Improved simulation of evapotranspiration for land use and climate change impact analysis at catchment scale

Evapotranspiration is not only one of the major components of the hydrological cycle, it also controls impacts of drivers such as climate and land use changes. One of the widely used simulation tools for climate and impact studies is the Soil and W ater Assessment Tool (SW AT). This study evaluates the evapotranspiration processes in SWAT in the Kenyan Mau forest within the Mara basin that drains to Lake Victoria. The study reveals that typical SWAT applications have flaws as in the implementation or parameterisation of tropical forests. To improve the use of SWAT for land use and climate change studies, the following adaptations were done for the Mau forest. First, the monthly values of Remote Sensing observations of Leaf Area Index were put directly in the SWAT model, to replace the erroneous SWAT simulations. Next, the plant parameters were further adjusted. The results show that correct LAI and parameterisation results in a significant increase of the evapotranspiration in forested areas, and resulting in higher correlations with MODIS products for evapotranspiration.