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The lands through which the Mekong river flows on its 4200-kilometre
journey through Southeast Asia to the South China Sea are bywords for isolation
and conflict. Tibet and Burma have been all but cut off from the outside
world for decades, while Vietnam, Cambodia and Laos have been engulfed by
warfare. Only Thailand, itself now under military rule, is regarded by the
West as firmly on the path of economic development. Before the shadow of
war fell over the region in the 1960s, American engineers had great plans
to develop the region by harnessing the single common thread that ran through
the Southeast Asian mainland, the Mekong river. With one of the largest
flows of any river on Earth, the Mekong appeared a bounteous natural resource,
ripe for exploitation. Now, with peace restored, the Americans, along with
the Australians, Japanese and others are back to build dams to tap the river’s
power.

Over much of the Mekong watershed, hardly any rain falls during the
early months of the year. The river level drops allowing salt water from
the South China Sea to penetrate 500 kilometres inland; as far as the middle
of Cambodia. Once the monsoon rains begin in May, however, the Mekong is
transformed. By September, the flow of water into its delta in Vietnam has
increased around 30 times. Along some stretches, the river rises as much
as 20 metres, or about the equivalent of six storeys of a building. There
is more water in the river than can reach the sea and huge amounts back
up into a sluggish wetland, Tonle Sap, in northwest Cambodia, turning the
region into a lake covering 10 000 square kilometres, the size of Yorkshire.
Tributaries also reverse their flows as the broad, swampy flood plains are
filled. In the Vietnamese delta region alone, more than 12 000 square kilometres
of forests and paddy fields are flooded each year.

The variability of the river can make living on its flood plain a risky
proposition for the 50 million residents who depend on the Mekong basin
for food. Yet, as a French colonial administrator observed in the early
1900s, ‘the rhythmical movement of the waters, regular, like breathing,
furnishes much of what is needed to improve the land. High waters deposit
on the soil a layer of rich silt and spare the farmer the drudgery of transporting
fertiliser to the fields, and when the water recedes he finds the ground
all ready to support rich and remunerative crops.’ For peasant farmers,
this still holds true. Cambodia’s low-lying farmlands receive a coating
of up to 10 millimetres of silt in a normal flood year, and up to 30 millimetres
during peak floods. In neighbouring Vietnam, the Mekong delta, much of which
floods each year, contains 34 per cent of the country’s farmland and provides
40 per cent of its agricultural output. Large dams upstream could upset
the delicate hydrological balances on which this productivity depends.

Flood cycles are also crucial in maintaining fish stocks. V. R. Pantulu
is a retired fisheries expert with the Secretariat of the Committee for
Coordination of Investigations of the Lower Mekong Basin (Mekong Committee),
an international organisation set up in 1957 by the United Nations to manage
development of the Mekong basin. Pantulu estimates that 90 per cent of the
fish in the Mekong basin spawn not in the rivers themselves, but in the
surrounding lakes, submerged fields and flooded forests that fill up during
the wet season. Between June and October, fish swim into the 30 or 40 kilometre-wide
band of flooded forest and shrubland around the edge of the Tonle Sap, where
they can avoid predators and feast on decaying vegetation in the shallow
water. As the water recedes, fattened fish, including three species of carp
and five of river catfish, return to the lake and into thousands of waiting
fishing nets.

Tonle Sap and other freshwater fisheries in Cambodia and Vietnam yield
more than 200 000 tonnes of fish per year; the whole Mekong basin yields
nearly half a million tonnes. In coming years, however, the Mekong’s fertile
cycles are likely to be considerably altered by the building of dams to
tap the river’s hydropower and by deforestation, either for the timber or
to introduce new farming methods. The Mekong Committee estimates that forest
cover in the basin declined from 50 per cent in 1970 to 27 per cent in 1985.
The rate of forest-cutting continues to escalate in Laos and Cambodia.

