Hamzeh Noor; Mahmood Arabkhedri; yahya parvizi
Abstract
IntroductionImplementation of watershed management measures in Iran to reduce the damage caused by the misuse of natural resources has begun many years ago and is still ongoing. Evaluating the performance of previous remedial work is essential for better planning of future watershed management projects. ...
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IntroductionImplementation of watershed management measures in Iran to reduce the damage caused by the misuse of natural resources has begun many years ago and is still ongoing. Evaluating the performance of previous remedial work is essential for better planning of future watershed management projects. In this regard, due to the monitoring of soil loss, runoff and sedimentation at slope and watershed scales, a suitable platform has been provided to assess the effects of watershed management measures. Material and methodsThe Kakhk paired watershed with an area of 217 ha is located at a distance of 300 km from Mashhad City and 35 km southwest of Gonabad City.The Kakhk paired watershed consists of two sub-watershds, the control and the treatment. A series of biological and structural watershed management measures have been implemented in the treatment sub-watershed. While the control sub-watershed is exploited according to the custom of the region. In this research, the impact of different watershed management measures on the soil loss, sediment yield and hydrology in the Kakhk paired watershed were evaluated. For this purpose, the recorded data of suspended sediment and discharge at the watershed scale, as well as the data of soil loss (by standard plots and erosion pins) and runoff (standard plots) were analyzed at the hillslope scale. Results and discussionThe results at plot scale showed that the average annual soil loss of the two treatment and control sub-watersheds is 0.05 and 0.27 ton.ha-1.y-1, respectively. These results indicate that the soil loss in the control sub-watershed is 536% higher than the treatment sub-watershed. The amount of runoff yield in the control sub-watershed was calculated to be 138% more than the treatment sub-watershed. At watershed scale, the results showed that the total amount of suspended sediment output from the control and treatment watersheds is 379 and 85 tons, respectively, which indicates the average specific sediment of 0.4 and 0.1 ton.ha-1 in the control and treatment watersheds, respectively. The volume of runoff in the control sub-watershed is 1.3 times more than treatment sub-watershed. On the other hand, despite the difference between the treatment and control sub-watersheds in soil loss, run-off production and sediment yield, the role of maximum events in soil erosion and runoff production in both sub-watersheds is very significant. So that one to three erosive events in both studied sub-watershes are responsible for more than 80% of the soil loss in the slopes and the production of runoff and sediment yield of watersheds. ConclusionThe results showed that a total of 136,000 m3 of runoff storage and 294 ton of suspended sediment control were achieved as a result of watershed operations in the treatment sub-watershed. Therefore, it can be stated that the watershed management measures carried out in the treatment sub-watershed on the one hand have reduced soil erosion and runoff production on the slopes compared to the control sub-watershed. This action has been done through increasing the vegetation, increasing the roughness of the land surface, reducing the carrying capacity of the flow and settling the materials being transported. Further, the flow from the slopes enters the waterway and is kept by watershed management structures, and as a result, the sediment yield and volume of runoff in the treatment sub-watershed is less than the control sub-watershed.
Mahmoudreza Tabatabaei; Amin Salehpour Jam
Abstract
Relationships between river water quality parameters and physical, geochemical and biological processes carried between basin resources (soil, vegetation, geology, land use, etc.), meteorological variables (temperature, precipitation, snowmelt, etc.), River hydrological variables (flow discharge), as ...
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Relationships between river water quality parameters and physical, geochemical and biological processes carried between basin resources (soil, vegetation, geology, land use, etc.), meteorological variables (temperature, precipitation, snowmelt, etc.), River hydrological variables (flow discharge), as well as human interventions are often very complex, nonlinear and non–deterministic in a way that makes their complete understanding impossible. In this situation, the use of computational intelligence (such as artificial neural networks) is a useful tool in simulating and estimating river water quality variables such as suspended sediment load. In the present study, by combining open source GIS libraries and neural network models (with and without supervisor), an intelligent GIS system has been designed and coded that can estimate daily suspended sediment load under univariate or multivariate conditions. The results of applying this system to Mazaljan River Watershed at Razin hydrometric station showed that this system is able to simulate suspended sediment load with proper performance and validation (with root mean square error of 1033 tonday-1, mean absolute error of 455 tonday-1 and Nash-Sutcliffe efficiency of 0.89 for the test data set). In general, this system can be used as a national infrastructure in the simulation and management of suspended sediment in all hydrometric stations in the country by relevant organizations.
