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Rethinking hydro power for energy independence
July 4, 2010 12:29 PM   Subscribe

Who knew that dams worsen global warming? Long ignored "run of river" or streaming hydro power now offers an alternative by avoiding a large reservoir.

By some estimates, impoundment dams are responsible for 4% of global warming, though formerly believed to be a solution to the problem. Recently, run-of-river projects were approved in British Columbia, after much political debate and concern over the hundreds of pristine locations identified as potential sources. Investors take up the cause. Nor is it the only hydro power strategy available for large-scale development.
posted by Brian B. (17 comments total) 1 user marked this as a favorite

 
Run of river is one of the most misleading names you could imagine - in BC at least, some of these are massive mega-projects which ruin huge stretches of otherwise pristine rivers and watersheds, the rights to which were sold off in a gold-rush atmosphere because the public was lulled into thinking it amounted to little more than dropping a tube into a river and spinning a little propellor. Nothing could be further from the truth. And the debate you refer to is happening after the sneaky selling off of the rights, not before, so now the corporations are all, "well if you don't let us do this thing we want compensation". It's an epic environmental fuckup in a province that has many such to choose from.
posted by Rumple at 12:39 PM on July 4, 2010 [4 favorites]


I think there are serious issues with the studies that unpin the conjecture that dams are a significant contributor to global warming.
No offsets are being considered resulting from irrigation, algae the lake, etc. This sounds like one old those a Prius is more dangerous than a Hummer.
posted by humanfont at 12:39 PM on July 4, 2010 [2 favorites]


Looking at the map I wondered what that hunk of red on the Baltic was; surely none of the Baltic states is large enough to have millions of hectares of dammed water. But then I remembered Russia's still got a hunk of discontinuous territory there. But that in turn raises the question of why Alaska's not colored red like the rest of the U.S.
posted by George_Spiggott at 12:42 PM on July 4, 2010


No offsets are being considered resulting from irrigation, algae the lake, etc.

The Brazilian example said 3.5 times worse than an oil-fired plant to produce the same electricity. I don't see how offsets would make that much a difference given those numbers. Plus you have to off-set the off-sets .. true agriculture stores some carbon in the soil by way of dead plant roots, but that would have happened anyway had the trees never been cut down. The big factor is methane which is like 10 or 20 times worse than CO2. Which is why we should all be composting our kitchen scrapes. And not farting.
posted by stbalbach at 1:30 PM on July 4, 2010


In sounds like the methane is dissolved in the water, and released into the atmosphere by the pressures and turulence of sending the water through the turbines. If that is the case, there is a (indoors) point-source where the methane is coming from, so it shouldn't be difficult to capture or burn it before releasing it into the atmosphere, in future dams at least.
posted by -harlequin- at 2:30 PM on July 4, 2010


According to the article the methane comes from decaying plant material. Some from the plants that were originally in the area that was flooded when the dam was built and the land flooded, and some from the plants that grow on the land that's covered when then the dam's full. And since methane causes roughly 12 times more warming per atom of carbon than carbon dioxide, having the cycle of carbon dioxide->reservoirside plants->decaying underwater plants->methane is bad.
posted by Zalzidrax at 2:47 PM on July 4, 2010


so it shouldn't be difficult to capture or burn it before releasing it into the atmosphere, in future dams at least.

Note that there are other problems with dams, including the loss of land, huge costs, gradually silting up and becoming useless, surface evaporation, distance transmission losses, preventing the migration of fish, and the dangers of failing.
posted by Brian B. at 3:02 PM on July 4, 2010 [1 favorite]


Further to Rumple, the boards of the private power companies in BC are riddled with former cabinet ministers and Liberal insiders. This is not a clean game.
posted by klanawa at 5:16 PM on July 4, 2010 [1 favorite]


I remain skeptical. It would appear that there has been only minimal scientific study on the co2 impacts of dams, and that those studies have been sponsored by groups with an agenda that is anti hydro. There are legitimate concerns with hydro, but global warming is very far down on the list and I don't think it is settled science.
posted by humanfont at 5:46 PM on July 4, 2010 [1 favorite]


Yeah, it seems a little sketchy to me. Methane may be worse per atom, but it's an unstable molecule and breaks down over time. The half life is just seven years.
posted by delmoi at 6:02 PM on July 4, 2010


Methane worse than thought.

