1. On 29-10-1886, a lease indenture for 999 years was made between Maharaja of Travancore and Secretary of State for India for Periyar irrigation works. By another agreement in 1970, Tamil Nadu was permitted to generate power also. The Mullaperiyar Dam was constructed during 1887-1895. Its full reservoir level is 152 and it provides water through a tunnel to Vaigai basin in Tamil Nadu for irrigation benefits in 68558 ha area.
2. In 1979, reports appeared in Kerala Press about damage to Periyar Dam. On 25th November, 1979 Chairman, CWC held meeting with the officers of Irrigation and Electricity, Deptt. of Kerala and PWD of Tamil Nadu and some emergency medium term measures and long-term measures for strengthening of Periyar Dam were decided. A second meeting under the Chairmanship of Chairman, CWC was held on 29th April 1980 and it was opined that after the completion of emergency and medium term measures, the water level in the reservoir can be raised up to 145 ft.
3. The matter became subjudice with several petitions. On the directions of the Supreme Court in its order dated 28.4.2000, Minister (WR) convened the Inter-State meeting on 19.5.2000 and as decided in the meeting, an Expert Committee under Member (D&R), CWC with representatives from both States was constituted in June 2000 to study the safety of the dam. The Committee in its report of March, 2001 opined that with the strengthening measures implemented, the water level can be raised from 136 ft. to 142 ft. without endangering safety of the dam. Further raising of water level to 152 ft. would be considered after balance strengthening measures are implemented.
4. The Supreme Court in its orders on 27.02.2006 permitted the Government of Tamil Nadu to raise the water level of Mulla Periyar dam from 136 ft. to 142 ft. and to carry out the remaining strengthening measures. After that the Government of Kerala passed the Kerala Irrigation and Water Conservation (Amendment) Act 2006 on 18th March 2006 which prohibited the raising of water level beyond 136 ft. in the Mulla Periyar Dam and placed it in the Schedule of ‘Endangered Dams’. Government of Tamil Nadu filed a suit in the Supreme Court on 31.3.2006 praying for declaration of above Act as unconstitutional in its application to and effect on Mulla Periyar Dam and restraining the State of Kerala from obstructing Tamil Nadu to increase the water level to 142 feet .
5. The Union Minister (WR) convened an inter-State meeting of the Chief Ministers of States of Tamil Nadu and Kerala on Mullaperiyar dam issue on 29.11.2006 at New Delhi. Both States reiterated their respective stand in the meetings and no consensus could be reached regarding a solution acceptable to both States.
6. Subsequently, Chief Minister of Tamil Nadu met Prime Minister on 18.12.2007 and Prime Minister suggested him to have a meeting with Chief Minister of Kerala on Mulla Periyar issue. Chief Minister of Tamil Nadu met Chief Minister of Kerala on 19.12.2007 in presence of Union Minister of Water Resources. Chief Minister of Tamil Nadu vide letter dated 20.12.2007 mentioned that in the above meeting, he had suggested to oversee the seepage measurement of the dam by engineers not belonging to either of the two States through CWC and Chief Minister of Kerala agreed to consider this. However, a consensus of both the states on such monitoring mechanism could not be achieved
7. In the meanwhile, Govt. of Kerala has done hydrological review studies through a professor of IIT, Delhi. It has been concluded in the report that the Mulla Periyar dam is hydrologically unsafe for passing the estimated Probable Maximum Flood. CWC examined this report and observed that the report does not appear to be well founded.
8. Secretary (WR) convened an interstate meeting on the Mulla Periyar Dam on 31.7.2009. In the meeting the representative of Kerala informed that the Kerala Govt. visualizes construction of a new dam as the only feasible solution. They could also consider the construction of a new dam at their own cost. Later, Govt. of Tamil Nadu vide letter dated 14.09.09 mentioned that there is no need for construction of a new dam by the Kerala Government, as the existing dam after it is strengthened, would function like a new dam.
9. The Mulla Periyar case was heard by five judges on 18.02.2010 and the Court directed Central Govt. to constitute an empowered Committee in this regard within four weeks time which would hear the parties to the suit on all issues that will be raised before them, and furnish a report, as far as possible, within six months from their constitution. The Committee was constituted vide notification dated 30.4.2010 and term of the Committee has been extended from time to time by the Supreme Court. The present term of the Committee is upto 29.02.2012.
10. The Empowered Committee had submitted its report to Supreme Court in April, 2012.