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The Environmental and Social Impact of the Mekong Dams



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7.2 The Environmental and Social Impact of the Mekong Dams.


What will be the effects of the Chinese Mekong dams on the environment and the people of Yunnan, and on the other riparian countries downstream? Most of the dams will be located in narrow gorges: the reservoirs will consequently be much more narrow and deep than those downstream proposed by the MRC. The gorges are sparsely populated, so relatively few people will have to move as the reservoirs fill up. Similarly, the natural environment of much of the gorge has been altered by extensive deforestation, although there are no doubt pockets which are of value in conservation terms. In the absence of Chinese Environmental Impact Statements, it is impossible to evaluate these.

It is often said in the defence of hydo-dams that they do not entail the permanent removal of water from the stream. Dams intended to provide irrigation inevitably direct water onto agricultural land, where it either evaporates, or is absorbed into the soil. Hydro-electric dams, on the other hand, retain the water temporarily in reservoirs, releasing it in measured quantities, usually back into the mainstream, as it is required to generate electricity. They are thus deemed to be more environmentally friendly than irrigation dams.

The factor overlooked in this argument is that hydro electric dams significantly alter the flow of the stream. Normally this flow, particularly in monsoonal regions, is seasonal, with a peak during the rainy season. However, the managers of hydro dams control flows according to the demand for power, which may peak at very different times from those occurring in an uninterrupted stream. This can adversely affect the seasonal rhythms of agriculture downstream. It can also affect the navigability of the stream.

The most important irreversible impact of the dams, however, is upon fish, and other riverine species. Quite apart from the pure conservation value of the marine creatures, they are important to the livelihoods of large numbers of people living on the river and its tributaries.

This issue has recently been dramatised by the suggestion that the Chinese dams may hasten the extinction of the pla buek, the giant catfish (Pangasiannodan gigas), a remarkable creature that can grow to a weight of 350 kg. The numbers of the pla buek have been declining rapidly in recent years due to overfishing. Previously, the fish was rarely caught by local people who were reluctant to eat a fish which they revered. However recent heavy demand by Thai gourmands has brought heavy exploitation.

The recent decline in the numbers of such a conspicuous species has given it a significance in the public mind, particularly in northern Thailand, as an indicator of the overexploitation of the Mekong generally. This is associated with concern about the development of the Chinese dams. Claims have been made that the spawning grounds of the fish lie in Yunnan, upstream from Chiang Khong, Thailand, where the largest catches are made annually each May and June. It is suggested that Manwan dam is preventing the fish from reaching its spawning grounds. These claims cannot be substantiated, as very little is known of the migratory or breeding habits of the fish. But they do highlight the fact that extremely little is known about the giant catfish, or about any of the host of lesser known creatures that inhabit the river in Yunnan.12

The effects of the Chinese dams on the river have already been noted in Laos and Thailand. In 1995, the Lao could not hold their traditional annual aquatic festival at Luang Prabang during the dry season because the river was too low. At the same time, farmers in Chiang Rai Province in northern Thailand noted that the level of the river had dropped to such an extent that it became difficult for them to lift the water onto their fields. A complaint was lodged by the governor of the province with his Chinese counterpart in Yunnan. The latter, while acknowledging that it ‘was necessary’ for Chinese engineers to temporarily curb the flow of the stream in connection with some tunnelling, was unrepentant, refusing even to agree to notify the Thai if such works were planned in the future (Hinton 1995).

These developments will cause alarm downstream. The Vietnamese, for example already know the adverse effects of water diversion upstream. Vietnamese authorities have been expressing growing concern about rising levels of salinity in the delta of the Mekong, the main rice growing area of the country. The Thai and the Lao may also be about to suffer the consequences of the acts of upstream neighbours upon the river although just what these might be, and their extent, remains unknown. One undoubted outcome will be increasing advocacy for the Chinese to become members of the MRC. If they were members, so the argument goes, they might be made more accountable for their actions. If past experience is any indication, however, they are unlikely to consider that it is in their interests to join as such membership will only constrain their use of the river. It is difficult to see, if they sustain this position, and what pressure can be applied to bring them to the conference table.


7.3 River Navigation


There has been considerable talk about the possibility of the Mekong mainstream itself becoming a water-borne transport route. Some of the major tributaries, particularly in northern Laos are already being used for this purpose. These tributaries - rivers like the Ou and the Beng - flow in a roughly northwestern direction so that it is possible for small vessels to reach well towards the Chinese frontier. This is particularly so during the monsoon season when the rivers are at their highest levels. They then are particularly useful conduits for trade because most of the roads in the region are impassible for much of the year. (Walker 1993; 1995)

Some prefectural authorities in Yunnan clearly have a high regard for the possibilities of the Mekong becoming an important transport ‘road’ for they have developed elaborate port facilities within their precincts. Particular noteworthy are facilities which are being established at Jinghong in Xishuangbanna Prefecture in the south of Yunnan, and at Simao Prefecture, not far to the north of Xishuangbanna. The latter has entailed a considerable investment by the local authorities, despite the fact that unlike Jinghong, the river is a fair way from Simao town. Yet they have built a complete port where there was once only a small village. Facilities include berths, docks, a ship repair yard, warehouses and administration services. Unfortunately, as of 1994, there was little sign that it had attracted much commerce.

The authorities at both ports are obviously looking south, towards Laos, Burma and Thailand, because not very far to the north of them, the river flows through a narrow gorge, with frequent rapids which render navigation impossible. In any case, one major dam (Manwan), completely blocking the river upstream has been completed, and several others are on the drawing board.

One of the major impediments to the further development of the navigational potential of the Mekong are several sections of rapids, particularly to the south of the northern frontier of Laos. The ADB has allocated funds for the placing of markers and other guides to navigation, but the Chinese, wishing to open the river to large craft capable of transporting commodities like bulk grains, minerals and cement have proposed that the rapids be blasted. The Lao authorities have, however, strongly objected to these proposals, on the grounds that fisheries, vital to the livelihood of local people, will be adversely affected. The rapids, they point out, are important breeding grounds for many species.





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