In the latest Electric Power Research Institute Journal, an article titled "Hydropower Reservoirs: A Question of Emissions" notes that reservoirs used for hydropower and for pumped-hydro energy storage are not necessarily as green as you might imagine. Or rather, they might be too green: carbon-rich organic material that accumulates on the reservoir floor can be the source of carbon emissions. A recent study of the 90-year-old Lake Wohlen, in Switzerland, for example, found high emissions of methane, as recently reported in the journal Environmental Science and Technology, in an article titled: "Extreme Methane Emissions from a Swiss Hydropower Reservoir: Contribution from Bubbling Sediments."
