Date: November 1, 2017
Source: Society of Environmental Toxicology and
Chemistry
Summary:
A
new study used American dippers to determine if run-of-river dams altered food
webs and mercury levels at 13 stream sites in British Columbia.
Run-of-river
dams are deemed "green energy" because they produce lower greenhouse
gas emissions, have lower water storage, barrier size, extent of flooding and
water level fluctuations than conventional hydropower facilities. They divert
part of a stream through turbines before returning it to the stream downriver.
The impact this process has on the ecosystem is unknown, particularly with
regards to the production of methylmercury as a result of the dam and the
disruption of natural flows. RoR dams can cause a spike in methylmercury in two
ways -- they can form small reservoirs, called headponds, which flood soil and
create slow-flowing, low-oxygen environments; or they can create higher
temperatures in the stream as a result of the reduced flow conditions when
portions of the stream are diverted to the turbines.
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