The claims by Karnataka is ridiculous. The cauvery water(meagre quantity) that karnataka releases to Tamilnadu is measured in Biliguntlu before entering Hogennakal and hence its Tamilnadu right to use the water in whatever way it chooses (in this case - a drinking water project to two water deficient districts of north Tamilnadu). Karnataka's business is to release water and doesn't have any right to determine how TN people should use it. Its their business.
Morover, Honenakkal project was sanctioned in 1999 with the largest aid coming from Japan but was closed due to various sanctions imposed on India (Pokhran tests).This project was long overdue. Karnataka never raised voice then!!!. They never claimed Hogenakkal during Veerappan days. Now suddenly they have woken up as they are doing on Belgaum and other land grabbing issues. One day, they may even claim the Wayanad of Kerala.