Parameter calibration is one of the most relevant issues in application of hydrological models. One reason for this is that many acceptable parameterizations can be found in the application of watershed models (equifinality) causing uncertainty in simulation and prediction. The “equifinality” issue in hydrology calls for methods that are powerful enough to evaluate and correct models and therefore must be ‘diagnostic’, i.e., capable of pointing to what degree a realistic representation of the real world has been achieved and how the model should be improved (Spear and Horberger, 1980, Gupta et al. 2008). Due to the high stability of the runoff regime in snow and glacier-melt dominated watersheds, a diagnostic calibration is required to find a realistic representation of the real world.

Usually, climate and runoff are the sole sources for model calibration. However, partitioning the hydrograph into periods when certain processes are dominating the runoff generation could be used to find model parameters only relevant for these processes in the model. In addition, high temporal (hourly) data not being used directly in the model application (daily fluctuation of the stream hydrograph in hourly data) could be used for diagnostic calibration. At the end, the improved parameter calibration will be compared to multi-objective calibration approaches using addition data (snow depth, snow distribution, glacier mass balance) to evaluate the potential of the diagnostic calibration approach.

Within the KHR Project “Snow and glacier melt contribution to the discharge of the river Rhine and its tributaries with regards to the changing climate” a range of study watershed have been ranging from highly glacierized to snow dominated watershed in the Swiss Alps. All necessary data (Climate, hydrology, catchment characteristics) have been combined and are available to be used in this Master project. A new version of the HBV model will be used that includes a glacier runoff module as well as different methods to include additional data for a multi-objective model calibration. The student will develop a new diagnostic approach by partitioning the hydrograph and using hourly hydrograph data to better inform the calibration of model parameters. The approach will be tested in several watershed to evaluate the potential of the new approach.

Markus Weiler in cooperation with University of Zürich, CH.

Integration into the international research project “Snow and glacier melt contribution to the discharge of the river Rhine and its tributaries with regards to the changing climate”

Markus Weiler markus.weiler@hydrology.uni-freiburg.de Tel. +49 (0)761 / 203-3530

Watershed Modelling, sensitivity analysis, R

German or English

Gupta, H. V., Wagener, T. and Liu, Y.: Reconciling theory with observations:elements of a diagnostic approach to model evaluation, Hydrol. Process., 22,3802-3813, 2008.

Spear, R. C. and Hornberger, G. M.: Eutrophication in peel inlet—II. Identification of critical uncertainties via generalized sensitivity analysis, Water Research, 14, 43-49, 1980.

Yilmaz, K. K., Gupta, H. V. and Wagener, T.: A process-based diagnostic approach to model evaluation: Application to the NWS distributed hydrologic model, Water Resour. Res., 44, W09417, doi:10.1029/2007WR006716. 2008.