Estimation of crop evapotranspiration through spatial distributed crop coefficient in a semi-arid environment

Accurate and reliable estimation of reference crop evapotranspiration (ETo) is important due to its critical role in determining crop water requirement in irrigated agriculture. The aim of the paper was to estimate the evapotranspiration (ETc) using spatially distributed crop coefficient (K-c) and open access earth observing datasets in a semi-arid environment. We have estimated the actual evapotranspiration (ETc) based on spatially distributed crop coefficient K-c using following models namely Surface Energy Balance Algorithm for Land (SEBAL), Makkink model, Hargreaves and Samani model, Camargo method and Jensen-Haise model. Further, these models estimates were compared with Penman-Monteith estimate. Comparative evaluation of models was performed through statistical tests, and it was found that the Makkink model performed satisfactory compared with standard Penman-Monteith model estimate (R-2= 0.88). Leaf area index (LAI) and the K-c was in strong (second order polynomial) relationship (R-2= 0.98). The analysis also shows distributed actual evapotranspiration based on Makkink model has good agreement with actual evapotranspiration from Penman-Monteith with R-2 of 0.84, respectively, for the study area. The finding suggests that the Makkink model estimates ETo are very close to the universally accepted Penman-Monteith model based ETo.