The livelihoods of 30,000 people in Stung Treng province are threatened by a plan
to build a series of hydroelectric dams in the Laotian part of the Sekong River Basin,
upstream of where the Tonle Sekong enters Stung Treng. Tens of thousands of people
living in Laos would also be affected.
Along the Sekong River in Stung Treng province, adults and children catch fish and other aquatic animals to feed their families and to sell at the market. Fish is the single most important source of dietary protein for people living in the vicinity of the Sekong River.
In Cambodia, the effects would extend into the Sesan and Srepok rivers, the Sekong's
main tributaries, into the Mekong River, and as far away as the Tonle Sap Lake.
The inevitably disastrous impacts of these dams on Cambodians living along the Sekong
River are not the subject of mere conjecture. According to Kim Sangha, Coordinator
of the 3S Protection Network ('3S' being the Sekong, Sesan and Srepok rivers), "More
than 55,000 Cambodian people living along the Sesan River, the Sekong's largest tributary,
are already suffering from the severe impacts of hydroelectric projects on the Sesan
These social, environmental and economic impacts on communities living along the
Sesan River in Ratanakkiri and Stung Treng provinces, caused by the state-owned Electricity
of Vietnam's Yali Falls dam, are internationally infamous although largely ignored
by the governments of Cambodia and Vietnam. The impacts on Cambodia's Sekong River
caused by the proposed dams in Laos would be very similar to the impacts already
occurring along the Sesan River.
The Sekong River Basin within Laos covers an area of approximately 23,000 square
kilometres (km2). Nine large dams would be built on the Sekong and its major tributaries,
and other dams may be constructed on smaller tributaries. Another 4,100 km2 of the
Sekong basin is located in Cambodia, where the Sekong flows for 140 kilometres through
the districts of Stung Treng, Siem Pang and Sesan in Stung Treng province, before
entering the Mekong River.
According to a forthcoming report by a Cambodian NGO, the Culture and Environment
Preservation Association (CEPA), there are 31 villages and 28,376 people living very
close to or directly adjacent to the Sekong River in Stung Treng province. The majority
of people living along the Sekong River are of the Lao, Kavet, Lun, Kuy and Khmer
Khe ethnic groups. They depend on the Sekong's fisheries for their major source of
dietary protein and income, while other aquatic animals, plants, and dry-season cultivation
of vegetables along the river's banks are important for food security and local economies.
The Laotian government's program of dam-building in the Sekong basin is largely designed
to generate electricity for sale to Vietnam and Thailand. One dam has already been
built on a Sekong tributary: the 76-meter-high Houay Ho hydroelectric dam was completed
in 1997. It was the first large hydroelectric project to be built in the Sekong River
Another dam on a Sekong tributary has recently been proposed. Although there are
few details about the project, the Kansai Electric Power Company of Japan has signed
a Memorandum of Understanding to build the Xekatam Hydroelectric Project. Kansai
is presently conducting a feasibility study for the project, and has already publicly
stated that it intends to complete construction of the 50-to-60 megawatt (MW) project
However, these two projects pale in comparison to the grandiose scale of the hydroelectric
dams proposed to be built throughout the Sekong River Basin in Laos.
On the Sekong mainstream, the Sekong 4 hydroelectric project would have a generating
capacity of 460MW. The Sekong 4 dam would cost US$600 million to build, be 170m high,
and would take at least 14 months to fill with water. In March 2006, the Region Oil
Company of Russia signed a memorandum of understanding (MoU) with the Government
of Laos to undertake an 18-month-long study of Sekong 4. However, only six months
later, Oley Kabardin, Managing Director of Region Oil Co, announced that "Following
the study, we have decided to construct three projects, Xekong 4, Xekong 5 and Nam
Kong 1, while we need to collect more data on Nam Kong 3." In 2004, a power
system development plan (PSDP) for Laos suggested that upstream of the Sekong 4,
the massive 250m-high Sekong 5 hydroelectric project would, according to Region Oil,
have a generation capacity of 400MW. According to the Lao Power System Development
Plan of 2004, it would take three years to fill the Sekong 5 dam's reservoir.
