The current water level of the dam is 136 feet and the status quo is to be maintained by orders of the Supreme Court, pending final decision by the Supreme Court. Tamilnadu wants it to be raised to 142 ft and even higher to the full water level of 155 feet, to meet its water supply requirements.
Kerala wants it to be lowered to 120 feet, citing safety concerns. The dam is an endangered scheduled dam under the Kerala Irrigation and Conservation of Water (Amendment) Act of 2006. The Act fixes 136 feet as the allowable maximum water level for the dam. The provisions of the Kerala dam safety Act have been challenged by Tamilnadu in the Supreme Court. The decision of the Supreme Court concerning this, is awaited.
The Supreme Court judgment of 2006 ruled that the water level could be raised to 142 feet from 136 feet, based on the technical report of Central Water Commission on the safety of the dam. The Supreme Court then did not consider the water requirements of Tamilnadu and whether those requirements could be met at a lower level. The earlier decision of the Supreme Court is now being revisited by the current case pending before the Supreme Court.
The question is: Should the water level be raised or lowered?
Safety considerations would require that the water stored in the reservoir must be at a minimum level to reduce hydrostatic pressure on the dam. Damages arising from a potential dam collapse would be minimized if the storage level is minimized.
Can Tamilnadu's water needs be met at a lowered water level of 120 feet or lower without affecting water supply to Tamilnadu?
Tamilnadu draws water from the dam from a water level of 104 feet upwards, since the upper level of the tunnel through which water flows down to the Cumbum Valley is 104 feet. The water flows down through the rock-cut tunnel to Forebay dam near Kumili (Errachipalem) in Tamilnadu. From Forebay dam, hydel pipe lines carry the water to the Periyar Power Station in Lower Periyar, Tamil Nadu. This is used for power generation (175 MW capacity) in the Periyar Power Station.
From Periyar Power Station, water is let out to Suruliyar, a tributary of Vaigai. Suruliyar carries the water to Vaigai Dam, from where water is distributed for irrigation, drinking water supply and industrial use through the network of water channels.
The water is thus used by Tamilnadu for power generation, irrigation, drinking water supply and industrial use. It is not clear how much water is actually drawn by Tamilnadu to meet these requirements.
Is it not possible for Tamilnadu to draw the water through the tunnels and store them in Forebay dam and also in Vaigai dam for the intended use, without storing the water in Tekkadi reservoir? Or is it a question of 'asking for more and more' without caring for the milking cow's age and safety?