Construction dans la province du Yunnan des barrages sur le fleuve Lancang en amont du Mékong

China’s Mekong Dam Plans


David Blake, Imperial College at Wye, Kent, U.K.


There has been a lot of discussion in recent years about the pros and cons of large dams and one might be forgiven for thinking that the subject has been debated to death. That was certainly the feeling for many towards the end of last year, following the almost constant media coverage of the events surrounding the Pak Mun controversy. Although the media tended to be polarised in its support for the various factions involved, every form of media became involved and dams had entered the national consciousness for good or bad.


It had taken ten years of almost non-stop protest and refusal to be pawns in the top-down development process by affected villagers in Ubon Ratchatani province to reach the stage of widespread recognition of their plight by the wider public, and the small concession granted by the government in late July to lift the water gates temporarily, finally seemed like a small victory in a larger war against perceived injustice. The stance of the villagers and other members of the Assembly of the Poor who had joined them at Pak Mun from other dam project sites in Isan was further vindicated in November 2000, with the release of the World Commission on Dam’s (WCD) report: “Dams and Development: A New Framework for Decision-Making”. This seminal work, which included a case study of the Pak Mun Dam, produced reams of evidence to show conclusively that many large dams had not only failed to meet their stated goals and benefits, but worse still, had led to the impoverishment, marginalisation and displacement of millions of persons worldwide.


A consequence of the constant bad publicity that has surrounded large dam schemes in Thailand is a growing local movement against further dam developments within the country. Even a spokesperson for the Electricity Generating Authority of Thailand (EGAT), Mr Banphot Sangkeo, admitted that the Pak Mun  Dam  would probably be the last major hydropower project in Thailand, when he spoke at the Foreign Correspondents Club of Thailand in May 2000. This sentiment though, masks the fact that EGAT and the government are actively promoting hydropower expansion in neighbouring countries to support ever-increasing electricity demands within the country. Laos now has 5 hydropower dams supplying power to Thailand and there are plans to build several more in a Power Purchase Agreement between the two countries signed by ex-Prime Minister Chuan Leekpai last year. Cambodia, Burma, Vietnam and China also have plans to supply the Thai power market through building hydrodams.


The most controversial of the dams presently on the drawing board and due for imminent construction is the Nam Theun 2 Dam on the Nakai Plateau in the south of Laos. This ambitious dam is expected to cost a total of $1.2 billion, generate 900 MW of power for export to Northeast Thailand and necessitate the relocation of 4,500 indigenous people. Due to the involvement of the World Bank and several Western companies in the Nam Theun 2 company consortium, there has been much attention paid to this dam by outside parties, concerned about the potential negative social and environmental consequences. Perhaps because of this interest, there has been a more thorough process of environmental and social impact studies conducted than in many other dams built in the region since the 1990s (Pak Mun, for example). However, some observers and environmental pressure groups claim the studies are still insufficient and the process has been less than transparent, in order for Laos to make a rational decision about the wisdom of this major project.  


In marked contrast to the debate simmering over the supposed benefits and threats of the Nam Theun 2 Dam is the wall of silence and secrecy surrounding the well-advanced plans for a series of dams on the upper Mekong or Lancang Jiang, as it is known in Yunnan, China. Perhaps because of the traditionally isolationist nature of the Chinese government or because the financing and construction does not involve Western institutions, news so far about the upper Mekong dam scheme has stayed out of the public arena. This state of affairs is quite surprising given that the middle and lower Mekong river is shared by 5 other countries (Burma, Laos, Thailand, Cambodia and Vietnam) and there is an organisation, the Mekong River Commission (MRC), which is supposedly concerned about the sustainable and equitable use of the river and its valuable functions for the member states (China and Burma are not members of the MRC).


Recently, a technical report entitled “Water Resources and Hydropower in the Lancang River Basin” by David Plinston and He Daming was released by the Australian Mekong Research Network, having been earlier submitted to the Asian Development Bank. It outlines the main characteristics of the eight-dam “hydropower cascade” system, presently being developed on the upper Mekong and the likely effects on river flows and sediment transfer downstream. It is the first English-language report in several years to explicitly describe the Yunnan scheme and how it might effect the hydrology of the Mekong. Unfortunately, the authors bias their report by starting with the assumption that hydrological control of the Mekong will benefit users downstream, rather than examining the likely outcomes from a neutral viewpoint or comparing the project with similar schemes elsewhere in the world. Had they done this, the conclusions reached may have been significantly different.


