Groundwater and the Basin

Santa Margarita Groundwater Basin The Santa Margarita Groundwater Basin is a primary source of water supply for Scotts Valley, San Lorenzo Valley, and Santa Cruz. It covers over 30 square miles in the Santa Cruz Mountains foothill forming a triangular area that extends from Scotts Valley to the east, Boulder Creek to the northwest and Felton to the southwest.

The major water purveyors that directly rely on the supply from SMGB are Scotts Valley Water District (SVWD), San Lorenzo Valley Water District (SLVWD), and Mount Hermon Association (MHA). SMGB is also the sole supply source for 13 small water systems and over 1,100 private well users. In addition, the City of Santa Cruz derives a major portion of its supply from San Lorenzo River watershed that overlaps the basin.

The decline of groundwater levels in many parts of the basin occurred during 1985-2004 representing a loss in groundwater storage in SMGB by an estimated 28,000 acre-feet resulting in diminished local water supply and reduced sustaining base flows to local streams that support fishery habitats. Thanks to conservation and other management efforts at local water agencies, the total pumping from SMGB has decreased by 45% since 1997. For the last 10 years, the demand and supply in the basin have been in balance.

Key Milestones

  • The early 1980s: SVWD began actively managing groundwater in the area to increase water supply reliability and to protect local water supply sources.
  • 1983: SVWD instituted a Water Resources Management Plan to monitor and manage water resources.
  • 1994: The agency formally adopted a Groundwater Management Plan in accordance with AB3030, also known as the Groundwater Management Act under Water Code section 10750.
  • 1995: SVWD, SLVWD, MHA, LCWD, City of Scotts Valley and County of Santa Cruz signed a Memorandum of Understanding forming Santa Margarita Groundwater Basin Advisory Committee that was actively involved in the cooperative groundwater management of the basin until its dissolution and substitution with Santa Margarita Groundwater Agency (SMGWA) in 2017.
  • 2017: SMGWA, a Groundwater Sustainability 

Under the Sustainable Groundwater Management Act of 2014, overdrafted groundwater basins need to be sustainably managed by a Groundwater Sustainability Agency (GSA) through the development of a Groundwater Sustainability Plan (GSP). The GSP must be completed by 2020, and the basin must reach sustainability by 2040.

The Santa Margarita Groundwater Agency (SMGWA) is a three-member agency comprised of the Scotts Valley Water District, San Lorenzo Valley Water District, and the County of Santa Cruz, which will oversee the groundwater management activities of the Santa Margarita Basin Area in Santa Cruz County, California. The Board of Directors of the SMGWA includes two Board members from each of the water districts, one from the County, one from the City of Scotts Valley, one from the City of Santa Cruz, one from the Mount Hermon Association Community Water System, and two private well owner representatives. More information is available at www.smgwa.org.

Santa Margarita Groundwater Basin