WWRC 96-04
Estimation of Mean Annual Precipitation in Wyoming Using Geostatistical Analysis
Abstract
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.
96-04 Table of Contents
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