In mid-1994, China closed the first dam on the mainstream Mekong at Manwan and started supplying power to the Kunming – Chuxiong urban-industrial axis and other cities on the eastern side of the Mekong. The 126 m high Manwan Dam has installed capacity of 1,500 MW and cost a reported $516 million. It was noticed that when the dam was filled in the 1992-93 dry season , exceptionally low water levels occurred downstream which prompted complaints from Thai authorities in the northern province of Chiang Rai. By the following rainy season though, the incident had been forgotten by most and little mention has been made of the scheme since.


After completing Manwan, the Yunnan Electric Power Group Corporation has started to construct another dam downstream at Dachaoshan (1,350 MW) and has completed detailed design studies and started site preparation for the much larger Xiaowan Dam (4,200 MW), upstream of Manwan. A Thai company is currently conducting a feasibility study for a further large dam downstream, nearer the Chinese – Lao border at Jinghong and a Memorandum of Understanding to purchase power in the future has been signed with Thailand. Altogether, a further four sites are under consideration for future construction on the mainstream Mekong in Yunnan to create an eventual 8 dam cascade.










Gonguoqiao 130 750 ? ? ?
Xiaowan 300 4,200 32,737 Site preparation 2012 – 13
Manwan 126 1,500 3,513 Completed 1996
Dachaoshan 110 1,350 6,054 Under construction 2003
Nuozhadu 254 5,000 23,826 Feasibility study 2017
Jinghong 118 1,500 2,264 Feasibility study 2003 – 10
Ganlanba ? 150 ? ? ?
Mengsong ? 600 ? ? ?



The MRC estimates that the proportion of the river’s flow at its mouth originating in China is approximately 16 %, but about half the sediment load reaching the Mekong Delta has derived from the upper Mekong river basin in China. Hence, the importance and contribution of China to the sediment loading carried down the Mekong each year is out of proportion to its contribution to annual flow regimes. This fact is vital in understanding the important influence the upper Mekong has on ecosystems, fisheries, agriculture and erosion - sedimentation relationships further downstream in the middle and lower reaches.


The dam cascade being planned and constructed in Yunnan will have drastic impacts on the hydrological flow regime and sediment levels of the Mekong, as highlighted in the Plinston and Daming report. They acknowledge that with the Xiaowan Dam completed, dry season flows will be significantly increased as far downstream as Mukdahan and flood peaks in the rainy season will be reduced, but to a lesser extent, owing to the major contribution of in flow from tributaries in Laos. The impact of the greater dry season flows will increase the further upstream one travels from the lower river, so the river in Chiang Rai province will be much higher than the seasonal norm than say at Nong Khai, which in turn, will be proportionally higher than the Mekong at Mukdahan. The predicted impacts on dry season flows at key stations are summarised in the table below.


  % Increase on average monthly discharges
Chiang Saen 32 48 73 89 80 28
Luang Prabang 22 38 52 80 66 27
Vientiane 22 38 52 72 60 27
Mukdahan 17 27 37 43 40 17


The report’s authors conclude that “higher dry season flows and some reduction in flood peaks will be of benefit to downstream riparians for the development of irrigation, navigation and hydropower.” How exactly these benefits will be realised they do not elaborate and nor do they pause to consider that there may be disbenefits or threats too, which might actually outweigh the supposed benefits.


For anyone who has ever visited the Mekong during the dry season and walked along its banks near any settlement, the chances are that sooner or later they would see villagers tending vegetable plots, using water out of the river. These river bank gardens are carefully dug as terraces on slopes that follow down the receeding river level at the beginning of the long dry season. Where the slopes are gentle and sandbanks or islands are exposed, larger plots can be cultivated with fences surrounding them to keep out wandering buffalo or cattle. The villagers grow such commonly occurring crops as cucumber, tomato, lettuce, mustard, Chinese kale, sweet potato, morning glory, yard long beans, coriander, shallots and sweetcorn, to name but a few. Some of the produce is consumed at home, the bulk is taken to market or sold to local traders. Depending on the size of plots and vegetable varieties grown, households can make from 500 – 3,000 Baht / month from these gardens. Between the Lao – Chinese border and Pakse in the south of Laos, there are literally tens of thousands of households cultivating riverbank gardens annually on the Mekong mainstream, not that anyone has ever bothered to count them all or seriously studied the economic and social importance of this farming system.


