This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Summer is called dam removal season by those who cherish the notion of dams being demolished. The hotter, dryer weather limits a river's flow and seasonal fish migrations pause, providing the necessary conditions for demolishing the commonly aging infrastructure once erected to provide irrigation, water storage, hydropower and/or flood control.
The summer of 2013 is no different. According to American Rivers, a non-profit group that works on river preservation, approximately 30 dams have been removed so far, adding to the over 1,100 taken down since the early 1900s. About 100,000 dams still stand today.
The dismantling of dams picked up speed almost two decades ago when the Federal Energy Regulatory Commission (in the first decision of its type) decided that the Edwards Dam, a hydroelectric dam on the Kennebec River in Maine, should come down. It was 1999, and the Commission deemed the dams' negative environmental impacts - the near annihilation of its river herring, Atlantic salmon, sturgeon and striped bass populations – outweighed its minimal electricity production. So out came the dynamite.
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Since then, both the health of a river's ecosystem and safety concerns due to aging infrastructure have topped the list for common reasons for dam removal. The average age of dams in the US is now around 40 years. The plan for these reincarnated rivers is the return of its natural cycle. This means seasonal flow variations, reinvigorated fish populations, lower water temperatures, and higher river tables. High hopes, yes, but possible.
Again, look at the Kennebec River and the Edwards Dam. Its diminishing herring population of the 90s is now one of the countries healthiest today. The river has also seen a resurgence of people and businesses returning to its recovering shores.
Still, not all stakeholders embrace dam removal as a river's remedy. From the aesthetics of the dam (some look like beautiful waterfalls) to the fears of turning the river to a pit of mud, to the yearning to preserve industrial history, change doesn't always come easy. There's also the issue of recreation and property values. While removing a dam may improve recreation for some, such as returning the froth and current to a flat water area, not all will rejoice in this choice, particularly some who live along a river. Finally there's the hydropower element. Though only about 3% of all dams produce hydropower and most of these are not dams aren't considered for removal, utility providers must still seek alternatives should generating capacity decrease.
These are some of the ongoing pros and cons affecting a number possible projects on the horizon:
On the West Coast, these dam removal projects include (listed in the order of likely to extremely likely to be removed): lower four dams on the Klamath River, which flows across the Oregon/California boundary; the Matilija Dam on the Ventura River in California; and the Bloede Dam on the Patapsco River, MD.
On the East Coast, there are two dams that are extremely likely to be removed: Off Billington and Plymco Dams on Town Brook in Maine; and the West Britannia Dam on the Mill River in Maine. Both of these involve efforts to restore free-flowing habitat on some of the most productive herring rivers on the East Coast.
Much of the information in this post was provided by Serena McClain, American Rivers. Photo courtesy of NOAA.