The validation of a modelling system for calculating water balance and catchment discharge using simple techniques based on field data and remote sensing data

In a regional case study, simulation runs of a simple hydrological conceptual catchment model were performed using a spatial data set, which covers a mesoscale catchment located at the moraine landscape of North-East Germany. This data set consists of a soil map, rivernet, landuse map, digital elevation model as well as meteorological time series. Furthermore for 3 years, a survey of the actual crop distribution in the catchment were carried out. The simulations cover the time period from 1993 to 1997. At first, the simulation quality of the model was estimated by comparing measured daily evapotranspiration rates, soil water contents and discharge rates with the corresponding simulated model outputs. Additionally, four Landsat-TM-Scenes covering the catchment were used to calculate the Normalized Difference Vegetation Index (NDVI). The NDVI was used for the estimation of the spatial distributions of transpiration rates. These data were used to check the simulated regional distributions of transpiration rates. The transpirations rates estimated by NDVI and simulated by the model were in different ranges of 0-1.8 and 0-6.5 mm day−1, respectively. However, the spatial distribution patterns of areas with high and low transpiration rates estimated by NDVI and simulated by the model were identical.