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

Abstract

Measuring soil hydraulic properties is a costly and time consuming task, especially when these are needed for large areas in e.g. application of physically-based distributed hydrological models on a catchment scale. The use of 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 parameters, (i) derived from lab measurements, (ii) calculated with PTF using USDA texture figures. and (iii) calculated with PTF using USDA texture figures, is compared and evaluated on their resulting uncertainty on the different 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 hydraulic parameters from the three methods. Depending on the fact whether a certain model output is sensitive to the soil hydraulic parameters, different results can be found for the simulated discharge, groundwater head and soil water content.