Posted on 02/24/2005 7:47:51 AM PST by samtheman
Contrary to popular belief, hydroelectric power can seriously damage the climate. Proposed changes to the way countries' climate budgets are calculated aim to take greenhouse gas emissions from hydropower reservoirs into account, but some experts worry that they will not go far enough.
The green image of hydro power as a benign alternative to fossil fuels is false, says Éric Duchemin, a consultant for the Intergovernmental Panel on Climate Change (IPCC). "Everyone thinks hydro is very clean, but this is not the case," he says.
Hydroelectric dams produce significant amounts of carbon dioxide and methane, and in some cases produce more of these greenhouse gases than power plants running on fossil fuels. Carbon emissions vary from dam to dam, says Philip Fearnside from Brazil's National Institute for Research in the Amazon in Manaus. "But we do know that there are enough emissions to worry about."
In a study to be published in Mitigation and Adaptation Strategies for Global Change, Fearnside estimates that in 1990 the greenhouse effect of emissions from the Curuá-Una dam in Pará, Brazil, was more than three-and-a-half times what would have been produced by generating the same amount of electricity from oil.
This is because large amounts of carbon tied up in trees and other plants are released when the reservoir is initially flooded and the plants rot. Then after this first pulse of decay, plant matter settling on the reservoir's bottom decomposes without oxygen, resulting in a build-up of dissolved methane. This is released into the atmosphere when water passes through the dam's turbines.
"Drawdown" regions
Seasonal changes in water depth mean there is a continuous supply of decaying material. In the dry season plants colonise the banks of the reservoir only to be engulfed when the water level rises. For shallow-shelving reservoirs these "drawdown" regions can account for several thousand square kilometres.
In effect man-made reservoirs convert carbon dioxide in the atmosphere into methane. This is significant because methane's effect on global warming is 21 times stronger than carbon dioxide's.
Claiming that hydro projects are net producers of greenhouse gases is not new (New Scientist print edition, 3 June 2000) but the issue now appears to be climbing up the political agenda. In the next round of IPCC discussions in 2006, the proposed National Greenhouse Gas Inventory Programme, which calculates each country's carbon budget, will include emissions from artificially flooded regions.
But these guidelines will only take account of the first 10 years of a dam's operation and only include surface emissions. Methane production will go unchecked because climate scientists cannot agree on how significant this is; it will also vary between dams. But if Fearnside gets his way these full emissions would be included.
With the proposed IPCC guidelines, tropical countries that rely heavily on hydroelectricity, such as Brazil, could see their national greenhouse emissions inventories increased by as much as 7% (see map). Colder countries are less affected, he says, because cold conditions will be less favourable for producing greenhouse gases.
Despite a decade of research documenting the carbon emissions from man-made reservoirs, hydroelectric power still has an undeserved reputation for mitigating global warming. "I think it is important these emissions are counted," says Fearnside.
just dam !
The real truth of the nut case left is they are so entrenched in self loathing they long for the elimination of the human race.
They want us to live in caves.
Actually, the nutcase left is also against building dams. But not because they cause greenhouse gas (most of the nutcase left didn't know about this previously) but because anything that aids in the economic development of the human race is evil to the nutcase left, and the nutcase left wants to destroy.
It is true, though, that nutcase left opposition to nuke power and fossil fuel power has made building dams more attractive than it might otherwise have been.
Ah, the nutcase left. Were would we be without them? I know! Way up there. Way far ahead of where we are now.
"This is because large amounts of carbon tied up in trees and other plants are released when the reservoir is initially flooded and the plants rot."
Gee, how about letting them harvest the trees first ?
( As if those plants and such were never going to die and release their methane at some point anyway... )
Let's see... they deride atomic energy (why? I have no real clue, we all know what they SAY)...
Burning things is out of the question (though I believe it makes up something like 70% of our energy)
Now hydro-electric energy is dangerous.
Next thing you know they'll tell us wind power decapitates endagered owls, and claims against solar power will include overheating the area around the solar cells.
The only thing we'll be left with is riding bikes to charge batteries! I think at that time, however, I will be instead strapping these libs to the wires, and not a battery.
Omigod!! We are doomed!!
That evil Kelp (millions and millions of square miles of it!) in the ocean that grows and dies and decays and releases carbon dioxide and methane in the air...those billions of trees in the forests, those massive rivers like the Mississippi, the Amazon, those miles and miles of grain that the cattle eat and turn into methane - they are killing us and turning our planet into a tropical Hell!!
Oh Woe is me. Woe is me. We must drain all the rivers and lakes, destroy all the trees, stop all the grain and grass from growing, fill the oceans with Roundup...!!
We are doomed. (Unless mebbe we could all hold our breath for one minute out of every five to reduce the CO2 from being released into the atmosphere.)
said Philip Fearnside from Brazil's National Institute for Research in the Amazon in Manaus
guess there are alot of dams in the amazon
Hydroelectric seems to kill more people (directly, anyway) than other forms of power production.
Ya THINK?!?!?
The left should just do the honorable thing and Hunter Thompson themselves. Since they hate life so much, then they should make a statement to prove it.
Yet-another-reason-for-more-nuclear-power-plants bump.
LOL!
It sounds more like they're opposed to ALL carbon-based lifeforms, animal and vegetable alike.
Man, as a conservative, I have a very strong pro-life philosophy.
But I don't think it's possible to achieve zero-emissions by legislating a ban on death, decay and decomposition of all biological matter.
The enviro-nazis will control every aspect of your lives including how many beans you consume and how many craps you take and how many squares of paper you use on each wipe.
Is this 'New Scientist' or Scrappleface.com?
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