Example Realignment of Water Conveyance Structures:

Project: Kuttiyadi Tailrace Cascade River:  Kakkayam Thodu Capacity: 5600 kW
Click to Go back to Main page State: Kerala Total Energy: 28.5 GWh/year
As there are no sluices in Irrigation Barrage and Diversion Weir Based Schemes , the layouts were designed especially with regard to realigning water conductor system so that they would not cause any permanent acquisition or waste of agricultural land.
The original layout (shown in red) required extensive civil works comprising an intake structure consisting of a 7.6 meter long weir to divert the tailrace discharges into the power channel; a water conveyance structure comprising of a 805 meter long power channel (1.5 meter bed width) which would link up to a head regulator (5 m. x 2.6 m) equipped with a hoist, a forebay-underground RCC tank (21 m diameter, 11.5 m deep), a 100 meter long penstock (1.65 m diameter); and a 126 meter long aqueduct (dimensions 3.4 meter x 2.6 meter) which would run alongside the power channel. The powerhouse itself would be a large structure (32.75 x 9 x 9.75) and designed to fully enclose two 2500 kW turbine-generator units. The tailrace of the mini-hydro scheme, a 50 meter long channel, would discharge into the Peruvannunmuzhy Irrigation Reservoir.

After an extensive inspection of the area, especially the topography along the banks of the river, the layout was revised (shown in green) to take advantage of the following features:

(i) the length of the river from the tailrace of the large power station to the irrigation river is 550 meters compared to over 800meters for the power channel in the original proposal;

(ii) there already exist drops at three sites along the river bed which if developed in a cascade, would provide the same cumulative head for power generation as in the original proposal.

Hence, a revised and simplified layout was prepared. Powerhouses would be located at three points along the river course: the first would utilize a 15 meter drop and would be linked to the tailrace of the large power station by a closed conduit; the second would be located at a 5.5 meter drop along the river bed; and the third would also located at a 5.5 meter drop at the point where the river discharges into the irrigation reservoir.
Small barrages (5 meter high) would be built at two points along the river bed to divert water into the intake structures for the second and third powerhouses. If necessary, flash boards, crest gates, and hoists would be installed at the main intake structure for the first powerhouse. In each case, the tailrace would consist of an open channel and a stop log to maintain the water level in the draft tube.

By realigning the entire power channel, the revised layout:

(i) reduces by 50% the length of water conductor system;
(ii) augments the overall energy production capacity at the site; and
(iii) obviates the need to destroy existing coconut trees along the path of the power channel which would have resulted in a potentially adverse environmental impact.

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