An international team of scientists has amassed the largest data set to date on greenhouse gas emissions from hydroelectric reservoirs. Their analysis, published August 1 in the online version of Nature Geoscience, posits that these human-made systems emit about 1/6 of the carbon dioxide and methane previously attributed to them.

Further putting things in perspective, hydroelectric reservoirs are responsible for less than 16% of the total carbon dioxide and methane emissions from all types of human-made reservoirs combined.

"Our analysis indicates that hydroelectric reservoirs are not major contributors to the greenhouse gas problem," comments Dr. Jonathan Cole, a limnologist at the Cary Institute of Ecosystem Studies and one of the paper's authors. "But there are some caveats. To date, only 17% of potential hydroelectric reservoir sites have been exploited, and impacts vary based on reservoir age, size, and location."

It seems that hydro-electric is a low carbon energy source after all, at least in higher latitudes where there is less biomass to degrade, although this takes no account of ecosystem damage.

In view of the inability of solar and wind to provide the majority of our energy use without storage and the ability of hydro to meet this requirement are we missing a trick here?

That sounds good.

There was an idea to harvest methane from reservoirs and burn it to produce electricity or heating.

Ivan B.T. Lima et al. (2007) "Methane Emissions from Large Dams as Renewable Energy"
http://news.bbc.co.uk/1/hi/6638705.stm

Emission controls on Dams, well I never!