Hirakud Dam

Hirakud Dam is one of India's largest multipurpose dam projects and the longest dam in the country when measured including its earthen embankments and flank dykes (25.79 km). Located on the Mahanadi river at Sambalpur in Odisha, the dam was completed in 1957 — making it India's first major post-Independence multipurpose project.

The project was conceived in 1937 by Sir M. Visvesvaraya and sanctioned in 1947 as one of the early flagship Nehruvian-era infrastructure projects. Foundation stone laid by Prime Minister Jawaharlal Nehru on 12 April 1948; full commissioning in October 1957.

The composite structure combines: a 1.1 km long concrete gravity main dam (with crest spillways), 4.5 km of earthen embankment dam on the right bank, and a network of flank dykes totalling 21 km on both banks — together forming the 25.79 km perimeter that gives the project its 'longest dam' designation. Mass concrete construction on Eastern Ghats granite bedrock.

The Hirakud reservoir impounds 5.8 cubic km of water — sufficient to irrigate 1.55 lakh hectares of farmland in coastal Odisha and provide flood mitigation for the Mahanadi delta (which previously flooded catastrophically). The 347.5 MW Hirakud Power Station (across two units) feeds the Eastern Grid.

The dam created a 743 km² reservoir — the largest man-made lake in India at the time. Major secondary infrastructure includes the Burla town that grew up to support project workers (now a heritage town). Hirakud has been a critical model for Indian water-resources development, with its lessons informing later projects like Bhakra and Sardar Sarovar.