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Lower kokawita

Lower kokawita
Design capacity
1900kW
Province
Sabaragamuwa
District
Ratnapura
Divisional Secretariate
Kalawana
Water source
Wewa Gaga
Catchments area to diversion point
70km2
Average annual rainfall
4600 mm
Design diversion capacity
12.8m 3/s
Headrace conveyance
4.00 x 2.30m Concrete canal
Length of headrace conveyance
850m
Penstocks
03x1.6m dia, 30 m long
NET Head
19.1 m
Expected average annual energy
6.35GWh
Plant factor
0.40
Grid connection
33k V single circuit, concrete pole line
Distance to interconnection
1000m approx
Project cost
LKR 478.0 Million
Power house
Open air type on Right bank of stream
Turbine
02x750KW+400KW, Francis

The proposed project is at Pitigala in Kalawana Divisional Secretarial Area, Rathnapura district. The project utilizes the hydro –potential energy of Wewa Gaga. The river Wewa Gaga originates from the dense forest reserve of Sinharaja Adaviya at an elevation of 1000m M.S.L. The catchments area is around 70sq.kms at the diversion point.

Construction of the Head Race Channel accounts for the 30% of the total project cost. The total Head race channel of the project is 850m long. Out of this, app 150m runs very close to the river on the left bank. As it vulnerable to the rising flood waters of the river, this section is constructed as Box section with top slab. The dimension of the channel is 4.0m x 2.5 m with cover slab. The balance section of the channel lies on left bank having a length of 250m runs straight through the tea plantations along the river as open section. Few aqua duct sections will have to be constructed for the purpose of bypassing small creeks. The channel will cross the river at chainage 400.0m and runs through right bank until meet the forebay Tank at chainage 850.0m. The cross over aquaduct would be 10m high and two low pressure pipes with 1.8m diameter to be used for water conveyance having a length of 60m. This cross over minimizes possible environmental damage.

The power house will be a single-story block where three units of Francis turbines of Chinese origin coupled to synchronous generators will be accommodated inside. The turbines and the generators and associated hydraulic units will be placed in the ground floor and the low voltage cubicle will be accommodated at an elevated level to protect them from flooding.