I see, that makes sense - though then it'd be a comparison of energy and emissions already put into the making of the dam, the power it outputs (which could oth

I see, that makes sense - though then it'd be a comparison of energy and emissions already put into the making of the dam, the power it outputs (which could otherwise be from fossil fuels) and the atmospheric impact of those methane emissions. My instinct would be the impact of pouring all that concrete etc. would be very large, so decommissioning would still be very costly, but it does strengthen the argument against new dam projects.