VIJAYAWADA: With the critical works of closure of gaps in the upstream cofferdam of Polavaram Irrigation Project (PIP) on Thursday, the stage is set for diversion of Godavari flood water via the spillway this season.
Ahead of the onset of monsoon, Megha Engineering and Infrastructures Ltd has completed the works related to the upstream cofferdam on a war footing and has lifted 14 of the 42 radial gates, which have been installed, for the flow of water.
Now that the upper cofferdam is in place without any gaps, River Godavari would be restricted by the cofferdam and would be diverted from left to right, essentially changing its natural course. This is because unlike traditional dams and reservoirs, PIP is a unique engineering design in which the earth-cum-rock fill (ECRF) dam (the main dam) is built across the river with its spillway in the right flank and the power house in the left flank.
The water will be diverted from the cofferdam towards the spillway and through approach channel, the radial gates of the spillway, the spill channel, and the pilot channel, before it rejoins the river’s actual course.
“Godavari water from Bhadrachalam will reach Dowleswaram and as the upstream cofferdam is now closed, the water flow will be stopped there. From there, Godavari River would be diverted to the spillway via approach channel, and then through river sluice gates, water will be released downstream. During floods, water will be released by lifting the gates. This entire diversion will be around 6.5 kilometres. MEIL has made all arrangements for this river diversion,” the officials said on Thursday.
“A total of 7.56 lakh cubic meter rock filling works related to upstream cofferdam, which is key for water diversion, have been completed so far. The works were divided into four reaches: reach 1 starts from point 0 to 480 metres and its height is at 35 metres, reach-2 from 480 metres to 1700 metres with height a of 38 metres, reach-3 from 1700 to 2100 metres, and reach-4 from 2100 to 2480 metres. Works up to a height of 34 meters are completed,” representatives of MEIL explained.
The downstream cofferdam works are also nearing completion, according to members of the executing agency. “So far, the downstream cofferdam has reached 25 meters in height. It must be raised to 30.5 meters height,” they added.
Both the upstream and the downstream cofferdams are being constructed near Angaluru of Devipatnam mandal in East Godavari.
Completion of both the cofferdams is essential to take up the works related to ECRF dam. Along with cofferdams, the agency is also simultaneously lifting the radial gates.
So far, 16 of the 42 erected gates have been lifted and after the completion of fixation of hydraulic power packs, the remaining would also be lifted. The approach channel, the spill channel and the pilot channel are also being readied for diversion of floods.