A practice commonly done in dams is threatening several insects and disturbing the ecological balance within rivers, says a new U.S. study.
Dams play a huge role in creating hydropower supply around the globe. It is currently the largest of all renewable forms of energy, supplying as much as 19 percent of the electricity demand of the world, according to the International Energy Agency (IEA). The United States Army Corps of Engineers' inventory has recorded 79,000 dams.
Like other renewable energy forms, hydropower is considered for its sustainability, but the same thing cannot be said on its surrounding environments where many insect colonies are rapidly declining or have completely disappeared due to hydropeaking.
Hydropeaking refers to the regulation of water levels and flow from the reservoir usually as a way of meeting the electricity demands on a regular basis.
"These large daily rises and peaks in river flows due to hydropower dams are not normal. Prior to the construction of dams, there were almost no major daily changes in river levels," said David Lytle, Oregon State University integrative biology professor.
Lytle and his colleagues from Utah State University, U.S. Geological Survey and Idaho State University ventured into Grand Canyon's Colorado River to obtain more than 2,500 different samples and study the effects of hydropeaking on river ecosystems, such as the presence of insects.
Based on their analysis, hydropeaking can be especially harmful on aquatic insects — some 75 percent of them — that tend to practice "cementing behavior," which involves attaching their eggs on substrates that can be present in shallow waters.
Hydropeaking increases the risk of damaging the eggs before they hatch by drying them out when the water levels suddenly decrease. This may lead to "acute mortality" of some of the most vulnerable insects.
Changes in the reproduction of aquatic insects can have a profound impact on the rest of the river's ecosystem since they provide food for bats and birds.
"The loss of these aquatic insects can have a major impact on fisheries and other aspects of ecosystem health," expressed Lytle.
While the group doesn't completely discredit the purpose and benefits of dams and hydropower, it suggests ways to reduce this problem by keeping the levels of rivers unchanged for at least a couple of days, particularly when the demand isn't high, to give the insects a chance to lay and hatch eggs.
Early in 2016, the American Rivers has identified the most threatened river systems in the country, some of which are being damaged by the presence of dams.
The study is now online on BioScience.
