Document Type : Original Article
1 Expert in the protection and exploitation of surface water، Regional water company of CHB
2 Department of Natural Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord City, Iran
Curve number is a dimensionless empirical method for predicting direct runoff. Since river discharge and sediment load are highly connected thus the relationship between runoff and bed load could be used to evaluate the continuous sediment load. This study proposes a new curve number that characterizes this parameter based on redefined lookup tables and a fuzzy approach for calculating sediment load. The developed distributed monthly Fuzzy Curve Number Sediment Simulation(CNS2) in Python was applied to predict runoff and sediment load using the rating curve concept. The model uses the fuzzy curve number and some factors such as the number of rainy days, the management of RUSLE-3D, slope, teta coefficient, and soil texture for simulating sediment load at a monthly time scale. The results of model sensitivity analysis indicated that rainfall, base-flow and runoff were the most critical factors affecting sediment load in the study area of interest. The Nash-Sutcliff index evaluated the effectiveness of the simulated runoff; the calculated metric value was 0.6 and 0.53 during two calibration and validation periods, respectively. The Nash-Sutcliff index for simulated sediment load was 0.54 and 0.43 during the calibration and validation periods, respectively. The distributed structure of the developed model provides the possibility for improving estimating spatial variability of sediment yield over the basins; therefore, it can capture the heterogeneity in affecting factors for sediment production.