Mostly generated via dams, hydroelectricity provides 16 percent of global power and is the world’s most widely used form of renewable energy. Hydroelectric dams have an advantage over other types of generators as they respond quickly to changing energy demands, do not depend on other resources or imports in order to be run, and produce almost no greenhouse gas emissions during operation.
In terms of environmental impact, when compared to fossil fuels and nuclear power, hydropower looks like a great deal: it simply utilizes the natural course of running waterways, generating “free” electricity in the process.
Yet the creation of large reservoirs and dams is not as green as it may seem. These projects often transform the natural geography of an area, destroying or altering a region’s biodiversity through permanent flooding, deforestation and habitat fragmentation.
In Asia, many believe that the Three Gorges Dam and dams along the Mekong River disrupt fish migration, as well as compound the effects of climate change, such as increased droughts and flooding, threatening the livelihood of millions. Controversies over the construction of Brazil’s Belo Monte Dam, located on the Xingu River in Pará State, include expectations that the project will displace some 20,000 people and submerge 4,000 square km of rainforest, not to mention opening up the Amazon to more pollution from mining projects and aluminum plants.
In Brazil, hydropower is being pursued aggressively, with a goal of supplying as much as 85 percent of the country’s energy through hydroelectric plants. Some sources state that Brazil is already meeting 80 percent of its energy needs through hydro. Yet rising temperatures and increased drought could drastically complicate a future hydro-dependent power supply, leaving the grid particularly vulnerable.
This vulnerability has been highlighted by droughts in the country during August, leaving major cities like São Paulo and Rio de Janeiro dangerously low on water. Naturally, when water is in short supply it must be prioritized over energy needs, but in hydroelectricity-dependent areas, this can leave many without power and agricultural industries “high and dry.”
Brazil is having its worst drought in decades, reservoirs in the southeast and central-west regions, home to most of the nation’s coffee plantations, are at less than 32 percent of capacity as of 24 August, compared with an August average over the previous 13 years of 59.3 percent, according to ONS, the grid operator for Brazil, which gets about 70 percent of its power from hydroelectric dams.
A recent report by International Rivers criticized the use of dams, examining their impact on the Earth’s waterways:
River basins fragmented by dams and polluted by mercury accumulation are public health emergencies that impoverish people’s quality of life and livelihoods. Yet, institutions such as the World Bank are investing with a renewed vigor in damming the world’s rivers. International Rivers questions these investments when the data show the negative effects on river basin health that dams have created.
Despite economic vulnerability as well as human and ecological concerns, Brazil plans to build a whopping 412 more hydroelectric dams in Paraná State and 254 in the Amazon River basin. According to global reinsurance broker Aon Benfield, during the first half of 2014, drought in the Brazilian states of Minas Gerais, São Paulo and Rio de Janeiro has cost the country US$4.3 billion in economic losses. Perhaps the rush to dam the country’s rivers in search of renewable energy should be re-evaluated.