For argument's sake, lets assume that we use "the underutilized" ground water in T.N. Lets say that next year Karnataka takes all the water in Cauvary. And T.N uses the ground water next year.
What will T.N do for year after next year? It is precisely for this reason that Commission was setup and they awarded the water according to the feedback from experts who actually seen the ground realities in both side of the border.