This digital dataset contains the monthly precipitation for the Central Valley Hydrologic Model (CVHM).
The Central Valley encompasses an approximate 50,000 square-kilometer region of California. The complex hydrologic system of the Central Valley is simulated using the U.S. Geological Survey (USGS) numerical modeling code MODFLOW-FMP (Schmid and others, 2006). This simulation is referred to here as the CVHM (Faunt, 2009). Utilizing MODFLOW-FMP, the CVHM simulates groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis from 1961-2003. The total active modeled area is 20,334 square-miles on a finite- difference grid comprising 441 rows and 98 columns. Slightly less than 50 percent of the cells are active. The CVHM model grid has a uniform horizontal discretization of 1x1 square mile and is oriented parallel to the valley axis, 34 degrees west of north (Faunt, 2009). The main climatic contributors to the CVHM are reference evapotranspiration (ETo) and precipitation. Parameter-Elevation Regressions on Independent Slopes Model (PRISM) data (Climate Source, 2006) provide the temperature and precipitation on a monthly basis for a 2-kilometer grid. The precipitation data were interpolated from the prism grid onto the CVHM one-square-mile grid. The CVHM is the most recent regional-scale model of the Central Valley developed by the USGS. The CVHM was developed as part of the USGS Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).