Water Balance of Forested Mountainous Watersheds using Satellite Derived Actual Evapotranspiration

Abstract

The use of actual evapotranspiration derived by satellite data at watershed scale in water balance modelling of forested mountainous watersheds is studied. Mean monthly maximum composites of the Normalized Difference Vegetation Index (NDVI), derived from the National Oceanic and Atmospheric Administration's (NOAA) / Advanced Very High Resolution Radiometer (AVHRR) were correlated with monthly actual evapotranspiration rates estimated by a water balance model. The water balance model was applied to three mountainous and forested watersheds of Central Thessaly in Greece and the actual basin-wide evapotranspiration was estimated using two methods for the estimation of basin wide precipitation and two methods of potential evapotranspiration. The derived values of actual evapotranspiration were then correlated to NDVI data, and the developed equations were validated temporally and spatially. The actual evapotranspiration estimates, derived from NDVI and used in the water balance model, resulted in equally accurate simulations of monthly runoff when compared with the simulations acquired from the classical application of water balance model.