Potential Evapotranspiration and Surfacemine Rehabilitation in the Powder River Basin, Wyoming and Montana

Abstract

Energy resource development in the Western United States must contend with the problem of water deficiency resulting from potential evapotranspiration rates which usually exceed precipitation rates. In this report the Blaney-Criddle method, with locally calibrated monthly natural vegetation coefficients, was used to estimate potential evapotranspiration (PET) for the Powder River Basin, Wyoming and Montana. In this area PET ranges from 15.02 inches per year to 26.76 inches. A radiation-based method for microclimatic adjustment of PET is presented. According to this procedure it might be expected that, for slopes of 20% inclination at 44° North latitude, annual PET is 17% less on northerly-facing slopes than a horizontal surface and 14% more on southerly-facing slopes.