These data are monthly median observed streamflow from 32 gages in the Central Valley for comparison to the updated Central Valley Hydrologic Model (CVHM2). The locations of these gages are shown in the shape file.

This digital dataset contains 61 sets of annual streamflow gains and losses between 1961 and 1977 along Central Valley surface-water network 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 USGS's 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. The CVHM includes complex surface-water management processes. The hydrology of the present-day Central Valley and the CVHM model are driven by surface-water deliveries and associated groundwater pumpage. The Streamflow Routing Package (SFR1) is linked to MODFLOW-FMP to facilitate the simulated conveyance of surface-water deliveries. If surface-water deliveries do not meet the farm-delivery requirement, the FMP invokes simulated groundwater pumping to meet the demand. The surface-water network represents a subset of the entire stream network in the valley. Quantitative observations of streamflow gains and losses were available for 57 reaches of 20 major stream systems in the Central Valley for water years 1961-77 (Mullen and Nady, 1985). These observations were included in parameter estimation process and in the model-fit statistics. The CVHM is the most recent regional-scale model of the Central Valley developed by the U.S. Geological Survey (USGS). The CVHM was developed as part of the USGS Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).

This digital dataset includes three sets of observational data (groundwater level, streamflow, subsidence) used to calibrate the updated Central Valley Hydrologic Model (CVHM2). CVHM2 is a tool that can be used to quantify the sustainability of groundwater resources in the Central Valley.

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The original Central Valley Hydrologic Model (CVHM) did not simulate tile drain discharge in the west side of the San Joaquin Valley. The updated Central Valley Hydrologic Model (CVHM2) does simulate on-farm drains. The data for the drain flow and locations were obtained from the Berkeley National Laboratory is from (WESTSIM2) (N. Quinn, Berkeley National Laboratory, written communication., 2010). This component of the data release includes:e (1) three datasets included are a spreadsheet of the available observations with the drain flows in acre-ft/month, (2) a shapefile of the WESTSIM2 drain cells, and (3) a shapefile of the original WESTSIM2 drain cells translated to the CVHM2 model grid.

This digital dataset contains the name and location for the diversions from the surface-water network 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 USGS numerical modeling code MODFLOW-FMP (Schmid and others, 2006b). This simiulation 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. The CVHM includes complex surface-water management processes. The hydrology of the present-day Central Valley and the CVHM model are driven by surface-water deliveries and associated groundwater pumpage. The Streamflow Routing Package (SFR1) is linked to MODFLOW-FMP to facilitate the simulated conveyance of surface-water deliveries. If surface- water deliveries do not meet the farm delivery requirement, the FMP invokes simulated groundwater pumping to meet the demand. The surface-water network represents a subset of the entire stream network in the valley. Even so, it covers about 3,000 kilometers of surface-water and is simulated using 208 stream segments that represent 2244 stream reaches, with 43 inflows and 66 diversion locations providing 64 routed and 41 non-routed deliveries. Most of these inflows are regulated by dams and most of the deliveries are conveyed through an extensive canal network. The routed deliveries are conveyed through the simulated surface-water network, while the non-routed delivery conveyance typically occurs through small canals or diversion ditches and are not directly simulated. Much of the surface-water diversion and delivery information was compiled by the California Department of Water Resources (DWR) for 21 water-balance subregions (WBSs) covering the valley floor (C. Brush, California Department of Water Resources, written commun., February 21, 2007). The CVHM is the most recent regional-scale model of the Central Valley developed by the U.S. Geological Survey (USGS). The CVHM was developed as part of the USGS Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).

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The dataset contain estimates of natural monthly streamflow for 135,118 stream segments in California, USA, from 1950 to 2012. Segments are identified per the medium resolution National Hydrography Dataset (NHD), Version 1. The dataset also contains observed monthly streamflows and estimates of natural monthly streamflows for 894 USGS stream gages in California, USA.