Hydro-electric energy accounts for the largest percentage of renewable energy generating capacity around the world by a considerable margin. More than 90% of all non-nuclear, non-fossil fuel global electricity generation is hydro-electric.
Hydro has long reigned as the absolute king among renewables. Starting in the early 20th century, engineers started damming entire rivers to provide the stable water pressure required to turn massive turbines which would in turn produce the electricity that was rapidly lighting up the globe. These great feats of engineering symbolized technological progress and man’s mastery over the forces of nature, while simultaneously providing the fuel for economic expansion in industrialized countries.
The sheer energy output of one large dam was enough to power a whole city and all its factories. Las Vegas as we know it wouldn’t exist without the nearby Hoover Dam’s turbines lighting up the strip starting in the 1930s. Even today, the installed capacity of the world’s largest single hydro-electric facility, the Three Gorges Dam in China, dwarfs all other power plants. With almost 23 GW of generating capacity, the dam’s 32 turbines would be enough to power all of New York City.
Hydro energy is clean, produces no air pollution or CO2 emissions, and provides reliable base-load electricity. It requires no externally imported fuel and produces no waste products. Yet despite these numerous advantages, the past few decades have seen most developed countries shy away from building big hydro projects because of the many unforeseen negative side effects of these disruptive projects.
First, large hydro requires the flooding of land to form the reservoir that sits behind the dam. This involves submerging vegetation, valuable agricultural land and even human settlements and ancient archeological sites depending on the location of the reservoir. Particularly in tropical areas, the natural decay of flooded vegetation produces large amounts of climate-changing methane, making those hydro-electric projects no longer carbon neutral. The massive lakes that make up the reservoirs behind large dams have a considerable impact on local ecosystems and can irreversibly alter traditional ways of life for people living around the reservoir.
Second, massive dams disrupt the river’s natural flow thereby preventing the migration of fish and altering the normal deposition of sediments downstream. For example, the Nile Delta in Egypt, home to millions of people, is actually shrinking as a result of the Aswan Dam constructed in 1970. A significant portion of the Nile’s fertile sediments, which were so essential to nourishing Egyptian civilization for thousands of years, are now being stopped by the concrete wall spanning the Nile hundreds of kilometers upstream.
In the United States, the many dams on the Colorado River have reduced its flow so drastically that by the time it reaches the Pacific Ocean the river is reduced to the size of small stream. The Columbia River in Washington State retains only a fraction of its once thriving salmon fishery because of the numerous dams spanning the river in both the US and Canada. A large dam can negatively affect the whole watershed of the river it is built on.
Third, the investment required for large dams is astronomical, ranking large hydro among the most expensive forms of electrical generation. The Three Gorges Dam cost upwards of $30 billion and its environmental costs have yet to be determined accurately. Many African countries became severely indebted to finance large hydro schemes that ended up providing little economic benefit to the millions of poor.
The 21st century, however, is seeing a renaissance of hydro mega-projects as developing countries hungry for energy are exploiting all available options to provide for their rapidly expanding economies. With environmental and social concerns brushed aside in favor of big engineering dreams, this new round of giant dams is set to break many records. Here is a list of the five biggest hydroelectric projects currently under construction.
5 #5. Grand Ethiopian Renaissance Dam, Ethiopia
Cost: $5 Billion
This 170m dam on the upper reaches of the famous Nile river will be Africa’s largest hydro-electric facility by the time the reservoir floods in 2017. It will provide 6 GW of electricity to the Ethiopian grid, with plans to sell energy to neighbouring Sudan and Egypt.
Unfortunately, critics say the dam poses an unacceptable risk to lowering the downstream water levels of the life-giving Nile and impeding sediment flow essential to the productive agricultural region of Egypt’s Nile Delta Region. Egypt has repeatedly tried to prevent the construction of this project, not least because of the negative side-effects of the infamous Aswan Dam, built in 1970.
4 #4. Xiluodo Dam, Yunnan Province, China
Cost: $12 billion
This 285m (935’) tall behemoth straddling the Jinsha river is nearing full completion in 2015 and will add almost 14 GW to China’s national grid. Including the cost of resettling more than 40,000 people, the dam’s construction will cost more than $12 billion and flood many valuable archeological sites.
3 #3. Baihetan Dam, China
Cost: $13 billion
Requiring the resettlement of more than 70,000 people, this mega-project will provide 13 GW of energy to China’s grid, enough to power a whole metropolis.
Though not as large nor as expensive as the famous Three Gorges Dam, this dam will similarly flood a huge area and no doubt negatively affect water levels downstream. It has been under construction since 2008 but will not deliver power until 2019.
2 #2. Belo Monte Dam, Brazil
Cost: $18.5 billion
This controversial project will flood thousands of square kilometers of Brazilian rainforest, an area filled with endangered species, and will also displace local tribes. First proposed in the 1970s, this project was shelved because of intense environmental and indigenous opposition. The revised plan includes a slightly different design that creates a smaller reservoir and diverts part of the river to avoid the most ecologically sensitive regions. Despite these changes, however, the dam’s construction still inspires extreme reactions.
In 2010 famous Hollywood director James Cameron produced a short documentary comparing the destruction the dam would cause to the plot of his blockbuster film “Avatar.” Unfazed, the Brazilian government is pushing ahead with the mega-project to provide 11 GW of power for its booming economy.
1 #1. Grand Inga Dam, Democratic Republic of the Congo
Cost: $80 billion
By far the most expensive proposal on our list, if completed this ultra-high cost investment will be THE African infrastructure project of the century. Already given the go-ahead by the World Bank and other funding partners, the plan involves damming the lower reaches of the mighty Congo River. The project will take place in a politically unstable region with very poor infrastructure.
The plan involves flooding thousands of square kilometers of rainforest and submerging the Congo Rapids, considered the world’s biggest waterfall by volume. The potential energy generation would reach 40 GW, almost twice that of China’s Three Gorges Dam, currently holding the title of the world’s largest hydro facility.
Critics say that the insanely expensive project would do little to help Africa escape poverty and only serve to intensify resource exploitation by multinational companies. Although construction has yet to begin, the planning is already finished.