Application of SWAT model to estimate the annual runoff and sediment of Duhok reservoir watershed

Estimation of runoff volume and sediment load is a problem that directly affects the performance of dams due to the reduction in the storage capacity of their reservoirs and their effect on dam efficiency and operation schedule. The simulation models can be considered for evaluation of sediment potential if the continuous field measurements are not available. Soil and Water Assessment Tool (SWAT) was applied to estimate the annual runoff volume and sediment load for Duhok Dam Reservoir in north of Duhok/Iraq for the period 1988–2011. The estimated annual runoff volume varied from 2.6 to 34.7 MCM. Those values are affected by rainfall depth, intensity and runoff coefficient, while the annual runoff coefficient for the studied area ranged from 0.06 to 0.33 (average is 0.19) causing an average runoff volume of 14.3 MCM. The sediment routing indicated that the values of sediment yields varied from 50 to 1400 t/km2/year depending on sub basin properties. The average annual sediment load from the whole watershed was 124.6 *103 ton. The estimated total sediment arrived to Duhok Reservoir for the considered period 1988–2011 was about 2.99*106 ton. Santos et al. 2010 applied these models and got good results on Apucaraninha River watershed in southern of Brazil. Doughlas-Mankin et al. 2010 reviewed and introduced a number of selected papers which present and applied the SWAT (soil and water assessment tool). Other researchers (Jain 2010; Betrie et al, 2011; Mohammad et al. 2012; Shawul et al. 2013) used the SWAT model to predict sediment transport and generally, the overall results of the SWAT model were reasonable. In this research the SWAT model was applied to evaluate the total sediment load accumulated in its reservoir since its operation in 1988 untill 2011. There are number of studies which were carried out concerning Duhok Dam and its reservoir. Mustafa and Noori 2013 applied the remote sensing technique and geographical information system to assess the change in water surface area of Duhok Dam reservoir for the period 2001 to 2012. Issazadeh & Govay 2014 applied Artificial Neural Network (ANN) of three layer back propagation to model the sediment load of Duhok Dam. The measured time series data of flow for the period 2010–2011 were considered as input, while the sediment loads represents the results of model output. Sulaiman 2010 applied a technique to estimate the sediment concentration at the outlet of Duhok