Why can’t the US build infrastructure that automatically siphons water from flood zones to the west during flood seasons?
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You’d ruin the ecosystems in the flood zone areas and I think you’re vastly underestimating how much infrastructure would be needed to collect/transport/disperse that much water
– The west is really, *really* far away from where the flooding would be happening, the piping alone would be enormously expensive
– The west is also *uphill* from where the flooding would be happening, and siphoning doesn’t work uphill, the outlet has to be lower than the inlet
– There’s not a continuous string of federal land between the flood areas and the zone that the piping could even be placed on. It would require an enormous exercise of eminent domain that would keep the project constantly bogged down in court battles
Cost.
The sheer size of that project would be insane. And you would be pumping water up a lot of hills.
If cost was no issue.
The size of the pipes and number of pipes required to transport that ammount of water is impractical. Then the energy required to pump that water up the water though the hills and across that distance would take the output of mutiple nuclear reactors alone.
Because you are talking about a massive undertaking of manpower, money and resources to harvest water from a different state every year.
You’re basically talking about re-routing at least one different river every year.
Also, compared to the volume of oil or gasoline sent via pipeline, the amount of water western desert cities would need is enormous. A typical person uses about 1 gallon of gas per day but uses 100 gallons of water per day.
Colorado is pretty much in the epicenter of this mega drought. However, Colorado is also like 1 mile above sea level. In order to move the water from the food zones to Colorado you’ll have to pump the water hundreds of miles west and a mile up. Alternatively, you could dig a canal a mile deep through the Rocky Mountains and let gravity do the work. But that would just be a human version of the Grand Canyon (and much bigger).
The Soviet Union [began a project](https://en.wikipedia.org/wiki/Northern_river_reversal) to reroute some of its arctic rivers to irrigate the arid steppes of Central Asia; you might be interested in reading some of the problems they faced and why they never got it done. While they calculated it as basically feasible, it would’ve taken immense resources (in their case, a lot of nuclear detonations). They also weren’t sure of the environmental impact of moving that much water on a permanent basis, since the water cycle is so important to climate. That meant doing it might cause more harm than good.
In the specific case of flood zones, you have to consider that any system that is good at capturing the floodwater is already going to achieve most of its benefit by stopping the flood. Once you have the levees that can keep the water within the river’s banks, you’d need to invest a huge amount of additional money to move it somewhere else instead of just letting it flow downstream–and you don’t get anything out of it until you actually get it to the West.
Basically for two reasons relating to how siphons work.
First is the target area is most likely higher in elevation than the source area. A siphon needs to move the liquid to a lower point overall in order to create a flow. That’s why when you siphon gas out of a car, the gas can needs to be sitting on the ground. That puts the gas can below the car’s gas tank.
The other is that (even if you found a flood that was higher elevation than some other desert place that needed water) siphoning is limited to about 30 feet of water depth between the openings of the tube and the highest point the tube.
Why about 30 feet? Because a 30 foot column of water an inch in cross section weighs 14 pounds. In other words, 30 feet of water exerts a pressure of 14 pounds per square inch (psi) and that’s enough to counter the air pressure around it.
That’s because the thing that “pulls” water into the tube is actually the air pressure *pushing* the water. A siphon works like a straw, except instead of creating “suction” with your cheeks, the suction comes from the water leaving the other end of the tube.
Well that “suction” that you get from a vacuum is actually pushing happening everywhere other than the vacuum. And that pressure is not unlimited, which means if you can create a “suction” scenario which involves as much pressure as the surrounding atmosphere, the suction fails.
I’m explaining this really badly.
Here’s a mental experiment: you take glass test tube, you dunk it underwater so all air is gone, then you invert the closed end of the test tube above the water level. What happens? As long as you keep the opening under water, there’s no way for air to get in and the tube stays full of water.
What happens if you use something bigger than a test tube? Some people put entire fish tanks jutting up over the surface of a pond and it lets fish swim *up* into the fish tank to look around.
The water stays up in the fish tank, again because there’s no way for air to get in.
So does that mean you can keep lifting more and more water above the surface of the pond, assuming you never let the opening to your glass tank come into contact with the air?
No. What happens eventually is the total water you’re trying to lift out becomes too heavy to be lifted that way, and you get a bubble at the top of the fish tank anyway. Except it’s not an air bubble; it’s a vacuum bubble. It’s a bubble full of empty space, not full of air.
There’s no way for air to get in, but vacuum doesn’t need to get in. Vacuum can be “created” anywhere just by pulling the matter out of a region of space.
You know what? I don’t think I’m explaining this well at all. TL;DR is the second reason you can’t siphon long distances is that if you’ve got a rise of more then about 30 feet, you get a vacuum bubble in your tube and it breaks the flow.
The why of this has to do with stuff you learn in fluid mechanics 101, and it’s a really great thing to understand but it takes a little concerted effort to memorize and internalize the rules about how pressure works in fluid.
Because 80% of the water in California goes to agriculture. And 10 to 12 % for watering lawns.
And Los Angeles sends it’s treated sewage water to the ocean instead of piping it back to spreading basins to recharge aquifers. (every US city on a river treats it’s sewage to drinking water standards before discharging into the river and the cities downstream make sure they do. )
So there is really no need for this massive project when they have not done other things to change water usage.
Among many, many, many other reasons, we can’t predict where floods will occur with any consistency. Knowing where to build this massive expensive infrastructure would be impossible
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