[water-data-dude]

Oh boy, lemme tell you: water management is one of those things that's More Difficult Than It Seems.

I'm going to recommend Cadillac Desert, which is by far the most entertaining and readable book on water. It goes into the history of water in the western US, a dry region that's very dependent on the Colorado River. The American West isn't a poor, war-torn area, and a LOT of money has been spent on various projects - but water is still a serious issue.

Things like "big pipelines to move water around" have been tried, but they're enormously expensive, and they don't really put as much of a dent in the problem as you'd imagine. Dams can store some excess water, but they cause problems of their own (which is why we don't build as many, and are getting rid of dams we don't need), and they're a bandaid at best. There's not a good solution to "how do we move a TON of water around", at least not now.

[repelsteeltje]

Indeed, it's easy to overestimate the capacity of a large tube and underestimate that of a small river.

[spwa4]

The problem is not capacity of a tube. Let's take a recent example, Teheran. And let's assume desalination is just totally free. The city needs 1.2 billion m3 cubic meters of fresh water, and is on average 1200 meters above sea level. Let's not even count actually transporting that water, let's just discuss pumping it.

E = mgh, blabla, this requires 500 Megawatt constant power, 24/7/365, JUST to move the water up. This is the theoretical minimum power required to lift it against gravity. Does not include pumping the water inland.

This does not include actually pumping the water (ie. horizontal movement) (30% inefficiency would certainly not be considered bad engineering), doesn't include electrical inefficiency (30% in the power plant + 10% in the motors), doesn't include desalination (100%), doesn't include building the massive bridges something like this would require, doesn't include ...

So let's say you need a 4 Gigawatt power plant, every single drop just to keep this one city alive.

And for Asian cities, Teheran is tiny, about the size of Greater London or Paris. Most Pakistani cities are easily double that.

What needs to happen is that people in Asia need to abandon quite a few cities (yes, European cities are largely in, when it comes to water, sustainable places. Africa is less ideal, but still reasonable, US is reasonable with some exceptions, it's a bunch of Asian cities that are the problem here)

[jjk166]

> The city needs 1.2 billion m3 cubic meters of fresh water, and is on average 1200 meters above sea level. Let's not even count actually transporting that water, let's just discuss pumping it.

> E = mgh, blabla, this requires 500 Megawatt constant power, 24/7/365, JUST to move the water up. This is the theoretical minimum power required to lift it against gravity. Does not include pumping the water inland.

The energy required to lift that water does not give you a power requirement, which is a rate that energy is consumed. Tehran has a water deficit of 101 million m3 per year which would require 38 MW to lift. That's a couple of wind turbines worth of power. Obviously there's a lot more to keeping the water system working, but you're off by an order of magnitude. Building a small power plant to keep a city of that size habitable is certainly achievable.

> And for Asian cities, Teheran is tiny, about the size of Greater London or Paris. Most Pakistani cities are easily double that.

Tehran's urban area is the 29th most populous in the world with over 14 million people. Pakistan has one larger urban area, Karachi, which is 40% larger.

[seanmcdirmid]

China is in a bind, though they have more money to deal with it than most countries. Their clean energy is in the west, but not much water out there (well, more than you think, but still not enough), their industry is the in the northeast, their water is in the south east (also in Tibet, but those glaciers are melting quickly), so they have to divert water from the southeast up north (the grand canal they build a decade or so ago), they have ultra high volatile wires to bring the energy from west to east, etc...

Why you just say move, you are still making a compromise. Maybe you have flat land with no water, and you are moving to somewhere that is mountainous with water, you now have to terrace a bunch of mountains before that area is productive, and let's say you use wind and solar, but that is even in another area, so you need wires to bring that in...etc...

[einszwei]

I'd also add that it is easy to underestimate the water usage.

Desalination could be viable if it was only for subsistence/drinking. But water use is extensive in every single product/service we use and thing we cconsume. Cost of water going up across the board will have effects that shouldn't be underestimated.

[api]

Isn’t the problem ultimately that water is heavy and it takes a lot of power to pump it and that’s expensive?

You can pump water faster through a big tube but then you need big pumps and tons of electricity. If it’s going uphill that’s going to be serious power.

[Loughla]

1 ton of water is only 240 gallons. So if we're talking a tube that is 4 feet in diameter and 10 miles long, that's 12.5 million gallons, or 52100 tons (or 104,000,000 pounds). While it wouldn't take that much to move that if your pushing downhill, I have to imagine the energy cost would be AMAZING moving it uphill at all.

But also fluid dynamics is the only college course I dropped because it was fucking witchcraft, so who knows.

[namibj]

About 3kW to move 1 ton up one foot in one second.