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Impacts of Hydropower Development on Mekong Fisheries Resources

Updated on December 11, 2018

The Mekong River has an estimated length of over 4350 km and travels through six nations, including China, Myanmar, Laos, Thailand, Cambodia and Vietnam. With rich and varied natural resources, Mekong Basin, at the present and in the future, play a key role not only in the economic development of each riparian state, but also in the development in economic and political cooperation of the region.

With projections for the world's population of about 10 billion people by 2050, the demand for electric power, especially from hydropower, continues its remorseless rise. This is more clearly reflected in Asia. The Mekong Basin is in the region of many excellent hydrological conditions, both on mainstream and tributary. Thus, the upstream countries have been and will be building myriad of hydropower plants on the mainstream. In addition, the downstream area is being “strangled” as well by various hydropower projects in the tributary.

Some of the projects in the mainstream deem to be bottlenecks and obstructions in migration routes of aquatic species. The construction of these dams has caused a series of dramatic and direct impacts on people of many countries, provoked recent droughts, saltwater intrusion, radically affected agricultural production and people's life, exerted massive impacts on the sustainable use of the Mekong river, the ecological environment of the Lower Mekong Basin in general, and the Mekong River delta of Vietnam in particular, in which brought about deleterious effects on fishes and fisheries in the Mekong area.

From a fishy river

Mekong is a unique river in the world due to the distinct differences between dry and rainy seasons. Given the seasonal rainfall difference, the rainy season rainfall in May-October was 30 times higher than the dry season in November-April, engendered a completely different habitat during two seasons and resulted in a variety of ecological conditions for fish and aquatic species.

A hydroelectric dam on the Mekong. Photo: National Geographic
A hydroelectric dam on the Mekong. Photo: National Geographic

The Mekong has the second largest fish stocks in the world, just behind the Amazon River. The fisheries report of the Strategic Environmental Assessment of the Mekong mainstream in 2016 demonstrated that freshwater fish productivity in the lower Mekong was about 2.1 million tonnes (headed by Thailand, Vietnam, Laos, Cambodia...), equal to 20% of total world freshwater fish production, not including marine fish which depends on annual nutrients brought about by Mekong sediment and silt.

A myriad of estimates insinuate that the Mekong Basin has up to 1,100 species of fish. Notwithstanding, there are now 850 species of fish identified in the basin. Particularly in the Mekong Delta, due to the interaction between river and sea, the region witnesses an extraordinary diversity of fish species. Experts estimated that the Mekong Delta has 486 species of fish, ranging in size from a few meters in length, weighing up to 300 kilograms, to a few centimeters. Fish is essential for food security in the lower Mekong. Downstream countries, including Cambodia, Thailand, Laos and Vietnam, feature the highest consumption of freshwater fish in the world, with Cambodia at the top (ICEM, 2010).

The Mekong Basin has one of the most effective fisheries management in the world. It is calculated that people in this area catch 2 million tons of fish and 0.5 million tons of other aquatic series a year. In addition, aquaculture brings about 2 million tons of fish each year. As a result, the lower Mekong Basin contributes 4.5 million tons of fish every year. Fisheries make a substantial contribution to the strategy of diversification of means of living for many people, most notably, for the poor who rely heavily on the river and its resources.

To the unrecoverable depletion

Studies in the world have shown that dams radically affect ecosystems, biodiversity and hydrology, with the negative effects weighing up the positive ones. Dams are like barriers to fish movement. A study of the Amazon River recommended that the presence of dams in the river basin has prevented the long-distance movement of some catfish species, causing a decrease of 70% in capture - fisheries production of the lower area. In addition, fish caught on the Mekong are largely migratory species. The impact of dams on migration routes varies from region to region, yet the impact of dams on fish migration is undeniable.

