"You are requested to instruct the officials of your water resources department to immediately open the gates of Kalma barrage and ensure free flow of water in Mahanadi river," Patnaik wrote to Raman Singh.
Stating that Kalma barrage was one of the six barrages unilaterally taken up by Chhattishgarh government across the inter-state river Mahanadi without any reference or regard to the downstream interests of Odisha and its inhabitants, Patnaik said, "The report available with my government definitely convey that your government has gone ahead and closed the gates of Kalma barrage stopping free flow of water."
In downstream areas of Odisha, the action has affected the drinking water supply of people in Sambalpur, Jharsuguda, Bargarh districts and many other districts have been affected, he said.
There is "widespread unrest" due to the "unilateral action", Patnaik said adding "This unrest may go out of hand, if free flow downstream of Kalma barrage in Mahanadi river is not restored immediately."
"I emphatically state that this unilateral action of your government in closing the gates of Kalma barrage and stopping free flow of water is wholly contrary to the inter-state riprarian rights as per the 1945 understanding (under the chairmanship of Dr B R Ambedkar) when the Hirakud Dam was planned," Patnaik said in his letter.
Odisha govenrment, he said, has already filed a statutory complaint under section 3 of the Inter-state River Water Dispute Act of 1954 and one of the disputes in the complaint specifically refers to the six barrages, including Kalma.
During pendency of the reference of the complaint to an Inter-state Tribunal, Odisha government has also filed an original suit in Supreme Court along with interlocutory application to restrain Chhattisgarh government from proceeding with the construction of six barrages, including Kalma barrage across Mahanadi river, Patnaik said.
"Your government has appeared in the Hon'ble Supreme Court through counsel and when the matter is pending before the apex court, it is expected of your govenrment to maintain status quo regarding free flow of water in Mahanadi river at Kalma barrage," he said.
The engineer-in-chief of Odisha government had written to his Chhattishgarh counterpart on May 31 giving technical details on the matter.
This apart, the principal secretary to the water resources department of Odisha government has also apprised the matter to the corresponding department in Chhattishgarh, he added.