The Nam Kong River is a large tributary of the Sekong, and Region Oil Co is proposing
to build two hydroelectric dams on this river. The Nam Kong 1 project would have
a generation capacity of approximately 240MW and a 32m dam. The probable cost of
the project is US$200 million. The 35MW Nam Kong 3 would be upstream of the Nam Kong
According to Region Oil Co, construction of these three projects would begin in 2007,
with the Sekong 4 expected to be completed by 2012, Sekong 5 in 2014, and the Nam
Kong 1 in 2013.
The Xekaman River is the major tributary of the Sekong. Three hydroelectric dams
are proposed: the Xekaman 1, Xekaman 3 and Xekaman 4. In March 2006, Viet-Lao Power
Investment and Development Joint-Stock Company began a study of Xekaman 1, a 465MW,
128m dam that would cost US$535 million. The Xekaman 1 reservoir would flood an area
of more than 200km2 and take three years to fill. Viet-Lao Power has not yet studied
the proposed 55MW Xekaman 4. Construction of the US$273 million Xekaman 3 project
began in April 2006. This 250MW project includes a 128 m dam located in the upper
Xekaman basin, and is the single largest investment ever made by Vietnam in Laos.
The Xepian-Xenamnoi project would consist of two large dams. A 35m-high dam would
divert most of the Xenamnoi River into the reservoir of an 85m-high dam on the Xepian
River, a large tributary entering the Sekong just upstream of the Lao-Cambodian border.
In August 2006, a Memorandum of Understanding was signed between the Government of
Laos and two South Korean companies, SK Engineering and Construction Company and
Western Power Company, to undertake a feasibility study of this proposed 400MW dam.
As each of the dams in the Sekong basin in Laos are built, the impacts on Cambodia
will steadily accumulate. Experience from the Sesan River indicates the type and
severity of the impacts that will occur in the Sekong and the communities living
First, most of the Sekong dams are designed as large storage dams. In other words,
during the rainy season, the dams will generate electricity but also capture and
store large amounts of water that would otherwise flow through the Sekong. During
the dry season, when water levels in the river are naturally low, huge amounts of
water would be released from the reservoirs to generate electricity and then enter
From this relatively simple exercise in hydroelectric engineering, some interrelated
•When water is stored in the reservoir, the submerged vegetation and organic matter
begins to rot. This process of decay consumes much of the oxygen in the water, and
also makes the water putrid. When this water is released through the dam into a river,
it is largely deoxygenated and often poisonous to aquatic life. Toxic blue-green
algae caused by dams are also a serious threat to aquatic life, domestic livestock,
wildlife and humans. Large-scale fish kills have been documented downstream of dams
as a result of the release of reservoir water. Along the Sesan River, the fisheries
declined precipitously following the release of water from the Yali Falls reservoir.
Depending on the amount of vegetation flooded by a reservoir, releases of deoxygenated,
rancid water into the river downstream of the dam can last for many years, and sometimes
for decades. The reservoir areas of all of the proposed dams in the Sekong basin
are densely vegetated, and long-term releases of very poor quality water from these
reservoirs and into Cambodia's Sekong River are a certainty.
•Water released from the reservoirs is often unfit for human consumption and use.
In all of the communities living along the Sekong River, people depend on the river
as a source of water for drinking and cooking. The river is also used for doing laundry
and for bathing. Children often swim and play in the river for hours a day, and it
is children who are particularly susceptible to the health impacts of exposure to
this water. People's livestock, including pigs, chickens, cattle and water buffalo
also depend on the river for drinking water.
•As a river's water flows into a reservoir, the silt and sediment being carried by
the water are deposited in the reservoir. When this sediment-free water is released
into the river downstream of the dam, it is known as "hungry water" because
it eats away the riverbanks to replenish its sediment load. Extensive erosion of
riverbanks along the Sekong River will deprive local people of the riverbank gardens
that they cultivate during the dry season. Houses, other buildings, trees and other
vegetation will collapse into the river as the water erodes away the riverbank.
•This erosion is exacerbated by the daily surges in water levels and volumes caused
by water released through the dam to generate electricity. All of the Sekong dams
are designed to supply electricity demand in Vietnam and Thailand, and all of these
dams will be supply "peak" electricity. In other words, when daily demand
for electricity in Vietnam and Thailand is highest, usually early in the morning
and in the late afternoon and evening, the Sekong dams will release water. At other
times of the day and during the night, they will stop generating electricity and
will not be releasing water. Along the Sekong in Cambodia, water levels will fluctuate
from very low levels during the night to higher levels during the day as surges of
water are released from the dams.