The vegetable gardens are thought to be an absolutely crucial source of income and food for villagers and absorbs labour at a time of year when few other options are available, avoiding migration out of the village to the cities. The gardens also provide organically grown, chemical-free food for urban consumers as artificial fertilisers are not necessary and pesticides are rarely used. This is because the bankside soils are replenished each rainy season by the fertile, brown, sediment and nutrient bearing river waters, which have predictably arrived each year since time immemorial. The river bank gardens represent a totally sustainable, highly productive agricultural system given the continuance of the natural flood – drought cycle of the river. Furthermore, it is a system that does not require expensive irrigation schemes or outside support to keep it profitable and if the farmers in Cambodia and the Mekong delta are taken into account is probably sustaining millions of people. Yet surprisingly, this invisible resource to the planners and decision makers, but invaluable resource to the rural poor, is now under imminent threat of irreparable damage from the Chinese dam scheme.


It does not take much imagination to picture what impact an 80 – 90 % increase in dry season flows would have on the riverbank gardens between Chiang Saen and Luang Prabang. Water levels would not fall to their normal dry season levels forcing villagers to reduce the area they cultivated each year or move to new plots far from the village. As everyone would be forced to do the same, competition for uncultivated riverbank might become intense and lead to disputes between villages.


Of much more concern than the physical loss of cultivatable land would be the loss of fertility from the annual flood cycle resulting from the capture of nutrients and sediments by the series of reservoirs in China. The Plinston and Daming report reveals that the Manwan Dam’s reservoir is silting up at a startling rate, three times faster than was expected by the designers. As the sediment (sand and silt particles mostly) enters the reservoir, it settles in the so-called “ dead storage” volume of the stiller waters of the lake and creates a cone that gradually reduces the usable volume of water. With time (16 – 20 years in the case of Manwan), the economic life of the dam is curtailed and the dam will become unprofitable through lack of water storage capacity. However, the life of Manwan may be extended slightly by the effect of construction of the much larger Xiaowan Dam upstream, which would then become the sediment trap for all the dams below. The net result by 2010 or so, will be that very little sediment at all will be present in the Mekong river for several thousand kilometres below Jinghong Dam for much of the year. The situation will be ameliorated somewhat in the rainy season through sediment inputs from tributary rivers in Thailand and Laos, but basically the Mekong’s sediment and dissolved nutrient carrying load will be radically altered. This will have several major impacts on the river system below:


·                     As the waters released from the lowest reservoir in the chain will be much “cleaner” than before, the flow will tend to scour the bed of the river more than at present causing much increased erosion downstream. This may erode physical structures bridges, piers and building supports as well as alter channel width and course, with serious political, social and economic consequences.

·                     The primary productivity of the water will decline drastically due to less dissolved nutrients, having knock on effects to all plants and animals in the food chain, right up to the already endangered Irrawady dolphin in northern Cambodia and southern Laos.

·                     Fish species and communities, closely evolved and adapted to live in the naturally turbid conditions of the Mekong, will have feeding and spawning conditions seriously disrupted and there will be a precipitous decline in catches and biodiversity. A few species may be favoured by the clearer conditions, but over all productivity will be much lower and spawning sites may be lost entirely from the higher water levels drowning rapids.

·                     Riverbank gardens will suffer both from reduced sediment deposition and the loss of nutrients such as nitrates, phosphates and potassium, plus a host of micronutrients vital to healthy plant growth. Hence, yields will decline and villagers will be obliged to buy artificial fertilisers to compensate, thus lowering profitability and increasing the costs of production. For many, however, the multiple impacts of restricted area for cultivation, increased land competition, and declining soil fertility will force them to cease this livelihood option and migrate to the cities for work.

·                      Because of the greater regulation of the flood cycle, fewer flood events on to the natural flood plain should occur, again reducing soil fertility restoring processes from sediment and nutrient deposition over a wide area. This will chiefly affect rice cultivation and long term yield declines can be expected, without a massive programme of artificial fertiliser use --- something that is becoming progressively more expensive for farmers to use.

·                     Natural bankside vegetation and flooded forests will decline and perhaps species will be lost through the impoverished sediment / nutrient loading and increased erosion.

·                     The effects will likely be felt as far downstream as the Mekong Delta in Vietnam, because if as indicated in the report “50% of the 150 – 170 million tons / year sediment load in the lower Mekong derives from China” is correct and most of this is captured in the reservoir cascade, then the delta region is gradually going to be deprived of fresh alluvial material deposition. This will allow more rapid sea and river erosion, loss of productive farmland, mangrove and loss of productive ecosystems.