Targeting methane has long been considered key to reducing global warming because it will have an impact within 9-15 years of reduction, and because it is 20 times more potent than C02, it will offer the biggest reduction per unit. It isn't really a tradeoff regardless.
posted by Brian B. at 6:23 PM on July 4, 2010


The emissions from decaying plant matter resulting from the initial flooding should be minimal when amortized over the (hundred?) years-long life of these facilities. As for the "yearly drawdown", the shallow areas the article mentions should have plenty of oxygen and little silt, so I don't think the anaerobic decomposition to methane would come into play. I'd like to read the paper though.

As for run of the river projects, my beef with them is cost per kilowatt. That said, WTF environmentalists? Why don't you support these things? Sure they're going to have an effect on the river, and you're going to have to tear down some forest to build a road, but isn't that way less impact than a new coal plant or hydro reservoir? All year I hear people gripe that science should invent them cleaner electricity, and when it does people still protest! Gah!
posted by Popular Ethics at 9:46 PM on July 4, 2010 [1 favorite]


The post is a little scattered. Lots of bits without much tie-in. Interesting bits though.

Pumped storage (the last link) is a good idea, but no one has been able to build it profitably (maybe with the carbon tax they will). Think about paying to build a hydrodam, only instead of generating money at the rate a hydro dam does, you generate only the difference in costs between daytime and night-time power. That's not a very compelling pitch. Not to mention the risk of catastrophic collapse you might incur.
posted by Popular Ethics at 9:50 PM on July 4, 2010


Kill all beavers.
posted by benzenedream at 11:45 PM on July 4, 2010


A few comments have made the assumption that silt is a one time occurance, which is a misconception. Quote from a random link explaining the problem:

All rivers contain sediments: a river, in effect, can be considered a body of flowing sediments as much as one of flowing water. When a river is stilled behind a dam, the sediments it contains sink to the bottom of the reservoir. The proportion of a river’s total sediment load captured by a dam – known as its "trap efficiency" – approaches 100 per cent for many projects, especially those with large reservoirs. As the sediments accumulate in the reservoir, so the dam gradually loses its ability to store water for the purposes for which it was built. Every reservoir loses storage to sedimentation although the rate at which this happens varies widely. Despite more than six decades of research, sedimentation is still probably the most serious technical problem faced by the dam industry.

Professor K. Mahmood of George Washington University in Washington, DC, "roughly estimated" for a 1987 World Bank study that around 50 cubic kilometres of sediment – nearly one per cent of global reservoir storage capacity – is trapped behind the world’s dams every year. In total, calculated Mahmood, by 1986 around 1,100 cubic kilometres of sediment had accumulated in the world’s reservoirs, consuming almost one–fifth of global storage capacity.

posted by Brian B. at 11:56 PM on July 4, 2010


Another major problem of constructed lakes, particularly those near coal power plants, is conversion of elemental mercury to highly toxic methyl mercury.

The emissions from decaying plant matter resulting from the initial flooding should be minimal when amortized over the (hundred?) years-long life of these facilities.

Algae and macrophytes (vascular aquatic plants) also count as vegetation. Huge amounts of this vegetation is produced every year, as constructed lakes tend to have high concentrations of growth-stimulating nutrients, imported both dissolved and sorbed onto particulates (silt) from the surrounding watershed, including agriculture, people's yards, and vehicle emissions. This provides a new, continuous form of fuel for greenhouse gas production.

As for the "yearly drawdown", the shallow areas the article mentions should have plenty of oxygen and little silt, so I don't think the anaerobic decomposition to methane would come into play.

Actually, shallow areas, like most shorelines of constructed lakes, can be quite anaerobic, because there is not much mixing in still water, they tend to be quite warm (the maximum saturation of oxygen decreases as water temperature increases), and they tend to be full of life (consuming more oxygen). You can compare them to wetlands, which are the largest natural sources of methane emissions on earth. Both wetlands and shallow lakes can be net producers of other greenhouse gases, including carbon dioxide and nitrous oxide.

I agree with those who are frustrated that there is no clean form of energy, but everything has consequences. It would be very short-sighted to trade greenhouse gas producing fossil fuels for greenhouse gas producing hydroelectric. I don't know nearly as much about run of the river generation, since it has not existed in areas where I've worked, but I would be hesitant to hail it as our savior, either.
posted by hydropsyche at 4:37 AM on July 5, 2010


Run of river in BC is an unmitigated disaster. The dams are being built as cheaply as possible: in thirty years, when they revert to public ownership, they're going to be an unmaintained, public danger that costs us a fucking fortune to repair or remove. They're also going to destroy the Pacific Salmon. Fuck Gordon Campbell and his business buddies for their wholesale rape of BC resources and BC's citizens.
posted by five fresh fish at 1:17 PM on July 5, 2010 [1 favorite]


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