Science, People & Politics, issue 4, Volume i, Volume II, published 6th July, 2009.

Weep for the Mekong.

By Fred Pearce

Contested Waterscapes in the Mekong Region.
Ed. Francois Molle, Tira Foran and Mira Kakonen.
Earthscan, 2009.
Hardback. Price £75.00.
ISBN 978-1-84407-707-6.

Weep for the Mekong. China is about to tame one of the world's last great wild rivers. And its neighbours have reason to fear the consequences, for the tens of millions of people who rely on the river's wildness for their supper could soon see their main source of protein dry up.

Last autumn, Chinese engineers completed construction of the Xiaowan dam on the upper reaches of the River Mekong, in the remote southern province of Yunnan. At 292 metres high, the Xiaowan dam is the world's tallest, as high as the Eiffel Tower. This summer, the dam will for the first time catch the great Mekong monsoon flood as it rushes out of the Himalayas and through the steep gorges of Yunnan. The hydroelectric reservoir will eventually be 170-kilometres long. When the first electricity is generated from it, it will help keep the lights on as far away as Shanghai, 2000 kilometres to the east.

China plans eight hydroelectric dams on the Mekong. Within five years, the Nuozhadu dam will be complete. It will be slightly lower than the Xiaowan, but will have an even larger reservoir. The Mekong is destined to become China's new hydroelectrical powerhouse.

The dams will form a staircase through the gorges of Yunnan, and will be able to store half the entire flow of the Mekong as it heads across the border to Burma, Thailand, Laos, Cambodia and, finally, Vietnam. In future, the annual flood will be tamed, and released gradually as turbines are switched on and off to supply power to industrialising China.

In May this year, the UN Environment Programme warned that these dams were now "the single greatest threat" to the future of the river, its ecosystems and the fisheries on which tens of millions of people depend. The new hydrology will eliminate most of the river's natural flood pulse. See: UNEP Fresh Water under threat, South East Asia (Link disabled by the editor for non contentious reasons. 22.10.11.)

In this book, edited by Molle et al, I expected to find more details about this profound change to a river which remains today one of the wildest on the planet. Yet, in this apparently authoritative work on "hydropower, livelihoods and governance in the Mekong region, the Chinese dam-building is barely discussed. Neither Xiaowan nor Nuozhadu even appear in the index.

A chapter on China's failure to discuss its dam-building with its neighbours on the Mekong regrets this state of affairs, and mentions in passing that the dams will be "the most significant human intervention ever made" in the Mekong ecosystem. But what will the nature of that interference be? Sadly we are left to guess.

I can understand their problem. Like other scientists, the authors of this volume have not had direct access to what the Chinese are up to. But to sideline the crucial issue of the Chinese dams on those grounds, while devoting whole chapters to far less significant projects on the river's side-channels, shows a narrow perspective. It may accurately reflect what the researchers have been able to investigate first hand, but it is a travesty when presented as an overview of one of the last near-pristine large river systems on the planet. And anybody paying the cover price of £75 for this volume would justly feel short-changed.

The waters of the Mekong have till now been a great natural resource for humans and nature alike. The 4500-kilometre river sustains the world's second largest inland fishery. That fishery has been the mainstay of the region's economy for thousands of years. It makes the Cambodians, who are among the world's poorest people, among the best fed. It is a direct result of the intensity of the river's summer flood, and, in particular, of one feature of the flood -- the river that runs backwards.

That river is the Tonle Sap, a tributary of the Mekong in Cambodia. It is the beating heart of the Mekong river system. But it is among the river system's most vulnerable elements. For seven months of the year, the Tonle Sap flows from a lake in the centre of Cambodia and joins the main river in front of the royal palace in Cambodia's capital city, Phnom Penh. But each June that downhill flow halts, and for five months until November the river reverses. This happens because the summer flood increase the Mekong's flow 50-fold.

So much water comes coursing down the Mekong that the river's main channel cannot contain it. The water instead backs up into the Tone Sap for some 200 kilometres, expanding its lake so that it floods surrounding forests. At the height of the monsoon season, this reverse flow swallows a fifth of the Mekong's waters.

During this flood, the submerged forest around the lake becomes the nursery for the Mekong fishery. Among the tree roots, billions of fish fry grow into fat adults. And each November, as the Mekong flood abates, the lake empties and the fish swim out into the Mekong, eventually migrating for thousands of kilometres -- filling nets that feed tens of millions of people.

This book contains some admirable discussion of the ecosystem around the Tonle Sap and its importance for fisheries and the wider river. It notes that "the conventional economic development path currently pursued in the Mekong is fraught with risks" for the Tonle Sap. Yet nobody appears to have attempted even the most rudimentary analysis of the likely effect of the huge Chinese dams on this system. What a shame.


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