Water and dams

Instructor: Tyler Cowen, George Mason University

Is the era of big infrastructure projects over?  Or is it just getting started?  How important are dams anyway?

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That is a very complicated question. It would depend upon the details of the situation. The algae growth removes CO2 from the atmosphere which can then settle into anaerobic sediments and be partially fermented to methane with a lot of the carbon remaining in the lake bottom sediment where it will be sequestered. This time scale for sequestration can be much longer than some trees and other temporary sinks for carbon (all is temporary on a geological time scale), before the dam goes away and the carbon is oxidized by bacteria back into CO2. The methane in an aerobic lake can then be oxidized by bacteria into CO2 and more bacteria which can then add, along with the algae, to the organic carbon.

Deep underwater emissions of methane never reach the surface as the bacteria will eat the stuff when both methane and oxygen are in the same water.

For the most part dams are a net sink for CO2 and nutrients. The activist don't like this reality so they either don't really understand the details or don't care about the truth. The one factor they can claim is that the production of cement itself releases a lot of CO2, but as demonstrated decades ago by that totally closed habitat in Arizona, where they tried to create a totally closed ecology including humans, CO2 does disappear back into concrete. In effect the organic carbon in the soils became CO2, using oxygen, and the CO2 reacted with the concrete decreasing the O2 in the atmosphere for the humans.

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