IMPACT OF SWAT INPUT DATA ON SOIL EROSION IN A SEMI-ARID CATCHMENT
Erosion is a complex and largely widespread phenomenon in the semi-arid countries because of the torrential nature of its rain, their spatial heterogeneity of soils as well as the impact of the human activities. In front of the aggravation observed during the twenty last years, several models of erosion were developed but the need for describing the heterogeneity natural systems makes their application difficult. The main objective of this work aims to study the model of erosion SWAT, a physically based and distributed model developed by the USDA - Agricultural Research Service, applied to the Sarrath Wadi located in the North-West of Tunisia over an area of 1520km². A dam is planned on this catchment. Application of this model requires the preparation of a database containing the digital elevation model, the soil and land occupation layers along with daily weather data. The simulations carried out by the model are based on subdividing the catchment area in units of hydrological response (HRUs) obtained by the combination of the different prepared cartographic layers. The input data can influence the coherence and the precision of the results obtained by modelling. Thus, we are interested in this article to evaluate the impact of two key input parameters on simulation of the sediment yield. These are the number of HRUs as well as the spatial variability of rainfall. The study of the first parameter consists in changing the mode of dividing the area into sub-basins and HRUs which induced an influence on the lengths of the water courses, on the variation of time of concentration and consequently on sediment yields. As for rainfall, we showed that the use of various scenarios of rain gages distribution influenced the determination of the soil losses.
SWAT; erosion; input data