There is a very beautiful saying in Tamil about Cauvery: “Only if Cauvery comes walking, she is prosperity. If she comes running, she is a disaster.” You can make her walk only if there is substantial vegetation in the catchment. Catchment does not mean just the one valley where the river arises. Every square inch of land in a tropical climate is catchment. Wherever you have trees, water will percolate into the soil. If there are no trees, the water will runoff.