Coastal Plain of Los Angeles – Santa Monica

Source: CA DWR

Coastal Plain of Los Angeles – Santa Monica


  • Basin Name
  • Coastal Plain of Los Angeles – Santa Monica
  • Basin Number
  • 4-011.01
  • SGMA Basin Priority
  • Medium
  • Critically Overdrafted
  • No
  • Hydrologic Region Name
  • Southern California
  • Counties
  • Los Angeles
  • Adjacent Basins
  • Coastal Plain of Los Angeles - Central 4-011.04, Coastal Plain of Los Angeles - West Coast 4-011.03, Coastal Plain of Los Angeles - Hollywood 4-011.02,


Located in California’s South Coast hydrologic region, the Coastal Plain of Los Angeles – Santa Monica is 31,779 acres in size. This Medium priority basin is home to an estimated 465,539 people (2010 value), which have been at a rate of 23.34.

Coastal Plain of Los Angeles – Santa Monica is a(n) basin with approximately 393 wells, of which approximately 10 are water supply wells. Groundwater accounts for approximately 21.82 percent of the basin’s water supply.

Source: CA DWR
Source: CA DWR

Basin Notes

2003: Bulletin 118 basin description 

2014: CASGEM basin prioritization: medium. Comment: MTBE contamination has led to significant reduction in groundwater production and locally high TDS.

2016: Basin prioritization comments –  Salt intrusion: Given Santa Monica’s proximity to the coast, saltwater intrusion is an ongoing concern. If the city were to over-pump from wells, its possible to reverse the natural water flow and actually pull seawater from the ocean into the local ground- water supply. Such seawater intrusion can occur for other reasons such as climate change or drilling new wells too close to salt water sources. To the best of the Citys knowledge, no such contamination has occurred in recent memory but it is assumed contamination could have, and probably did, occur at some point in the Citys history. Historic records are incomplete but city wells in the Marine Park area were contaminated and abandoned in the 1930s due to salt water intrusion. Experts have concluded that Lincoln Boulevard is the boundary for any potential salt water intrusion and therefore the western edge of the citys underground water supply. Source: The Water Issue, City of Santa Monica, 2015

2018 Final Basin Prioritization: Basin priority remains unchanged at medium priority.

GSA Information

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