It is estimated that there are approx. 75,000 dams in the United States.
This is based on data provided by the US Army Corps of Engineers’ (Corps) National Inventory of Dams (NID). To be counted a dam must meet minimum height and impoundment requirements. There were approx. 82,642 entries in the NID as of June 2009.
The NID consists of dams meeting at least one of the following criteria;
2) Significant hazard classification – possible loss of human life and likely significant property or environmental destruction,
3) Equal or exceed 25 feet in height and exceed 15 acre-feet in storage,
4) Equal or exceed 50 acre-feet storage and exceed 6 feet in height.
In other words, there are a lot of dams that the NID doesn’t track. No one knows the exact number of dams that exist in the United States.
To put things in perspective, an estimated 75,000 dams in the United States works out to be about .92 dams built per day since the adoption of the Constitution of the United States. (The Constitution was adopted on September 17, 1787.)
That’s a lot of dams. We really loves us some dams.
You might be thinking that a lot of power gets generated by those dams. However, an organization known as American Rivers estimates that only 2,500 of those 75,000 generate hydroelectric power.
An organization known as Pacific Coast Federation of Fishermen’s Associations says that more than 106 major salmon runs in northern California and the Pacific Northwest are already extinct and another 214 are at risk of extinction in the near future.
Dams do offer benefits to humans like hydropower, flood control, irrigation, and recreation. But do those benefits outweigh the costs?
When the mighty Colorado River was untamed it used to flow all the way from Colorado to the Gulf of California. Since Hoover Dam was built, 90% of the river is diverted for irrigation purposes and the river now slows to a trickle and evaporates in the Sonoran Desert miles before it reaches the Gulf of California. Here’s a link to a NASA Earth Observatory image showing the Colorado River Delta as it appeared in March 2001.
In my neck of the woods two nearby dams were removed recently. This caused a lot of outcry and anger from many local residents. These days it seems that many dams are being considered for removal and many have already been removed, like the Sandy River Dam shown in the picture above. To learn more about dam removal you can visit the American Rivers web site.
I’ve heard of “dam busters” who go around and demolish unnecessary dams to help return the area to its natural state. As long as no one’s house gets flooded, I think this is a great idea.
I’d never heard of that, but not surprising.
Even way out in the woods there’s a little creek with a swimming hole we like. Someone went to a lot of effort to stack rocks and logs to create a makeshift mini-dam to help make the hole bigger. (It’s about exactly the size and shape of a backyard swimming pool.) I always wondered about that. I’ll bet there are tens of thousands of homemade dams like this.
wow, this is something I don’t think I’ve ever heard about!
Locally, we have Bagnel Dam, which at least used to be used for energy…it certainly was used to create Lake of the Ozarks, which is quite a Thing (wiki, if interested; wouldn’t think anybody is). The only outcry I’ve heard lately was about local levees to “protect” Fenton and another small town downstream–the deal with that was the small towns FARTHER downstream complained (rightly so) that they were flooded in areas that virtually never did before because the levees basically bottle-necked flood waters and debris that came down to them with greater force (or something…I *so* do not know what I’m talking about but it’s the only river-themed thoughts I own).
Insomuch as they are!
Can you even imagine how staggering that simple statistic is? That’s almost one dam a day ever single day since the adoption of the Constitution. That really blows me away!
Some of them, no doubt, at one time or another generated hydropower. But what was the cost/benefit analysis on these? Did the amount of power generated justify the environmental impacts? Back then, did people really give much thought to such things, or was the equation a bit more simple than that? “We need power. They’re only animals.”
Perhaps some were worth the impacts, perhaps they weren’t. My gut tells me that in most cases the question of “should we build a dam?” was answered with, “We wants it. We do.”