By Panu Wongcha-um and Kay Johnson
BANGKOK (Reuters) – China has notified downstream neighbors that it is holding back the flow of the Mekong River at a hydroelectric dam on the upper course of the waterway for 20 days as part of a new data sharing pact, the Mekong River Commission (MRC ) and Thailand said on Wednesday.
The statements were made a day after a new US-backed monitoring system said China had not notified downstream countries of the water restrictions that began on December 31.
China agreed last October to share water data with MRC, an advisory body for Thailand, Laos, Cambodia and Vietnam that has long sought information for planning.
More than 60 million people in these countries depend on the river for fishing and agriculture.
The National Water Command Center of Thailand said that China notified on Tuesday that its Jinghong dam will reduce the water discharge rate from 1,904 cubic meters per second from 5 to 24 January to 1,000 cubic meters per second, which is equivalent to a reduction of about 47%.
That was for “maintenance of transmission lines” on his power grid, he said.
The MRC said it received a notification the same day, although it first detected water levels dropping on December 31. The level would probably drop by 1.2 meters and river navigation and fishing could be affected.
The MRC said the Chinese notification ensured that the flow “will be gradually restored to its normal operating status on January 25” without specifying an exact volume rate.
The new Mekong Dam Monitor on its Facebook page on Tuesday said that China did not notify neighbors when the Jinghong dam began to restrict water on December 31, “causing a sudden 1-meter drop in river level” downstream, which could devastate the fish population.
The monitor uses cloud-drilling satellites to track levels of 11 dams upstream in China and other countries. Partly financed by the US State Department, it started operations last month, increasing rivalry between the China and the US superpowers in Southeast Asia.
Chinese officials were not immediately available for comment. Beijing has rejected suggestions that its Mekong dams harm downstream countries.
(Reporting by Panu Wongcha-um and Kay Johnson; Editing by Martin Petty)