Explosive growth in Las Vegas, Nevada, has stimulated demand for additional water supplies. To meet these needs, local officials hope to obtain rights to about 200,000 acre-feet (246.70 million cubic meters [m³]) per year from a regional groundwater aquifer extending from Salt Lake City, Utah, to Death Valley, California. Officials from satellite communities are pursuing rights to an additional 870,487 acre-feet (1.07 billion m³) per year. If granted, these new permits would trigger declines in groundwater across at least 78 basins covering nearly 130,000 square kilometers. Water-rights decisions have historically interpreted economic development as a more compelling public interest than maintenance of natural systems. If economic development continues to drive allocation decisions, consequent declines in the water table, spring discharge, wetland area, and streamflow will adversely affect 20 federally listed species, 137 other water-dependent endemic species, and thousands of rural domestic and agricultural water users in the region. Reducing consumption and implementing cost-effective technologies, such as recovery of urban runoff and shallow saline groundwater, indirect reuse of potable water, and desalinization, offer ways to meet metropolitan and ecological needs within the limits of the resource.