Santa Cruz County Primary Water Sources
Practically all of Santa Cruz County 's potable water supply is locally derived from surface water sources (20%) and groundwater (80%). While there are numerous small water diversions on many of the county streams, most of the stream water used is diverted from the San Lorenzo River Watershed, North Coast streams, and Corralitos Creek. Most groundwater is contained in permeable geologic basins, typically referred to as aquifers. There are three major groundwater basins in the county: the Santa Margarita, Purisima, and Aromas.
Stream flow is inadequate to meet demands during a drought and all the major groundwater basins in Santa Cruz County are in some level of overdraft (i.e. more water is being extracted from the aquifers than is naturally recharged through the soils and stream valleys). In the Pajaro Valley (Aromas Groundwater Basin), agricultural use far exceed sustainable yield. In other parts of the County, development contributes to the overdraft by both through demand but also because development covers the ground surface with impervious layers that greatly reduce groundwater recharge. Negative consequences of overdraft include declining groundwater levels, a decrease in groundwater quality, reduced streamflow, and seawater intrusion along the coast that destroys wells.