Overall, this imbalance between the number of small factories and their overall production is similar. Small generating stations represent about 91% of all hydroelectric installations, but account for only 11% of hydroelectric production. And yet they’ve seen a global boom in recent years – along with a growing body of evidence from around the world suggesting their impact runs deeper than previously thought.
“The biggest problem associated with small hydroelectric plants is their number,” says Thiago Couto, an aquatic ecologist and postdoctoral associate at the University of Miami. He has studied the effects of small hydropower plants around the world, including countries like Brazil. “Today, for every large hydroelectric dam in operation, there are 11 other ‘small’ ones, and the number is expected to continue to increase in the future. The cumulative impact of all these small dams on hydrology, Fish migration and water quality is a matter of great concern, especially in rivers that are home to multiple dams.”
Small hydroelectric dams, for example, can play a disproportionate role in interrupting the natural flow of rivers, known as river fragmentation, as research by Couto and others shows. This can prevent migrating fish from traveling. Environmental activists have described the impact of such an accumulation of small, disruptive plants on rivers as “death by a thousand cuts”.
From an environmental perspective, “small” isn’t a particularly meaningful term, Couto notes, because it generally refers to productive capacity – rather than the factors that actually matter for the ecological impact of the plant. plant, such as the amount of water diverted and how much remains in the creek bed. And while SSHP is often marketed as a good solution for unconnected communities, globally, “the proliferation of SSHP is not primarily driven by rural electrification,” he says, but rather through incentives and subsidies that make it a lucrative business investment.
Remote communities are also not necessarily SHP friendly. Sami reindeer herders in northern Norway have opposed the development of small hydropower in the past, out of concern about its impact on reindeer pasture.
Scientists also pointed to the lack of knowledge about small hydropower plants, as they are only beginning to fully understand how different factors affect a plant’s overall impact.
A team of scientists carrying out a long-term ecological research project in the Matschertal valley (Val di Mazia), led by the Institute for the Alpine Environment of the Eurac Research Center in South Tyrol, has made a surprising discovery. The main objective of their project was to study the impact of climate change on an alpine river ecosystem. But a few years into the study, a small run-of-river diversion hydroelectric plant with a spillway was added to the steep, glacier-fed, fast-flowing stream they were monitoring. They took the opportunity to do a before-and-after comparison of the plant’s impact on benthic macroinvertebrates – small aquatic animals such as sandfly larvae that live in water bodies and are commonly used as indicators. of their ecological status. They expected the plant to have a significant impact on macroinvertebrates – but these expectations were not confirmed.
Instead, results from the five-year study showed “no significant variation in benthic macroinvertebrate communities from hydropower plant activity.” A second study looking specifically at the functional traits of macroinvertebrates before and after plant establishment—that is, their interaction with their environment and with other species—also found no significant differences. .
“A really important point is that there are no fish in this particular part of the river”, explains Roberta Bottarin, limnologist and vice-director of the Institute for the Alpine Environment of Eurac, co-author of the study. “If there had been fish, we probably would have had very different results.” In his view, other factors, including the relatively large amount of water left in the original stream, may also have helped to cushion the impact of the plant.
Still, she cautions against interpreting the results as a green light for high mountain small hydropower, pointing out that the team only measured the impact on macroinvertebrates, not the wider ecosystem. “From an ecological point of view, these high mountain streams are very sensitive. And if you build a factory there, you risk disturbing this ecological continuity and disturbing the natural balance. must be weighed very carefully.”
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