What will PM do if DMK pulls plug on Cauvery?

The dramatic announcement by the Prime Minister Manmohan Singh today that all divestment proposals of the UPA government have been put on hold following the threat by the DMK to pull out support in the Neyveli Lignite Corporation issue, throws up a simple question: what will the coalition government do if the DMK and the PMK resort to similar brinkmanship on the Cauvery water issue? Yes, it is raining copiously this year, so the question doesn’t arise. But, what if?