Numerical Analysis Of The Infiuence Of The Main Canal's Operation Mode In Donglei Irrigation District On Channel Silting

The main canal of Donglei irrigation district has been running for many years,and the problem of sediment in the canal is very prominent.The most serious is that the water delivery capacity of the canal is less than 40%of the design,which seriously affects the irrigation efficiency of the irrigation district.This paper used the mathematical model to study the operation mode of the main canal,which is very significant to control the canal deposition.First,this paper summarized the basic law of changes of sediment in the main canal by the systematical analysis of the data,includes the inflow of water,sediment from the head and the process of erosion and siltation of the canal,the actual allocation of water in the system and so on,which is measured since Donglei irrigation district was put into operation.Secondly,On the basis of the existing 1-D non-uniform suspended sediment transport mathematical model,the paper improved and modificated it to be suitable for the water sediment conditions and canal boundary characteristics of the main canal in the Donglei irrigation district,and used the measured siltation data ofthemaincanal to verify it,theresultshowsthat the calculated value of the accumulated siltation is basically consistent with the measured value.Finally,according to the situation of water and sediment coming from the head of the canal in typical year withthe under different operation modes,the verified mode is used to simulate the process of erosion and deposition of the main canal.Based on the analysis and comparison of the calculation results of different schemes,it is considered that the canal sediment deposition situation cannot be improved according to the current application mode,and the feasible scheme to control the canal sediment deposition is to use the drainage canal to increase the flow of the main canal.The results show that:(1)the optimal period to increase the flow of the main canal is in spring irrigation,when the main canal is in low sediment concentration,that is 23 days from April 7 to April 29 every year;(2)the optimal flow of the main canal is 45m3/s.According to the scheme,the maximum silt reduction of the main canal is 59.63%,the water consumptioncost is only 1/5 of the artificial dredging cost,which is feasible in both technical and economic aspects.