ANALYTICAL STUDY FOR SEDIMENT CONTROL AND DISCHARGING CAPACITY OF WATER INTAKE

Abstract

Water intake is being used to divert the water from water body like river, reservoir, canal etc. for various purposes like hydropower, irrigation, water supply etc. Special consideration is required for the design, of water intake, so that it will carry design discharge and minimize sediment,, control at the intake. Sediment control at the water intake, invert level of.the crest, operation of the gates and use of various sediment control structures like deflecting vanes, submerged vanes, and undersluices etc. The present study was aimed at examining the discharging capacity and sediment entry to the intake of Madhya Ganga Canal located at Bijnor, UP, India. In addition, the discharging capacity and sediment transport capability of the Madhya Ganga Canal has been also studied. Relevant data related to discharge sediment and water surface data of Ganga River and discharge, water surface level and gate opening of water intake of Madhya Ganga Canal were collected from the site. In Madhya Ganga barrage, the angle of off-take is 107° and the level of the under sluice is 0.5 m lower than the floor level of other bays. The height of sill of the head regulator is 3.2 m, which is 0.46 times to the depth of the pond. Madhya Ganga Canal system shall be kept running. only during monsoon periods and start only when the river supply exceeds the 300 m3/s i.e. the overall requirement of Upper Ganga, lower Ganga & Agra canals. On the basis of observed data of water availability in a three year period (July 1St week to Sept. 3rd week, 2004 to 2006) the Madhya Ganga Canal could not be run with the design discharge. Design discharge of the Madhya Ganga Canal 232.43 m3/s, but, maximum actual supply of water was 204.08 m3/s i.e. Canal was running with 88 % of its design capacity. Total estimated water requirement is 30987x 106 m3 of water in monsoon season, but the actual water supplied were 26636x 106 m3, 22889x 106 m3 and 26155x 106 m3 in 2004, 2005 and 2006, respectively, which are 14%, 26% .and 15%, respectively less from the design water requirement. By analyzing the discharging capacity of the head regulator on the basis of three years data, it is clear that the computed values of the discharge coefficient Cd varies from 0.6 to 0.87. These values are higher than generally accepted values for head regulator. So there might be lack of precision in discharge measurement. To rectify this deviation, discharge coefficient of intake Cd = 0.64 is proposed. III Stage discharge curve for Cd = 0.64 is found that, it is very close to stage discharge curve for Manning's rugosity coefficient n= 0.026. Thus finally Stage discharge curve correspond to n = 0.026 is adopted and same is recommended for its use. In Madhya Ganga Canal performance ratio of the head regulator is 0.05. It shows that the head regulator can exclude only 5 % of sediment concentration transported in the river without any sediment control measures. Sediment trap efficiency of the silt ejector is 50 %, but the extraction ratio is 29 % of the canal discharge.. Madhya Ganga Canal was carrying 0.713; 0.822; and 0.646 million tonnes suspended sediment in 2004, 2005 and 2006, respectively during monsoon period. In Madhya Ganga Canal bed load / suspended load ratio is found 0.0328 (3.28 %)