This polygon shapefile depicts boundaries of Stormwater Runoff Catchments for outfalls greater than or equal to 18 inches in diameter, in the County of Santa Clara, California. The original Hydrograph Modification Program (HMP) data set was completed in 2003. This update is based on data collected in 2004 and 2005. New data include field observations, newly acquired storm drainage maps and reinterpretation of existing data. The catchment areas (sq. ft), area per land-cover type and associated percent impervious were calculated for each catchment and added to the attribute table. Catchments were updated based on Creek and Watershed Maps of the greater Santa Clara Valley, as well as the most up to date storm drain maps available at the time of this revision. Catchment areas, land cover and percent impervious were derived by GIS analysis of remotely-sensed land cover data (3 foot grid cell resolution), acquired in the summer of 2002 by Space Imaging Corporation. The Santa Clara Valley Water District manages an integrated water resources system that includes the supply of clean, safe water, flood protection and stewardship of streams on behalf of Santa Clara County's 1.8 million residents. This layer is part of a collection of GIS data for Santa Clara County, California. To assist the Santa Clara Valley Water District in studies for compliance with National Pollutant Discharge Elimination System Permit regulation C.3f. This coverage can be used for basic applications such as viewing, querying, and map output production, or to provide a basemap to support graphical overlays and analyses of geospatial data. None.These datasets were developed for use by the Santa Clara Valley Water District (SCVWD) for its internal purposes only, and were not designed or intended for general use by members of the public. SCVWD MAKES NO REPRESENTATION OR WARRANTY AS TO ITS ACCURACY, TIMELINESS, OR COMPLETENESS. SCVWD MAKES NO WARRANTY OF MERCHANTABILITY OR WARRANTY FOR FITNESS OF USE FOR A PARTICULAR PURPOSE, EXPRESSED OR IMPLIED, WITH RESPECT TO THESE PRODUCTS OR THE UNDERLYING DATA. Any user of this data, accepts same AS IS, WITH ALL FAULTS, and assumes all responsibility for the use thereof, and further covenants and agrees to defend, indemnify, and hold SCVWD harmless from and against all damage, loss, or liability arising from any use of this product, in consideration of SCVWD having made this information available.Independent verification of all data contained herein should be obtained by any user of these products, or the underlying data. SCVWD disclaims, and shall not be held liable for, any and all damage, loss, or liability, whether direct, indirect, or consequential, which arises or may arise from these products or the use thereof by any person or entity. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.