Central Coast Blue: Creating a Sustainable Groundwater Supply and Combating the Threat of Seawater Intrusion

Groundwater Basins along the Central Coast of California have been severely stressed due to the historic drought conditions which has resulted in declining groundwater levels and in some cases intensified the threat of seawater intrusion. The Northern Cities Management Area (NCMA) of the Santa Maria Groundwater Basin (SMGB), located along the coast of Southern San Luis Obispo County, is a coastal aquifer that has observed increased chloride concentrations in previous prolonged droughts and been drastically impacted by the current drought. The NCMA has significantly reduced groundwater pumping to combat the threat of seawater intrusion and groundwater levels have continued to decline. As a result of the decreased groundwater pumping, the NCMA have increased their reliance on local surface water reservoirs (Lopez Lake Reservoir) and imported supplies (State Water Project) which are also sensitive to drought conditions, to meet the water demands of the NCMA.

Central Coast Blue is a regional recycled water project that will develop a sustainable water supply and protect the SMGB from seawater intrusion by creating a seawater barrier through a series of wells that will inject purified recycled water. Currently, the water from the Pismo Beach Wastewater Treatment Plant (WWTP) and the South San Luis Obispo County Sanitation District (SSLOCSD) WWTPs is being treated and discharged to the ocean.

This talk will focus on how the Central Coast Blue project will optimize groundwater production and create a drought proof source of supply to ensure that reliable water supplies will be available for future extended droughts though the use of a calibrated groundwater model and the development of an adaptive basin level response plan.