Dams & Greenhouse Gas

Here we go again. The International Rivers Network, based in Berkeley, California, an organization with some incredibly great ideas, now reports that dams (and the reservoirs behind them) cause greenhouse gas emissions. Courtesy of the IRN, read “Fizzy Science: Loosening the Hydro Industry’s Grip on Reservoir Greenhouse Gas Emissions Research.” This report (click here for full report), of course, damns dams, and demonizes yet another industry – this time those evil people who build devices to store water for irrigation, control flooding, and generate electricity for terrible things like stoves.

Aswan High Dam
Aswan High Dam

Before we go any further, let’s be clear about one thing; this is almost certainly less than meets the eye, and even if it isn’t so what? CO2 as a boogyman seems to have become the fulcrum upon which pivots all environmentalist logic and reason. But are we so sure CO2 emissions are bad? There is evidence to support theories that the more atmospheric CO2 concentrations increase, the less warming impact occurs per additional unit of CO2. This would mean our climate may have already seen the biggest effects of increasing CO2 emissions. For much more on this, read our “Global Warming” posts.

Remember when nuclear power plants were deemed to cause dangerous levels of CO2 emissions? This was determined based on the amount of CO2 that is emitted when pouring cement. Apparently nuclear power stations require prodigious amounts of cement. But shortly after this press release went out, gobbled up as usual by mainstream media, a perspicacious blogger named Tim Worstall penned a gleeful comparison wherein he demonstrated that more cement per megawatt is required when installing windmills than when installing nuclear power stations. Others were also chiming in. Thank you hive-mind. And hence nuclear power is again touted as alternative energy by many environmentalists.

Back to our new problem of dams and greenhouse gasses, taking a look at the facts indicates scant evidence for alarm. Hitting its stride, the IRN piece states as follows: “available evidence strongly suggests that reservoirs are a significant global source of greenhouse gases.” They back this up with the following footnote: “reservoirs worldwide release 1,000 million tons CO2 annually (4% of CO2 from other known anthropogenic sources).

Even if this statement is completely true, that 4% of anthropogenic CO2 emissions come from dams and reservoirs, so what? Does this mean the benefits of dams – irrigation, flood protection, and renewable electricity, are not worth putting out 4% of anthropogenic CO2? Per gigawatt-year (or quadrillion BTU’s), hydroelectric power would still be far more greenhouse gas efficient than, say, coal or natural gas.

That’s not the half of it, however. In the remainder of the same footnote, IRN discloses the following: “These estimates are based on a calculation of 1.5 million km² global reservoir area. This calculation is likely an overestimate. A more recent analysis estimates that reservoirs cover a global area of 260,000 km².”

This means IRN is saying the information they just gave you – that reservoirs cause 4% of anthropogenic CO2 emissions – is overestimated by a factor of 5.8 times! IRN’s revised estimate of global reservoir area isn’t 1,500,000 square kilometers, the figure they used to calculate their 1.0 million ton estimate of annual CO2 emissions from reservoirs. Rather IRN acknowledges the global reservoir area is more likely only 260,000 square kilometers, which equates to 176,000 tons of CO2 per year, or .7% (seven-tenths of one percent) of anthropogenic CO2 emissions per year.

Needless to say, if dams only emit .7% of anthropogenic CO2, which itself is only 3% of all CO2 global emissions (the rest come from mother nature), they are not a factor. To use the CO2 emissions of dams and reservoirs as a reason we must demolish them, and demonize the hydroelectric power industry to boot, is not useful information, it’s propaganda.

The International Rivers Network might instead have on their website the letter that one of their members, Peter Bosshard wrote to the New Yorker (published in their December 4th, 2006 issue). Instead of brandishing the CO2 demon to scare us into destroying existing dams, he advocates an alternative to construction of new dams. Listen to this great idea:

“The 2006 Human Development Report on water presents an alternative to large dams. It estimates that, with an initial investment of seven billion dollars, extending small check dams across India’s rain-fed farming areas could quintuple the value of the country’s monsoon crop from thirty-six billion dollars a year to a hundred and eighty billion. Such an approach would not only protect rivers and the groundwater table; it would also create jobs and give the poor the means to buy the food they produce.” More on this, if you please.

3 Responses to “Dams & Greenhouse Gas”
  1. At my organization’s public Web site, we’ve compiled a number of studies on total lifecycle emissions from all sources of electricity generation. In each case, nuclear and hydropower are at the low end of the scale:


    Some folks simply believe that if you repeat the same lie often enough people will start to believe it. I guess that’s the case here too.

  2. Ed Ring says:

    It is appropriate to rely on a “footnote” to point out discrepancies if the footnote provides the primary quantitative data. Here is the footnote in its entirety:

    “(2) St. Louis et al. (2000) estimate that reservoirs worldwide release 70 million tons CH4 and 1,000 million tons CO2 annually (20% of estimated CH4 emissions from all other human activities, and 4% CO2 from other known anthropogenic sources). These estimates are based on a calculation of 1.5 million km² global reservoir area (0.9m km² temperate; 0.6m km² tropical). This calculation is likely an overestimate. A more recent analysis estimates that reservoirs (>0.01km²) cover a global area of 260,000 km² (Downing et al. (2006)).”

    We stand by our contention that it is misleading to overstate the contribution of any greenhouse gas to the atmosphere by a factor of 5.8x – and require the reader to do the math in the footnotes to realize this.

    Taking into account this correction, it isn’t 20% of all anthropogenic methane that comes from reservoirs, it is 3.4%, a much less alarming figure.

    Our goal is not to mock environmental groups. We like environmental groups – we support environmental groups – we are environmentalists, too. We agree that mega-dams are not always a good idea, and that there are often worthy alternatives. What we object to is trying to tie anything we don’t like to global warming and greenhouse gas. We also object to the notion that all large water projects are bad, or that the entire hydro-power industry is evil. For a large water project we would love to see, read “Arctic to Aral – Siberian Waters Save the Aral Sea.”

  3. Tim Kingston says:

    It is unfortunate that both the article and the first posting about the “Fizzy Science” report by International Rivers Network misrepresent the information on hydropower dam emissions with reference to methane emissions, while continuing the global warming is not such a bad thing after all idea.

    As the author builds a “case” against CO2 emissions, the author fails to note a significant portion of the report is based on methane emissions, which is a far more potent greenhouse gas emitter than CO2. The reading of the report is selective. The entire critique is based on an alleged discrepancy in a footnote. Nowhere does the author address the central contention of the report, that reservoirs in tropical areas can be potent greenhouse gas emissions, it would be helpful if this were at least noted.

    The author also accuses IRN of being reflexively anti-dam, this is unfair as it is inaccurate. IRN simply opposes mega projects that invariably make overblown promises about electricity production and irrigation benefits. They fail to mention all the people who are flooded out of their homelands. The power produced in developing nations usually benefits urban elites or is shipped out of the country where the dam is built. IRN does not oppose small recharge dams and other projects of local benefit and as the author notes, IRN is involved in proposing alternatives.

    As to the posting it suffices to say accusations of lying are to say the least unhelpful in any discussion. At this point the consensus in the field is not whether dams create greenhouse gases, but just how high the level of their emissions are.


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