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Mahadayi River
The Mahadayi (also known as the Mandovi) is a trans‑state river that originates in the Western Ghats of Karnataka and flows westward into Goa before emptying into the Arabian Sea. It supplies drinking water to thousands, supports agriculture, and underpins a major hydro‑electric project. In 2018, the Supreme Court allocated 188.5 cusecs to Karnataka and 71.5 cusecs to Goa.
Mahadayi River, also known as the Mandovi in Goa, is a trans‑state watercourse that rises in the Western Ghats of Karnataka and courses westward into the coastal state of Goa before discharging into the Arabian Sea. Its 81 km length and a catchment of roughly 2,200 km² make it a vital source of drinking water for over two million residents, a backbone for rice‑paddy cultivation on about 10,000 ha, and the linchpin of a contested 340 MW hydro‑electric scheme.
Geographic Origin and Course
The river originates near the village of Amboli at an elevation of approximately 800 m in the Sahyadri range of Karnataka’s Belgaum district. From its source it traverses the hill stations of Mahabaleshwar and Haliyal, descending through the dense forests of the Western Ghats before crossing the Karnataka–Goa border near Sanguem. In Goa the river is renamed Mandovi, widens near the capital Panaji, and empties into the Arabian Sea at the Mandovi estuary, a tidal zone that supports mangroves and a historic port.
Historical, Cultural, and Economic Significance
For centuries the Mandovi served as the principal inland navigation route for Portuguese traders, who established the first European settlement in Goa along its banks in 1510. Local folklore records the river as “Mandavya,” a name derived from the Sanskrit sage Mandavya, reflecting its deep cultural resonance among Konkani‑speaking communities. Economically, the Mahadayi supplies potable water to the Karnataka districts of Belgaum, Dharwad, and Haveri, where municipal treatment plants draw an average of 150 cusecs daily. In Goa, the river’s lower reaches irrigate paddy fields and sustain a fisheries sector that contributes roughly ₹1.2 billion to the state’s annual revenue.
Inter‑State Water Dispute and Supreme Court Allocations
The divergent water needs of Karnataka and Goa sparked a formal dispute in 2006, prompting Karnataka to file a petition before the Supreme Court of India under the Inter‑State River Water Disputes Act, 1956. After a tribunal was constituted in 2010, the apex court delivered its landmark judgment on 31 May 2018, allocating 188.5 cusecs to Karnataka, 71.5 cusecs to Goa, and reserving 30 cusecs for ecological flow to preserve the Mandovi estuary’s salinity balance. The same judgment mandated the creation of a joint monitoring committee chaired by the Union Water Resources Minister, a provision that remains operative despite a 2020 stay order that temporarily halted the Kalasa‑Banduri diversion works pending further environmental review.
Mahadayi Water Project: Infrastructure and Contemporary Issues
The Mahadayi Water Project, popularly called the Kalasa‑Banduri scheme, envisages a 35 km tunnel and a series of lift‑irrigation stations to convey the allotted 188.5 cusecs from the river’s upper catchment to Karnataka’s drought‑prone interior. Construction began in 2015, and by early 2024 more than 2.5 km of the tunnel had been completed, with an estimated cost of ₹12,500 crore funded jointly by the central and state governments. Parallel to the diversion works, the Mahadayi Hydro‑Electric Project at Kankumbi is slated to generate 340 MW, a capacity that would rank among the top ten hydro‑electric installations in the Western Ghats. Critics from Goa and environmental NGOs argue that reduced freshwater inflow threatens the estuarine mangrove ecosystem, prompting the Ministry of Environment, Forest and Climate Change to demand a supplemental impact assessment before the project can proceed to commissioning, expected in 2025.