Evaluation of Sediment Deposition in a Mediterranean Reservoir: Comparison of Long Term Bathymetric Measurements and SWAT Estimations

This study aims to demonstrate that the SWAT model can be used to predict discharge and sediment yield values in reservoir contributing catchments helping also to define the main factors that determine sedimentation rates in semi-arid Mediterranean environments. This aim was achieved by comparing SWAT simulation results with water flows (over 29 years) and sediment deposition (over 47 years) volumes collected (by a campaign of bathymetric surveys) in a Sicilian reservoir. The mean monthly runoff coefficient calculated for the period 1980–2008 was 0·17. The mean sedimentation volume in the reservoir during the period 1963–2009 was 51,000 m3 year−1. Field surveys and collection of spatially distributed databases of soil, topography and climate were carried out in order to characterize the contributing catchment. The SWAT model was applied to simulate sediment volumes cumulated over group of years as well as water flow volumes reaching annual and monthly the reservoir. The performance of the hydrological and erosion components of the model was evaluated by a combination of both summary and difference statistical measures after a sensitivity analysis and a calibration/validation process. The model was able to simulate observed runoff volumes at both annual and monthly scale. The mean sedimentation volume simulated by SWAT during the whole period was 8·1% lower than the value obtained by the bathymetric measurements (equal to 72·103 Mg) with very good values of the efficiency coefficient (equal to 0·91).