Kaptai Dam (Bengali: কাপ্তাই বাঁধ) is located on the Karnaphuli River at Kaptai, 65 km upstream from Chittagong in Rangamati District, Bangladesh. It is an earthfill embankment dam with a reservoir (known as Kaptai Lake) water storage capacity of 11,000 km². The primary purpose of the construction of the dam and reservoir was to generate hydroelectric power. Construction was completed in 1962.[1][2]
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A brief reconnaissance was carried out in 1906 when the Karnafuli Hydropower Station was first contemplated. A second study was carried out in 1923. In 1946, E. A. Moore recommended the proposed project at Barkal about 65 kilometers upstream of present dam site at Kaptai. In 1950, Marz Rendal Vatten Consulting Engineers proposed a site at Chilardak, about 45 kilometers upstream of Kaptai. In 1951, the government engineers proposed a site at Chitmoram which is 11 kilometers downstream of the present site. Under the guidance of then Chief Engineer (Irrigation) Khwaja Azimuddin, the construction site was chosen at present location of the dam in 1951. The International Engineering Co. Inc. (IECO) was engaged for a study on the project. Utah International Inc. was selected as construction contractor. The construction of the dam started in 1957.
Starting in 1957, the initial phase of the construction was completed in 1962. By this time the dam, spillway, penstock and two units of powerhouses were built. Each of the powerhouses was capable of generating 40MW of electricity. In November 1981 another 50MW generating unit was completed. In October 1988 the 4th and 5th generating units were installed which raised the total generation capacity to 230MW. The total cost of Unit 1, Unit 2 and a part of Unit 3 was Rs. 503 million and the total cost of extension was Tk. 1,900 million. The project was financed by the government, ICA and DLF loan.[3]
The earthen dam is 670 meters long and 45.7 meters wide with a 16-gated spillway on the left side of the main dam. The catchment area of the reservoir is 11,000 km². The dam has provided significant flood control as well as power generation.[1] The construction of the dam submerged 655 km² area. This included 220 km² of cultivable land, 40 percent of the cultivable land in the area, and displaced 18,000 families and 100,000 tribal people, of which 70% were Chakma. The dam also flooded the original Rangamati town and other structures.[4]
Kaptai Dam and the Spillways At a Glance:
The Dam
| Feature | Description |
|---|---|
| Body of the Dam | Earthen |
| Length | 670.6m |
| Height | 45.7m |
| Width | 7.6m (At Crest), 45.7m (At Bottom) |
| Maximum Water Level | 33.5m (110ft above MSL) |
| Minimum Water Level | 20.1m |
| Reservoir Capacity at 33m | 6,477x106m3 |
| Reservoir Area | 777km2 at 33m |
| Average Annual Flow | 15,646,000,000 cubic metres3 |
| Installed Capacity | 230 MW |
The Spillways
| Feature | Description |
|---|---|
| No. of Gates | 16 |
| Total Length | 227 m |
| Size of the Gates | 12.2 m x 11.3 m |
| Crest Level | 21.9 m |
| Bridge Level | 39.9 m |
| Maximum Discharge | 16,000 m³/s |
| Gate Hoist | 75 Tons |
| Tailrace Length | 1219 m |
| Tailrace Width | 122 m |
Local inhabitants living in the storage reservoir area who lost their homes and farmland due to flooding were not compensated. More than 40,000 Chakma tribals emigrated to India. The scarcity of land is considered a main cause of the continuing conflict in the area today.[4]
The building of the dam and reservoir also caused destruction of wilderness and loss of wildlife and wildlife habitats.[1]