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Comment by azlev | Hacker News Reader

Not every hydroelectric project is zero carbon. Big lakes inside amazon forests (as an example, I'm brazilian) cause a huge carbon footprint due devastation, rotten submerse wood, and also bring uncertains.

Also, those damns were designed to extract water from a fragile environment.

Those huge projects bring a lot of uncertain too.

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It's probably more accurate to say that most of the zero carbon hydroelectric that can be built already has been (and some of the not so neutral ones as well). That was the conclusion I came away with years ago when I wanted to know more about the topic of both why we weren't building new and why we were breaching old.

So even looking at the average footprint of existing projects will steer you wrong because most new ones will drag us back to the mean, which is pretty bad.

Mercury build up is also a know and awful issue about hydroelectric dams.

This has become a big issue in the north in Quebec:

https://www.nytimes.com/2016/11/11/world/canada/clean-energy...

We are doing something fundamentally wrong with sediment management in dams. Practical Engineering talks about how dams cause erosion downstream because the suspension capacity of the water is not occupied with material from upstream, and nature abhors a vacuum.

We need some way to continuously siphon sediment and expel it with the exhaust from the hydro and overflow pipes.

One of the more terrifying things about the destruction of the dam over the Dnipro in Ukraine is thinking about what will be in the clouds of dust that are going to blow off the bottom of that reservoir.

I feel like the UN is going to ratify some new rules of engagement when this is all over.

I don't know about for dams, but definitely for nuclear facilities.

We are talking about the same UN where Russia has veto power on the security council?

I wonder how much longer that’s going to last.

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