Washington and Phnom Penh –

Climate change and upstream dams, most of which are controlled by China, are threatening Cambodia’s vast Tonle Sap Lake and its surrounding communities, putting the country’s protein supply and the Greater Mekong ecosystem at risk.

The three years from 2019 to 2021 were the driest on record. Tonle Sap’s vital pulse of flooding appears to be dying, taking with it the lake’s abundant fish stocks. During the rainy season, water typically flows into the Tonle Sap Lake for 120 days, swelling six-fold before flowing back into the Mekong River at the end of the rainy season (usually in late September). This fluctuation is the pulse.

Experts and officials told VOA Khmer that although rainfall has increased in the past two years, lake expansion is close to normal in the wet season and water flows have reversed normally, this temporary relief cannot offset the long-term impact of the lake crisis.

“The new normal is uncertainty,” said Brian Eyler, director of the Stimson Center’s Southeast Asia and Energy, Water and Sustainability Programs. “The predictability of traditional expansion occurring almost every rainy season or every monsoon season cannot be relied upon.” The Stimson Center is located in Washington.

Given that Tonle Sap is one of the most productive inland fisheries in the world and is the source of much of the protein consumed by Cambodians, concerns about the ecosystem’s disappearance have attracted international attention.

Overall flow in Tonle Sap has reached nearly normal levels over the past two years, according to data from the Stimson Center’s Mekong Dam Monitoring Project. However, in 2022, due to heavy rainfall, most flows occurred late in the rainy season, meaning the lake missed out on early-season inflows that carry sediment, larvae and fish vital to annual fish populations Important nutrients.

According to the Stimson Project, monthly flows last year were nearly close to historical averages, which produced a decent fishing season. Data from the Cambodian Fisheries Management Authority shows that 413,200 tons of freshwater fish were caught in 2019, 383,050 tons in 2021, and only 368,059 tons in 2022. A fisheries spokesman told VOA Khmer that 426,750 tonnes of freshwater fish were caught in 2023. Each ton is equal to 1,000 tons kilograms.

“Right now, the Mekong ecosystem seems…different than it used to be, but it’s still there. It’s not completely gone,” Eller said in a January interview on the Zoom platform.

The Mekong Dam Monitor is seeking to track where the flow originates, where it is intercepted upstream, and how decisions made by each country affect other nearby countries.

According to its data, if water had not been intercepted upstream, mainly in Chinese reservoirs, the total flow into Tonle Sap would have increased by 12.4% in September, when it would have reached its peak in 2023.

Monitoring programs show that China appears to have intercepted less water over the past two years compared with previous years. But it’s unclear whether that’s because it’s responding to concerns from downstream communities or because it has less need, according to the Stimson Project.

One phenomenon Stimson researchers are watching closely is how the rainy season changes. It comes later and lasts longer than historical norms, which may reflect climate change.

“If that is indeed true, and [if] We can confirm this, then the dams upstream have reason not to store water at the beginning of the rainy season, but at the end of the rainy season. ” co-principal researcher at the Mekong Dam Monitoring Center in a January interview.

The Chinese embassy in Washington said the “rational development” of the Mekong, which China calls the Lancang, is in the overall interest of all countries that depend on it.

A spokesman for the embassy said: “China has always attached great importance to the concerns and needs of downstream countries, maintained close communication with downstream countries, and is committed to carrying out water resources cooperation with relevant countries such as hydrological data sharing, flood control and drought relief.” Liu Pengyu said in a speech on February 26 in an email.

The Mekong River Commission (MRC) is the main regional body tasked with bringing countries together to coordinate water management and negotiate on potential new dam projects on the massive river and its tributaries.

In 2020, the Mekong River Commission attributed the delay in rising water levels to lower rainfall in 2019 and the operation of hydroelectric dams in the upper Mekong, two of which are in Laos and 11 in China.

But in a February email to VOA Khmer, the MRC secretariat said it was too early to tell what the “new normal” would look like, given the recent drought and “human activities within the basin,” It’s also unknown how the changes will ultimately affect surrounding communities.

Mak Bunthoeurn, a project manager at the Cambodia NGO Forum, which works with communities along Cambodia’s Mekong River and its tributaries, said that despite the recent relative increase in total flows, they see no reason for optimism.

Mak Bunthoeurn added in a Zoom interview in late January that advocacy groups working with these communities want more data, particularly from China. “I recommend that Mekong governments must work together and cooperate to ensure that downstream communities do not suffer.”