Groundwater overdraft in California's Central Coast Region

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A watershed-related issue examined by the ENVS 560/L Watershed Systems class at CSUMB.


Overdraft of groundwater occurs when use exceeds replenishment. In California's Central Coast Region there are several areas where overdraft is occurring:

One key example of overdraft in the Central Coast is in the Salinas Valley where a high dependence on groundwater for agricultural water needs has led to critical overdraft conditions[1]. This has resulted in abandonment of agricultural and urban supply wells due to rising salinity levels[2] in the aquifers. Over 524 thousand acre-feet of groundwater was extracted during the 2014 water year, 91.55% of which went to agricultural use and 8.45% for urban use.[3] Groundwater overdraft can lead to numerous problems such as seawater intrusion, aquifer storage reduction, loss in groundwater quality, and lowering of water levels.[4] The concern over these adverse effects has led to the development of a statewide groundwater management plan[5] and new supplemental water supplies from the Salinas Valley Water Project.

Mitigation Strategies

In 1961, Nacimiento Dam was completed to supply irrigation water to the Salinas Valley agricultural community and to recharge the aquifers. Attempts to change structural and operational practices at the dam have met severe local opposition resulting in several lawsuits[6].


  1. California Department of Water Resources, 2016. Critically Overdrafted Basins.
  2. Salinas Valley Water Project Description
  3. Monterey County Water Resource Association Groundwater Extraction April 2017 Summary Report
  4. California Ag Water Stewardship Initative on Groundwater Management
  5. California Department of Water Resources: Sustainable Groundwater Management
  6. Water Table Elevations in the Salinas Valley, California: Animated Visualization using GIS by April McMillian



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