Per megawatt of energy produced, small tributary dams in some cases can have negative environmental impacts that are many times greater than large, main stem dams.
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.
Policies 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.
As a result, mitigation actions and governance structures that would limit social and environmental impacts of small hydropower stations are not adequately implemented.“One 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.”
Desiree Tullos | EurekAlert!
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