Evaluation of Precipitation Estimates from PRISM for the 1961–90 and 1971–2000 Data Sets, Nevada

Nevada is the driest of all States, making water an extremely valuable resource to sustain agriculture, industry, mining, and rapid urban growth. Much of the State depends on ground water because few rivers and streams are perennial. Regional water budgets have been developed for much of the State using average annual precipitation to estimate the amount of ground-water recharge (the fraction of precipitation that reaches the water table).
The distribution of precipitation typically is estimated from either long-term precipitation rates generally determined from data interpolated from recorded sites with poorly known accuracy, from isohyetal precipitation maps (Hardman and Mason, 1949; Hardman, 1965), or more recently from computer modeled precipitation data (Daly and others, 1994). Reconnaissance-scale water budgets for Nevada used the Hardman and Mason map (1949; Maxey and Eakin, 1949; Eakin and others, 1965; Eakin, 1961). More recent studies by the U.S. Geological Survey (USGS; Berger, 2000a and 2000b; Nichols, 2000) used 30-year averages generated from the computer program Parameter-elevation Regressions on Independent Slopes Model (PRISM; Daly and others, 1994; Oregon Climate Service, 2004). The Hardman and Mason (1949) and Hardman (1965) isohyetal map are based on the distribution of vegetation communities in the State and precipitation data collected during the first decades of the 1900s.