Dams, especially those with large reservoirs, create artificial fluctuations in river flow that can affect aquatic life.
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Flow alteration can result from both natural and man-made causes. To understand its effects, you need to consider the entire equation, beginning with its cause. From there, you can determine whether the impact is negative and if water quality has consequently suffered. Flow alteration can occur from something as simple as a tree blocking water to the installation of a dam. Pollution is defined as the introduction of harmful substances into the ecosystem; in some cases, flow alteration fits this definition.
Purpose
Water flow serves several purposes. It brings a fresh supply of dissolved oxygen that benefits both plants and wildlife, and it circulates nutrients through the resource to benefit all aquatic life. Some aquatic organisms like clams are filter feeders, depending upon the flow of water for food sources. With some ecosystems like wetlands, water flow may vary seasonally. Plants and wildlife of these habitats can adapt to these changes. However, abrupt changes can negatively affect aquatic life. Flow alteration can affect both the water chemistry and its temperature; the effects depend upon the cause. (See Reference 1)
Causes
You must first determine the reason behind the flow alteration. One cause may be an obstruction in the flow of water that leads to flooding as the water moves around whatever is blocking its path. This can lead to a build-up of sediment on one side and a reduction in flow on the other. The change in flow can cause the water to become stagnant; vegetation may die from the lack of fresh water and oxygen, leading to a contamination of the resource. Other causes may be soil erosion that leads to cloudiness or turbidity in the water; plants and wildlife may both suffer from the suspension of particles in the water. (See Reference 2)
Man-made Forces
A common cause of flow alteration in urban areas comes from impervious surfaces like roads; water can flow freely and run faster in creeks and culverts. Flow alternation can worsen soil erosion on stream banks and negatively affect water quality because of sedimentation. The accelerated flow may also bring other toxins into the waterways such as oil, salt and other contaminants from roads, an effect known as nonpoint source pollution. This can come from a myriad of sources, explains the U.S. Environmental Protection Agency. (See Reference 3)
Consequences
The consequences of flow alteration depend upon the resource. For example, increased water flow in urban areas can leave an area more vulnerable to flooding. Water pollution may increase from contaminants entering the waterway. A disruption of water flow can lead to stagnant water, which can become a breeding ground for mosquitoes and increase the risk for vector-borne illnesses such as West Nile virus. In these cases, flow alteration brings about negative effects that compromise the water quality, such as an increase in water temperature. This represents a more subtle form of pollution. (See Reference 4)
Chris Dinesen Rogers has been online marketing for more than eight years. She has grown her own art business through SEO and social media and is a consultant specializing in SEO and website development. Her past work experience includes teaching pre-nursing students beginning biology, human anatomy and physiology. Rogers's more than 10 years in conservation makes her equally at home in the outdoors.
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