Hydroelectric Projects in Sikkim: Teesta, Rangit & Dams
The major hydroelectric projects in Sikkim use the steep river gradients of the Teesta and Rangit systems. Important names include Teesta III, Teesta V, Teesta VI, Rangit and Rangit IV. They differ substantially in capacity, ownership, engineering layout and present operating status.
The most important recent distinction concerns the effects of the October 2023 flood. Teesta III’s dam was destroyed and became the subject of reconstruction review, while NHPC reports that the 510 MW Teesta V power station was restored in July 2026. Describing both projects simply as “damaged and closed” would now miss a significant update. Source 3 Source 4
This guide explains the principal projects, their rivers and capacities, the difference between installed power and generated electricity, and the environmental questions raised by development in a Himalayan basin. The project table is a selected overview, not a claim to list every generating installation in Sikkim.
Major hydropower projects and their status
| Project | River system | Installed or planned capacity | Status distinction in this review |
|---|---|---|---|
| Teesta III | Teesta | 1,200 MW; six 200 MW units | Original project commissioned in 2017; reconstruction following the 2023 disaster |
| Teesta V | Teesta | 510 MW; three 170 MW units | NHPC reports restoration in July 2026 |
| Rangit, also called Rangit III | Rangit | 60 MW; three 20 MW units | Established NHPC generating project, commissioned in 2000 |
| Teesta VI | Teesta | 500 MW; four 125 MW units | Construction project; capacity is not treated as current operating output |
| Rangit IV | Rangit | 120 MW; three 40 MW units | Construction project; NHPC’s listed expectation was November 2026 |
The state project register and NHPC’s project information support the capacity and commissioning distinctions. November 2026 is still a future date relative to this article’s 4 October 2026 review, so it is not presented as an achieved milestone. Source 1 Source 2 Source 6
Project names are particularly easy to confuse. Teesta III in Sikkim is not the same project as Teesta Low Dam III in West Bengal. A Roman numeral alone is insufficient identification; always check the full name, state, river and generating capacity.
Why Sikkim has substantial hydropower resources
Hydropower depends on moving water and a usable difference in elevation, commonly called head. Sikkim’s rivers descend through steep mountain valleys, creating locations where water can be conveyed from an intake towards turbines at a lower elevation.
The physiography of Sikkim explains the physical setting. High relief provides potential energy, while river discharge determines how much water is available to use. Neither factor remains uniform across the year or along the length of a river.
A promising location on a map is only the beginning of project assessment. Geological conditions, sediment, access, river ecology, downstream settlements and the consequences of extreme events all affect whether a particular scheme is feasible and acceptable.
This is why “hydropower potential of Sikkim” should not be treated as a single number equivalent to electricity already available. Theoretical resource estimates, technically developable sites, approved projects, installed capacity and actual generation describe different stages. Combining them produces misleading claims about what the state can supply today.
Teesta III: capacity and reconstruction context
Teesta III is a 1,200 MW project associated with Chungthang in Mangan district. Its six-unit configuration made it a major installation in the Teesta cascade. Environmental review documents identify the original commercial-operation milestone in March 2017 and subsequent proposals connected with restoration after the October 2023 flood. Source 4
The disaster changed the meaning of its capacity figure. A historical installed capacity does not establish how much plant is currently available for generation after major infrastructure failure. An article should therefore retain the capacity as a project characteristic while explaining the reconstruction context separately.
Rebuilding also involves more than replacing a damaged structure. Design assumptions, flood routing, sediment and debris, upstream hazards and downstream consequences need to be considered together. A review document is evidence that a proposal is being examined; it is not evidence that reconstruction is finished or commercial generation has restarted.
For readers assessing a future announcement, the essential questions are the same: what work has actually been completed, which approvals apply, and has the operator confirmed commercial operation? A revised plan or projected completion year cannot answer those questions by itself.
