Simulation of the hydro-sedimentary balance assessment of a little dam in Mediterranean marly zone (Saboun’s dam, Morocco)
The objective of the present study was to monitor and simulate the water and sediment balance in a small dam, by using a distributed physical hydrological model to estimate the outflow and the erosion rate of a small marl watershed. The “Mina” model was applied to the Saboun watershed, which is located in north-western Morocco and contains a small dam at its outlet. The simulation was based on the partitioning of the watershed into homogeneous hydrological units, and on infiltration and humidity parameter values deduced from rainfall simulation experiments. The model was validated by comparing the simulated data to hydrological and sedimentation data measured between 1997 and 1999. The analysis of this comparison showed that the model underestimated the watershed outflows for rainfall events that had a high antecedent humidity index (IK > 15 mm), and overestimated the outflows for rainfall events that had a low antecedent humidity index 0 < IK < 15 mm. This observation is explained by the hydrodynamic behaviour of the marl soils, which crack under dry conditions and fill up quickly during wet conditions. To reduce this variability, the initial permeability values were decreased or increased, respectively, for the rainfall events with low and high antecedent humidity indexes. This resulted in the improvement of simulated volumes by about 80% and a better prediction of the water balance and accumulation of silt in the reservoir upstream from the Saboun dam.