MODELLING RESERVOIR SEDIMENTATION AT BIN EL OUIDANE DAM, MOROCCO

Abstract

This study was conducted in the Oued El Abid watershed upstream of the Bin El
Ouidane dam, in Tadla-Azilal province (Morocco) to quantify the dam siltation
rates. To assess the annual soil erosion and the sediment yield the universal soil
loss equation (USLE) was used. A geographic information system (GIS) was used
to generate and integrate maps of the USLE factors. A spatial distribution of soil
erosion in the Oued El Abid watershed was obtained. The soil erosion was
determined for each rural commune in order to identify the soil erosion hotspot and
estimate the amount of soil that has been transported downstream (Bin El Ouidane
Dam). Soil erosion ranged from very limited values for flat and well covered areas
to over 2100 t /ha/y in mountainous areas with sparse vegetation. The total annual
soil loss within the watershed is estimated at 19. 6 million tons per year. An
equation of sediment delivery ratio (SDR) based on river gradient was calculated.
It was found that the value of SDR at the outlet of the watershed Oued El Abid was
0. 65 with a sediment yield of 12. 74 million tons per year which affect the
durability of the dam.