This latter point will almost certainly be exacerbated by the predicted rising sea levels, leading to a severe crisis in the delta region, as is occurring in the Nile delta in Egypt following the construction of the Aswan dam. There, the entire inshore fishery of the southeastern Mediterranean was impacted by the dam and erosion is gathering pace, so the scenario described is not without precedent. Thus, the report’s claims that one of the unintended benefits of the dam cascade could be reduced saline intrusion in the Mekong estuary during the dry season, may be a limited compensation when balanced against the far greater loss from reduced soil fertility and greater erosion potential.


All the points raised so far as being potential threats from the upper Mekong dam cascade scheme are not even considered in the Plinston – Daming report that is now sitting on the desks of planners in the ADB, far removed from the reality of the everyday livelihoods of farmers and fishers along the Mekong. Yet, these same points are not exactly new or revolutionary ideas. Moreover, all are mentioned at some point or other in connection with other river systems in the WCD report, to which the ADB was a contributory partner. Similar disastrous cases are documented for rivers around the world, but especially on the African continent (e.g. Senegal river in West Africa; the Zambesi in Zimbabwe and Zambia and the Tana river in Kenya). In all cases, valuable flood plain farming systems were damaged or destroyed causing increased poverty amongst the affected indigenous peoples and the proposed benefits from the dams were never fully realised. Is the Mekong heading down the same road to ruin, but on an even grander scale?


The number of people who live in the middle and lower Mekong basin relying on the existing natural resource base of the main river for their livelihood maybe in the order of 5 – 10 million.  The value of the Cambodian wild freshwater fish catch has been estimated at US $ 250 million, if it was put through the market. However, most of it is not, but is eaten at a subsistence level and never enters the official national statistics. The same is true for most of the other natural resources that local villagers rely on for income and survival. Just because it has not yet been quantified by economists does not mean that it does not exist. If the development “specialists”, technocrats and bureaucrats in the ADB, MRC and other organisations traditionally pushing dams in Southeast Asia, spent a little more time observing the existing wealth of the Mekong and its people and a little less time fantasising about total control over nature, then maybe they would not be so hasty in wanting to destroy it. 



(This article is written by David J.H. Blake, MSc student in Sustainable Agriculture and Rural Development at Imperial College at Wye, Kent, UK.)  


MekongForum note:For more references, please consult:   Downstream Implications of China's Dams on the Lancang Jiang (Upper Mekong) and their Potential Siginficance for Greater Regional Cooperation, Basin-Wide. - E.C. Chapman & He Daming.


21.04.01 : China Prepares for Gigantic New Power Station in upper Mekong

China is busy preparing for another world-class hydroelectric power station, second in size only to the mammoth Three Gorges Power Project !

The Xiaowan Hydroelectric Power Station is to be built on the middle reaches of the Lancang River, the fifth longest in China.
Construction of the Xiaowan station will start this year, Yunnan Provincial Governor Li Jiating announced here recently.
The new power plant will be the third large power project on the Lancang (Upper Mekong) River, after the 1.5-million-kw one at Manwan and the 1.35-million-kw one at Dachaoshan. It will have six generating units with a designed capacity of 4.2 million kw.
The major feature of the station will be a concrete hyperbolic arch dam that stands 292 meters high, which is equivalent to the height of a 100-story skyscraper.
The dam, believed to be the highest dam in the world, will be able to hold 15 billion cubic meters of water, the combined amount of all reservoirs in Yunnan, said Kou Wei, general manager of the Lancang River Water Resources Development Co. Ltd.
Lancang River, which rises in the Tanggula Mountains on the Qinghai-Tibet Plateau, flows for a total of 4,500 kilometers from Tibet to Xishuang Banna in Yunnan Province, joins the Mekong River, and then flows into Laos, Myanmar, Thailand, Vietnam and other countries.
China will build six new hydroelectric power stations on the middle and lower reaches of the Lancang River this year in addition to the Manwan and Dachaoshan power stations. The combined installed capacity of the eight power stations will be 15.55 million kw.
The cost of the Xiaowan power station is estimated at 32 billion yuan, the largest sum spent on a project of this kind in Yunnan in the past 50 years. Tens of thousands of workers will be needed to build roads, bridges and other auxiliary projects.
The first generating unit of the project is expected to start operation in 2010, and the last one will be finished in 2013. By then, its annual power output will be 18.9 billion kwh, half of which will be transmitted to Guangdong and other provinces in coastal areas.
Xiaowan station is an important part of China's strategy of transmitting electricity from resources-rich western areas to power-shortage Shanghai Municipality, Guangdong, Jiangsu and other eastern provinces.
Yunnan this year will provide 900,000 kwh of electricity to Guangdong Province. The figure is to climb to eight million kwh in 15 years.
Source : People's Daily,


AFP   November 12/1997

China dams third major river in a month  

N.B. Lancang is the Chinese name for the upper Mekong

BEIJING - China has dammed its third major river in a month in an effort to boost hydro-electric power capacity, the China Daily reported Wednesday.

