From July 18 to 22, Jinghong Dam’s discharge remained stable at about 1,400 cubic metres per second, the ministry said, but due to the rainfall in the interval, the water level increased by 4,770 cubic metres per second within five days.

Mekong River group says water levels have decreased despite China pledge

This resulted in a 3.8-metre increase in water level which gradually declined, it said, pointing out the Mekong River Commission (MRC) had also reached the same conclusion in a statement issued on July 28.

The MRC is an intergovernmental commission which focuses on the sustainable development of the 4,909km waterway. Commission members include four of the six countries that the Mekong River flows through – Thailand, Laos, Cambodia and Vietnam. China and Myanmar are the two remaining countries.

Citing the same report, the Chinese ministry said that the dramatic fluctuation in water levels during this period was also due to the discharge from hydropower stations located on the Mekong’s tributaries.

“Currently, the Mekong River is going through the rainy season. Affected by rainfall and other factors, the water level fluctuates more frequently than in the dry season, which is a normal hydrological phenomenon,” it said.

Due to the increased need for energy in the region, hundreds of dams have been or will be built on the Mekong’s tributaries, and experts have said in the past that these dams have also contributed to the irregular water levels on the Mekong.

Last week, the MRC said even though China had pledged not to restrict water flows from the Jinghong Dam until the end of this month, the Mekong River’s flow below the hydropower dam had fallen from 1,507 to 997 cubic metres per second.

In terms of overall water level, the decline was about 0.8 metres, from 536.32 metres on July 28 to 535.52 metres on August 3.

On 30 July, China’s Ministry of Water Resources said the plan to hold back water from the Jinghong Dam to facilitate “power grid construction” would be postponed until late August, citing the need for technical preparations.

The initial plan to restrict water flow from 900-1,300 cubic metres per second to about 700 cubic metres per second from July 31 to August 20 was announced two days earlier.

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Pianporn Deetes, International Rivers’ regional campaigns and communications director for Southeast Asia, said despite the Chinese announcement that outflows from the Jinghong Dam had been delayed, locals in Thailand’s northern Chiang Rai province had witnessed drops in water levels.

“While rainfall is a factor, the fluctuations in Chiang Saen and Chiang Khong have been exacerbated by the Lancang cascade, not tributary dams, given they are located upstream of where key Lower Mekong tributaries such as the Nam Ou enter the Mekong,” Deetes said.

Experts and activists have argued that a sudden change in river levels will pose a threat to biodiversity and fisheries and could affect the livelihoods of the roughly 60 million people living in downstream countries.

Earlier this year, they also called for more timely warnings from China if water from the hydropower dams situated along the upper Mekong, which is known as the Lancang in China, are to be held back or released.

In its reply this week, the ministry also added that rainfall in the Lancang-Mekong river basin is unevenly distributed while frequent floods and droughts have become one of the most important factors restricting regional economic and social development.

Pointing out that China’s water production is only 13.5 per cent of the entire river basin, the ministry also noted that coping with the threat of floods and droughts in the river basin requires the joint efforts of all riparian countries.

“In recent years, the six countries in the basin have jointly promoted the Lancang-Mekong water resources cooperation and have achieved fruitful results. The cooperation channels are currently open,” the ministry said, adding that the Mekong countries have repeatedly expressed their gratitude to China for providing the annual hydrological information of the upper Lancang River.

Deetes said the 13.5 per cent figure is the amount of the Lancang’s contribution to the Mekong Delta, but in Chiang Saen, the contribution is much greater, at more than 90 per cent during the dry season.

“Thus, the way the Lancang cascade is operated has major impacts in Northern Thailand and beyond,” Deetes said. Brian Eyler, project co-lead of the Mekong Dam Monitor, a Washington-sponsored programme, said that according to its estimates from August 2 to 8 Chinese dams had restricted 985 million cubic metres of water to charge their upstream reservoirs.

“This translates to a flow restriction of about 1,600 cubic metres per second which is consistent with the flow changes observed downstream in Chiang Saen,” Eyler said.

Satellite data and imagery from the Monitor had also clearly shown that the major reservoirs at Xiaowan and Nuozhadu in China had been filling over the last few weeks, Eyler said.

“Filling reservoirs results from restricted flow out of those dams and that restricted flow is dropping the river level downstream at Chiang Saen,” Eyler said.

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The ministry also said the six countries are jointly building the Lancang-Mekong water resources cooperation information sharing platform, and plan to further increase information sharing among the countries of the river basin.

Deetes said these joint studies must involve and draw on local people’s knowledge and experiences of the changes in the river.

“The studies should also recommend changes to the operational regimes of the Lancang cascade, which has been a key cause of adverse impacts on the river and communities in Northern Thailand and beyond,” Deetes added.