Abstract:
The construction of a barrage on river Sanjay in the district of Saraikela Kharsawan, Jharkhand was taken up to provide irrigation in 688 ha Gross Command Area. Sanjay river is a tributary of Kharkai river and meets it at a distance of about 11 km downstream from the proposed barrage location near village Dugni. There is another barrage nearing completion on Kharkai river about 1 km downstream of this confluence. After full impoundment of Kharkai barrage its back water will also reach upto the Dugni village.
Two dimensional mathematical model studies were conducted with the aid of 2-D HEC-RAS, reproducing reach of river Sanjay from 10 km upstreamupstream of proposed barrage location 3 km downstream it i.e. total reach of about 13 km. The studies were conducted with existing condition and barrage of 50 m and
60 m waterway in place. Water levels and velocities were computed for discharges of 1900 m3/s and 2407 m3/s in the river. Based on the analysis of results of mathematical model study , data supplied and observations during the site inspection the barrage location at proposed location no.2 was finalized. Afflux of 0.65 m was computed for 50 m waterway and that of 0.39 m for the waterway of 60 m. Flow conditions and velocity distribution in the vicinity of barrage location were observed and found satisfactory with barrage waterway of 60 m. It was recommended to dress rock protrusions smoothly in the vicinity of proposed barrage location. Although flow velocities were higher in the centre of river and lower towards the bank, bank protection works in the form of gabion mattress were recommended to minimize any damage to the river bank in the vicinity of existing/ upcoming establishments.
