Site-characteristic and hydrologic data for selected wells and springs on U.S. Bureau of Land Management, National Park Service, U.S. Fish and Wildlife Service, and U.S. Forest Service land in Clark County, Nevada, were updated in the U.S. Geological Survey’s National Water Information System (NWIS) to facilitate multi-agency research. Data were researched and reviewed, sites were visited, and NWIS data were updated for 231 wells and 198 springs, including 36 wells and 67 springs that were added to NWIS and 44 duplicate sites that were deleted. The site-characteristic and hydrologic data collected, reviewed, edited, and added to NWIS include locations, well water levels, spring discharges, and water chemistry. Site-characteristic and hydrologic data can be accessed from links to the NWIS web interface; data not available through the web interface are presented in appendixes to this report.