Teesta V: restoration in July 2026
Teesta V is NHPC’s 510 MW project, originally commissioned in 2008. In its statement about August 2026 generation, NHPC expressly credits the successful restoration of Teesta V in July 2026, after the station had been out of service following the October 2023 flash floods. Source 1 Source 3
That is the appropriate dated status for this review. Older reports describing restoration as an expected future event should not be repeated as if they were still the latest position.
Restoration does not mean that a station generates at its full rated capacity continuously. Output varies with water availability, operating conditions, maintenance and grid requirements. Nor does a restored plant make every nearby slope or road immune to future disruption.
The case illustrates an important reporting principle: capacity, availability and generation are different measurements. A plant can have a rated capacity of 510 MW, an operating status that changes over time, and an annual electricity output expressed in units of energy. Each figure answers a different question.
Rangit and Rangit IV
The Rangit, also written Rangeet, is another important river system in Sikkim’s hydropower geography. NHPC’s established Rangit project has a capacity of 60 MW. It should not be confused with the separate 120 MW Rangit IV development. Source 1
Rangit IV’s project information identifies three 40 MW units and a construction-stage commissioning expectation. As with Teesta VI, the figure describes a planned generating installation rather than proof of present commercial output. Source 6
The use of river names and Roman numerals can make separate schemes appear like units of one station. In practice, each project has its own location, water-conveyance system, generating equipment and administrative history. The numbering is useful for identification, but it is not a substitute for checking the individual project record.
For map work, keep the Rangit branch distinct from the main Teesta stem. A basin diagram that places every project in one straight sequence conceals the tributary structure and may imply an incorrect upstream–downstream relationship.
Teesta VI and the construction pipeline
Teesta VI is a 500 MW project with four 125 MW generating units. NHPC’s project material records the acquisition of the earlier project company and its subsequent integration into NHPC. These institutional changes help explain why older sources may name a different developer. Source 5
A change in ownership is not itself a commissioning event. Construction progress must be assessed through the actual works: diversion arrangements, underground excavation, water-conveyance structures, powerhouse equipment, transmission connections and testing.
The difference between a project pipeline and the operating fleet matters when estimating power supply. Adding Teesta VI’s planned capacity to existing stations and describing the total as current generation would confuse both project status and units.
Other hydropower developments also belong to Sikkim’s wider energy sector. However, a short list of major schemes is more useful when its scope is clear than an apparently exhaustive table mixing small projects, proposed dams, damaged installations and operating plants without explanation.
Hydropower map guide: dams, tunnels and powerhouses
The following is a basin-reading guide, not an engineering alignment or a flood-risk map.
- Upper Teesta: mountain tributaries and high-elevation catchments contribute water, sediment and potential upstream hazards.
- Main Teesta corridor: projects including Teesta III, Teesta V and Teesta VI occupy different parts of the river system.
- Rangit branch: Rangit and Rangit IV belong to the tributary system and must be mapped separately from the main stem.
- Lower basin: river connections continue beyond Sikkim into West Bengal and farther downstream.
A dam and its powerhouse may not sit beside one another. In a diversion-type scheme, water can enter a tunnel at one location and reach turbines some distance away. Mapping only the dam symbol can therefore hide a substantial part of the project footprint.
A good map also shows the river reach between the intake and the return of water to the channel. That reach remains important for ecology, local uses and environmental-flow management. A tunnel on the map does not mean that the original river channel becomes irrelevant.
The broader Sikkim geography guide helps place these river corridors within the state’s administrative and settlement pattern.
Run-of-river does not mean no impact
Many Himalayan projects are described as run-of-river schemes. The term generally distinguishes them from large seasonal-storage developments, but it does not mean there is no dam, no impoundment or no alteration of river flow.
Water may be diverted through tunnels, temporarily stored or operated through a powerhouse in a way that changes the timing of downstream releases. Construction also requires roads, excavation and disposal of excavated material. These effects should be assessed for the specific design rather than inferred from a convenient label.
Environmental flows concern the water needed to maintain downstream ecological and social functions. The appropriate assessment depends on the river and its uses. A single percentage quoted without its season, measurement point or regulatory context gives an incomplete picture.
