Darbandikhan Dam - Design and Operation

Design and Operation

The dam is located within a gorge on a foundation of sedimentary rocks. It is a rock-fill embankment type with a central clay core. The dam is 128 m (420 ft) tall and 445 m (1,460 ft) long (535 m (1,755 ft) if the spillway section is included). Its crest is 17 m (56 ft) wide and at an elevation of 495 m (1,624 ft). The structural volume of the dam including rock, clay and filters is 7,100,000 m3 (9,286,449 cu yd). The dam collects water from a catchment area that covers 17,850 km2 (6,892 sq mi). Its reservoir, by design, has a storage capacity of 3,000,000,000 m3 (2,432,140 acre·ft). Of that capacity, 2,500,000,000 m3 (2,026,783 acre·ft) is active (or useful) storage while 500,000,000 m3 (405,357 acre·ft) is dead storage. At a normal elevation of 485 m (1,591 ft), the reservoir covers an area of 113 km2 (44 sq mi). To protect the dam from flooding, it is equipped with a controlled chute spillway on its right bank. It is controlled by three 15 m (49 ft) x 15 m tainter gates. At the terminus of each chute there is a ski-jump to help dissipate energy. The maximum discharge capacity of the spillway is 11,400 m3/s (402,587 cu ft/s). The dam's power plant is located at its toe and contains 3 x 83 MW Francis turbine-generators. They are each afforded a rated hydraulic head of 80 m (262 ft) and can each discharge 113 m3/s (3,991 cu ft/s). Above the tail-race for each turbine is an irrigation outlet. Each of the three outlets can discharge up to 175 m3/s (6,180 cu ft/s) downstream.