sedigeh mohamadi; Ali Salajegheh; Hassan Ahmadi; Jamal Ghoddousi; Ali Kianirad
Abstract
Suspended sediment load is the biggest non-point pollution source and a major factor of degradation of surface water quality. Because of hydraulic models of sediment transport can not predict the suspended sediment load, sediment rating curves as usual hydrological methods are utilized spread for this ...
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Suspended sediment load is the biggest non-point pollution source and a major factor of degradation of surface water quality. Because of hydraulic models of sediment transport can not predict the suspended sediment load, sediment rating curves as usual hydrological methods are utilized spread for this goal. Cause of regression equations of rating curve have a lot of bias due to logarithmic convert, correction factors in optimization of sediment rating curve were used for eliminating of logarithmic conversion effect and bias of extrapolation in 20 hydrometric stations in up streams and major rivers of Sefidrood watershed. Comparing of 9 rating curve methods as one-linear, one-linear with correction factors as CF1, CF2, FAO, two-linear, mean loads within discharge classes, mean loads within discharge classes with correction factors as CF1, CF2 and FAO was conducted by RMSE and NASH criteria. Results showed that mean loads within discharge classes, mean loads within discharge classes with CF1 and CF2 correction factors have the most fitting to Sefidrood watershed stations. Our findings illustrated that CF1 and CF2 correction factors in majority of stations have compensated underestimation of rating curves and increased efficiency of models. Power of equation between sediment load and area was more than of one. According to results 30 million ton suspended sediment load enter to reservior of Sefidrood dam annually. Key words: sediment rating curve, Sefidrood, model efficiency, logarithmic conversion, NASH criteria.
yahya Parvizi; mohammad gheitury; Mosieb Heshmati
Abstract
The WEPP physically model is able to dynamically simulate runoff and soil erosion using physical concepts of erosion and hydraulic of overland flow science considering plant growth, residue decomposition, winter process. Determination of the capability of this model in runoff and erosion estimation in ...
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The WEPP physically model is able to dynamically simulate runoff and soil erosion using physical concepts of erosion and hydraulic of overland flow science considering plant growth, residue decomposition, winter process. Determination of the capability of this model in runoff and erosion estimation in different range type with investigation the effects of management were the main objectives of this research. This research was conducted in the Kabode placed across the Gharasoo watershed by installing erosion plot with dimension of 10×3 meter and three replications in three range types at the slopes of 25, 35 and 45%. Climate data including rainfall and air temperature was recorded in the site and additional data including wind velocity and direction, solar radiation and dew point temperature was prepared from Kermanshah synoptic climate station. Event based erosion and runoff was simulated in each plot by the v2008.9 version of the model. Results from model assessment for prediction of runoff indicated that the maximum model accuracy was in 45% slope. Also, mode relative error in runoff in 25 and 35% slope was about 0.61 liter. Overall, model performance in runoff estimation was sought in all three slopes, so that Nash-Sutcliff index was 0.96 to 0.73. Minimum and maximum estimation error in erosion prediction was occurred in 35 and 45% slope, respectively. Model prediction results indicated under-estimation in all the slopes. Negative amounts of Nash-Sutcliff index indicated confirms the low efficiency model especially in conditions prevailing in two slopes of 25 and 35%.