Sedigheh Mohamadi
Abstract
With regard to financial and technical problems normally measured sediment data are limited in developing countries; therefore a model that uses water discharge data as input can be a reliable option for estimates of sediment. Due to widely application of the variety of models to predict the suspended ...
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With regard to financial and technical problems normally measured sediment data are limited in developing countries; therefore a model that uses water discharge data as input can be a reliable option for estimates of sediment. Due to widely application of the variety of models to predict the suspended sediment, this study aims to determine optimal prediction model based on the amount of discharge flow gauging stations of Halilrood River including, Soltani, Henjan, Cheshmeh Aroos, Meydan and Konaruiyeh. In this regard, efficiency of some rating curves models including one-linear, two-linear and the intermediate categories ones (by and without coefficients as CF1, CF2 and FAO) and black box models including artificial neural networks and neural-fuzzy in modeling sediment were evaluated. The results of the evaluation of the model using the parameters of MAE and RMSE showed that neuro-fuzzy models in major hydrometric stations studied, including Pole Baft, Henjan and Konaruiyeh with an equivalent amounts of 35.07, 11958.74 and 34235.27 ton/day for MAE and 42.07, 28672.78 and 52735.92 ton/day for RMSE, respectively are the best models to simulate the suspended sediment. The artificial neural network model of radial basis function in Meydan with 384.83 ton/day MAE and 669 ton/day RMSE amounts is the optimal model. Also two-linear sediment rating curve resulted the best simulation in Cheshmeh Aroos Station with MAE and RMSE as 1.7 and 4.1 ton/day and one-linear sediment rating curve with CF1 correction in Soltani Station with MAE and RMSE 9723.2 and 41235.6 ton/day, respectively are the best. According to changes of efficiency of models with varying location of gauging stations, it can be concluded that ecological conditions and statistical community determine the optimal model of the suspended sediment simulation.
Ayyub Moradi; Ali Najafinejad; Majid Ownegh; Choghi Bairam Komaki
Abstract
Simulation of runoff and sediment in watersheds require different modelling approaches, each provided for certain condition. Semi-distributed hydrological model (SWAT model) is one of the most widely used modelling approaches in this context. Among the most important spatial information needed by SWAT ...
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Simulation of runoff and sediment in watersheds require different modelling approaches, each provided for certain condition. Semi-distributed hydrological model (SWAT model) is one of the most widely used modelling approaches in this context. Among the most important spatial information needed by SWAT model, is the map of digital elevation model (DEM) which plays an important role in the model results for the exploration of hydrographic properties of watersheds, estimation of the spatial distribution of runoff and sediment load and its accuracy. The aim of this study was to evaluate the effect of different digital elevation models on runoff and suspended sediment in Galikesh watershed, Golestan Province. For this purpose, three types of DEM with the spatial resolutions of 30, 90 and 1000 meters were selected and for a period of 27 years, SWAT model was implemented. SWAT-CUP software and SUFI2 method were used for the model calibration and validation. Nash-Sutcliffe (NS) criterion for discharge and in calibration phase (1990-2007) for the resolutions of 30, 90 and 1,000 meters, was obtained respectively, 0.63, 0.63 and 0.62 and for suspended was obtained respectively 0.69, 0.68 and 0.67 which is considered satisfactory, given the presumed numerical ranges acquired from the previous studies. The amounts of watershed’s annual runoff for the resolutions of 30, 90 and 1000 meters, were respectively, 11.23, 11.30 and 11.39. The results that the use of different of digital elevation models would result in essentially similar results in runoff and sediment estimations, although changes in suspended sediment was slightly overestimated. This is attributable to the inverse modelling logic and lack of considering the parameters which arise directly from the DEM map. , due to data limitations in the Swat model calibration, the digital elevation model used to simulate the runoff did not have much impact on runoff and sediment estimations.
