Some countries are already exploiting this potential. Since 2000, they have refurbished 36 dam turbines in the U.S., adding more than 500 megawatts of renewable generation capacity. There is even greater potential there: a 2016 U.S. Department of Energy report found that 4.8 gigawatts of more electricity could be generated. renewal of food-free dams over the next three decades. In the U.S. and Western Europe, where the mid-century dam boom has long since faded, upgrading may be the only option left for governments looking to extract a little more hydropower. “If there are dams that will stay in place, let’s try to find solutions and work together to find the best solution,” McManamay says.
But before anyone can start renovating all of these dams, they might want to take another look at the numbers. It is not easy to predict exactly how much electricity a renovated installation will produce, because it turns out that not all dams are suitable for conversion. Say someone wants to put turbines in a dam built to hold water so they can be used to irrigate farmers ’fields. During the growing season, much of this water would normally be diverted to agriculture, rather than passing over the dam to generate electricity. Or maybe for part of the year the water is in an area that is sufficient to generate electricity. Suddenly, those restored dams might not seem so smart an idea.
A new study Renovated dams in the USAlso ordered by the Department of Energy, he saw that their power output forecasts were turning in a positive direction: on average, these projections were 3.6 times higher than the actual output. The study found that the most successful were the early-built concrete dams to support navigation. (Dams are often used to widen or deepen waterways to make boats easier.) “This is a complex issue. It’s not an easy fix, ”says McManamay.
But in countries like Brazil, big dams are still on the agenda. “If they are to develop and really raise their standard of living across the country, they need energy. That’s long and short, ”says Michael Goulding, a senior aquatic scientist at the Wildlife Conservation Society. The country’s last 10-year energy plan identifies nine major new dams completion is planned Before 2029. Rather than the expectation that these dams will not be built, it is important to ensure that appropriate studies are conducted to minimize environmental destruction, Goulding says, “Often the environmental impact areas are not very good. takes into account all the impacts downstream and the upward impacts as well ”.
The Belo Monte Dam is a demonstration of the extent to which large dams have an impact on the environment. The dam complex redirected 80 percent of Xingu’s flow away from a 62-mile stretch of the river known as the Big Bend. This part of Xingu is also the only known wild habitat of the Zebra Pleco, a striking striped fish that is loved by aquarists. “This species is at high risk of extinction,” says Thiago BA Couto, a postdoctoral researcher at Tropical Rivers Lab at Florida International University. The impact of dams on fish species is well documented in other parts of the world. In Washington state, the Elwha Dam disconnected the upper and lower slopes of the Elwha, and 90 percent of the available habitat for salmon. Some local species in the river became completely extinct, and the populations of others — Chinook, for example — fell to part of previous levels.
In the end, however, even large dams can exceed their usefulness. In 2014, the last remnants of the Elwha Dam were removed permanently. Chinook salmon, which has been locked up behind two dams for decades, is now slowly making his way back up the river. A full recovery is expected to take a few decades. “Dams don’t last forever,” Couto says. “Many are plentiful, but they don’t provide the minimum benefits.”
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