Radar Precipitation Estimates for a Soil Water Balance

Abstract

ABSTRACT MANY agriculturally-related decisions require accurate and timely information concerning soil water status and its impact upon crop growth and development. The inherent spatial variability of precipitation makes it difficult to obtain detailed and timely information on aerial precipitation totals for determining soil water status. Relationships, stratified by time of year and precipitation type, to estimate precipitation for an area were developed from National Weather Service radar data and/or data from a single rain gage. These relationships were used to estimate daily and weekly precipitation totals for input into a soil water balance model and comparisons were made between soil water values calculated using measured on-site precipitation and using precipitation estimated with the developed relationships. Errors in estimating daily and weekly aerial precipitation totals from radar data and/or from a single gage were large. When precipitation estimates were input to a water balance, soil water errors were reduced relative to precipitation errors. Soil water errors were the same whether daily or weekly precipitation estimates were used as water balance inputs. Soil water values computed for a location with estimated precipitation were consistently below measured soil water values because of underestimated early season precipitation. A single gage used to estimate aerial precipitation totals was as accurate as using the gage and the National Weather Service radar data.