Evapotranspiration Parameters Research Articles

Spatial and Temporal Errors in Estimating Regional Evapotranspiration

Current methods of computing regional crop evapotranspiration (ET), the prime variable in estimating irrigation demand, largely ignore the spatial and temporal variability of ET parameters, thus introducing errors. In this research, a methodology was developed to estimate regional ET while considering the spatial and temporal 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). The Cache la Poudre Basin was selected as the study area due to the availability of field verified land-use survey data. A spatial simulation ET model (GISETMA) was used to develop a baseline estimation of regional ET, incorporating analytical GIS functions of map algebra and map overlay to calculate ET for each field in the system and for each day of the growing season. Various scenarios were developed and compared to the baseline scenario to explore spatial and temporal errors from point estimate of climate data and weather station use, daily versus monthly time-steps, and land-use classification.

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.

Calibrating the USDAHL Hydrologic Model on Grassland Watersheds

ABSTRACT THE USDAHL model was calibrated on a 6.3 ha grassland watershed using three different methods. The vegetative parameter, A, depression storage parameter, VD, evapotranspiration parameter, ET/EP, and groundwater recharge parameter, GR, were varied until each type of calibration was accomplished. Then to evaluate the types of calibration, the parameter values were transferred to a 7.8 ha grassland watershed without further manipulation. The Type II calibration proved best by predicting runoff with a 1.7 percent error on the second watershed. The Type II parameter values were A = 0.6, VD = 1.27 mm, ET/EP = 0.88 and GR = 0.0229 mm.