Model-Based Impact Analysis of Climate and Land Use Changes on the Landscape Water Balance

Changes in the water balance in landscapes can be easily observed by measuring water levels, runoff, etc. Determining the causes of changes in the water balance is much more difficult, because of the complex interrelations between the interacting hydrological processes. However, revealing the causes and processes is necessary to understand the source of changes and to evaluate management options. With the help of modelling and scenario analyses, it is possible to differentiate between the effects of, for example, land use/land cover and climate on the water balance, taking the underlying hydrological processes into consideration. Two case studies are presented: the Ngerengere river catchment in Tanzania, Africa and a forested area in North-East Germany. In these areas the observed water balance has changed considerably in the last few decades. The influence of climate conditions and land use change are analysed and determined with the help of the SWAT model, the WaSiM-ETH model and statistical analyses. Both the suitability and the limitations of this methodology of model-based impact analysis are demonstrated.