Context

Two spillway shutters of the Mullaperiyar dam in Idukki district were opened recently after the water level crossed 138 feet.

About

About the Mullaperiyar dam

• The Mullaperiyar Dam is a 126-year-old composite gravity dam located in the upper reaches of the river Periyar, which flows into Kerala after originating in Tamil Nadu.
• The reservoir is within the Periyar Tiger Reserve.
• The water diverted from the reservoir is first used for power generation in lower Periyar (by Tamil Nadu) before flowing into the Suruliyar, a tributary of Vaigai river, and then for irrigating nearly 2.08 lakh hectares in Theni and four other districts farther away.

History/Background

• In 1886, the then Maharaja of Travancore signed the ‘Periyar Lease Deed’ with the British government, which considered the Periyar waters useless to Travancore and wanted to divert the water into arid regions of Tamil Nadu.
• After 20 years of resistance, the agreement was signed and the dam was constructed in 1895.
• The Madras government started hydel power generation in 1959, the capacity of which was increased to 140 MW.
• Kerala brought up the issue of safety before the Central Water Commission in 1961.
• After a joint inspection by Kerala and Tamil Nadu in 1964, the water level was reduced for the first time, from 155 ft to 152 ft.
• In the following years, Tamil Nadu witnessed public agitations demanding that the level be increased.

Timeline of the Mullaperiyar Dam Dispute

• In 2000, the Centre appointed an expert committee to look into safety and suggest storage levels.
• In 2006, the Supreme Court allowed Tamil Nadu to raise the water level to 142 ft.
  • The Kerala Assembly amended the Kerala Irrigation and Water Conservation Act, 2003, in March 2006, bringing Mullaperiyar in the schedule of ‘Endangered Dams’ and restricting its storage at 136 ft. Since then, the issue has shifted to the safety of the dam.
• In 2007, the Kerala Cabinet permitted preliminary work on a new dam which was opposed by Tamil Nadu in Supreme Court.
• In 2010, the Supreme Court formed an empowered committee to look into the dam’s safety.
• In November 2011, Kerala sought the Centre’s intervention to bring down water levels to 120 ft after the area witnessed minor tremors.
• In 2014 came the Supreme Court order allowing Tamil Nadu to fix the water level at 142 ft.

What is the current dispute?

• In October 2021, the Supreme Court directed that the maximum water level in Mullaperiyar dam should be 139.50 ft.
• The order came out after a court-appointed supervisory committee had suggested 139.50 ft as the permissible level and the court ordered both states to comply with the committee’s recommendation.
• Tamil Nadu had wanted the level increased to 142 ft as fixed by the Supreme Court in 2014, while Kerala wanted it within 139 ft as per a rule curve fixed.
• Kerala, while seeking a limit of 139 ft, pointed to a Supreme Court directive in August 2018 following the devastating floods in the state.
• One of the factors contributing to the floods was sudden discharge from the Mullaperiyar dam, after its water level went beyond 142 ft and all spillway shutters of the dam suddenly lifted.
• The excess water from Mullaperiyar had then flowed to downstream Idukki reservoir, which was also at maximum storage level. The unexpected flow forced Kerala to increase the discharge, leading to flooding of several parts of central Kerala. The situation in 2021 is not different.

Is there a need for a new dam in place of Mullaperiyar Dam?

• The Mullaperiyar Dam is a 126-year-old composite gravity dam and that seismic forces were not given consideration while building the dam which, despite strengthening measures having been undertaken taken twice, is in a deteriorating condition due to its age.
• The dam has a large catchment area but only limited storage capacity which further increases its vulnerability.
• The consequences of any failure of this dam could be extremely catastrophic and beyond human imagination.
• In 2008, a flood routing study by IIT Delhi found the dam was unsafe; in 2009, IIT Roorkee reported the dam was in an earthquake-prone area and would not survive a major quake.
• Construction of a new dam would also give rise to a new water-sharing treaty; at present, only Tamil Nadu has rights over the dam water.