Similarly, renewable electricity and ecological responsibility are related but separate questions. Hydropower uses replenished water flows, while a particular project can still have significant local impacts. Readers can explore Sikkim’s biodiversity to understand why river management belongs within a wider conservation discussion.
The 2023 flood and basin-wide risk
Peer-reviewed reconstruction of the October 2023 event describes a large slope failure at South Lhonak Lake, a displacement wave, lake outflow and a destructive downstream cascade. The flood involved water, sediment and debris, rather than a simple increase in clear-water discharge. Source 7
For hydropower planning, the implication is that upstream lakes, valley slopes, river channels and infrastructure cannot be assessed entirely in isolation. A disturbance in one part of the basin can affect structures much farther downstream.
The state’s September 2026 GLOF-preparedness meeting discussed priority lakes, monitoring and proposed interventions. These measures belong to a developing risk-management effort; proposals should not be described as completed protective systems. Source 8
Practical resilience includes maintaining communication, identifying exposed facilities, planning emergency response and examining how one failure could affect neighbouring structures. It also requires clear information for communities. Engineering design and public preparedness address different parts of the same problem.
Reading capacity and generation figures
Megawatts, or MW, measure power capacity. Megawatt-hours and million units measure energy generated over time. One million units of electricity equals one million kilowatt-hours, or one thousand megawatt-hours.
As a purely illustrative calculation, a 100 MW plant operating at full output for ten hours generates 1,000 megawatt-hours. Real output depends on whether enough usable water is available and whether the plant can operate during those hours. The example is not a production estimate for a Sikkim project.
This distinction prevents three common mistakes: treating capacity as annual generation, assuming a restored station produces continuously at its rating, and adding future projects to an existing operating total.
When comparing projects, use the same reporting period and identify whether the statistic describes gross generation, net supply or installed capacity. The labels are as important as the numbers.
Frequently asked questions
Which is the largest project in this Sikkim hydropower list?
Teesta III has the largest stated project capacity at 1,200 MW. Its reconstruction context must be stated alongside that figure; historical capacity alone does not establish present generating availability.
Is Teesta V still closed after the 2023 flood?
NHPC reports that Teesta V was restored in July 2026. This is the dated status used here, replacing older expectations about when restoration might occur.
Are Rangit and Rangit IV the same project?
No. The established Rangit project is 60 MW, while Rangit IV is a separate 120 MW development. Their capacities, project records and commissioning status must be checked separately.
Is Teesta VI already generating 500 MW?
The reviewed project information places Teesta VI in the construction category. Its 500 MW figure is project capacity, not evidence of current commercial generation or a continuously available supply.
Are all Teesta dams located in Sikkim?
No. The Teesta basin crosses state boundaries. Teesta Low Dam projects in West Bengal should not be confused with similarly numbered Teesta projects in Sikkim.
Does a hydropower map show flood safety?
No. A project-location map identifies infrastructure. Flood-inundation modelling, slope assessment and evacuation planning require different information and cannot be inferred from the positions of dam symbols alone.
Sources and data notes
Installed capacity is not annual generation. Teesta V restoration in July 2026 is supported by NHPC’s own statement. Reconstruction documents for Teesta III and completion targets for new projects do not establish present commercial operation.
- Sikkim Power Department: hydel-project register; historical commissioning and capacity data
- NHPC: hydropower-project directory and construction categories
- NHPC: August 2026 generation statement, confirming Teesta V restoration in July 2026
- MoEFCC / PARIVESH: January 2025 review documents for restoration of the 1,200 MW Teesta III project
- NHPC: Teesta VI project information, 500 MW
- NHPC: Rangit IV project, 120 MW, with expected commissioning date
- Sattar and colleagues: The Sikkim flood of October 2023, Science 387, eads2659 (2025); DOI 10.1126/science.ads2659
- Government of Sikkim: high-level coordination meeting on GLOF preparedness, 10 September 2026