southern Region
Hemet-San Jacinto Watermaster
- Number of Wells
- Hydrologic Region Name
- South Coast Hydrologic Region
Located in California’s South Coast hydrologic region, the San Jacinto is 181,455 acres in size. This High priority basin is home to an estimated 479,879 people (2010 value), which have been at a rate of 33.02. San Jacinto is a(n) basin with approximately 1950 wells, of which approximately 1950 are water supply wells. Groundwater accounts for approximately 41.47 percent of the basin’s water supply.
2003: Bulletin 118
2014: CASGEM basin prioritization – high. Comment: Basin is in overdraft (MWD). Groundwater quality issues documented in DWR B‐118. Pumping has increased some contaminant distribution in the basin.
2018: Draft basin priority – high. Comments:
- Groundwater level – 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR 2) The Hemet/San Jacinto Groundwater Management Area monitors around 200 wells twice a year, but report has no hydrographs and does not summarize long-term history. There is a Basin Storage graph that shows delining storage. Source: Hemet/San Jacinto Groundwater Management Area 2015 Annual Report 3) Historically, extraction in excess of recharge has resulted in lowered groundwater levels and altered directions of groundwater flow. Source: Hemet/San Jacinto Groundwater Management Plan.
- Subsidence – 1) Subsidence related to tectonic deformation and aquifer compaction; reported subsidence of 2.3 feet between 1939 and 1959 Lofgren (1976) measured compaction of aquifer materials with a 377-m deep extensometer from 1970 to 1974 and concluded that inelastic compaction of aquifer materials in the depth range of the extensometer amounted to about 1 cm /yr (0.04 ft/yr) and that tectonic subsidence amounted to 0.3-0.6 cm/yr (0.1-0. 2 in/yr). That is, most permanent subsidence (70-80 percent) resulted from groundwater withdrawal, with the remainder from tectonic downwarping of the valley. Source: Land subsidence and aquifer-system compaction in the San Jacinto Valley, Riverside County, California – A progress report
Reference note: 33.13% of basin is adjudicated