The Rangit dam is 45 metres (148 ft) high concrete gravity structure of 100 metres (330 ft) length.
The reservoir created behind the dam has a storage capacity of 1,175,000 cubic metres.
The storage created is utilized for hydropower generation at a surface Powerhouse located on the left bank of the Rangit River.
The diversion of flow from the reservoir to the surface Powerhouse is effected through an Intake leading to a concrete lined Head Race Tunnel (HRT) of 4.5 metres (15 ft) diameter (Horse shoe shaped and concrete lined) of 3 kilometres (1.9 mi) length, a Surge Shaft (14 metres (46 ft) diameter and of 60 metres (200 ft) depth at the end of the HRT with control arrangement followed by one main penstock pipe (of 3.5 metres (11 ft) diameter and length of 270 metres (890 ft)) trifurcating into three lines of 2 metres (6.6 ft) diameter each (with a total length of all three lines is 59 metres (194 ft)) to connect to the three Francis Turbine Generating Units of 20 MW capacity each, through the MIVs.
The tailwaters from the turbines are led back into the river through a combined short tailrace channel.
The firm power generation is of the order of 39 MW corresponding to annual energy generation of 340 GWh (in a 90% dependable year).
The ruling levels for power generation are: in the reservoir, Full Reservoir Level (FRL) of 639 metres (2,096 ft) and Minimum Draw Down Level (MDDL) of 627 metres (2,057 ft)), the Normal Tail Water Level (NTWL) in the Tail Race Channel from the Powerhouse of 512 m and under an operating gross head of 127 m. Since it is owned by coastal projects ltd, the power generated is shared and Sikkim gets a share of 13.33%.

The project was funded by the Government of India and built by its parastatal organization namely, the National Hydroelectric Power Corporation (NHPC).
The construction of the project was completed in December 1999 and operation started in January 2000.
Operation and maintenance of the project is also with the NHPC.

This power project was the third stage of the five-stage cascade development conceived on the main stem of the Rangit River, and was the first to be built in the series of Rangit Stage I to IV initially conceived by the Central Water Commission.
Three other projects on the Rangit River planned and under development are the Rangit Stage II (60 MW capacity), Rangit Stage IV (3×40 MW = 120 MW capacity) and Jorethong HEP (96 MW); the last two projects are now under construction.
The Rangit dam is 45 metres (148 ft) high concrete gravity structure of 100 metres (330 ft) length. The reservoir created behind the dam has a storage capacity of 1,175,000 cubic metres. The storage created is utilized for hydropower generation at a surface Powerhouse located on the left bank of the Rangit River. The diversion of flow from the reservoir to the surface Powerhouse is effected through an Intake leading to a concrete lined Head Race Tunnel (HRT) of 4.5 metres (15 ft) diameter (Horse shoe shaped and concrete lined) of 3 kilometres (1.9 mi) length, a Surge Shaft (14 metres (46 ft) diameter and of 60 metres (200 ft) depth at the end of the HRT with control arrangement followed by one main penstock pipe (of 3.5 metres (11 ft) diameter and length of 270 metres (890 ft)) trifurcating into three lines of 2 metres (6.6 ft) diameter each (with a total length of all three lines is 59 metres (194 ft)) to connect to the three Francis Turbine Generating Units of 20 MW capacity each, through the MIVs. The tailwaters from the turbines are led back into the river through a combined short tailrace channel. The firm power generation is of the order of 39 MW corresponding to annual energy generation of 340 GWh (in a 90% dependable year). The ruling levels for power generation are: in the reservoir, Full Reservoir Level (FRL) of 639 metres (2,096 ft) and Minimum Draw Down Level (MDDL) of 627 metres (2,057 ft)), the Normal Tail Water Level (NTWL) in the Tail Race Channel from the Powerhouse of 512 m and under an operating gross head of 127 m. Since it is owned by coastal projects ltd, the power generated is shared and Sikkim gets a share of 13.33%.
The project was funded by the Government of India and built by its parastatal organization namely, the National Hydroelectric Power Corporation (NHPC). The construction of the project was completed in December 1999 and operation started in January 2000. Operation and maintenance of the project is also with the NHPC.
This power project was the third stage of the five-stage cascade development conceived on the main stem of the Rangit River, and was the first to be built in the series of Rangit Stage I to IV initially conceived by the Central Water Commission. Three other projects on the Rangit River planned and under development are the Rangit Stage II (60 MW capacity), Rangit Stage IV (3×40 MW = 120 MW capacity) and Jorethong HEP (96 MW); the last two projects are now under construction.
Rangit Dam