Characteristics And Management Of Sediment In The Main Channel In Dengkou Pumping Water Irrigation District

Dengkou Pumping Water Irrigation District in Inner Mongolia is one of the largest irrigation areas and an important food production farming area in Inner Mongolia.After years of running the irrigation district was experiencing some problems such as rise of the intake pool bottom elevation,siltation of the main canal.Based on the problems occurred in the irrigation district,the sediments were monitored and sampled at the intake pool and the selected sections along the main canal.The theory of water and sediment conditions was applied and the causes and process of the siltation in the main canal were analyzed to determine the sediment carrying capacity,sedimentation properties,and the main factors that caused the siltation.The siltation level was analyzed and the development trend was predicted.The engineering and management measures were suggested which would be suitable to regulate the siltation process.The monitoring results showed that the problem of sediment deposition in the main canal was solved to a large extent through the suggested regulating and adjusting operation management and engineering approaches.The water transport capacity of the main canal was basically restored.The research results mainly include:1.The amount of sediment entering the pump station increases significantly with a percentage of about 20%coarse sand that was easier to settle in the main canal.This was supposed to be one of the main reasons for the siltation in the main canal.2.The sediment deposition thickness in the intake pool was not only proportional to the period of time the when the pump station was out of operation,but also affected by the selected stop pumping time to a certain extent.3.Under the current operating conditions,the critical velocity of non-scouring and non-silting of water in the main canal was determined through theoretical calculations and field tests.Through setting a stop log gate in the intake pool,regulating the pump rates to wash out the sediment in the main canal before operation,controlling the operating flow rate within the non-scouring and non-silting velocity in the main canal,and regulating canal sections prone to sediment deposition,the sediment pumped into the canal was greatly decreased,the sediment transport capacity in the main canal was improved effectively,and thereby the water use efficiency in the irrigation district was improved.