Discharge and Sediment Transport Modeling before and after the Construction of a Dam at the Inlet of a Basin

The purpose of this study is the simulation of runoff and sediment transport in the basin of the Nestos River, Northern Greece, downstream of the Platanovrisi dam, whose construction was completed in 1997. The basin is predominantly forested and its area is 884 km(2). The model used for the simulation was AnnAGNPS, which is based on the Revised Universal Soil Loss Equation (RUSLE), combined with a GIS interface. AnnAGNPS requires daily rainfall and climatic data and should be calibrated and validated before its use. The purpose of calibration was to obtain values of K factor, for which the difference between simulated and measured values of discharge and sediment yield for year 1980 was minimum. The model was validated comparing simulated and measured values of discharge and sediment yield for year 1981, using the K factor values obtained from the calibration. Two different simulations were conducted, one for the years 1980-1990 and another for the period 2006-2030, before and after the construction of the dam, respectively. For the simulation for the period 1980-1990, existing meteorological data available on a daily basis were employed, and the results were in good agreement with those of a different study. The simulation for the period 2006-2030 was based on rainfall and climatic data generated from the software packages GLIMCLIM and ClimGen. The mean discharge was by 5% lower and the mean annual sediment yield by 20% lower than the corresponding values for the period 1980-1990.