Received from an anonymous source...
Here is an interesting link to the tussle of almost 150 years over the Cauvery waters between what started out as Mysore and Madras presidencies and now Karnataka, Kerala and Tamil Nadu. Thanks to the last few rulers in the south and Tipu Sultan, the "Tamil" portions receded into the arid parts and Kerala and Karnataka received the more fertile parts, the only exception being the areas in the Karnataka, Kerala and Tamil Nadu borders.
The last 40 years have been especially fun, since Kannadigas have become more aware of their identity and started asserting it. The relatively obscure Mysore presidency became Karnataka and the political mismanagement of Tamil Nadu allowed it to become more economically stronger. The presidencies themselves were not linguistically divided, hence the relative lack of malice among the various South Indian ethnicities. Tamil Nadu's economic demise is owned in part to it's own "kick them out" movement related to the educated upper class, many of whom are now settled in Karnataka and speak poor Tamil and bear the brunt of being Tamilians there.
The Hogenakkal dam is an absolute waste of money, but it can be done. The maximum amount Karnataka seems to have released during drought times seems to be 19 TMC against a supreme court directive of 205 TMC. Even those were accompanied by torching Tamil Nadu related items or violence against ethnic Tamilians. Ofcourse the Hogenakkal dam is not needed if Karnataka releases the required amount of water. But that is not going to happen as the water is diverted at very high costs to other parts of Karnataka and there are no votes to be gained by letting the water run its natural course. If the water ran it's natural course, Tamil Nadu will definitely get more that what Karnataka finds in its heart to release. But that is water under the bridge now. Dam it!