Effects of watershed subdivision level on semi-distributed hydrological simulations: case study of the SLURP model applied to the Xiangxi River watershed, China

Abstract

-P., 2013. Effects of watershed subdivision level on semi-distributed hydrological simulations: case study of the SLURP model applied to the Xiangxi River watershed, China. Hydrological Sciences Journal, 59 (1), 108-125. Abstract This study investigates the impacts of watershed subdivision on hydrological simulations. The SLURP (Semi-distributed Land Use-based Runoff Processes) model was employed in the Xiangxi River watershed, China, with eight watershed subdivision schemes. Under each scheme, the SLURP model was calibrated using both manual and automatic methods to simulate watershed hydrological processes over the period 1991-1998. The results indicate that model performance could be enhanced by increasing the degree of subdivision. However, there is a threshold level, beyond which no significant improvements can be obtained. The simulated water balance components and runoff contributions from different land types were found to vary among subdivision levels. Differences were slight when the watershed was divided into more than 73 sub-watersheds. These results were partly caused by the altitude-based precipitation correction, where the reduced generalization of terrain characteristics could lead to increasing consideration of small watersheds in the weighted Thiessen polygon technique; thus, the elevation-correction adjustments in deriving distributed meteorological inputs were increased. Parameter sensitivity analysis revealed that increasing the subdivision level was likely to enhance model efficiency. However, the difference became negligible among fine subdivisions. Although a threshold was identified in this study, determination of an appropriate subdivision level should also be based on the modelling objective, the quality of model inputs, the complexity of the watershed system and the resulting uncertainty.Key words hydrological modelling; sub-watershed; water balance component; land type; sensitivity; Three Gorges Reservoir Effets du niveau de subdivision du bassin versant sur les simulations hydrologiques semidistribuées: étude de cas sur le modèle SLURP appliqué au bassin versant de la rivière Xiangxi en Chine Résumé Cette étude examine les effets de la subdivision du bassin versant sur les simulations hydrologiques. Pour cela, nous avons appliqué le modèle SLURP (Semi-distributed Land Use-based Runoff ProcessesProcessus de ruissellement semi-distribués basés sur l'utilisation des sols) au bassin versant de la rivière Xiangxi avec huit schémas de subdivision du bassin. Pour chaque schéma, le modèle SLURP a été calé en utilisant des méthodes manuelles et automatiques pour simuler les processus hydrologiques du bassin au cours de la période 1991-1998. Les résultats indiquent que les performances du modèle ont pu être améliorées en augmentant le nombre de subdivisions. Cependant, il existe un seuil au-delà duquel aucune amélioration significative n'a pu être obtenue. Nous avons trouvé que les composantes du bilan hydrologique simulé et les contributions au ruissellement des types de sols varient selo...

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