Will the Mekong be damned?

As China celebrates the 60th anniversary of Communist Party rule today, there are many signs of the country's growing international influence. One of the least recognised is China's role as Asia's dominant headwater power.

Geography has made China the source of some of the most important rivers that flow into South and South-East Asia. They include two of South Asia's great rivers, the Indus and Brahmaputra, and two of South- East Asia's the Salween and Mekong.

All have their headwaters on China's Qinghai-Tibetan plateau, a region so high that it is known as the "roof of the world". These four trans- national rivers flow for much of their early course through Chinese territory.For South-East Asia, by far the most important is the Mekong. Back in 1986, when China began building the first of a series of dams on its section of the Mekong River, hardly anyone in the downstream countries paid attention. But today, as China races to finish the fourth dam for generating electricity on the upper reaches of South-East Asia's biggest river, concerns about possible environmental impacts are rising.

The sheer scale of China's engineering to harness the power of the Mekong and change its natural flow is setting off alarm bells in South- East Asia, especially in Vietnam, Cambodia, Thailand and Laos, the four countries of the lower Mekong basin where more than 60 million people depend on the river for food, water and transportation.

A report in May by the United Nations Environment Program and the Asian Institute of Technology warned that China's plan for a cascade of eight dams on the Mekong might pose "a considerable threat" to the river and its natural riches.

Some analysts say that if the worst fears of critics are realised, relations between China and its neighbours will be severely damaged. But mindful of the growing power and influence of China, South-East Asian governments have muffled their concerns. Meanwhile Laos, Cambodia and Thailand have put forward plans to dam their sections of the Mekong mainstream, prompting Vietnam to object and undermining the local environmentalists' case against China.

The Mekong River Commission, an inter-governmental agency formed in 1995 by the four lower-basin countries to promote sustainable development of the river, is in the midst of a cost-benefit analysis of mainstream dams, including the influence of dams in China on the river system as a whole. However, the MRC's authority is limited and China has refused to join.

Although the Mekong is widely regarded as a South-East Asian river, its source is in the glaciers and snow high in Tibet. Nearly half of the 4880km river flows through China before it reaches South-East Asia.

Since there is no international treaty governing use of trans-boundary rivers, China is in a dominant position as the Mekong's headwater power. It has the right to develop its section of the river as it sees fit.

The Mekong River basin drains water from an area of 795,000 square kilometres. The commission estimates that the sustainable hydro- power potential of the lower basin alone is a massive 30,000 megawatts.

But it says there are major challenges in balancing the benefits of electricity, water storage and flood control from the dams' negative impacts.

These include population displacement, obstruction to fish movements up and down the river, and changes in water and sediment flow.

The cascade of dams being constructed on the upper Mekong in China will generate more than 15,500MW of electricity for cities and industries, helping to replace polluting fossil fuels, particularly coal and oil, with clean, renewable hydropower.

The eight dams will produce about the same amount of electricity as 30 big coal-burning plants.

The fourth of China's Mekong dams, at Xiaowan, is due to be completed by 2012 at a cost of $A4.5billion. Rising to 292m, the dam wall will be the world's tallest. In terms of water storage capacity, the first three Chinese dams on the Mekong, completed between 1993 and 2004, are relative minnows.

Between them, their reservoirs hold back just over 2.9 billion cubic metres of water.

The Xiaowan reservoir will hold 15billion cubic metres of water, more than five times the combined capacity of the first three Chinese dams. With a capacity to generate 4200 MW of electricity, Xiaowan will be by far the largest dam so far on the Mekong. However, by 2014, China plans to finish another dam below the Xiaowan at Nuozhadu. It will not be quite as high but will impound even more water, nearly 23 billion cubic metres, and generate 5000 MW of power.

Chinese officials have assured South-East Asia that the Yunnan dams will have a positive environmental impact. They say that by holding some water back in the wet season, the dams will help control flooding and river bank erosion downstream. Conversely, releases from the hydropower reservoirs to generate power in the summer will help ease water shortages in the lower Mekong during the dry season.

But the UNEP-AIT report said that Cambodia's great central lake, the nursery of the lower Mekong's fish stocks, and Vietnam's Mekong Delta, its rice bowl, were particularly at risk from changes to the river's unique cycle of flood and drought.

Vietnam worries that dwindling water volumes will aggravate the problem of sea water intrusion and salination in the low-lying Mekong Delta, where climate change and sea level rise threaten to inundate large areas of productive farmland and displace millions of people by the end of this century.

The MRC says it has been discussing with Chinese experts technical cooperation to assess downstream river changes caused by hydropower development. But neither China nor Burma has joined the MRC or agreed to observe its resource management guidelines. In the case of Burma, this may not matter much, since only 2 per cent of the Mekong basin's annual water flow comes from Burma. However, 21 per cent of the water is from China.

Despite this, China has so far balked at full membership of the MRC, preferring to remain a "dialogue partner". Full membership would intensify scrutiny of its dam plans by downstream Asian states and increase pressure on China to take their interests into account.

While China's program to dam the Mekong is moving ahead on schedule, proposals to do the same on the South-East Asian section of the river have been put on hold. So far, only China has actually built dams on the Mekong mainstream. In the lower Mekong basin, Laos, Cambodia and Vietnam have all developed hydropower dams on rivers that flow down from mountains into the Mekong.

There is now more than 3200 MW of electricity being generated on Mekong tributaries and more dams, with a generating capacity of nearly the same amount, are under construction.The temporary economic slowdown in South-East Asia has reduced demand for electricity. It provides a breathing space to assess how the Mekong mainstream dam projects will affect the interests of people in the river basin. But without China's full cooperation, no Mekong management plan can be effective.

Michael Richardson is a visiting senior research fellow at the Institute of South East Asian Studies in Singapore