Hydrostratigraphy and Aquifer Characteristics of the South Las Posas Basin, Ventura County, California

K. L. Neil and M. A. Tabidian
California State University, Northridge, CA, [email protected], [email protected]

Groundwater is the primary source of water for Ventura County, California. Whereas approximately 66% and 23% of the county’s water supplies are derived from local groundwater reservoirs and imported water, respectively, the remaining supply is from local surface water resources. In order to avert rising water supply costs and demands and lessen dependency on inter-basin water transfers, a better characterization and management of local basins such as the South Las Posas Basin (SLPB) groundwater resource in Moorpark, Ventura County, is warranted. The basin encompasses an area of approximately 10,560 acres and by volume is ninth of the top ten groundwater basins in Ventura County. Although SLPB has an estimated 1,600,000 acre-feet of storage capacity, the local population relies heavily on imported water. It is of paramount importance to plan the utilization and conduct the management of the aforementioned groundwater resources. In addition, with increasing population and environmental concerns, additional constraints are being placed upon imported water resources.

The purpose of this research was to characterize the basin aquifers by developing the hydrogeologic framework and delineating the water-bearing (hydrostratigraphic) units. A hydrologic budget was developed to better estimate basin storage values. A comprehensive subsurface analysis of the aquifers was also conducted, providing an overview of the area’s geology, hydrology, hydrogeology, and water quality. For better water resource management and planning, all available hydrologic data were assembled in a geo-referenced format. RockWorks™ was used to integrate geologic, hydrologic, and hydrogeologic data into a 3D hydrostratigraphy model of the basin. Information obtained from this research can be utilized by local and regional water agencies to improve current water resource management and provide a means to assess new water resources as additional or emergency supplies during prolonged periods of drought.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009