These fluctuations in water levels will be particularly evident during the dry season.
It is certain that these high water levels and the releases of poor quality "hungry
water" and resultant erosion will cause severe damage to the aquatic habitat
and ecosystems of the Sekong River. Critical habitat such as wetland forests and
rapids, which are naturally exposed during the dry season, will become submerged
and eventually be destroyed. Deep pools, which serve as a dry season refuge for most
of the fish species living in the river during the dry season, will become filled
with silt eroded from the riverbanks. River birds, monitor lizards, soft-shelled
turtles and other riparian wildlife are also dependent on the river's waters.
Local people living along the Sekong report that they do most of their fishing during
the dry season, and that their most important fishing grounds are in the vicinity
of rapids and in deep pools. The destruction of the rapids and deep pools will have
long-term and irreversible impacts on the fisheries of the Sekong, and on the food
security of local people.
One of the widespread observations of Cambodians living along the Sesan River is
that the "river isn't like it used to be" and that the "river doesn't
flow naturally" as a result of the Yali Falls dam in Vietnam. The water storage
and operation of a large hydroelectric dam radically alters the natural flow of a
river. The dams in the Sekong basin will significantly increase water volume and
flows in the Sekong River during the dry season, and noticeably reduce volume and
flow during the early part of the rainy season, when the reservoirs of the dams are
at their lowest and can begin to store water again. This alteration of the Sekong's
natural flow will very likely have impacts on the seasonal feeding and reproductive
migrations for fish in the Sekong and between it and the Mekong River, delaying or
even preventing these migrations and having a direct impact on the productivity of
the Sekong fisheries.
As these inter-related impacts accumulate, the Sekong River, its fisheries and aquatic
life, and the food security and economies of the communities living along the river
will be devastated.
Furthermore, there is clear evidence linking fish in the Sekong, Sesan and Srepok
rivers in Laos and Cambodia and the Mekong River in Cambodia, Laos and Thailand.
In a peer-reviewed journal article published in the Natural History Bulletin of the
Siam Society in Thailand in 2003, scientists have clearly linked important fish migrations
from the Tonle Sap Lake in Cambodia with the Mekong, Sekong, Sesan and Srepok rivers
in Laos and Cambodia. Another article published in Asian Fisheries Science in 2004
has shown that other important fish species migrate annually between the Sekong,
Sesan and Srepok rivers and the Mekong River in Cambodia and southern Laos, travelling
the Mekong River as far as northeast Thailand. Therefore, dam-inflicted effects on
fish populations in the Sekong River Basin in Laos and Cambodia can be expected to
have serious negative consequences for fish and fisheries throughout much of the
lower Mekong River Basin.
Cambodia and Laos are signatories to the "Agreement on the Cooperation for the
Sustainable Development of the Mekong River Basin," generally known as the Mekong
Agreement. Article 7 of the Agreement requires that states "make every effort
to avoid, minimize and mitigate harmful effects that might occur to the environment,
especially the water quantity and quality, the aquatic (eco-system) conditions, and
ecological balance of the river system."
"It is clear that there will be harmful effects on the environment, water quantity
and quality, aquatic and ecosystem conditions, and the ecological balance of Cambodia's
Sekong River if any of these dams are built in the Sekong basin in Laos," says
Tep Bunnarith of CEPA. It is also clear that so far the Government of Laos has not
made any effort to avoid or minimise these effects, as it continues to approve and
participate in the planning and construction of these dams. As experience along the
Sesan River, and throughout the Mekong River Basin indicates, once these dams become
operational and the impacts occur, governments and investors have no interest in
"The Government of Cambodia has recourse through the Mekong River Commission
to make known its concerns about the likely impacts of the Sekong dams to the Government
of Laos," Bunnarith says. "At the very least, Cambodia should demand that
an independent, cumulative environmental and social impact assessment of the Sekong
basin dams and the Sekong, Mekong, Sesan and Srepok rivers should be undertaken before
construction of any of these dams commences. Communities living along the Sekong
River in Stung Treng province should be fully informed of these impacts and should
have the opportunity to voice their concerns to their government and the Government
of Laos. But in the end, it can only be hoped that the Government of Laos will realise
that being a good neighbor means not inflicting harm on Cambodians."
* Dave Hubbel is a researcher who has been working in the Mekong Region for the past