Commercial logging and modern agriculture are exposing upland soils
to sun, wind and rain, resulting in soil compaction, erosion and loss of
natural fertility. Soil compaction in particular can alter seasonal flows
in upland streams. Compacted soils are less able to store water from monsoon
storms, which means that streams flood more often in the wet season and
are empty for longer in the dry season because there is no moisture left
in the hill soils to feed them. Eroded soil can also clog up streams with
silt. Siltation attributed partly to local deforestation has already made
Tonle Sap shallower, warmer and less hospitable to fish, reducing yields.
In the Thailand Natural Resources Profile, published in 1987, the Thailand
Development Research Institute reports that a quarter of Thailand’s farmland
is now subject to severe or very severe soil erosion, and many small irrigation
systems have become choked with silt. On the left bank of the river in Laos
and Vietnam, the mountainous upper watersheds of many Mekong tributaries
retain their tree cover. However, if these areas are opened up to extensive
logging and new methods of farming, the results are likely to be severe.

The biggest development project pending in the Mekong basin is a series
of hydroelectric dams that would change the face of the river for most of
its length. On the books since 1957, the scheme has been held up by three
decades of war. It originated when UN planners, enthusiastic about the hydropower
potential of the basin, helped to form the Mekong Committee, with members
from Laos, Thailand, Cambodia and Vietnam. Raymond Wheeler, chief engineer
at the US Army Corps of Engineers, which has built many of the US’s largest
dams, arrived to determine research priorities. And Western construction
companies began studying potential dam sites. The completed plan emerged
in the early 1960s. It called for a total of 100 dams to be built on the
mainstream of the Mekong and its tributaries. One dam, the High Pa Mong,
which would straddle the Mekong near Vientiane, where it forms the boundary
between Laos and Thailand would, if built today, displace a quarter of a
million people. Another proposed dam, the 28-kilometre long Stung Treng
in Cambodia, would have generated 7200 megawatts of electricity, many times
the then energy requirements of all four countries in the lower Mekong region.

It is hardly surprising that such a costly scheme made little progress
during or after the Vietnam War, which hotted up in the mid-1960s. By 1970
only a half-dozen small projects on minor tributaries of the Mekong had
been built. All of them, including the 150-megawatt Nam Ngum Dam in Laos,
serve Thailand, which escaped most of the fighting. Since 1970, although
the committee’s planners have kept busy with continued support from the
UN and over a dozen industrialised countries, they have not completed any
large projects.

Now, several big schemes are in the offing, including the first dams
to be built across the mainstream of the Mekong. The Mekong Committee is
currently recommending that $5 billion be spent in the next few years,
mostly on hydropower, with much more to follow. Chuck Lankester, a senior
official from the UN Development Programme who has recently taken charge
of the secretariat, says that the dams ‘are an idea whose time has come’.

As the governments of Southeast Asia turn from warfare to economic development,
the region’s little-exploited resources, including its great river, will
become increasingly attractive. As more roads, industry and commercial agriculture
are introduced, hydroelectric dams will power the economic transformation.
Already, hydropower is feeding industrialisation in Thailand, whose economy
is the fastest-growing in the world. Agencies such as the World Bank and
the UN Development Programme are contemplating loans and funding studies
for the construction of dams. Ray Oram, the Mekong Committee’s information
officer, identifies Sweden, Australia and Japan as the countries with the
greatest potential role in supporting hydropower in the region.

Thailand’s hunger for electricity is a prime reason for undertaking
the scheme. National demand for electricity has risen 70-fold in the past
30 years and is still rising at a phenomenal 10 to 15 per cent per year.
Feasible sites for hydropower within its own borders are being used up fast.
Existing dams, moreover, are often so short of water (possibly because of
deforestation) that it is difficult for them to satisfy the needs of irrigation
and power. What sites do remain tend to be in forests or other areas that
conservation-minded Thais would like preserved.

Many Thai farmers also oppose dams. In recent years, there have been
local uprisings against planned dams on at least four Thai rivers by villagers
concerned about losing their land, and about forest destruction, water pollution
and the risk of catastrophic floods triggered by earthquakes that could
crack the dams. A start on the Mekong Committee’s own $120 million Pak
Mool Dam, designed by the French firm Sogreah for the River Mool, a major
tributary of the Mekong in northeast Thailand, has been delayed several
times by resistance from villagers whose land it would flood. In June 1990,
villagers from around the country gathered in Bangkok to call for a nationwide
moratorium on building dams. In March this year, 12 000 villagers signed
a petition opposing the Pak Mool Dam and hundreds of them occupied the site
in protest when construction work began in May. Late last year, the World
Bank’s local chief, Philippe Annez, said that dams in Thailand have become
‘too political’ for the bank to touch. But the bank now seems to have changed
its tune and is considering lending money for the project.

