New scientific study: Dams on Sesan River polluting water and poisoning downstream communities

Address: PO Box 89007, Village 4, Banlung Town, Ratanakiri,
CAMBODIA
tel: (855) 75 974 112
Email: sesan@online.com.kh
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PRESS RELEASE
8th September, 2009

New scientific study: Dams on Sesan River polluting water and poisoning downstream
communities.
Ratanakiri Province, Cambodia - A new report has linked upstream hydropower reservoirs to
high levels of toxic algae and bacteria found in the Sesan River, which exceed World Health
Organisation (WHO) limits for safe drinking water.
Adverse environmental and social impacts caused by hydroelectric damming of the Sesan River
are reflected in a report released by STRIVER; a research strategy for improved water resource
management jointly coordinated by the Norwegian Institute for Agricultural and Environmental
Research (BIOFORSK) and the Norwegian Institute for Water Research (NIVA). The report
illustrates how detrimental dams on the Sesan River in Vietnam have been to the quality of water
in the Sesan River and the health problems faced by communities living downstream in
Ratanakiri province, Cambodia.
These research findings are especially relevant given proposals are in place to construct 5 dams
on the Sesan River and its tributaries in Cambodia, including the large 400MW Sesan II dam in
Stung Treng, which is anticipated to resettle over 5,000 people, inundate more than 33,000 ha of
land, and have large scale impacts on fisheries and the livelihoods of both upstream and
downstream communities.
The 2009 STRIVER technical brief entitled “A limnological study of the Sesan River in
Cambodia in the dry season: focus on toxic cyanobacteria and coliform bacteria” is based on
scientific research carried out by Anna Madeleine Tiodolf, Norwegian University of Life
Sciences with field assistance provided by the 3S Rivers Protection Network (3SPN). The report
presents the results of a water quality study conducted during the dry season over a two-week
period in March 2008 in which water samples were taken in two different locations along the
Sesan River in Ratanakiri province; Andong Meas, 30 kilometres downstream of the Vietnamese
border, and Vuen Sai, 130 kilometres downstream of the Vietnamese border.
The study confirmed the occurrence of cyanobacteria and cyanotoxins in the Sesan River
mainstream, however no cyanobacteria were detected in the water samples taken in three
different tributaries, indicating the polluted water to originate from a more stagnant mainstream
source such as an upstream hydropower reservoir.

The water is not suitable for human consumption
Research by Tiodolf found concentrations of toxic algae (cyanotoxin) and presence of the
indicator species E.coli, coliform bacteria, in the Sesan River exceed World Health Organisation
(WHO) limits for safe drinking water.
Cyanotoxins are cancerous to the liver after longer periods of exposure, while excessive levels of
E.coli concentration are commonly associated with many health problems and present an
increased risk to communities through the spreading of waterborne disease.
Results are consistent with the gastric disorders and skin problems experienced by Sesan River
communities since the construction of the Yali Falls dam. Approximately 28,000 people rely on
the Sesan River for their drinking water, fishing, bathing, and feeding livestock and according to
a report prepared by the Fisheries Office in 2000 entitled “A study of the downstream impacts of the Yali Falls dam in the Sesan River Basin in Ratanakiri Province, Cambodia.” The 2000 report stated that 952 people had died along the Sesan River, with large numbers of domestic animals, as a result of diseases believed by local communities to be directly associated with the Yali Falls dam.
A 2007 Environmental Impact Assessment (EIA) report on the Sesan River similarly identified
toxic algae as the likely reason for villagers’ illnesses. The EIA report prepared by the
Norwegian Institute for Water Research and Nordic hydropower consultants, SWECO Grøner,
confirmed that there are strains of toxin-producing cyanobacteria present in the Yali Dam
Reservoir, and that water quality in the Sesan River has “seriously deteriorated since the
construction of the Yali Power Plant” with the cyanobacteria producing “exactly the same
symptoms” as reported by Cambodians downstream.
Mr. Meach Mean, Coordinator of the 3S Rivers Protection Network which works with
communities along the Sesan River in Ratanakiri, indicates that this study confirms what
villagers have been reporting for years. “The research by STRIVER clearly demonstrates the
disastrous ecological and social effects large dams can have on rivers and the associated health
problems for downstream communities. We hope this report will help initiate remedy for the
communities who have been waiting for mitigation and compensation from the past and present
impacts of Vietnam’s dams”.
Construction on Vietnam’s Yali Falls dam began in 1993 by the Electricity of Vietnam on the
Sesan River and is located approximately 70-80 km from the border of Cambodia. Since its
construction and operation in 2001, villagers living downstream have experienced large-scale
social, economic, and environmental impacts. Despite complaints and requests from
communities for mitigation no solution has been forthcoming.
Mr. Say Duen, from Koh Peah Commune, in Vuan Sai district confirmed that health problems
started approximately 5 to 10 years ago. “When we use the river water to cook, or to wash, we

sometimes get a skin rash or diarrhea, and children who swim and drink the water get sick,
especially during the dry season. I hope that this message will be received by the government and
dam builders and they use their responsibility to find a solution for our people.

END
For more information, photos, or documents mentioned in this press release:
Contact: Mr. Meach Mean, Coordinator, 3S Rivers Protection Network, sesan@online.com.kh,
+855 (0)11 758 970.

The 3S Rivers Protection Network (3SPN) is a civil society organisation representing indigenous
people living along the Sesan, Srepok (and Sekong) Rivers in Cambodia