Climate change puts dams in check

Climate change puts dams in check. Once considered particularly reliable among renewable energies, hydraulic energy is threatened by long periods of drought and heavy rains. Climate change would be the end of hydroelectricity.

Once built, a hydroelectric plant can reliably produce electricity at any time: for many years this has been the main argument for generating electricity from water energy. According to Paris-based think tank Ren21, more than half of the world’s renewable electricity in 2019 was generated by hydropower.

But that advantage appears to be being lost as climate change advances. In 2021, climate-related droughts were responsible for the biggest drop in hydropower generation in decades.

Global losses in power generation

On Lake Mead, not far from the American metropolis Las Vegas, the Hoover Dam holds the Colorado River and supplies more than 140 million citizens with water. Currently, however, the large reservoir contains only a third of its potential. In July 2021, due to low water levels, his plant generated 25% less electricity than normal. Recently, the Federal Water Resources Agency decreed that the locations downstream of the dam should receive less water as of January 2022.

In the south of the American continent, the situation is similar in many places. The Paraná River, which crosses Brazil, Paraguay and Argentina, is experiencing a historic low, as the south of Brazil, where Paraná is born, has been suffering a severe drought for three years.

Compared to the average of the last two decades, water levels in reservoirs in Central and Southern Brazil have fallen by more than half, currently retaining just under a third of their capacity. As Brazil obtains 60% of its electricity from hydroelectric dams, the country is at risk of blackouts.

This Thursday (26/08), President Jair Bolsonaro even asked the population to turn off a light point at home to save energy: “It helps, thus, to save energy and water from hydroelectric plants. And in large part of these dams we are already around 10%, 15% of storage. We are at the limit of the limit. Some will stop working if this hydrological crisis continues to exist,” Bolsonaro appealed on social networks.

Back to fossil fuels

To prevent this from happening, the Brazilian authorities decided to reactivate the thermoelectric plants, powered by natural gas. This leads to a further increase in greenhouse gas emissions as well as the costs of light.

Something similar is happening in the US: The California state government has allowed industrial consumers and ships to meet their electricity demands with diesel generators. Natural gas plants must also be allowed to burn more gas in order to generate electricity.

Not only dry spells threaten to paralyze electricity generation by hydroelectric dams, but also heavy rains and floods. In Malawi, for example, two large hydroelectric plants were damaged by flooding after Cyclone Idai in March 2019, causing power supplies to collapse in parts of the country for several days.

Africa still bets on hydroelectricity

In countries such as Malawi, the Democratic Republic of Congo, Ethiopia, Mozambique, Uganda and Zambia, the share of hydroelectric power plants in electricity generation is over 80%, according to the International Energy Agency (IEA). In total, around 17% of electricity in Africa was generated from hydropower at the end of 2019. According to forecasts, the proportion is expected to increase to over 23% by 2040.

Another problem, according to the IEA, is that in most plans for new hydropower projects in Africa the possible effects of climate change are not taken into account or only insufficiently.

Many of the hydroelectric plants in operation also face another problem: age. According to a study by the United Nations University, dams reach the end of their useful life 50 to 100 years after construction. due to the wear of the construction material, which increases the risk of dam failure.

Warnings against hydroelectric expansion

According to the authors of the study, constructions of 25 to 35 years may already require dam maintenance measures that can considerably increase the operating costs of hydroelectric plants.

In this context, it would be disastrous if, by eliminating fossil fuels, investments were made precisely in the expansion of hydroelectric energy in poorer countries, says Thilo Papacek, from the German non-governmental organization Gegenstrom, which defends socially and environmentally compatible actions by German entrepreneurs abroad .

Generally speaking, hydroelectric plants not only have a major impact on the ecosystem, but can also pose a threat to humans, warns Papacek. This is because dams and dams not only prevent fish migration, but also the transport of sediments, that is, solid matter, further downstream.

“Without the accumulation of sediment on the banks of the river, the river sinks more and more closely into the landscape behind the dam. In heavy rains, it can develop enormous strength, especially if the water also has to be drained from the reservoir.” This would therefore increase the risk of flooding in neighboring settlements.

“In fact, we cannot give up hydropower in the future,” admits Klement Tockner, director general of the Senckenberg Society for Natural Research and professor of Ecosystem Science at Frankfurt’s Goethe University. “But the question is: where do we build, how do we build and how are we going to operate hydroelectric plants in the future?”

More “natural” energy instead of mega dams

According to Tockner, power plants should not be built in protected areas. where there are still plenty of free-flowing rivers. If necessary, there must be compensatory measures for the negative effects of the plants on the ecosystem, such as the restoration of damaged waters or the dismantling of dams.

New systems would have to be built so that rivers remain as permeable as possible – both to water currents during floods and to fish and sediment. And the systems management must also mimic the natural dynamics of the waters.

“This means that the flow velocity must not be changed too much, and the river must hold enough residual water, as well as cover flood areas,” explains Stefan Uhlenbrook, hydrologist at the International Institute for Water Management (IWMI, for its acronym in English). “If necessary, the sediment must be mechanically brought back to the river.”

According to Uhlenbrook, large systems tend to become increasingly ineffective as a result of climate change. In principle, he points out, hydroelectric plants would have to be smaller and supply more decentralized.

Technology just isn’t enough

So-called ecological turbines, which are suspended in the middle of rivers and generate electricity from the speed of water flow, are particularly permeable. They also work when the water level is low, do not require any complex work and are suitable for remote areas. Only they cannot be used to supply metropolitan areas.

The Technical University of Munich (TUM) shaft plant, approved for nature conservation areas, also promises a high degree of permeability and safety against flooding. A pilot system in the state of Bavaria, in southern Germany, supplies around 800 families.

By itself, however, the new technology does not help against severe droughts. “We can reduce the effects of droughts through changes in land use. Better preserved forests store a lot of water, which they later release during droughts. We need to figure out how to reduce droughts and floods with sustainable measures,” says researcher Tockner. But one thing is clear: “In view of the increase in extreme weather events, hydropower will no longer be the reliable source of energy that it has been until now.”

Hydrologist Uhlenbrook also recalls an aspect, in his view that is often overlooked, when talking about the energy of the future: “We need to focus, above all, on saving as much energy as possible in the future.”