Through plans for a coordinated development of the Mekong’s hydroelectric
potential, the Thai government is trying to place Thai dams across the border
in Laos andother countries where population is sparse and hydropower potential
high. Complaining that ‘you can’t build dams in this country any more’,
Subin Pinkhayan, the former Thai Foreign Minister, last year likened proposed
dams inside Laos to ‘sleeping beauties’ awaiting the touch of their Thai
‘Prince Charmings’.

The Laos government, while wary of Thailand’s intentions, finds it difficult
to turn down the opportunity to trade in hydropower. Selling electricity
abroad is one of the few ways that the country can earn foreign exchange.
Power and timber already account for over 60 per cent of Laotian exports.

What would be the social and environmental effects of the new dams in
the Mekong basin? A look at two of the best-studied projects suggests some
disquieting answers. The $3 billion Low Pa Mong Dam (a more modest replacement
for the 1960s High Pa Mong scheme on the border between Laos and Thailand)
could, at peak flow, deliver 2250 megawatts to Thailand. Combined with other
proposed mainstream dams such as Upper Chiang Khan, High Luang Prabang and
Sambor, it could also store runoff after the rains for release during the
dry season. That would both reduce flooding during the wet season and check
the rush of seawater into the delta during the dry season, which can poison
crops with salt. Engineers calculate that the lowest flows in the delta
during the dry season, at about 2000 cubic metres per second, could be augmented
by at least 10 per cent with water from the Pa Mong reservoir, and tripled
if the chain of eight planned dams on the mainstream were built.

However, according to William van Liere, former director of the agricultural
division of the Mekong Committee, all the dams would need to keep their
reservoirs at high levels in order to generate steady amounts of electricity.
In effect, this gives urban demands for electricity priority over those
of farmers who want greater releases of water and reservoir levels kept
low. During the dry season, farmers need the water to serve their crops;
during the wet season, they want the reservoirs to be able to absorb incoming
flood waters.

Even if Low Pa Mong and other mainstream dams were given over entirely
to moderating the Mekong’s flow, it could take generations for Vietnamese
farmers to adjust their current delicately balanced farming systems to the
new quantities of fresh water. As Mekong Committee documents suggest, current
crops are ‘well adapted to the present pattern of salinity’. Regulating
the flow by mainstream dams would also affect coastal ecosystems such as
mangrove forests and, by reducing the supply of nutrients that reaches the
sea from the river’s mouth, even damage marine fisheries.

The Low Pa Mong is also likely to disrupt the spawning and migration
habits of the wide variety of species that roam the river. These include
the indigenous catfish, Pangasianodon gigas. At its adult length of two
metres and weight of up to 300 kilograms, this is the biggest freshwater
fish in the world. Tyson Roberts, a specialist on freshwater fish from the
University of California, Berkeley, says that the Mekong has the ‘richest
riverine fauna in all of Asia’, with more species than either the Yangtze
or the Ganges. He warns that continued dam construction will have a serious
effect on fishlife.

According to John Dennis, who has studied natural resource developments
for the UN Development Programme, Low Pa Mong would remove from the flood
zone about 1840 square kilometres of land around Tonle Sap and a further
2000 square kilometres along the Mekong and Bassac rivers. And, by eliminating
peak floods and reducing variation in river levels, it would reduce silt
deposition in Cambodia by 90 per cent, which would threaten the fertility
of farmland.

Downstream of Low Pa Mong, erosion of the banks of the Mekong would
increase because of the scouring effect of water released from behind the
dam. The secretariat estimates it would cost $80 million to protect the
banks.

A more immediate concern is resettlement. Although plans for the High
Pa Mong Dam, which would have displaced 250 000 people, were scrapped in
the mid-1980s, the more modest substitute, with a reservoir level rising
to 210 metres above sea level instead of 250 metres, will still require
the evacuation of more than 42 000 people, three-quarters of them from Thailand.

