Annual Runoff and Sediment in Duhok Reservoir Watershed Using SWAT and WEPP Models

Estimation of runoff volume and sediment load is the main problem that 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 this purpose if the continuous field measurements are not available. Soil and Water Assessment Tool (SWAT) and Water Erosion Prediction Project (WEPP) models were 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 2.3 to 34.7 MCM for considered period. Those values were affected by rainfall depth, intensity and runoff coefficient. The resultant annual runoff coefficient for the studied area ranged from 0.05 to 0.35 (average was 0.18) causing an average runoff volume of about 14 MCM. The results of 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 is about 120 × 103 ton. The estimated total sediment arrived to Duhok Reservoir for the considered period 1988-2011 was about 2.9 × 106 ton. The results indicate that both models gave reasonable results in comparison with measured values. Based on statistical criteria, the results of both models are close to gather.

Performance evaluation of a water erosion tracer using plot-scale experiments and process-based modeling

Socioeconomic and environmental losses caused by water erosion have highlighted the importance of quantifying and understanding the dynamics of soil redistribution in the landscape to develop effective soil management practices.Several methods are applied to estimate erosion/deposition rates and identify sources of sediments,among them,the one that uses rare earth elements(REE)as a tracer stands out.However,an alternative not yet explored that can benefit the accuracy of the estimates provided by the method is using a tracer containing a chemical signature composed of more than one REE.The present study aimed to evaluate the performance of a new water erosion tracer based on montmoril-lonite labeled with rare earth elements(La40-MMT).The innovative aspects of this La40-MMT tracer include its highly stable multi-chemical signature(Nd^(3+),La^(3+),and Pr^(3+)),which enhances tracer detection in the environment,and its low production cost due to the use of an industrial residue in the synthesis process.The tracer was evaluated for a typical soil of the Cerrado biome,using a natural rainfall field-scale plot-NRFP(5 m × 20 m)and a physical predictive erosion model(WEPP).The results showed that the La40-MMT tracer could be used to estimate erosion/deposition rates,with agreement between the values observed with the tracer and the WEPP model.Thus,this study confirmed the great potential of La40-MMT as a tool to identify patterns of soil redistribution at the field scale and aid in the validation of erosion models.