Researcher to limit environmental impacts of dams in Asia

Subject: [Lancang-Mekong] Researcher to limit environmental impacts of
dams in Asia
Date: Tue, 20 May 2008 11:20:37 +0700
From: Ame Trandem
Reply-To: ame@ngoforum.org.kh
Organization: NGO Forum on Cambodia

Researcher is working to limit the environmental of hydroelectric dams
in Asia

Science Centric | 15 May 2008 12:57 GMT



Rivers around the world are being tamed by massive hydroelectric dams,
with high-profile projects under construction in Laos and China and
several proposed for the Mekong River in Southeast Asia. Researcher Guy
Lanza of the University of Massachusetts Amherst is working to limit the
environmental impact of these projects, which he says often deliver a
legacy of economic hardship and health problems instead of prosperity
for people living near the dams and downstream.

'After dam construction, there is an immediate drop in water quality
that destroys useful fish populations and poses a threat to livestock
and humans,' says
Lanza, an aquatic biologist and microbiologist who consults for the
environmental organisation International Rivers. 'Converting river
systems into lakes also creates more habitat for the snails and
mosquitoes that carry malaria, dengue fever and schistosomiasis, leading
to an increase in the number of cases of these diseases.'

Lanza recently critiqued the Nam Theun 2 Hydroelectric Project, a 1,200
foot wide expanse across the Nam Theun River in Laos that will be
completed in December 2009. Dam gate closure and reservoir filling will
begin in June 2008, and power from the dam will be exported to Thailand
as part of the Laotian government's plan to generate export revenue by
building more than 30 dams by 2020.

After reviewing the NT2 Environmental Assessment and Management Plan,
Lanza worked with International Rivers, and together their efforts
helped to convince the Nam Theun 2 Power Company to remove some of the
biomass, in the form of fallen trees and leaves, prior to filling the
reservoir instead of simply leaving it behind to rot. The experience
with Nam Theun 2 has highlighted the importance of clearing biomass from
future dam projects, a requirement the Laotian government is reportedly
considering.

Lanza says, however, that the Nam Theun 2 biomass clearance plans, which
include cutting and burning biomass from part of the reservoir area, may
not prevent significant water quality problems. 'Burning biomass adds
air pollutants, including carbon dioxide
, ozone and other
greenhouse gasses, and toxic substances such as mercury,' he says.
'Burning will also release mercury to the soil and greatly accelerate
the release of nutrients such as nitrogen and phosphorus from the biomass.'

After burning, nutrients from the ash would trigger and support the
sudden growth of excess bacteria and algae
in the water as the
reservoir fills, triggering a cascade of water-quality problems,
including greatly reduced dissolved oxygen, fish kills, the formation of
toxic metabolites by cyanobacteria and the release of toxic gasses and
metals such as hydrogen sulphide and mercury from reservoir sediments.

Leaving the biomass behind would also be problematic, says Lanza, since
rotting vegetation would increase greenhouse gas emissions from the
reservoir, use the available oxygen in the water, cause fish kills and
result in water that was unsuitable for drinking and irrigation.

Lanza started his career as an aquatic
ecologist for the
Smithsonian Institution in 1971, living in Thailand and doing the
detective work to predict the ecological impacts of a proposed
hydroelectric dam on the Mekong River. That research led to two new
discoveries: a new species of schistosome parasite (the Mekong
schistosome), and a new species of snail that transmits the Mekong
schistosome. He says it was obvious then that water quality would
decrease, and the shores of lake behind the dam would provide the ideal
habitat for the snails and insects
that carry disease.

In 1996, Lanza reviewed the environmental impact report for the Nam Leuk
Hydropower Project in Laos and visited the site after the dam was
complete, which reinforced his concerns and confirmed his predictions.

'After the completion of Nam Leuk, there was a sharp drop in the oxygen
content of water in the lake and blooms of cyanobacteria that release
toxins that are deadly to livestock and can cause liver cancer in
humans,' says Lanza. 'The data show that water-quality problems
eliminated useful species of fish that people depend on for food and
livelihood, replacing them with less desirable species.'

Villagers downstream of the project were experiencing water-quality
problems, and the Nam Leuk reservoir provided expanded habitats for the
snails and mosquitoes that carry schistosomiasis and malaria,
threatening a rise in the number of cases of these diseases.

'Midstream dams are again being proposed for the Mekong River, and we
are finding that disease-causing schistosomes are much more prevalent in
this area than we originally thought. This must be considered when
developing future environmental assessment and management plans,' says
Lanza.

Source: UMass Amherst Office of News and Information




http://www.sciencecentric.com/news/08051525.htm


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