Estimating evaporation in seasonally snow-covered catchments in the Sierra Nevada, California

We used Mortonʹs CRAE model, a simple model based on the complementary or advection–aridity relationship, to estimate annual evaporation for six alpine and sub-alpine catchments in the central and southern Sierra Nevada for periods of four to six years. Ten-day averages of air temperature, dew-point and sunshine duration were used as input. Modeled winter evaporation compared well with mean-profile calculations at the meteorological stations, and average annual totals were similar to those calculated from water balances and the evaporative concentration of conservative ions, i.e. chloride and sulfate. Regression relationships between weather stations were used successfully to extend limited meteorological data. Using standard lapse rates to provide data for catchments without weather stations was less successful, but still useful. The average annual catchment evaporation estimated by the model was ∼36% of annual precipitation (the average water balance and evaporative concentration estimates were 31 and 38%, respectively), showing that annual evaporative loss in the Sierra Nevada is appreciable.