“(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.”

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.

http://www.nei.org/index.asp?catnum=2&catid=260

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.