Slashdot Mirror
Scientists Identify Another Source of Dangerous Greenhouse Gases: Reservoirs (popsci.com)
A team of researchers from Canada, Holland, China, the U.S. and Brazil "found that greenhouse gas emissions from man-made reservoirs were likely equal to the equivalent of one gigaton of carbon dioxide being released into the atmosphere every year...a little less than one-sixth of the United State's greenhouse gas emissions." An anonymous Slashdot reader quotes Popular Science:
A reservoir is usually created by damming a river, overflowing the banks and flooding the surrounding area, creating a man-made lake...the perfect conditions for microbes to generate greenhouse gases like carbon dioxide and methane (a gas that is about 25 times more potent than carbon dioxide)... "When reservoirs are first flooded there's organic matter in the soil and vegetation that can be converted by microbes into methane and carbon dioxide," John Harrison, a co-author of the paper, tells Popular Science.
"Also, reservoirs because they are in line in rivers, they receive a lot of organic matter and organic sediment from upstream that can fuel the production of methane, carbon dioxide and nitrous oxide." Harrison says that reservoirs also tend to occur in areas where fertilizers are used on the surrounding land. Runoff from those fertilizers into bodies of water can cause algal blooms that can also produce more methane and carbon dioxide.
If the world's reservoirs were a country, they'd be #8 on a list of polluters -- right behind Brazil, China, the EU and the U.S.
"Also, reservoirs because they are in line in rivers, they receive a lot of organic matter and organic sediment from upstream that can fuel the production of methane, carbon dioxide and nitrous oxide." Harrison says that reservoirs also tend to occur in areas where fertilizers are used on the surrounding land. Runoff from those fertilizers into bodies of water can cause algal blooms that can also produce more methane and carbon dioxide.
If the world's reservoirs were a country, they'd be #8 on a list of polluters -- right behind Brazil, China, the EU and the U.S.
The headline and summary makes it sound like it is a large effect. It's not.
The estimate was 25% too low, and
"All told, reservoirs used for everything from power to flood control to irrigation account for roughly 1.3 percent of our global carbon footprint, much higher than previous estimates."
Wow. We're talking about a 1.3 percent contribution, and the original estimate was off by 25%.
So, the original estimate undercounted greenhouse emissions by a little under half a percent.
Some other sources:
http://www.smithsonianmag.com/smart-news/whoops-dams-and-reservoirs-release-tons-greenhouse-gases-180960645/?no-ist
http://gizmodo.com/scientists-just-discovered-a-major-new-source-of-carbon-1787222994
http://www.geoffreylandis.com
These are fair and cogent questions... How did you get it here?
I think they are making the issue about fresh soil providing nutrients for microbes at a higher rate due to submersion induced mobility of both the microbes and the nutrients. The thing is, if you have real soil (i.e. dirt+biomass+microbes±other_critters) then that process was happening, albeit at a reduced rate. It's called composting and that has been happening since the first green thing died. And microbes would have gotten around to all the available nutrients at some point. As to rivers fueling the process, I would be very concerned about the fertilizer load carried down stream, but the normal "payload" of biomass was going to break down somewhere in any case. If the rivers biomass were to travel to the sea uninterrupted, I would expect different critters to be waiting to snack the stuff back into farts. Have to add one more sentence because I don't want to end a post with the word farts.
OK, trying again this time we end with egg salad...
You have the right to remain sentient. If you give up the right to remain sentient, you will be elected to public office
Okay... these are not going to be an issue in a un-dammed river (or natural lake)?
Rivers are very different than reservoirs when it comes to hydraulically shaped biological activity, so yes. Just check out any number of effects of human infrastructure on rivers like the Nile, the Tigris and Euphrates, the Yellow, the Thames, the Mississippi, etc.
these are not going to be an issue in a un-dammed river? And ... they are going to blame reservoirs for non-associated (man caused) pollution?
Blame? Try recognizing the impact of other actions that in turn contribute to a local effect.
But yes, flow to the sea is also an issue. See marine dead zones for more.
I'm not nearly as poetic as you, but:
> To hydro, or not to hydro--that is the question
That question was answered in the 1930s, 1940s, and 1950s. We did put hydroelectric dams in most of the places where geography makes it attractive to do so.
There's a lot to be said good about hydro-electric, and some bad. Like nuclear, it provides steady, reliable, clean energy, and like nuclear a worst-case accident could be really bad. The collapse of the Banqiao hydroelectric dam killed about a quarter million people, for example.
Differences between hydro and nuclear include:
Political feasibility: until recently, it was fashionable in environmental circles to bash nuclear and promote hydro. That's changing.
Scalablity/growth: As mentioned, most of the good hydro spots are already in use. New nuclear plants can be built in many places.
Safety record: While both could theoretically cause many causalties in worst-case scenario, hydro actually does have such accidents occassionally, and a million people have actually been affected. Nuclear has had three pretty scary close calls, but nothing has actually happened like Banqaio etc have for hydro.