The influence of different methods to derive soil hydraulic properties on the uncertainty of various model outputs of a distributed hydrological model

Measuring soil hydraulic properties is a costly and time consuming task, es pecially when these are needed for large areas in e.g. application of physi cally-based distributed hydrological models on a catchment scale. The use o f pedo-transfer-functions (PTF) to derive the soil hydraulic parameters can be a suitable solution. In this study the spatial uncertainty involved with the soil hydraulic para meters, (i) derived from lab measurements, (ii) calculated with PTF using f ield texture measurements and (iii) calculated with PTF using USDA texture figures, is compared and evaluated on their resulting uncertainty on the di fferent model outputs of a physically-based distributed hydrological model. A Latin Hypercube Simulation with MIKE SHE as the distributed hydrological model was performed for a small catchment in Germany using the soil hydrau lic parameters from the three methods. Depending on the fact whether a cert ain model output is sensitive to the soil hydraulic parameters, different r esults can be found for the simulated discharge, groundwater head and soil water content. (C) 2000 Elsevier Science Ltd. All lights reserved.