Options to mitigate the impacts of the Lower Mekong Basin river damming to fisheries

Photo: Wikimedia Commons

Newly constructed dams threaten the delicate ecosystem of the Lower Mekong Basin. The solutions are available but as is so often the case, politics stands in the way.


On the 4th of December, the Greater Mekong Forum on Water, Food and Energy will meet at the Inya Lake Hotel in Yangon, Myanmar. The event makes up the single largest knowledge-sharing event in the region, as NGO’s, private companies, policymakers, and local development agencies meet to share research on the impact economic development will have on the Lower Mekong Basin.

Among the most pressing issues plaguing the Lower Mekong ecosystem is the impact river damming is having on local fish populations. The Laotian government is on a mission to unlock the energy potential of the Mekong. But unless measures are taken to protect fish navigation, the developments could trigger catastrophic environmental and human consequences.

Laos is striving to become “the battery of Southeast Asia”

The Laotian government launched a campaign to boost Laotian energy exports through the construction of dozens of hydroelectric dams on its section of the Mekong and other tributary rivers.

The project, seeking to establish Laos as the “battery of Southeast Asia”, has resulted in the construction of more than 46 hydroelectric plants, with a further 54 plants in the pipeline.

Among these, four dams are on the mainstream of the Mekong River. The most recent proposal was submitted in June for the 770-megawatt Pak Lay dam in Xayaboury province.

The full environmental and human impact of the dams has not been fully considered

The Laotian government sees the dam scheme as a sustainable way to ease poverty in the country. But although hydroelectric plants are a clean source of energy, that does not mean they don’t have a large environmental impact.

The Mekong River is the world’s largest inland fishery. An estimated 25% of all global freshwater catches take place on the Mekong’s waters, providing more than 60 million people with a livelihood and economic lifeline.

The Mekong River is the artery which brings life to the region. Its fish feed the local people. Its tributaries provide water for crops, and the sediment it carries downstream creates fertile soil for agriculture.

But the proposed dams put the region under threat. In February, the Mekong River Commission (MRC) released the findings of its US$4.7 million study. The study, which took seven years to complete, found that the 11 hydroelectrical dams proposed for construction on the Mekong’s mainstream, along with the 120 dams proposed and constructed on its tributaries, would pose a serious threat to the ecological health of the region.

It estimated fish stocks would fall by up to 40%. Sediment transportation downstream would also be reduced by a staggering 97%, invoking significant consequences for the Vietnamese and Cambodian agriculture industry.

There are already signs that the completed dams are wreaking havoc on the Lower Mekong Basin ecosystem.

Construction on the Don Sahong dam in Laos began in 2016. Since then, fish stocks have been in sharp decline in the stretch of river downstream. A local fisherman in the nearby Hang Sadam village said, “in the past, there were a lot of fish in the Mekong River, nut nowadays we catch only 30% of what we could five years ago”.

The endangered Irrawaddy dolphin population is also suffering. There are now only four left in Laos. The pod lives in a habitat just 500 metres away from Don Sahong. “Recently there were five, including a little one that died last month because of the severe impact [on its environment]”, a Laotian official said under the condition of anonymity.

There are innovative solutions available to allow the free movement of fish

The construction of dams prevents fish from freely travelling upstream to their spawning grounds. As a result, they cannot complete their life cycle.

There are solutions that allow for the free movement of fish, which do not interfere with the dam’s ability to produce hydroelectricity. Spillways which maintain water flow allow some fish to escape, but not all.

It is possible to construct transport pipes alongside the dams allowing fish free passage. Rotating fish screens or acoustic deterrents divert the fish away from the turbines intake canals and into channels leading to the transport pipes. These pipes then spit the fish out downstream, away from the dam.

This method is effective in allowing fish to move downstream, however, it is offering passage to fish travelling upstream that is proving more difficult.

Several strategies have proven successful. In Queensland, Australia, Paradise dam employs a fish lift to minimise the dam’s impact on the local fisheries. At the end of the approach channel, against the dam walls, is a hopper chamber. The fish swim into the chamber, after which the intake route is closed, and the hopper is elevated up the dam wall on a guide track.

Once at the top, a hoist pulls the hopper over the wall, submerges it in the reservoir, and releases the fish to continue their journey upstream.

Other innovative solutions are already being utilised in Laos. Charles Sturt University, with funding from the Australian and US governments and the MRC, established its first “fishway” in Pak Peung village.

The fishway is essentially a step ladder for fish. It features a succession of pools connected with ascending steps. The steps are small enough to allow the free flow of water. This cascading water attracts the fish. They can then leap to each pool, gradually climbing up the ladder.

Pilot fishway operating in Pak San District in the central Lao province of Bolikhamxay.
Photo Credit: Flickr

The obstacles are not technical but political

With the solutions available, the difficulty in mitigating the impacts of the dams lies not with technological advancement, but political ones.

Despite the MRC’s comprehensive study, there is little governmental appetite to invest in solutions. The MRC released its study in February, however, by June, no government in the Lower Mekong Basin had formally recognised or enforced the study.

The mechanisms for ensuring the environmental risks of each dam project are fully considered are also failing. Although proposed dams must be submitted to the MRC under its Procedures for Notification, Prior Consultation and Agreement (PNPCA), there have been major misgivings over the quality of the information submitted.

There are still unresolved concerns over many existing dam proposals. Construction began on the Don Sahong and Xayaburi dams before these concerns had been addressed.

Only the Pak Beng dam suffered delays after it became the subject of a lawsuit in Thailand’s Administrative Court.

Tides could be changing

Part of the issue is that the MRC lacks the legal weight to hold governments to account. Its PNPCA mechanism does not significantly influence government decision making.

That being said, there are signs that the tide is changing. Laos announced in August that it would suspend the approval of new dam projects. But it isn’t environmental concerns that are driving the change.

The announcement came four months after the Thai government released its Power Development Plan (PDP) for 2018, which unveiled Thailand’s ambitions to produce half of its power from renewables by 2036.

Thailand is currently the largest energy importer from Laos, and Thai demand was a major factor in the Laotian government’s decision to construct the dams in the first place. As Thailand expands its own energy capabilities, it will reduce its reliance on imported energy.

Money talks. The decreased energy demand may slow the construction of new dams, but it will do nothing to disrupt those already underway and those nearing completion.

From the fisherman of Thailand and Cambodia to the farmers of Vietnam, the whole region depends on the Mekong and the unhampered movement of silt and fish. The solutions are there. Now it is time for governments to take steps to implement them. The fate of 60 million people hangs in the balance.