Dam it all to hell
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.
Lake Mead, the largest reservoir in the United States, is located about 30 miles southeast of Las Vegas, Nevada. It was created in the late 1930’s after the construction of Hoover Dam on the Colorado River. After the opening of Hoover Dam it took approximately six years for Lake Mead to fill, during which time the flow of the Colorado River was virtually non-existent resulting in environmental impacts all the way to the Colorado River Delta (where the Colorado River flows into the Gulf of California (the Sea of Cortzez).
Lake Mead is named for Elwood Mead who headed the Bureau of Reclamation from 1924 until his death in 1936 (the same year that Hoover Dam was completed).
Lake Mead serves as the main source of raw water to Las Vegas, which has been the fastest growing metropolitan area for more than a decade. The Las Vegas Valley has grown by approx. 500,000 residents since 2000.
As of May 2009 the reservoir was at 43 percent of capacity and the word “crisis” is used to describe the situation. Even though above-average rainfall in early 2010 raised the level of Lake Mead more than a foot at Hoover Dam, as of April 2010 the water level was reported at 1,100 feet. At 1,025 feet Hoover Dam loses the capacity to produce electricity.
The Southern Nevada Water Authority (SNWA) is pressing ahead with a rural groundwater pipeline project that will bring 150 million gallons of water a day from counties located in northeastern Nevada up to 300 miles away. An initial 75-mile segment of the project could be operational by 2012.
The SNWA web site says, “The Colorado River system is facing the worst drought on record. Lake Mead’s water level has dropped approximately 100 feet since January 2000.” (Source.)
“But that’s not soon enough. The primary raw water intake at Lake Mead could become inoperable as soon as 2010 based on current drought and user projections, spelling potential disaster for Las Vegas.” (Source.)
Graph of Lake Mead water level.