ELi5 Why can’t we build massive transnational water pipelines (like with oil) to transport water from large fresh water sources to drier areas?

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Obviously this wouldn’t relieve the issues caused by low snowpack and decreasing precipitation, but it could supplement the water used for everyday living or agriculture during times of drought right?

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Not an expert but doing something like this would be incredibly expensive and require the cooperation of hundreds of different municipalities to approve something like this.

This is not a bad question, but it does underestimate exactly how much water humans need, and how heavy it is.

The average domestic user needs 250L of potable water every single day. If you’re going to provide water to lots of users, you’re going to need a very big pipe.

For example, there is a small nation in Africa called Lesotho, which is entirely surrounded by South Africa. Lesotho has mountains with lakes in them, and they sell water to South Africa. The tunnel that takes water from Lesotho into South Africa is 5 m in diameter and 38 km long. It’s about an 8 billion dollar project, and that hasn’t exactly solved South Africa’s water problems.

Well, you have a few problems to contend with, and some of them don’t have good solutions – plus you have an issue of scale.

First of all, you’ll be driving a tunnel through land that’s geologically active. The ground moves, and not all of it is going in the same direction. Over small scales, like a subway or a city aqueduct, that’s not much of a concern since (barring things like earthquakes) movements are small and generally along the same axes. But a transcontinental tunnel will be put under a lot of strain by ground shifting – and that drift can be in all three axes. But, really, this is the least of our worries.

A bigger problem is the geology you’ll have to deal with, particularly mountain ranges. In North America, for example, you have the Rocky Mountains. Hard rock, loads of pressure, and as an added bonus a lot of geological strain energy which leads us back into the first problem of ground shifting and snapping your pipeline (or at least cracking it and causing leaks). You’ll also have to contend with ground unsuitable for load bearing (which means shoring up your pipeline to keep it from sinking under its own weight and causing a break) and ground hydrology causing problems (saturated soils causing buoyancy or loss of support, depending on the strata involved). Even drilling a subway involves dealing with most of these problems, and that’s only over the area of a city, not several thousand miles of terrain. Sure, you could try to sidestep the problem by only drilling through bedrock, but that’s going to add to the project cost by a magnitude of hundreds.

You’d have to source water for the pipeline, of course, and that’s another problem. Moving water from where it’s wet to where it’s dry sounds sensible when you’re looking at footage of floods and droughts (just move one to the other!) but in reality that floodwater isn’t captured. It’s all runoff. Building a system to capture that water would be an enormous headache on lots of levels, to say nothing of actually making water that badly contaminated by runoff usable. And lest we forget, just because an area isn’t in lake-drying levels of drought doesn’t mean it’s flush with water, either.

Finally, though, you have a massive problem of scale. In order to make any kind of dent in a water shortage like you see in the American Southwest, you’d need a transcontinental pipeline a kilometer across or more just to move enough water. A normal aqueduct the size of a subway tunnel won’t move enough water to do more than fulfill the water needs of a neighborhood or two at most. Shifting enough water to actually cure – or even substantially alter – a severe water deficit just isn’t practical; you’d need the largest tunnel diameter ever built, and the engineering of the tunnel alone, even ignoring the problems with the land it’ll travel through, would be immense. Factor in all the other issues and building a hundred desalination plants is a financial and engineering snap by comparison.

We already do this. The main reason we don’t have giant pipelines running across the country is because there’s usually water much closer to the places that need it compared to the area between where oil is refined/distributed and where it is extracted.

Also the water displacement would harm environments it’s collected from. Most people living by a lake wouldn’t be cool with it being taken from their water cycle to help the people in Vegas.

This was considered in the early 60’s it was called the North America Water and Power Alliance (NWAPA). For starters, the project would have been *Extremely* detrimental to the environmental landscape and the marginal gain of water transferrence was not enough to justify that scale of environmental damage. Yes, this is done with oil lines, but a project like this requires tons of dams and connections to multiple bodies of freshwater and would be much more intricate.

Second, the cost adjusted for inflation would be nearly 2 Trillion dollars just to complete the project. That doesn’t even include the cost and nightmare logistics of maintaining something of that magnitude across multiple state (and in this case country) borders.

The amount of water necessary in drier areas wouldn’t be satisfied and the fresh water source would dry up.

Fresh water lakes all over the world (most notably the Aral Sea) are drying up as it is, without adding additional stress.

The cost for installing this is also incredibly high. The investment in gas pipes makes sense for businesses, as they profit immensely from selling gas. However, water is a rather cheap commodity, so spending all that money to transport water that you’ll need to sell at higher rates will never fly.

Explaining with my smol brain.

1. Costs. Oil has more value than water and people are more willing to pay for the electricity, maintenance, and construction of pipelines for oil because of money.
2. Water is much heavier than Oil meaning it would need a more powerful pump to move the liquids from one place to another, circling to the first one which is cost. More fuel or electricity would be burned off by transporting water.

I read some articles about the US planning to create an Interstate water system where they transport water around their country and it is doable but right now, oil is just ‘more important’ for everyone. a dollar in price increase gets the whole world racking their brains.

We can. There have actually been proposals to bring water from the Great Lakes to the SW of the country. States in the Great Lakes region have created laws that prevent this from occurring. No one wants to give up precious water supplies, ecosystems are fragile, water rights different depending on location, and problems with cost/price/profitability make it unattractive.

Like our aqueducts literally do, or?

We do on a smaller scale. There are multiple several hundred mile long pipelines/aqueducts all over the country that transport water.

I have a similar question: Why can’t we build ways to transport people from drier areas to wetter areas so that people who want water can move to where it is?

We would do this if it was affordable. There is plenty of water, but not at the “almost free” price people want to pay. When a pipeline is the right answer, there is just no water, because you can’t run the pumps to pump water through the pipeline for what it sells for. There are giant pipelines in CA and tunnels in NY, with prices to match.

We kind of have. California has an aqueduct that takes water from the San Joaquin/Sacramento basin to drier parts of SoCal, near Santa Barbara and LA.

It’s really expensive, and as others have noted, it’s pretty detrimental to the environment. Also, the places they’re taking from actually need it, too. Northern and Southern CA fight about water almost constantly, because the whole state is really ag-heavy, and generally pretty dry.

Also, it should be noted that “everyday living” and “agriculture” are vastly different. Ag takes a whole heckuva lot more than the average municipality uses for things like drinking water, cooking, sanitation, and yes, even the average homeowner watering their stupid useless lawn.

Where I live there are hundreds of kilometers of channels dug into the mountainside to bring fresh water from the colder and more humid north side to the hotter and drier south. Your idea does exist

Agriculture is only profitable if the water used is super cheap. Piping in water from far away is really expensive, with the cost going up the farther away the water has to come from. Oil is pretty expensive already and people are OK paying a few extra dollars per barrel to pipe it far away, but a few extra dollars per barrel of water would be uneconomical for agriculture.

We do actually pipe water for agriculture and residential use but past a certain distance it doesn’t make economical sense. It would become so expensive that it would make more sense to invest in ways to reduce water consumption like more efficient irrigation, aquifer injection of treated wastewater, etc.