Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 11 4 2007 10.5194/hess-11-1323-2007 http://www.hydrol-earth-syst-sci.net/11/1323/2007/ http://www.hydrol-earth-syst-sci.net/11/1323/2007/hess-11-1323-2007.html http://www.hydrol-earth-syst-sci.net/11/1323/2007/hess-11-1323-2007.pdf 1323 1339 2007-05-15 Implementation of a process-based catchment model in a poorly gauged, highly glacierized Himalayan headwater M. Konz markus.konz@stud.unibas.ch S. Uhlenbrook L. Braun A. Shrestha S. Demuth University of Basel, Department of Environmental Sciences, Applied and Environmental Geology, Basel, Switzerland UNESCO-IHE, Department of Water Engineering, Delft, The Netherlands Bavarian Academy of Sciences, Commission of Glaciology, Munich, Germany Department of Hydrology and Meteorology, Snow and Glacier Hydrology Unit, Katmandu, Nepal University of Freiburg, Institute of Hydrology, Freiburg, Germany IHP/HWRP Secretariat, Federal Institute of Hydrology, Koblenz, Germany The paper presents a catchment modeling approach for remote glacierized Himalayan catchments. The distributed catchment model TAC^D, which is widely based on the HBV model, was further developed for the application in highly glacierized catchments on a daily timestep and applied to the Nepalese Himalayan headwater Langtang Khola (360 km²). Low laying reference stations are taken for temperature extrapolation applying a second order polynomial function. Probability based statistical methods enable bridging data gaps in daily precipitation time series and the redistribution of cumulated precipitation sums over the previous days. Snow and ice melt was calculated in a distributed way based on the temperature-index method employing calculated daily potential sunshine durations. Different melting conditions of snow and ice and melting of ice under debris layers were considered. The spatial delineation of hydrological response units was achieved by taking topographic and physiographic information from maps and satellite images into account, and enabled to incorporate process knowledge into the model. Simulation results demonstrated that the model is able to simulate daily discharge for a period of 10 years and point glacier mass balances observed in the research area with an adequate reliability. 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