The Rule Curve comes into effect between June 10 and November 30, during which the dam gets maximum inflows from the South West Monsoon.
The Rule Curve comes into effect between June 10 and November 30, during which the dam gets maximum inflows from the South West Monsoon.
What is the Rule Curve?
Rule Curve is a tabulation which specifies quantum of storage of water or empty space to be maintained in a reservoir during different times of a year, based on the rainfall data for 35 years.
It is a ready-reckoner in decision-making for officials in charge of the dam, for smooth operation of shutters, especially for moderation of flood, during monsoon times without having to seek permission from the top hierarchical ladder.
First dam to have Rule Curve:
According to Tamil Nadu Water Resources Organisation, Mullaperiyar is the first reservoir to have Rule Curve implemented, in the country.
Water of the Mullaperiyar dam, has remained a bone of contention between Tamil Nadu and Kerala for over four decades. After a long legal battle, the Tamil Nadu Government was allowed by Supreme Court to raise the water level from 136 feet to 142 feet in 2014. However, Kerala insisted urged the Supreme Court to insist that Tamil Nadu, which maintains and operates the dam, prepare a Rule Curve for flood control and flood management.
It had earlier alleged that sudden and unannounced release of flood water through Mullaperiyar dam caused severe damage to Kerala. Though Tamil Nadu Government delayed it with various reasons, it prepared the draft Rule Curve for the reservoir in consultation with Hydrology Wing of the Central Water Commission. And it was first implemented in October 2021. Water was released from the dam much before it could touch 142 feet, raising a huge hue and cry among the farmers and politicians of the State.
Restriction of water level:
The Rule Curve comes into effect between June 10 and November 30, during which the dam gets maximum inflows from the South West Monsoon.
The upper limit of the water level has been fixed for every block period of 10 days of each month based on 35 years of data on water inflow and irrigation pattern. It has been fixed between 136 feet starting June 10 to 142 feet in September 20. Then again, the upper limit is reduced from September 30 and then gradually raised to the maximum permissible level of 142 feet by November 30.
The fear of Tamil Nadu is that Kerala was indirectly trying to restrict it from maintaining the water below the maximum level of the 142 feet permitted by the Apex Court, in the reservoir which has 152 feet as the full reservoir level and to dissolve the sub-committ
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