• ground-water hydrogeology;
  • ground-water modeling;
  • water management;
  • natural recharge;
  • Las Vegas Valley;
  • Nevada;
  • precipitation

ABSTRACT: Published estimates of natural recharge in Las Vegas Valley range between 21,000 and 35,000 acre-feet per year. This study examined the underlying assumptions of previous investigations and evaluated the altitude-precipitation relationships. Period-of-record averages from high altitude precipitation gages established in the 1940s through the 1990s, were used to determine strong local altitude-precipitation relationships that indicate new total precipitation and natural recharge amounts and a new spatial distribution of that recharge. This investigation calculated about 51,000 acre-feet per year of natural recharge in the Las Vegas Hydrographic Basin, with an additional 6,000 acre-feet per year from areas tributary to Las Vegas Valley, for a total of 57,000 acre-feet per year. The total amount of natural recharge is greater than estimates from earlier investigations and is consistent with a companion study of natural discharge, which estimated 53,000 acre-feet per year of outflow. The hydrologic implications of greater recharge in Las Vegas Valley infer a more accurate ground-water budget and a better understanding of ground-water recharge that will be represented in a ground-water model. Thus model based ground-water management scenarios will more realistically access impacts to the ground-water system.