Zones in this data set represent spatially contiguous areas that influence ground-water flow in the Death Valley regional ground-water flow system (DVRFS), an approximately 45,000 square-kilometer region of southern Nevada and California. The zones typically represent areas of differing material properties; however, they may also represent spatially similar areas, such as areas of similar infiltration rates. Material properties, such as horizontal hydraulic conductivity, vertical anisotropy, or storage characteristics may vary within a single hydrogeologic unit and be represented by numerous zones; or they may be the same for multiple hydrogeologic units and be represented by a single zone. The DVRFS zones were typically derived from geological or hydrological analyses by Sweetkind and others (2004) and Faunt and others (2004) and were used as input in the DVRFS transient ground-water flow model, a regional-scale model developed by the U.S. Geological Survey (USGS) for the U.S. Department of Energy (DOE) to support investigations at the Nevada Test Site (NTS) and at Yucca Mountain, Nevada (see "Larger Work Citation", Chapter A, page 8, for details).