"I don't know on what basis the Prime Minister took the decision asking Karnataka to release 9,000 cusecs of Cauvery water to Tamil Nadu till October 15. The decision is unscientific and aimed at pleasing one section of the people," he told reporters in Bangalore.
Mr Yeddyurappa said the Prime Minister issued the direction without taking into account the existing ground realities when Karnataka is facing severe drought and drinking water problems. "The decision will disturb harmony between the two neighbouring states," he said.
The meeting of the Cauvery River Authority on Wednesday failed to produce a solution with both Karnataka and Tamil Nadu rejecting Prime Minister Manmohan Singh's award of 9000 cusecs to save standing crops in the delta region.
Terming September 19 as a 'black day' in the annals of Karnataka politics, Mr Yeddyurappa said Karnataka cannot release Cauvery water to Tamil Nadu when there was no water in store.
Coming down heavily on state Congress leaders, Mr Yeddyurappa said Union Ministers and Opposition Leader in State Assembly Siddaramaiah failed to convince Mr Singh.
Meanwhile, the 'Cauvery Hitharakshana Vedike' (Cauvery Protection Committee), headed by former Congress MP G Made Gowda, said in Mandya that the forum has decided to hold a week-long token agitation in Mysore, Chamarajanagar and Mandya districts.
The Committee at its meeting hailed Chief Minister Jagadish Shettar's resolve not to release water and appealed to him to adhere to it.
Protesting against the award, Karnataka Chief Minister Jagadish Shettar had staged a walkout from the CRA meeting, saying the state was not ready to give "even a drop of water" to Tamil Nadu.