The Tamil Nadu Water Resources Department has already communicated the same to the Kerala government on Wednesday night as an evacuation in Idukki district is required for the opening of the spillways.
Kerala Water Resources Minister Roshy Augustine had earlier requested the Tamil Nadu government to inform the state well in advance so that the evacuation process is smooth.
The spillways of the dam are to be opened following incessant rains in the catchment areas of Mullaiperiyar.
The water level in the dam crossed 137.80 ft at 9 p.m. on Wednesday. The maximum water level in the dam set up by the Central Water Commission (CWC) is 138 ft and the water level is all set to cross this rule curve by Thursday morning.
Tamil Nadu has been drawing 2,300 cusecs of water from the dam and the inflow was 5,800 cusecs on Wednesday.
Meanwhile, Kerala has expressed its dissent in Supreme Court on Wednesday after the Mullaiperiyar dam supervisory committee had submitted that that there was no need to change the 142 ft water height in the dam which was set by the apex court.
Tamil Nadu Chief Minister M.K. Stalin on Wednesday night wrote a letter to his Kerala counterpart Pinarayi Vijayan stating that his state was monitoring the situation of the Mullaiperiyar dam and the water flow into it.
Stalin also mentioned that officials of both Kerala and Tamil Nadu are in constant touch with each other and that the situation was under control.
He added that the state was pumping out maximum water from the Mullaperiyar dam through the Vaigai tunnel into Tamil Nadu.
Stalin was responding to a letter sent by the Kerala Chief Minister on Monday that the water level in Mullaiperiyar was rising rapidly and requested the Tamil Nadu side to take maximum water through the Vaigai tunnel for the state.
The Mullaiperiyar dam constructed in 1895 by British Engineer John Pennycuck is under major discussion between the states of Kerala and Tamil Nadu.
While the Kerala side wants to construct a new dam by deactivating the present one, there were several objections from the Tamil Nadu side.
The UN Research University had recently in a report said that Mullaiperiyar dam had outlived its life span and that like several dams that are above 50 years of age, it was also in danger.
The Chief Ministers of Tamil Nadu and Kerala along with the water resources ministers of the respective states are slated to meet in Chennai in December regarding the future course of action on Mullaiperiyar.