Mahadayi diversion project will have less impact on Goa: Study

Karnataka’s plans for diversion of Mahadayi water, as approved by the Mahadayi Water Disputes Tribunal (MWDT), would have less of an impact on Goa and can be mitigated by measures, says a paper by the National Institute of Oceanography (NIO), Goa.

The paper - The water budget of the Mahadayi river and its implications for the inter-state dispute - by researchers K Anilkumar, D Shankar and K Suprit, published in Journal of Earth System Sciences, says while the diversion from the Kalasa tributary could have “significant impact” on the northern part of the Mhadei Wildlife Sanctuary, the impact of diversion from the Bhandura Nala is negligible for the Mahadayi’s runoff in Goa.

The researchers say by creating check dams and storage facilities inside the wildlife sanctuary the ecological impact of river diversion can be minimised.

Both Karnataka and Goa have been tangled in over two-decade-long legal battle over the utilisation of Mahadayi waters.

In 2018, the MWDT had allocated 5.4 tmc ft of water for Karnataka, out of which 3.9 tmc ft could be diverted outside its basin for drinking water purpose in parched areas of Belagavi, Dharwad, Gadag and Bagalkot districts. Though the order was notified in 2020, the matter is still being disputed in the Supreme Court by both the states.

The Mahadayi basin covers an area of 2,032 sq km of which 380 sq km (18%) is in Karnataka, 72 sq km (4%) in Maharashtra, and 1,580 sq km (78%) in Goa. The tribunal has permitted Karnataka government to utilise 1.72 tmc ft of water from Kalasa Nala and 2.18 tmc ft from Bhandura Nala (two of the main tributaries of Mahadayi).

Shankar, Chief Scientist at CSIR-NIO and the co-author of the paper, said that the water that would be diverted by Karnataka works out to less than one fourth of one standard deviation or less than the natural variations in river flow during the monsoon months.

The paper also debunks Goa’s argument that diversion of Mahadayi water will adversely impact the drinking water availability for major cities, including Panjim, and the ecology at Mahadayi estuaries.

“Estuaries are critical ecological sites and the salinity at the Mahadayi estuaries is dynamic and varies based on the rainfall,” he said.

The paper says if both the states “co-operate” it could resolve their drinking water crises.

“Instead of building multiple reservoirs inside the thickly forested area to divert water from three major streams (Surla stream) of Mahadayi, both the governments can co-ordinate and construct storage dam at the confluence of Mahadayi and Bandura nala as it falls on the leeward side of the Ghats. This would result in lesser impact on forest area.  Like Goa and Maharashtra are sharing drinking water from Tillari dam, a similar system can be found from Mahadayi river also,” he say.