Hydropower projects in Mekong Basin: (a) existing, under construction, and proposed LMB mainstream projects; (b) existing, under construction, and proposed hydropower development in 3S basin
Hydropower projects in Mekong Basin: (a) existing, under construction, and proposed LMB mainstream projects; (b) existing, under construction, and proposed hydropower development in 3S basin

The construction of dams disrupted the natural flood cycle that fish have adapted for thousands of years, hardened the river bed due to the rock floor below the exposed dam, fish habitat degradation and losses. Dams also retain the sediment, deprive fish of nutrient source, change the temperature, and directly affect the number and habitat of fishes.

Dams will mess up the “signal”. There are four water seasons in the lower Mekong and the Mekong Delta, the two main seasons are wet season and dry season, and the two transitional seasons last for only a few weeks. Transitional seasons play a very crucial role in the whole ecosystem. Fish and other species receive “signal” to initiate migration, reproduction, or other activities in the life cycle. For instance, when water level increases then sesbania sesban begin bloom and fish migrate to lay eggs. If the hydropower dams are constructed, due to the impact of storage and discharge of hydropower dams, these transitional seasons will be shortened or completely lost, and the dry season will change to the wet season and vice versa. The transition will also happen suddenly for a few days. At that time, the species will be subject to seasonal fluctuations and disturbances and can not carry out activities in the life cycle such as migration, prey, reproduction, et cetera.

According to the Strategic Environmental Assessment of the Mekong mainstream hydropower projects, the dam system also affects marine fisheries in the Mekong Delta. Marine aquaculture takes a radical part in the economy of the Mekong Delta region of Vietnam, with output of about 500 thousand to 726 thousand tons per year. Around 100 million tons of sediment and 16,000 tons of nutrients are introduced into the coastal waters of the Mekong Delta each year. The hydropower dam’s sediment retention will have a considerable impact on Vietnam's marine fisheries, fisheries trade and production. This also has a catastrophic consequence on the aquaculture sector in Vietnam on account of the loss of protein as a feeding for fish farming.

Fatal outcome on the diversity of aquatic resources

The construction of dams bears upon the environment and local livelihoods in the river basin. By the end of 2017, the Mekong River Commission (MRC) announced its five-year study results, showing that hydropower development contributes up to 50% to economic development in the Mekong Basin, nevertheless, the hydropower growth still harms fisheries in the Mekong from Cambodia through to Thailand.

For the environment, the emergence of hydroelectric dams also modifies the downstream and upstream fish migration, from upper basin to lower basin and vice versa, and evokes concern that construction of dams will make some species extinct. According to MRC, there are about 867 different aquatic species throughout the Mekong River. In the northern part of the Mekong River, the Xayaburi Hydropower Project region has more than 260 different aquatic species. The second effect on the environment is to restrict silt flows and sediment transports in the Mekong. And thirdly, building a hydroelectric dam will alter the equilibrium of Mekong ecosystem.

Construction of dams in Laos is threatening the livelihood of fishermen, like these shown in the southern Mekong region of Champasak.
Construction of dams in Laos is threatening the livelihood of fishermen, like these shown in the southern Mekong region of Champasak.

It goes without saying that hydropower has long been considered a “green energy” source for the reason that it can be renewable and does not emit greenhouse gases in the production process. Moreover, dams, in theory, also help control flow, regulate river flow, control flood or prevent drought in downstream region and help develop agriculture. But the development of hydropower on major rivers such as Mekong will be “undesirable”, so painstaking research is needed in all countries from the Upper Mekong Basin to the Lower Mekong Basin. As it relates to a number of migratory fish species as well as the impact of river flow alteration, siltation should be made clearer via scientific research with detailed results. This would avoid the “bad precedent” for possible future projects and commitments of Laos, Cambodia, Thailand and Vietnam when joining the Agreement on Cooperation for Sustainable Development of the Mekong Basin are convinced.

