Application of satellite data in the quantitative assessment of evapotranspiration in northeastern Poland

Abstract

We describe a method of calculating one of the basic phenomena influenced by groundwater recharge, namely evapotranspiration ( ET ). The Operational Simplified Surface Energy Balance (SSEBop) algorithm was applied to calculate actual evapotranspiration ( ET a ), being modified to include spatiotemporal changes of substrate humidity and so referred to as mSSSEBop. Calculations were performed within the Szkwa and Rozoga River catchments (NE Poland). Quantitative ET a assessment was based on the analysis of Landsat satellite images, hydrometeorological and hydrogeological data. The results obtained for the original SSEBop algorithm and the modified mSSEBop one were compared with the water balance and data from a MOD16A2 dataset. The calculated water balance gave ET a values close to results using mSSEBop (with differences of 9–54 mm/year). In the case of the original algorithm, differences were in range of 42–218 mm/year. When compared with MOD16A2 data, the differences were within the range of –16.7 to 23.2 mm/8 days, with the mSSEBop algorithm giving on average lower ET a sums (~14%) than MOD16A2 while SSEBop gave results higher than MOD16A2 by ~12%. The studies performed indicate that the method presented, using satellite data, gives a reliable, spatial and temporal ET a assessment for the mid latitudes.