MULLAPERIYAR DAM - GEOGRAPHY

News: Water level in Mullaperiyar touches 136 ft, first warning issued 

What's in the news?

       Tamil Nadu has issued the first warning with water level in the Mullaperiyar dam reaching 136 ft on November 9 evening.

       The upper rule level is 141 ft till November 20, as per the present rule curve for the dam. The maximum storage level as per the Supreme Court order is 142 ft.

Mullaperiyar Dam:

       The Mullaperiyar dam, built 126 years ago, is located in Kerala's Idukki district at the confluence of the Mullayar and Periyar rivers.

       The dam has a height of 53.66 meters and a length of 365.85 meters.

       Tamil Nadu owns, operates, and maintains the dam under a 999-year lease contract signed in 1886 in between Maharaja of Travancore and the Secretary of State for India for Periyar Irrigation Works.

       Tamil Nadu maintained it for a number of reasons, including irrigation, drinking water supply, and hydropower generation.

       It is a masonry gravity dam built of concrete and stone, with the weight of the dam pressing it down onto the foundation.

       In November 2014, the water level hit 142 feet for the first time in 35 years.

       The reservoir again hit the maximum limit of 142 feet in August 2018, following incessant rains in the state of Kerala.

       Indeed, the tendency to store water to almost the full level of reservoirs is becoming a norm among water managers across States.

Rule curve:

       A dam’s rule curve determines the reservoir’s fluctuating storage levels.

       A dam’s gate opening schedule is determined by the rule curve.

       It is a component of a dam’s “core safety” mechanism.

       The level of the rule curve is fixed to avoid emergency dam shutter opening in the event of a flood-like situation.

       It aids in maintaining a stable water level in the dam during the monsoon season.

Periyar river:

       The Periyar is the longest river in the state of Kerala with a length of 244 km.

       It is also known as ‘Lifeline of Kerala’ as it is one of the few perennial rivers in the state.

       It originates from Sivagiri hills of Western Ghats and flows through the Periyar National Park.

       The main tributaries of Periyar are Muthirapuzha, Mullayar, Cheruthoni, Perinjankutti.