For thousands of years, dams (also referred to as reservoirs) have been utilized as water storage method with a variety of uses, including agricultural and industrial purposes. Most people probably don’t think about dams until a major failure happens, but dams are more prevalent than one might think.
In fact, just during the 20th century, about $2 trillion was spent building dams worldwide. Previously, dams were mainly powered by non-renewable energy sources. However, newly-constructed dams are powered by hydroelectricity, which is somewhat better for the environment.
Despite their widespread use, dams can be detrimental to ecosystems in a variety of ways. Additionally, they can pose major threats to people in the event of failure. Here, we look at how dams pose a threat and what can be done to manage risk.
The Oroville, California Disaster
The catastrophic dam failure that occurred in California during February 2017 is a reminder that man-made reservoirs can be quite dangerous. After heavy rains, the dam gave way and created a huge mess causing large-scale evacuations.
Aerial images showed how devastating the resulting damage was after California’s Department of Water Resources resorted to using the spillway after weeks of heavy precipitation. Once the rain subsided, ecologists and other officials were able to fully view the damage to the spillway, which was designed to withstand about 250,000 cubic feet of water per second.
Despite its large capacity, the Oroville dam had a significant amount of erosion. This is a common problem with man-made dams. As it stands now, the Oroville reservoir levels have gotten low enough that the spillway will not need to be utilized again this season. The spillway will need to undergo extensive repairs before next year. However, in addition to dam failures, there are variety of other negative environmental impacts that these structures have on the environment.
Danger to Natural Habitats
One of the main causes of extinction is habitat loss, and freshwater habitats are among the most at-risk. Dams can damage natural habitats, since building them in a river or near a river changes the entire ecosystem in the area.
First, dams serve as barriers, which can prevent fish from following their normal migratory patterns. In addition, dams confine fish, causing their lifespans to decrease. When combined with a decline in water quality, both of these factors can contribute to extinction.
Dams also cause changes in water temperature and chemical composition, especially salinity. Changes in salinity occur because water flow is diminished downstream. This can make the water hazardous to aquatic species as well as make them more susceptible to being attacked by predators.
One real-world example of this involves the extinction of freshwater dolphins in China after the construction of the Three Gorges Dam on the Yangtze River. In other waterways, fish are at risk of extinction as a result of the presence of dams. A similar outcome occurred at The Glines Canyon Dams in the Elwha River in Washington, where salmon and steelhead trout populations were completely decimated.
Dams Are Prone to Sedimentation
Another major problem directly related to man-made dams is sedimentation. This occurs when water flow is decreased, subsequently sending sediments to the bottom of the reservoir. As sediment builds up at the bottom, the storage capacity of the dam is diminished.
Not only that, but sediment is prevented from being carried downstream, leading to less nutrient-dense soil vital for animals and foliage. Depleted soil also inhibits proper tree growth, thus making the soil erode faster. Fewer trees can also make removing greenhouse gases from the air more difficult.
Dams Contribute to Greenhouse Gas Emissions
As reported by Brazil’s National Institute for Space Research, dams emit methane in amounts that account for approximately 4 percent of the global warming attributable to human activity. Methane gas produced at the reservoir bottom is responsible for much of this pollution. However, scientists estimate that 95 percent of dam-related greenhouse gases are emitted by turbines, spillways, and downstream areas.
Plant matter located beneath reservoirs gives off greenhouse gases as it is broken down by anaerobic bacteria. The anaerobic bacteria then emit carbon dioxide and methane gasses, negatively affecting air quality and contributing to climate change. On top of that, if the reservoir isn’t properly filled, greenhouse gas emissions could equal those of coal-powered stations according to the Whale and Dolphin Conservation.
Dams pose a considerable threat to wildlife and natural habitats. Concerned citizens and environmental activists have concentrated on removing existing dams and replacing them with more efficient and eco-friendly alternatives.
Due to environmental concerns, environmental groups are looking forward to finding sustainable solutions for fixing problems that lead to dam failures. That way, a situation like the one in California can be avoided in the future.