If you were to guess how many dams there are in America, what would you say? Maybe a couple hundred? A couple thousand? The answer is that there are over 85,000 dams in the United States, the equivalent of building a dam on an American waterway every day since we declared our independence in 1776.
Over 2,200 of those 85,000 dams can generate hydroelectric power, an excellent source of renewable energy. But, while people reap the benefits of dams every day from the power they generate, irrigating crops or recreational purposes, dams can also have a detrimental impact on the environment.
Dams are designed to interrupt a river or stream’s natural flow which can cause numerous ecological side effects. They can increase water temperature by slowing water, and causing harm to native fish species. When water is released from a dam, it’s usually from the bottom of the reservoir, which contains less dissolved oxygen, potentially harming or killing aquatic life.
Sediment also builds up behind dams, which can cover up vital fish spawning areas. In addition, dams can create barriers that inhibit fish returning from the ocean swimming upriver to spawn, and they block freshwater fish from their prime spawning, rearing and foraging habitat.
Currently, there is a growing awareness in the U.S. to remove dams no longer serving their intended purpose. Removing a dam from a waterway restores the natural flow and brings back the aquatic ecosystem. An organization called American Rivers, which has worked to remove dams for almost 40 years, has an abundance of valuable information, including videos about the benefits of dam removal for restoring rivers.
In 2006 a dam was removed in Manatawny Creek, in eastern Pennsylvania as a result of a conservation plan developed by the Berks County Conservancy. Numerous partners and stakeholders, including EPA, contributed to removing this “orphaned” dam, which was no longer in use and becoming dilapidated. Removing orphaned dams is usually much easier than removing dams which are still in use because they are structures that do not have a modern day purpose.
Do you know of any dams in your area? Has a dam been removed nearby and you have seen the benefits? Share your thoughts on our comment page!
Editor's Note: The opinions expressed in Greenversations are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.