The three states benefit from both the southwest and northeast monsoons and encompass a major portion of the Western Ghats, which give rise to most of South India's rivers.
A petition was filed before the Supreme Court on Monday seeking directions to resolve the issue and ensure that Tamil Nadu receives its rightful share of Cauvery water within the stipulated time.
The demonstration, attended by farmers and DMK cadres, demanded immediate steps to halt Karnataka's proposed Mekedatu dam project, and declaration of the Cauvery Delta districts as drought-hit.
