China has notified downstream neighbours it is holding back the Mekong River flow at a hydropower dam on the waterway’s upper reaches for 20 days.
The statement came a day after a new US-backed monitoring system said Beijing had failed to notify downstream countries of water restrictions that started on Dec 31.
China agreed last October to share water data with the Mekong River Commission (MRC), an advisory body to Mekong users Thailand, Laos, Cambodia and Vietnam that had long sought the information from China for planning purposes.
More than 60 million people in those countries depend on the river for fishing and farming.
Thailand’s National Water Command Center said China had on Tuesday notified Bangkok that its Jinghong Dam will until Jan 24 reduce the water discharge rate by nearly half, from 1,904 cubic metres per second to 1,000 cubic metres per second, for “maintenance of transmission lines” in its electricity grid.
The MRC said it received notification the same day, though it first detected water levels dropping on Dec 31.
The river level would probably drop by about 1.2m and navigation and fishing could be affected, it said.
The MRC said the Chinese notification assured the flow “will be gradually restored to its normal operation status on Jan 25”, without specifying an exact volume rate.
The new Mekong Dam Monitor, which is partly funded by the US State Department, started operations last month, adding to China-US superpower rivalry in Southeast Asia.
On its Facebook page the monitor said China had not notified neighbours when the Jinghong dam starting restricting waters, “causing a sudden one-metre drop in river level” downstream that could devastate the fish population.
The monitor uses cloud-piercing satellites to track levels at 11 upstream dams in China and other countries and so does not need to rely on China’s notifications.
Beijing has rejected suggestions its Mekong dams harm downstream countries.
Chinese authorities could not immediately be reached for comment by Reuters.