In Laos the Nam Theun 2 dam, which is designed to generate electricity
for export, is expected to cause deforestation. The site is the unspoiled
upper reaches of the Theun tributary in the middle of more than 3000 square
kilometres of Laos’s evergreen forest, an area that harbours an abundance
of rare wildlife, including elephants, big cats, such as tigers, leopards
and clouded leopards, wild cattle and primates. So far, this remote wilderness
has been subject to little human interference, aside from some logging near
the area’s single road, Highway 8 to Vietnam, and scattered rice farming
by a few thousand inhabitants.

Construction of the dam, which could begin in a few years with aid from
the World Bank, the Asian Development Bank and the German and Japanese governments,
would bring devastating changes to the entire area. Current plans developed
by Australia’s Snowy Mountains Engineering Corporation call for a reservoir
300 square kilometres or larger feeding a 300 to 600 megawatt power plant.
The estimated cost is $500 million. Ultimately the project could be expanded
up to 1200 megawatts. Nearly 4000 people would have to be evacuated to make
way for a reservoir of such dimensions.

Water from the dam’s reservoir would overwhelm the stream in the neighbouring
Kathang river system to which it is scheduled to be diverted. Flow in the
Theun river itself would cease entirely for up to 10 months of the year.
For the rest of the time, the water would be undrinkable even by animals,
according to a study in 1987 by the Motor Columbus engineering firm of Switzerland
on behalf of the World Bank. Salt deposits in the valley that are now being
exploited by local villagers would be covered by the reservoir and would
be likely to find their way into local watersheds, further damaging water
quality, says Prinya Nutalai, a geologist at the Asian Institute of Technology.
Malaria-carrying mosquitoes would find an ideal breeding ground in the vast
mud flats created between high and low-water marks of the shallow reservoir.
The risk of liver fluke, lung fluke, schistosomiasis and filiariasis would
also increase.

No less damaging would be the effects of dam construction itself. Quarries
would be dug, timber taken out, transmission lines laid and over 200 kilometres
of road built or upgraded. Forests and streams would be obliterated and
new settlers, loggers and wildlife poachers attracted to the edge of the
reservoir. The Motor Columbus study concludes that the area’s ‘undisturbed
forests of great variety’ would be ‘irrevocably affected’.

Because they use no fossil fuels, large-scale hydropower plants are
often put forward as the correct response to global warming and the need
for ‘sustainable’ sources of electricity. The case of the Mekong dams suggests,
however, that the hydropower ‘solution’ will create more problems than it
solves. Growing environmental degradation and uncertainties over the effects
of global warming are only the latest reasons to slow the momentum of these
giant projects.

Larry Lohmann is associate editor of The Ecologist magazine. In the
late 1980s, he worked in Thailand for the Project for Ecological Recovery,
a local environmental pressure group.

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The high risks of knowing too little

Waiting in the wings to ambush any attempts to develop the Mekong basin
is the greenhouse effect. Some recent climate models predict heavier Asian
monsoon rains in a warmer world.

If this is correct, it would increase runoff during the wet season,
and, ultimately, swell the flow of the Mekong. That would flush the delta
with larger amounts of fresh water and silt during the wet season, forcing
farmers to plant lower-yielding, deep-water rice in fields now reserved
for more productive varieties.

At the same time, rising sea levels would push salt water further up
the river in the dry season. More of the Mekong’s delta would be exposed
to salt water. Because rice has a low tolerance to salinity, this influx
of salt water would also reduce crop yields.

Even without the effects of global warming, the presence of salt water
is one factor keeping rice from being grown closer than 40 to 50 kilometres
to the coast in the delta.

However, it may be dangerous to base development programmes on any single
analysis of the effects of global warming. ‘It will be many years before
we can have confidence in model forecasts,’ warns Mick Kelly, atmospheric
scientist with the Climatic Research Unit at the University of East Anglia.
Kelly has been studying the implications of climate change for development
planning in the region.

The message for planners, Kelly says, is that while climatic changes
are ‘near-inevitable’ in the region, not enough is known about them to base
development projects on model projections. Instead, he suggests, planners
should ‘try to ensure that long-term projects are climate-proof. It would
be undesirable to add further stress or change to the system through human
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