25 April 2012


From Wikipedia ~ "Dam removal is the process of removing out-dated, dangerous, or ecologically damaging dams from river systems.  There are thousands of out-dated dams in the United States that were built in the 18th and 19th centuries, as well as many more recent ones that have caused such great ecological damage that they are proposed for removal.  Catastrophic dam failures .... remind people of the dangers dams can present.

"Many of the dams in the eastern US were built for water diversion, agriculture, factory watermills, and other purposes that are no longer useful.  Because of the age of these dams, over time the risk for catastrophic failure increases.  In addition, many of these dams block anadromous fish runs, such as Atlantic salmon, and prevent important sediments from reaching estuaries.

"Many dams in the western US were built for agricultural water diversion in the arid country, with hydroelectric power generation being a significant side benefit .... Dams in the Pacific Northwest and California block passage for anadromous fish species such as Pacific Salmon and Steelhead .... In the Desert Southwest, dams can change the nature of the river ecosystem.  In the particular case of the Glen Canyon Dam, the originally warm, sediment-filled, muddy water instead turns cold and clear through the Grand Canyon, which has significant impacts on the downstream ecosystems .... So much water is taken out of the Colorado River for agriculture, urban use, and evaporation behind the dams, that the river no longer flows into the Gulf of California.

"While the need for clean, alternative energy sources is important, with so many considerations involved, sometimes it makes sense to evaluate whether the benefits of dams outweigh the costs of safety concerns, ecosystem functions, and management expenses."

In response to ecological, safety, and economic concerns, a number of dam removal projects have been completed in the United States, among them two dams on the Elwha River (see embedded video) in Washington state.  Additionally, along with many smaller dams, several large dams are under consideration for removal, including (significantly) Glen Canyon Dam.  GCD has been a touchstone in the environmental movement since it was completed in 1966.  Tracts have been written and public protests staged, urging its removal.  The Southwestern writer Edward Abbey was among the most vocal of the dam's opponents.  Over the years he made numerous suggestions, only half tongue-in-cheek, for eco-sabotaging the Dam.  Again according to Wikipedia, "The 710 ft (220 m) Glen Canyon Dam (see image above, click to enlarge) has been proposed for removal because of the negative effects it ha on the water quality and riparian habitat of the Colorado River in Grand Canyon National park.  In addition, the reservoir impounded behind it, Lake Powell, has filled all of the canyons for up to 100 miles (160 km) above the dam.  This lake, while providing recreational opportunities, has eliminated .... habitat for endangered Colorado River fish species.  If it were to be removed, it would dwarf any dam removal project in history."

There are those voices who will ask "What about all that hydroelectricity?  What about irrigation water for agriculture?"  To which I would suggest that it is precisely our assumption that we can interfere with natural conditions which has created so many disasters in the first place.  And not just disasters which impact nature.  Think about the Mississippi River levee system constructed by the US Army Corps of Engineers.  The intent was flood control, but intent has not equated with effect.  Flooding, like wildfires, is a natural process in which river channels are scoured of sediment, which is carried laterally to enrich soil in the watershed, and also downstream to form fertile estuaries and natural barrier islands.  When they stand, levees channel an unnatural volume of water into a restricted space during flood season (runoff from spring snow melt upstream), increasing the risk of levee failure downstream.  Communities which have grown behind the ephemeral protection of the levees are suddenly at great risk of being flooded out when the levees fail.  And the sediment which would normally have been deposited annually at the Mississippi estuary on the Gulf of Mexico, is carried out to sea by the force of the restricted water.  As a result the estuary's wildlife habitat (and the storm erosion protection it afforded to inland areas) is shrinking year by year, reclaimed by the sea.

Nor is flood risk limited to spring runoff.  The failure of Mississippi River levees during Hurricane Katrina was a core cause of the catastrophic flooding which wiped out entire neighborhoods in New Orleans in 2005.

The point is, when we consider placement of a home, a farm, or a city, it only makes sense to take into account local conditions.  Building homes on a floodplain, even in areas which may flood once every 500 years, is foolish.  Equally foolish is trying to farm or ranch in arid regions, unless the water table is close enough to the surface to provide sufficient well water for survival.  It's called thinking ahead, something we humans do far too little.  I'm encouraged that on at least a few fronts like dam removal, more rational minds are making an effort to repair the inestimable damage we've caused to the natural world, and to ourselves.

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