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for people who care about the West

No free lunch for hydropower


Editor-in-Chief Brian Calvert described dams as “providing clean hydropower” (“Compromise amid the canyons,” HCN, 9/4/17). Actually, a spate of new research shows that there is basically no free greenhouse-gas lunch when it comes to generating electricity, and the burden of hydropower is increasingly coming into focus. The news is not good. For example, a recent peer-reviewed study published in the journal PLOS ONE predicts that the greenhouse gas emissions from Lake Mead, compared against the hydropower it produces, are as bad as burning coal on a kilowatt-hour basis.

Reservoirs are basically methane factories, and methane is a potent greenhouse gas, carrying more than 80 times the warming effect of carbon dioxide on a pound-per-pound basis. Reservoirs contain a stew of microbes that feed on organic matter in the water column, and in the deeper depths where oxygen is depleted, the microbes release methane as a by-product of their metabolism. Concentrations can reach extremely high levels in the depths from which water is channeled into the turbines that produce hydroelectricity. Once that methane-rich water exits downstream, it’s off-gassed into the atmosphere, where it joins the increasingly dangerous mix of greenhouse gases that are radically warming our planet. Manufacturing the concrete used in constructing hydroelectric dams also carries a giant burden of emissions that silently continue warming the planet for centuries to come.

Mark Easter
Fort Collins, Colorado