Spatial Estimation of Regional Crop Evapotranspiration

Current methods of computing regional crop evapotranspiration (ET), the prime variable in estimating irrigation demand, largely ignore the spatial variability of ET parameters, thus introducing errors. In this research, a method was developed to estimate regional ET while considering the spatial variability of parameters. To consider this variability, spatial databases were developed for agricultural land-use, relevant climatic parameters, and topographic data using geographic information systems (GIS). Analytical GIS functions of map algebra and map overlay were used to calculate regional crop ET for the Cache la Poudre Basin in Colorado. The Cache la Poudre Basin was selected as the study area due to the availability of ground truthed land-use survey data. This research uses land-use classification, climatic variables and elevation adjustments to determine the value of using a spatial/GIS approach instead of current nonspatial approaches.