Estimation of Mean Annual Precipitation in Wyoming Using Geostatistical Analysis

Precipitation is a function of many topographical land features as well as geographical locations. Spatial correlations between precipitation and topographical and geographical features can be used to improve estimation of precipitation distributions. In this study, kriging with external drift of topographical information was utilized for determining precipitation spatial distributions in Wyoming. Relationships between precipitation and elevation, slope, exposure, latitude, and longitude were used to improve the precipitation estimation. Application of the relationships in the external drift kriging resulted in reduction of kriging variance about 30 to 40% in different parts of the studied area with the maximum reduction up to 70%. The method was especially useful in mountain areas sparsely covered with observations. The external drift kriging allowed to utilize geographical coordinates in the estimation. The addition of geographical coordinates resulted in reducing kriging variance about 54% and increasing the correlation coefficient between observed and estimated values from 0.4 to 0.8 for the precipitation estimation.