Résumé
A limited number of studies have been conducted in Morocco to estimate dams siltation rate based on suspended solids concentration (SSC) field measurements. The present article provides an evaluation of the siltation rate through an inventory of field measurements data which has been collected upstream of Sidi Mohamed Ben Abdellah (SMBA) Dam reservoir. The analysis was based on measurements performed according to a predefined protocol at four hydrological stations located immediately upstream of the dam during the hydrological years of 2016/2017 and 2017/2018. The analysis was also based on several bathymetric field surveys performed throughout the reservoir area since the construction of the dam. Field measurements show that recorded sedimentation depth at the four stations during the first year was 14% higher than the second year although it had an excess of rainfall and runoff compared to the first year. Estimated correlation coefficients between flow rates and suspended solids concentration was ranging from 0.20 to 0.42. Those between solids and liquids flow rates have higher correlation coefficients ranging from 0.75 to 0.91. Seasonal analysis and the adoption of the threshold did not improve significantly the relationships between these parameters. Moreover, only 18% of the dam siltation originates from upstream sources. The main hypothesis that we can formulate is that the dam's sediments most likely come from the erosion of its banks.