The mullapperiyar issue
Mullapperiyar is a dam on the Kerala-Tamil Nadu border (Check out Mullapperiyar dam on wikimapia. ) which is more than 100 years old. Mullapperiyar dam even though is located in Kerala, is used by Tamil Nadu. Tamil Nadu wants to increase the height of the dam. Obviously Kerala opposes this since there are strong concerns about the safety of the dam (Click here for dam cross section).
It seems that spillways on the dam are not sufficient if there is heavy rain for a long period and it happened recently. As can be seen from the above map, if anything happens to mullapperiyar dam, everything will flow to the main Idikki dam. No one knows what will happen in such a case. Destruction of Idikki dam will submerge at least 3 districts, causing huge loss of life.
This issue is now affecting Kerala-TamilNadu relationship. Kerala is dependent on Tamil Nadu products and there are lot of Keralites in Tamil Nadu and vice versa. Unfortunately politicians on both sides have made the issue worse by irresponsible comments.
I think only reasonable solution is to strenghten the dam, keep the water height as it is now and then build a new one!
Further Reading
Roy Mathew's report