underlying assumption that small hydropower systems pose fewer ecological
concerns than large dams is not universally valid, scientists said in the
report. A five-year study, one of the first of its type, concluded that for
certain environmental impacts the cumulative damage caused by small dams is
worse than their larger counterparts.
findings http://bit.ly/14XWxBu were reported by scientists
from Oregon State University in the journal Water Resources Research, in work
supported by the National Science Foundation.
conclusions were based on studies of the Nu River system in China but are
relevant to national energy policies in many nations or regions -- India,
Turkey, Latin America -- that seek to expand hydroelectric power generation.
Hydropower is generally favored over coal in many developing areas because it
uses a renewable resource and does not contribute to global warming. Also, the
social and environmental problems caused by large dam projects have resulted in
a recent trend toward increased construction of small dams.
Kyoto Protocol, under Clean Development Mechanism, is funding the construction
of some of these small hydroelectric projects, with the goal of creating
renewable energy that’s not based on fossil fuels,” said Desiree Tullos, an
associate professor in the OSU Department of Biological and Ecological
energy may be renewable, but this research raises serious questions about
whether or not the overall process is sustainable,” Tullos said.
is damage to streams, fisheries, wildlife, threatened species and communities,”
she said. “Furthermore, the projects are often located in areas where poverty
and illiteracy are high. The benefit to these local people is not always clear,
as some of the small hydropower stations are connected to the national grid,
indicating that the electricity is being sent outside of the local region.
result can be profound and unrecognized impacts.”
study was one of the first of its type to look at the complete range of impacts
caused by multiple, small hydroelectric projects, both in a biophysical,
ecological and geopolitical basis, and compare them to large dam projects. It
focused on the remote Nu River in China’s Yunnan Province, where many small
dams producing 50 megawatts of power or less are built on tributaries that fall
rapidly out of steep mountains. There are already 750,000 dams in China and
about one new dam is being built every day, researchers say.
the findings of the report as it relates to this region of China:
The cumulative amount of energy produced by small hydroelectric projects can be
significant, but so can the ecological concerns they raise in this area known
to be a “hotspot” of biological diversity.
Per megawatt of energy produced, small tributary dams in some cases can have
negative environmental impacts that are many times greater than large, main
Many dams in China are built as part of a state-mandated policy to “Send
Western Energy East” toward the larger population and manufacturing centers.
Small dams can have significant impacts on habitat loss when a river’s entire
flow is diverted into channels or pipes, leaving large sections of a river with
no water at all.
Fish, wildlife, water quality and riparian zones are all affected by water
diversion, and changes in nearby land use and habitat fragmentation can lead to
further species loss.
The cumulative effect on habitat diversity can be 100 times larger for small
dams than large dams.
encouraging more construction of small dams are often developed at the national
or international level, but construction and management of the projects happen
at the local level.
a result, mitigation actions and governance structures that would limit social
and environmental impacts of small hydropower stations are not adequately
of the things we found generally with small dams is that there was much less
oversight and governance with the construction, operation and monitoring of
small hydropower,” Tullos said. “On the large, main stem dams, people pay
attention to what’s going on. On a small hydropower project, no one notices if
minimum flows are being maintained. Or if a pump breaks, the hydropower station
might sit idle for long periods of time.”
said the key finding of the research, contrary to prevailing but unvalidated
belief, is that “biophysical impacts of small hydropower may exceed those of
large hydropower, particular with regard to habitat and hydrologic change.”