Efforts of regional countries to ensure water security

In 1995, four countries (Cambodia, Laos, Thailand and Vietnam) signed the Mekong Cooperation Agreement and established the Mekong River Commission (MRC). This Agreement is the only legal basis in the region for the management and development in the Mekong Basin to help countries cooperate with the ultimate goal of developing all potentials for the sake of sustainability of all Mekong riparian countries and prevention of waste water use in the Mekong Basin.

The MRC has 23 years history, yet, the MRC itself inherits the history of sustainable development and use of the Mekong river from 1952 onwards with the first United Nations project on the Mekong. The first experience is to reckon the Mekong Agreement as a success, an advance in promoting cooperation in the Mekong Basin that the world has acknowledged. Secondly, the Mekong Agreement sets out the sustainable use of water resources as well as equality between countries. This reflects the fact that all parties have a mind for countries in the region to make use of the Mekong in a sustainable way that is beneficial to the entire basin and different nations.

Together with the four countries, namely Cambodia, Laos, Thailand and Vietnam of the MRC, China and Myanmar also have to uphold their responsibility as a relevant country in the Mekong Basin. ASEAN countries, which are in the same community of common interests, must unite in order to better manage and sustain water in the Mekong River, focusing on three solutions. Firstly, ASEAN needs to focus more resources on water security and should reckon this as a matter of particular concern. There are currently a vast majority of 60 million inhabitants of ASEAN member states living on the Lower Mekong Basin. Secondly, ASEAN should play a more effective role in coordinating member countries in the full implementation of the Mekong Agreement (1995), creating a balance between countries by force the issue of water source security as a common concern of all member states rather than a subregion issue at the moment. Thirdly, ASEAN should establish a regional body responsible for ensuring water source security to provide comprehensive, holistic and objective research. Accordingly, the implementation of activities in the Mekong Basin should not affect the environment and ecosystem of the river, securing the volume and quality of water on the river and the legitimate interests of all both countries in the river basin.

Hydropower in the Mekong Basin: Impacts and Alternatives | Conservation International (CI)

Fully comply with the signed cooperation agreements and consult, exchange of experiences before the construction of hydropower on the Mekong River

It should be noted that hydropower construction is in the sovereignty of the Mekong countries. Therefore, every Mekong people need to understand that when the upstream countries build dams, they are exercising their sovereignty. In spite of that, consultations and exchanges of experience prior to the implementation of any hydropower project are required to ensure water and livelihood security of the people throughout the region and mitigate impacts of hydropower development on fisheries resources in the Mekong Basin. Over and above consultations, countries in the Mekong region have to comply fully and seriously with regulations, agreements in which they are a member of, such as the Mekong Agreement on Sustainable Development Cooperation (1995), The GMS under the 1992 ADB initiative (including Vietnam, Laos, Cambodia, Thailand and two autonomous provinces of China, namely Guangxi, Yunnan), Mekong – Lancang cooperation (MLC) (including Vietnam, Cambodia, Laos, Myanmar, Thailand and China), Development Triangle Area of Cambodia – Laos – Vietnam (CLV), Four countries Forum of Cambodia – Laos – Myanmar – Vietnam (CLMV) ...

In recent years, particularly since 2010, countries with hydropower construction on the mainstream of the Mekong have consulted within the MRC. The MRC has consulted 3 times on building hydropower on the mainstream. These consultations are of significant value and except the MRC, no organization or country in the world has ever had such experience so far. These consultations were very complex, lasting for 6 months. It requires the efforts of all parties involved. Consultations have included consultations with communities along the Mekong River who were affected by hydropower projects. The MRC invited experts to review all technical documents on the project and conducted workshops as well as seminars for the parties to exchange ideas. At the same time, the Mekong issues also needs to be discussed in depth at a number of international and regional forums, conferences to exchange experience in resource conservation in general and fisheries resources in particular on the river basin in the context of the construction and development of hydropower systems, as well as seek solutions for reasonable state management and sharing of water resources among countries in the international river basins.


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