عنوان مقاله [English]
In this study, the sedimentation status of Qazvin irrigation network was investigated before and after the construction of the reservoir reservoir of Taleghan. Sediment field studies show that the main source of network sediments before the construction of reservoir dam was sediment produced in the catchment area of the Taleghan river basin. After the construction of the dam, most of these sediments deposited in the lake of the reservoir, and now clear water flows through the tunnel to the Zayaran River. With the construction of a reservoir dam, it was expected that the problem of deposition in the network would be resolved, but there is already a precipitate in the network due to various factors. For example, despite the removal of the major part of sediments in Taleghan Dam reservoir, due to the existence of intermediate watersheds, some of the sediments are entering the Qazvin Irrigation Network between the tunnel output and the dam site. Other factors include the inadequate route of the main canal service and second grade canals and the entry of soil from the service roads into the canal. The debris of the rubble, especially in the intervals of the canal, passing through the residential areas, the entry of municipal waste and sewage into the canals, the car wash in the canal service road, the entry of surface water from the rain into the canals, and, finally, the heavy traffic of heavy machinery On the road, canals can be considered as one of the other important factors in the formation of sediment in the network. Another important factor in the formation of sediment in the grid is the manipulation of the hydraulic performance of the amyl valves (by inserting sand traps on the valves) by farmers, which reduces the flow velocity at the upstream of the valve and the accumulation of fine grained sediments in the upstream valley The coarse-grained amylate and torn bags also introduce coarse deposition into the canal right after the amyl valve. Meanwhile, since the sediments of the Taleghan River (before the construction of the reservoir dam) still exist within the canals, it is therefore necessary to dredge the entire network in order to remove the precipitates.