Abstract
Abstract. This study analyses the impact of vertical model discretisation on modelling snow covered area and the consequential effects on runoff formation of the semi-distributed water balance model HQsim. Therefore, the parameters relevant for snow modelling are varied within the frame of a uniformly distributed Monte Carlo Simulation (MCS). Since the model is based on the hydrological response unit (HRU) approach, the effect of building the HRUs with different elevation steps (250 m and 500 m) is tested for two alpine catchments. In total 5000 parameter combinations were generated for simulation. The results of modelled snow covered area were compared with thirty MODIS (Moderate Resolution Imaging Spectroradiometer) snow cover maps for the melting periods in 2003–2011. Based on a contingency table the comparisons were evaluated by different skill measures. Finally, the pareto optimal parameter settings of each skill measure were detected. Evaluation of runoff variability within the MCS and their pareto optimal runs show reduced variances of model output resulting from an improved simulation of the snow covered area.
Highlights
Snow represents an important component of the hydrological cycle
We identified the pareto optimal parameter settings (Gupta et al, 2005) of each of the five skill measures
The aim of this study is to analyse the impact of the vertical model discretisation on the variability of runoff, which are introduced by the correctness of the modelled snow covered area
Summary
Snow represents an important component of the hydrological cycle. For mountain regions the snow influences runoff generation in several ways. Precipitation, stored as snow in winter, contributes essentially to runoff generation in spring and early summer. Snow has the potential to affect flood events. By storing melt water and rain, unsaturated snow acts as a buffer reducing the runoff (Schober et al, 2012). When rain and snowmelt add up, the runoff may increase rapidly (Weingartner et al, 2003; Woo, 2005). The estimation of snow is a considerable factor for rainfall-runoff modelling, especially for flood forecasting in alpine catchments
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