Here are 10 points on the dispute:
About 76 km of Mahadayi's 111-km length runs through Goa and the rest is in Karnataka. It passes through Maharashtra briefly before emptying into the Arabian Sea.
The dispute over the sharing of river waters started in the 80s when Karnataka designed a chain of dams and canals under the Kalasa-Banduri Nala project to channel Mahadayi's water to the Malaprabha basin in north Karnataka.
While proposing the project, it said the water will be used for irrigation purposes in the districts of Dharwad, Belagavi, Bagalkot and Gadag, which are known to face acute water scarcity.
Karnataka pegged its demand for Mahadayi water at 7.56 thousand million cubic feet to meet the "drinking requirement" of farmers in northern districts, but Goa, which had raised objections to the project.
Goa says that it is water-deficient and sharing any water with its neighbour would cause ecological damage to the state. Therefore, the project wasn't given a go ahead.
In 2002, Goa demanded that a tribunal be set up to assess the situation. After several attempts at negotiation failed, the Mahadayi Water Disputes Tribunal was finally set up in 2010.
Karnataka sought the tribunal's green signal for the Kalasa-Banduri project, arguing that the river must be used for drinking purposes instead of letting it out into the sea. But in 2016, the tribunal rejected the demand triggering protests in the state.
The tribunal is expected to hear the final arguments in the matter next month.
In July last year, farmers held a silent protest before going big towards the end of 2017. They protested outside the BJP office in Bengaluru in December claiming that state BJP chief BS Yeddyurappa had not lived up to his promise to resolve the water sharing issue by the end of the year.
With elections due in Congress-ruled Karnataka, political parties will go all out to woo voters and the Mahadayi issue seems to be among every party's preferred choices.