When you look at the ranking of the world’s largest countries, China is virtually tied with the United States in total area (6.5%) as the third largest behind Canada (6.7%) and Russia, the world’s largest (11.5%) in total area. By coincidence, China’s Yangtze River (longest river in Asia) is also the third longest river in the world (behind the Nile in Africa and the Amazon in South America).
And, while there are three scenic gorges along the Yangtze River’s 6,300 kilometer length after which the Three Gorges Dam is named (Qutang Gorge, Wuxia Gorge and Xiling Gorge), that is where the similarity ends.
Three Gorges Dam is the World’s Largest Hydroelectric Power Station by generating capacity (22,500 MW) followed by the Itaipu Dam in Brazil/Paraguay (14,000 MW). However, the Itaipu power plant currently produces the most hydroelectricity power in the world in a single dam because the Parana River that feeds the Itaipu Dam has a much lower seasonal variance in flow than the Yangtze River. The result of this variance is that the Three Gorges Dam experiences six months per year when there is very little water available to generate power.
To put those dams in perspective:
- Churchill Falls Dam (Canada) generates 5,429 MW (#9);
- Tarbela Dam (Pakistan), 3,478 MW (#17);
- Aswan Dam (Egypt), 2,100 MW (#41);
- Hoover Dam (United States), 2,080 MW (#44);
- Bureya Dam (Russia), 2,010 MW (#48).
In spite of these impressive numbers and the environmental benefits of hydroelectricity versus fossil fuel energy generation, there remains a lot of controversy around dams.
A Heinz Center Report: Removing Dams provides an introduction to the problem.
“Dams are the most common and widespread form of direct human control on river and stream processes. Until recently, the installation of dams has been a widely supported method of river management in the United States. American rivers are collectively the most closely controlled hydrological system of its size in the world. The nation now has the capability to store almost a full year’s runoff in reservoirs behind more than 76,000 dams (counting those 6 feet high or more). Many of these structures have contributed to the economic development of the nation and the social welfare of its citizens. Irrigation water diverted from streams and temporarily stored by dams has supported agriculture in western states, and lock and dam structures sustain an inland water transportation system for bulk commodities worth billions of dollars throughout the nation.“
That is good stuff. Rivers have been and remain vital to the prosperity and health of nations around the globe. But not all of the changes from dams have been good.
“The environmental changes brought about by dams include drowning of channels and valued floodplains. Dams have changed downstream conditions, altering the physical bases of ecosystems in every region of the country. In concert with other human-imposed changes, especially those realized through river engineering and land use alterations, dams have contributed to the loss or change of riparian and aquatic habitat, including ecological systems that support endangered or threatened species of plants, animals, birds, and fishes.”
To understand the importance of riparian rights, I refer back to two earlier posts: Everyone Has a Right to Water – UNTIL…..; and The Middle East: Looking Through its Many Cracks and Fissures.
- Small: reservoir storage of 1–100 acre-feet
- Medium: reservoir storage of 100–10,000 acre-feet
- Large: reservoir storage of 10,000–1,000,000 acre-feet
- Very Large: reservoir storage of greater than 1,000,000 acre-feet
There should be little doubt that Three Gorges Dam is considered Very Large. Its impact on the environment is even “very larger”.
On first glance, the evidence in support of dam construction is significant.
“Among other things, dams have reduced flood hazard and allowed humans to settle and farm productive alluvial soils on river floodplains; they have harnessed the power of moving water for commerce and industry; and they have created reservoirs to augment the supply of water during periods of drought.”
So where is the controversy?
To better understand the controversy, it is important to understand the scrutiny being given to their removal. Perhaps highlights from the following reports: How Dams Vary and Why It Matters for the Emerging Science of Dam Removal; and International Rivers: Dam Decommissioning will outline the threat that dams pose to our environment.
One criterion might be a “society’s changing needs for, and concerns about, dams, including the emerging recognition that dams can impair river ecosystems.” A second could be their “scientific limitations”. Although dams date far back into history, dams do not live forever. From the Report: Dammed to be Divide:
“Although there is some controversy over which dam is the oldest, there are two main theories. The first theory holds that the earliest recorded dam was constructed on the Nile River at Kosheish around 2900 BC. The second theory asserts that the earliest recorded dams, for which there is sufficient evidence, were located about 100 kilometers northeast of Amman, the present capital of Jordan. Regardless of whether the earliest dams existed on the Nile or in Jordan, experts acknowledge, and to some extent agree, that dams have been in existence since roughly 2900 BC.”
Very large, modern dam building got serious in the 20th Century.
A dead or dying dam may have silted up, stopped producing electricity, or become increasingly unsafe, at which point it may be a candidate for removal. Not all dams slated for removal are targeted for safety reasons, however: another major reason prompting activists to call for the removal of dams is the decimation of fisheries.
Obviously, there is a lot of variance in benefit to things related to dams. Important detail to the impact of Three Gorges Dam is contained in the following excerpt from the Heinz Center report. The panel defined the following:
“dam size categories based on reservoir storage rather than height or other measures because the size of the reservoir is related most directly to the magnitude of potential effects on river hydrology.”
As the world’s most populous country, China is undergoing rapid change. It’s need for energy to support its rapid growth in manufacturing and urban modernization. With the global concern for unsustainable carbon emissions affecting air quality and climate, all countries are being forced to reevaluate strategies for sustainability. Hydroelectricity is an obvious choice to displace the proliferation of coal-burning power generators.
The Yangtze River is an obvious target for such a massive scale program because of its size and volume of water. The thought of a dam across the river dates back to Mao Zedong in the early 1950s. How significant is the potential environmental benefit of the Dam? From Wikipedia:
“At full power, Three Gorges reduces coal consumption by 31 million tonnes per year, avoiding 100 million tonnes of greenhouse gas emissions, millions of tonnes of dust, one million tonnes of sulfur dioxide, 370,000 tonnes of nitric oxide, 10,000 tonnes of carbon monoxide, and a significant amount of mercury. Hydro power saves the energy needed to mine, wash, and transport the coal from northern China.”
While these numbers are impressive, as well as the quantity of electricity produced, as well as the beneficial impact to shipping on the river, the environmental consequences are and will be larger than the river itself.
The following articles from The Guardian and the WashingtonPost tell the story. This YouTube video: Un-gorgeous 3 Gorges provides the visuals to this growing challenge. Before China begins to export their engineering prowess to countries with rivers waiting to be tamed, sufficient time should elapse to better understand whether the Three Gorges Dam is An Enormous Mistake or Engineering Marvel.