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Comment by ggm | Hacker News Reader

Excluding systems which put water into the air, Atmospheric water is a zero sum game AFAIK so if this causes rain to fall where the Chinese want it, somebody else misses out.

Freshwater from high mountains in the India/China region is a hot topic. They're running out of glaciers.

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It worth to mention that the southern part of China has a different climate than the north. It is very normal that during summer, there is flood in South but drought in North. The situation may different from year to year but the trend is very clear. That is also why there is South–North Water Transfer Project[1]

1. https://en.m.wikipedia.org/wiki/South%E2%80%93North_Water_Tr...

Came here to ask if this was a zero sum game (verbatim, actually). So, thanks for this.

Given how much human conflict has erupted over access to rivers and other water sources, I can't imagine it will go well if a lot of countries start to do this at scale...

It's also fascinating how we muck-up water management in seemingly contradictory ways. I live in a temperate climate with a good amount of rainfall, but my town is already jockeying with its neighbors for the last remaining access points on the local water reservoir. Meanwhile, every time we get a heavy downpour, local creeks overflow due to excessive runoff from parking lots and what not and end up flooding all kinds of places (the local mall floods pretty much once every year or two, it seems). Fascinating how we can have not enough fresh water and too much fresh water all at the same time.

Water, water everywhere and not a drop to drink.

I'm glad I'm not the only one who thought of this immediately after reading the article.

You mentioned another point that's worth investigating with this technology - some places see excessive rainfall to the point where it disrupts populated areas.

Perhaps in the long-term we can learn if there are specific areas these systems tend to draw from and determine how weather patterns contribute to that. Eventually, we may be able to use these systems in a way that takes just the right amount of excessive rainfall from areas where it's becoming a nuisance and evenly distributing them to areas where water is scarce.

One could hope that countries experimenting with this across the globe would be willing to find ways to make that happen, although that could create huge dependency chains that quickly fall apart as soon as one country backs out suddenly.

The "stolen" rainfall doesn't have to be spatial, necessarily; it could be temporal as well. It might provide a way to control seasonal floods caused by excessive rainfall during a short period.

It's hard to see how moisture can stay in the air for months at a time, but I am not a climate scientist, so who knows.

Air contains water. The amount it contains is defined by pressure, temperature and availability.

I dunno. Can it carry 3 months worth of rain at once?

You don’t necessarily need to keep water in the air, either. You can just cause it to drop out en route before it floods a particular area.

Wouldn't higher temperatures and lower humidity due to water vapor extraction lead to an increase the evaporation from the oceans to maintain the balance?

Not saying that wouldn't have other effects, just wondering if atmospheric water is really a zero sum game.

Based on this [0], it looks like the weather systems head out over the pacific after passing China, so should have ample time to refuel?

[0] http://wasatchweatherweenies.blogspot.com/2012/02/jet-stream...

It's not a 0 sum game so much as an equilibrium expression.

They're just putting their thumb on one side of the scale. Where the extra evaporation comes from and how it affects global climates is too tricky to predict but that's not going to stop them so we'll just have to live through it.

You're right, but it would depend a lot on the weather conditions downwind

I wonder how much of it is equivalent to depriving the Pacific Ocean of rainfall, and whether that has meaningful implications.

It's not fully zero sum - the air that water is taken out of gets humid again when it goes over the sea.

That's the start of a new cycle, so yes, it gets taken out, unless it evaporates again before it reaches the oceans.

I don't think that is necessarily true. Whatever rain falls evaporates again. If you increase the amount of rain in one place then evaporation also increases. You have increased the capacity of the water cycle at least in a local area. Also most of earth is ocean so increasing rain on land does not necessarily take from other land.

Agree. It would work out if the rain was destined for the ocean or other unusable area. Otherwise they are taking it from other people.

I'm not the best at reading meteorological maps but, if I understand this jet stream forecast right, it looks like it's Beijing and South Korea that are going to miss out.

http://www.weatherstreet.com/international/asia-10-day-forec...

What if they're "stealing" rainfall that otherwise hits oceans?

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