Feasibility Study of Developing a Water Balance Model Using Global Gridded Evapotranspiration Products

Evapotranspiration is one of the most important part of hydrologic cycle that sinks the watershed moisture as an outward flux from the existing water resource. Most of the current relationships equation for estimating actual evapotranspiration are empirical, which are based on local condition that their calibration or selection must be based on status of region of interest. The main goal of the current research is the evaluation of the effect of using global gridded evapotranspiration products on the performance of water balance model in Snow-covered region in a mountainous watershed located in western Iran; Gheshlagh watershed. To do this, three global gridded products including GLEAM, SSEbop and MODIS organized in four calibration scenarios (three scenarios using these products and reference model) are evaluated. Finally, due to the need for evaluating the interaction of using these data on structure of water balance models, the uncertainty of the model parameters has been evaluated by GLUE method. Simultaneous calibration results of evapotranspiration and runoff showed that model operation is better once using GLEAM and SSEbop products. In all scenarios, GLEAM had best function that improved runoff simulation.