Utilization of PISA Model and Deduced Specific Degradation Over Semi-arid Catchment: Case of Abdelmomen Dam in Souss Basin (Morocco)

Rainfall-runoff soil erosion is the most frequent form of land degradation. Soil erosion and sediment yield assessment are essential to develop suitable land and water resource management practices. Siltation impact assessment plays a major part in the choice of sustainable development projects for watershed management and can be thus a base to plan appropriate strategies for decision-makers to avoid soil erosion risks and consequently lengthen dams’ life. The current study aims to estimate annual sediments deposit in the Abdelmomen dam, Morocco, using the Previsioni Interimento Serbatoi Artificiali (PISA) model integrated with GIS. Various geospatial layers were used, including ALOS Digital Terrain Model (DTM), historical climate data, high-resolution ESRI land use land cover (LULC) map, etc. The PISA-based model results reveal an average annual degradation of 1044,71m3/km2/yr is estimated, which is equivalent to a soil erosion rate of about 14.62 t/ha/yr, and to a total annual potential soil loss of 1,900,600 (t y−1). These results are significantly higher than that measured in situ by a bathymetric survey (Er), where the ratio Y(PISA)/E(Er) is about 1.24. This model overestimates soil erosion in the study area, as well as for other studies, areas in the Greater Maghreb. In general, the application of the PISA-based model has until now not provided very satisfying results for the prediction of soil loss for large-sized catchments and still encounters severe problems. This model allows an indirect assessment of water erosion and the scope of degradation and soil loss on the siltation of the dam lake. Further, a moderate hazard of water erosion was found throughout the study area. Moreover, the highly eroded areas, which are quite frequented over the study area, require delineation and immediate action. These findings can help the water resource managers to develop a new insight from a multi-scale approach and a new model for delineation of vulnerable areas to water erosion, especially, in mountain regions.