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Seawater intrusion in Northern Salinas groundwater basin with water basin hydrogeology documented by Monterey County Water Resources Agency since the 1950s.


This report provided the Salinas groundwater basin hydrogeology informaion documented since the 1950s in order to provide a better understanding of the advancement of seawater intrusion into groundwater zones. Since the later 1990s, well logs, geopyhsical and lithological data supporting a three-dimensional study of the inter-related ancestral fluvial and alluvial-fan depositional environments making up the groundwater bearing zones (180-Foot and 400-Foot aquifers) and their implications on seawater intrusion pathways.

The economic importance of a detailed rendition of hydrostratigraphic characteristics was to assist in the construction and placement of future water supply and monitoring wells within the study area. Seawater was intruding into the groundwater zones from the submarine outcrops of and directly into the Pressure 180- and Pressure 400-Foot aquifers. Stratigraphic analysis demonstrated with notably more detailed lithologic data that mixing and vertical migration of seawater was highly possible in several localized areas between the coast and the City of Salinas. Vertical movement of seawater/groundwater is likely across leaky aquitard and areas of the absence of confining clay unit between the Pressure 180-Foot and Pressure 400-Foot Aquifers. It was therefore of importance to the public water supply of the northern Salinas Valley that the 3-D permeability distribution of the lithology be mapped with enough detail to assist in the design of future engineering measures to mitigate the seawater intrusion problem.


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2003 - Geohydrologic Framework of Recharge and Seawater Intrusion in the Pajaro Valley, Santa Cruz and Monterey Counties, California