In our last post, “Dams & Greenhouse Gas,” we took the International Rivers Network to task for putting out a study that claimed dams are a “significant global source of greenhouse gasses.” Because if you dug into the underlying facts, the estimated contribution greenhouse gasses make to total anthropogenic CO2 emissions are a whopping .7% (seven-tenths of one percent).
There are many problems with dams, and greenhouse gas emissions (itself a topic not beyond debate) are not one of them. For a serious discussion of the problems with dams, we turn to the Property and Environment Research Center, who recently published an essay by James Workman entitled “Deadbeat Dams.” Workman is succinct and comprehensive in his descriptions of why dams have outlived their usefulness: “antiquated dams have a lot going against them: seismic shifts shake them from below; compound water pressures scour them from behind; sediment fills reservoirs; evaporation drinks more than people; and invasive species choke intake and out flow.” Let’s not forget all those salmon…
Not only does Workman explain that most dams have a useful life and afterwards can cause more harm than good, he presents a practical way to get rid of obsolete dams: “businesses seek out credits generated by third-party projects for environmental services in advance of their proposed development—and pay handsomely for them…the average obsolete dam may be worth far more broken up than left intact; the sum of its removed parts are worth more than the integrated whole. Busting the dam could release a net gain in legitimate, measurable economic value, which can be brought to market and sold to willing buyers.”
Workman estimates there are 79,000 dams in the United States, and that 85% of these dams are no longer providing economic benefits. Meanwhile there are developers throughout the USA who are trying to provide new industrial, commercial and residential facilities for a country whose population just topped 300 million and grows by over 3 million per year. All of them are required to mitigate whatever land and habitat their developments encroach upon, usually by ratios well beyond one-to-one.
Another noteworthy point regarding dams is the value of an alternative to mega-dams, which is to build small check dams. These dams catch seasonal flows and divert the water to temporary basins where they refill aquifiers. This is a terrific way to recharge the water tables, particularly in areas where wells for crop irrigation have drawn underground water reserves to dangerously low levels. Here are some references, including links to reports on communities in India who have successfully built check dams:
Check Dams in Utility canyon running into Bay of Bengal
Check Dams and Sustainable LivelyhoodsCheck Dam through Shramdan
For more about water issues in India, read our feature “India’s Water Future.”
Human Development Report 2006
Read the section on water harvesting; pages 195-197