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Comment by ChuckMcM | Hacker News Reader

In terms of cost it seems way way cheaper. The water is stored near where it is needed (so no canals to dig), and you can throw up another one for $125K vs the millions of $ to build a dam.

So I'm guessing the evaporation challenge isn't a deciding factor here.

That said, I wonder how much longer you could keep the ice if you had reflective blankets to cover them once you've "grown" them as much as you can (enter the dry season).

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Long if you have high-tech blankets https://www.snow-forecast.com/whiteroom/finnish-resort-to-cr... but you can also low a tech version with saw dust https://www.swissinfo.ch/eng/sawdust-slows-rate-of-melting-s... which is also good.

Since white is reflective, why do you need blankets ?

Dirt and dust settle on top, those particles trap heat and facilitate melting

Doesn’t it settle on the tarps / covering too?

It's a lot easier to remove dust from a dry surface (the wind may do it for you - I recently listened to an interview about Mars rovers[1], and they mentioned most of the dust that gets on their cameras gradually blows away).

[1] https://embedded.fm/episodes/371

I'm having trouble remembering the name (it's obtuse and my searching is bringing up different, similar phenomena - cryo-something iirc), but once the warm dust starts to dig a little hole with some fresh water in it, biofilms of algae and fungi begin to form at the bottom. They're dark colored and accelerate the process further (increasing the size of their habitat).

At least, that happens with real glaciers. It may take a while for a similar phenomenon to arise on artificial glaciers. But sure as sunshine, if there's sunlight and fresh water, the algae will figure out a way to exploit it.

Is the term you're looking for "cupping", ie the formation of "sun cups"?

Interesting, I hadn't heard that before, but it's certainly related. The word I was searching for was the term for this particular biofilm/community, so it's some long technical term.

I always wonder that about seemingly-spontaneaous fungus and algea appearance: where do these organisms come from? Are they somehow airborn, or rainborn?

Yes to both. There are plenty of organisms on any drop of water you can find on nature, and plenty of spores on the air.

Those are called "cryoconites." If the debris over a glacier exceeds a millimeter or two, it will actually reduce melt instead.

Thank you! That's so interesting that it can actually slow the melting.

I imagine a shiny reflective blanket will reflect more infrared than just snow, and also trap coldness in the air between it and the snow, acting as insulation.

Color only hints to heat reflective properties. Most of the heat of the sun is not carried in by the visible spectrum. And concerning snow, it is not particularly good at reflecting IR (1).

More a conceptual objection to using blankets. Feels like overengineering. The Ice Stupa idea of Sonam Wangchuk is brilliant IMO and if this minimalist approach would work would be fantastic.

(1) https://apps.dtic.mil/sti/pdfs/ADP000147.pdf

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