Subansiri Lower Hydroelectric Project (SLHEP)

Source: DH

Subject: Mapping

Context: India’s largest hydropower project, the 2,000 MW Subansiri Lower Hydroelectric Project, has become operational after nearly 20 years, with the commissioning of its first 250 MW unit.

About Subansiri Lower Hydroelectric Project (SLHEP):

What it is?

• The Subansiri Lower Hydroelectric Project is a run-of-the-river hydropower project with an installed capacity of 2,000 MW, making it India’s largest hydropower project once fully commissioned.

Located in: Gerukamukh, on the Assam–Arunachal Pradesh border

• Implemented by NHPC Limited (National Hydroelectric Power Corporation)

River flow through: Built on the Subansiri River, the largest tributary of the Brahmaputra River

Project History:

• Approved: 2003

• Challenges (2011–2019): Progress was delayed by environmental impact studies, seismic safety reviews, and public protests in downstream Assam.

• Operational Launch: The first 250 MW unit began operation in December 2025.

• Completion Schedule: The remaining seven units (250 MW each) are scheduled for commissioning between 2026 and 2027.

Key Specifications:

• Type: Concrete Gravity Dam

• Height: 116 m (from riverbed) / 210 m (from deepest foundation)

• Length: 284 m

• Engineering Highlights: The dam features several landmark achievements for India’s hydroelectric sector, including:

• The country’s heaviest hydro generator rotors. Its largest stators and inlet valves. The first use of the Rotec Tower Belt system for dam concreting.

• The country’s heaviest hydro generator rotors.

• Its largest stators and inlet valves.

• The first use of the Rotec Tower Belt system for dam concreting.

• Strategic Benefits: Beyond power generation, the project will provide:

• Flood Control: Moderation of downstream flooding in Assam. Grid Stability: Enhanced resilience and reliability of the national power grid. Clean Energy Goals: Direct support for national Net Zero and renewable energy targets.

• Flood Control: Moderation of downstream flooding in Assam.

• Grid Stability: Enhanced resilience and reliability of the national power grid.

• Clean Energy Goals: Direct support for national Net Zero and renewable energy targets.