Daily Archives: November 23rd, 2010

Dam it all to hell

Sandy River Dam

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;

1) High hazard classification – loss of one human life is likely if the dam fails,
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.