Upper Kotmale Dam

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Upper Kotmale Dam
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Website https://ceb.lk/

The Upper Kotmale Dam (also known as the Upper Kotmale Hydropower Project, or UKHP) is located in

. The dam feeds the third largest hydroelectric power station in the country.

History

The project was initially planned in 1968 by the local authorities, before the

. The feasibility study included five sites and eight alternative development schemes, and concluded with two sites which were technically and economically more feasible.

The two sites were a

, and thus the Caledonia site was dropped. Further funding was then provided by Japan for the engineering study, which included a review of the feasibility study, selection of an optimal development plan, development of the detailed design, and the preparation of tender documents and an environmental impact assessment report.

The environmental impact assessment report was completed in September 1994, with the final design report completed in March 1995. The environmental assessment identified key issues associated with the project, which includes impact on St. Clair's Falls aesthetics due to stream flow reductions, social impacts due to resettlement of affected people, possible effects on ground water due to tunnelling, impacts on downstream water uses due to de-watering of streams, and impacts on biodiversity. These impacts led large delays in project development.

As per the National Environmental Act of 1998, the environmental clearance was then granted to the project. The project initially faced several objections, before being officially permitted by courts of law. Construction work on the project then began in 2006, and is expected to be completed by the end of 2011.

Construction and development

This project is estimated to cost a total of up to Rs.44 billion, of which Rs.5.931 billion was funded by the Ceylon Electricity Board, and ¥33.265 billion by the Japan Bank for International Cooperation. The entire project covers an area of approximately 540 km² (208 sq mi), and is developed in five phases:

• Phase 1: Site preparations, construction of employers and workers living quarters, construction of access roads, and relocation of affected people.
• Phase 2: All key civil engineering works, such as construction of tunnel, dam, underground power house etc. This takes about 50% of the project cost.
• Phase 3: Hydro-mechanical works such as construction of spillways, penstocks, intake gates, etc.
• Phase 4: Electro-mechanical works such as generation installations, construction of the switchyard, fire fighting system, communication system, etc.
• Phase 5: Construction of the 15.5 km (10 mi) 220-kV double-circuit power transmission line.

A total of 2,250 construction workers are employed at the site, of which 2,100 are locals, and 150 are foreign.

Dam and reservoir

The

.

Tunnel

The 4.5–5.2 m (14.8–17.1 ft) diameter, 12.89 km (8.0 mi) long Upper Kotmale Tunnel, the longest excavated tunnel in Sri Lanka, will be used to deliver the water to the powerhouse. The tunnel begins at the dam site, and stretches north at a distance of approximately 7.4 km (4.6 mi) towards

Powerhouse

The powerhouse measures 66.3 m (217.5 ft) long, 18.8 m (61.7 ft) wide, and 36.5 m (119.8 ft) tall, and is located underground at

. The initial 745 m (2,444 ft) of the penstock is single-lane, while the latter 48 m (157 ft) splits into two lanes, feeding the two 75 MW generators respectively.

The powerhouse consists of the two three-phase 77

(GIS) substation. An outdoor switchyard measuring 36.5 m (119.8 ft) by 130 m (426.5 ft).

Transmission line

The 220kV transmission line of the Upper Kotmale Hydro-power Project connects the power station located at Niyamgamdora, Kotmale, to the national grid via Kotmale switch yard located in Atabage,

MW

per circuit.

Social and environmental impact

The construction of the dam, tunnel, and powerhouse, required the relocation of families from 495 houses. New homes were built away from the site with access to vital facilities such as water and power. The relocated families are provided with concessionary loans to start new self-employment ventures, while additional facilities such as the Talawakele Central College, places of worship, a cinema hall, a library, and a community centre, are being established.

Similar most other dam's impacts on rivers around the world, the Upper Kotmale Dam will periodically stop the St. Clair's Falls, located 2.2 km (1.4 mi) downstream of the dam, and a further 2.9 km (1.8 mi) of the Kotmale River downstream of St. Clairs Falls, before the river is restored by water from the Devon River, the river forming the picturesque Devon Falls. As ordered by the Government Extraordinary, the St. Clair's waterfall will maintain a continuous flow of 47,250 m³ (1,668,618 cu ft) of water for 10 hours and 30 minutes daily, between sunrise and sunset.

See also

• Electricity in Sri Lanka
• Kotmale Dam
• List of dams and reservoirs in Sri Lanka
• List of power stations in Sri Lanka

References