Decision Support System for Estimation of Regional Evapotranspiration in arid areas: Application to the Republic of Yemen

Evapotranspiration (ET) constitutes an important component of the water fluxes of the hydrosphere and the atmosphere. It is a process of the result of complex interaction between water and energy fluxes subjected to changing atmospheric, soil and vegetation conditions. These complex variations complicate our attempt to quantify the ET at a regional scale adequately. This study is an attempt to develop a regional reference evaporation model, which can be used as a Decision Support System (DSS) to estimate daily ET for hydrological and agricultural planning aspect. The model was envisaged to estimate daily reference potential ET (PET) and actual ET (AET) from the existing limited data applying by any of the available ET methods such as modified SEBAL biophysical models, Temperature based, Radiation based and combination method. Soil Energy Balance Algorithm for Land (SEBAL) model and biophysical model ware used to estimation ET from remote sensing, and traditional models were used Stochastic Time series model to transfer information from gauged to ungauged location (grid raster). The procedure involves estimation of PET and AET using any one of the ET methods, standardization of all methods to FAO Penman Monteath model estimates, deriving regional parameters to be used in case of complete lack of data in all the variables and the model was effectively used to estimate regional average ET for hydrologic models. a Decision Support System proposed in this study used handle the selection of the best or most probable model for estimating ET in the study areas.