Sequential Development of a Conceptual Hydrological Model Considering Alpine Basin Processes

In the frame of an applied research project the authors had to develop a runoff forecast tool to enable a prediction of the hydropower potential with a lead time of four days. Therefore procedures for runoff, snow accumulation and snowmelt were sequentially generated, leading to model types ranging from a statistical approach via one storage/single outflow type, one storage/two outflow model to a two storage/triple outflow concept. This contribution presents a procedure to adapt model complexity as far as necessary to improve runoff simulation while still keeping the type of a parsimonious, conceptual model. The improvements of the results are interpreted in terms of hydrological process consideration and are evaluated by means of temporal efficiency criteria like the Nash-Sutcliffe and the correlation coefficients. The seasonality of alpine runoff processes could only be achieved with consideration of snowmelt and evaporation concepts. The model reliability increased with increasing model complexity but the increment of goodness was reduced and thus makes the choice of an appropriate model type dependant from the final application demands.