Document Type : Complete scientific research article
Authors
1
Department of Water Engineering, Faculty of Water and Soil, University of Zabol, Iran
2
Department of Water Engineering, Faculty of Water and Soil, University of Zabol
3
Graduated in Water Resources Engineering, Faculty of Water and Soil, University of Zabol
Abstract
Abstract
Background and objectives: Rivers are one of the cheapest and most accessible water resources. The construction of lateral intakes is one of the oldest methods of using river water. The Sistan plain in the southeast of the country is highly dependent on surface water resources. Currently, due to the years of drought, the only water source in the Sistan region is Chah Nimeh Reservoirs. The Feeder one intake canal is the first way for directing water from the Sistan River to the reservoirs of Chahnime. In recent years, the Feeder two intake canal was built due to the need to increase the water intake of Chah-Nimeh reservoirs from the Sistan River. The low slope of the Sistan plain has made its channels prone to sedimentation and because of this, a lot of money is spent on dredging the Sistan River and the network of related canals
Materials and methods. River hydraulic studies, sediment transport and waterway changes are carried out through physical or mathematical models. The HEC RAS mathematical model is one of the models for solving steady and unsteady flow equations in order to determine the water level and hydraulic characteristics of the flow and it can perform calculations of moving bed sediment with quasi-unsteady flow data. In the current study, HEC RAS 6 was used to simulate the sediment deposition in the intake canals of feeder one and feeder two in the conditions of the minimum water level of Chah Nimeh reservoirs. The simulation of the flow in the model was carried out in the quasi-unsteady method, using the standard step-by-step method and based on the annual flood hydrograph with a volume of one billion cubic meters. In this research, the toffalti sediment transport equation was considered to determine the sediment capacity of sections.
Results: Based on the results of this research, the tuffalti sediment transport equation with Root Mean Square Error (RMSE) index equal to 52162 tons and determination coefficient (R2) index equal to 0.89 was chosen as the best sediment relationship in HEC RAS model in the Sistan river. Based on the modeling results, in both scenarios of water intake of Feeder one and Feeder two intake canals, in the condition of the minimum water level of Chah-Nimeh reservoirs, the cross sections of the Sistan River will be eroded also, an erosion volume equal to 125000 cubic meters occurs in the intake canal of feeder one, which causes the level of the bed of feeder one canal to decrease by 2.9 meters, while under the same conditions in Feeder two canal, the volume of sedimentation is equal to 1572000 cubic meters, which increases its bed level by 5.2 meters.
Conclusion: In the conditions of the minimum water level of the Chahnimeh reservoirs, the intake canal of Feeder One is erodible and the intake canal of Feeder Two is Sedimentary. Therefore, Feeder One canal is superior to Feeder Two canal due to lower dredging costs.
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