Following the blocking of the Yellow river on October 28 and the damming of the Yangtze on November 8, Chinese engineers completed a barrage across the Lancang River on Monday.

The barrage will allow for the construction of the Dachaoshan Hydropower Station on the river, which will have an annual generation capacity of 5.9 billion kilowatt-hours by completion in 2003.

Located in southwest China's Yunnan province, the power station is one of a series that will be built on the river to boost electrcity supplies.

"This dam symbolizes China's new efforts in developing hydropower resources on the river," said Yunnan governor He Zhiqiang.

But Laos, Burma, Thailand and Cambodia have all protested the plans as the Lancang becomes the Mekong as it travels south and China's schemes will reduce the power of other projects downstream.

There were no such objections to the damming of the Yangtze, which flows exclusively through China.

The barrage completed on November 8 will lead to the construction of a massive power station with an annual capacity of 84.7 billion kilowatt-hours to supply central China.

Expertise du grand barrage voûte Xiao Wan

Lieu :


Province du Yunnan, sur le Mékong

Date(s) :

Octobre-novembre 1995 (1 mois)
Participants :
Brice WONG, Michèle WONG, Xavier DUCOS

Partenaires :

Divers bureaux d'études : MSDI (Design Institute du Huan), KHIDI (Design Institute du Yunnan), NWDI ( North West Design Institute), CHIDI (Design Institute du Sichuan)
Descriptif :

Ce projet est situé sur la rivière du Lancanjiang (Mékong) dans la province du Yunnan.

Belle voûte à double courbure de 292 m de hauteur, elle est implantée sur un verrou topographique favorable (L/H<3). Cependant, d'importantes failles ont été découvertes par les galeries de reconnaissance et dans les 80 m supérieurs de cette voûte en rive gauche, et surtout en rive droite. Cette découverte condamne le projet actuel de voûte classique, à moins de changer de site... ce qui est difficilement envisageable après 20 ans de travaux de reconnaissance comprenant une cinquantaine de galeries totalisant plus de 6 km de longueur et près de 30 km de sondages carottés. D'autre part, les calculs menés par différents Instituts de Recherche chinois font état de contraintes difficilement acceptables : 200 bars de compression en pied aval et 40 à 80 bars de traction en pied amont de la voûte.

En 1995, un projet de fin d'études de Xavier DUCOS (étudiant à l'ENSAIS au sein de l'entreprise SOGREAH et en coopération avec HSF) semble avoir réussi à diminuer de façon significative les contraintes dans cette voûte en modifiant légèrement la répartition des volumes de béton et les courbures des arcs.

Situation : La Chine connaît une croissance forte et a besoin d'énergie pour son développement économique et sa population. Le gouvernement chinois s'est lancé dans l'équipement de ses sites hydroélectriques. Par ailleurs les barrages sont conçus et utilisés également pour l'écrêtement des crues et donc la protection des populations et des industries.
Brice WONG, Président de HSF, de par ses origines et son passé professionnel a noué des relations avec des ingénieurs chinois concepteurs de barrages.
En 1989, une mission fut réalisée pour les sites de LONG TAN et de GAO TANG.
En 1992, de nombreux sites de barrages furent visités du Nord au Sud de la Chine: SAN BAN XI, LA XI WA, LIU JIA XIA.
En 1994, une nouvelle mission fut réalisée notamment pour les barrages de XIAO WAN.

Travail réalisé : Les bureaux d'étude chinois avaient besoin de conseils pour la conception de leurs barrages. Le travail réalisé par H.S.F. fut celui d'ingénieur conseil auprès des bureaux d'étude chinois responsables de la réalisation des barrages. Tous les barrages projetés par les ingénieurs chinois étaient des barrages-poids. En particulier, H.S.F. leur conseilla de les remplacer par des barrages-voûtes, pour réduire le coût et améliorer la sécurité. Pour chaque ouvrage, des plans de principe furent réalisés.


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