Presiding over the agitation, MDMK chief Vaiko, also coordinator of the movement, alleged that Karnataka was trying to build new dams across the inter-state river by flouting orders of the Cauvery Tribunal.
If new dams were built, Tamil Nadu will not receive water and its consequences would be 'unimaginable', he added.
Opposing methane extraction, he said prevention was better than cure, and demanded that the project proposed in the Cauvery Delta region of the state be scrapped.
The movement had staged similar protest on February 18 last in 13 districts including Thanjavur and Nagapattinam.
On January 1 this year, Vako launched the movement to mobilise public opinion and spearhead agitations on issues including Mekedatu and Methane project.