SEDIMENT CONTROL IN CANALS

Abstract

The water flowing through rivers generally carries sediment which creates several problem for the system. The major canal systems usually take off from these rivers. During medium and high floods these canals are closed also to avoid deposition of excessive sediment* With the increasing irri-gation demand during monsoon and the power generation it becomes difficult to close the canal frequently. Means are devised to reduce the sediment entry into the canal by generating outer cirvature of flow in front of the head re-gulator with the help of guide bunds, divide wall, angle off take, still pond regulation etc.The entry of coarse par-ticles is checked by tunnel type excluders. It has however been observed that in spite of these measures some sediment enters the canal and, causes silting in the head reaches. Tunnel type ejectors are developed to eject coarse particles that enter the canal. The design of excluders and ejectors and their performance at various sites have been discussed in this dissertation. The study has shown that these are very effective in the shingle and upper alluvial reaches of a river, where considerable percentage of sediment is coarse. In case of fine sediment they are not very effective as has been experienced at Easstern,Kosi Canal (India). In such cases settling basins seem to be the only alternative for effective sediment exclusion. The model and prototype studies have indicated that for the selection and design of iv a sediment device on any canal system, hydraulic model studies are very helpful• Also there is need for collection of proto-type data at existing works for better understanding of and improving the functioning and efficiency of the existing method of sediment control and exclusion•