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The Los Angeles Aqueduct Is Wild

practical.engineering

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Re: The Los Angeles Aqueduct Is Wild

#91

Post by devilbunny »

andrewflnr wrote: post #71
ceejayoz wrote: post #62

Earlier quoted context omitted.

https://www.nycfoodpolicy.org/10-facts-you-may-not-know-abou... > New York City’s water (including drinking water) is unfiltered, making it the largest unfiltered water system in the country. Were New York to begin filtering its water, it would cost the city approximately 1 million dollars per day to operate the filtration plant. They have hundreds of sampling stations to check daily. https://www.nytimes.com/2025/05/…

Ok, but unfiltered does not imply untreated. Maybe that's where they got the idea, though.

It is, indeed. I'd edit the post but... too late.

Re: The Los Angeles Aqueduct Is Wild

#92

Post by rtkwe »

bombcar wrote: post #87
rtkwe wrote: post #81

Earlier quoted context omitted.

They wouldn't if you switched just Urban water use from natural sources to desalination. To do that you need to replace the ~5 million acre feet of water, ~6,167,400,000 m3, that goes into the Urban bucket which is all of the water used to keep people alive, clean, and all industrial uses of water. [0] That comes to ~ 12BkWh of energy needed to scale up batched reverse osmosis to take over just the life and job requi…

Those are the numbers I was looking for - that means that (ignoring build-out costs) total desalination for CA would be on the order of 10% of the 3 gorges dam yearly output (max).

Using a system that's currently in a lab scale only and ignoring other energy costs like moving the water to the plant, mixing the briny output back down to acceptable levels, and then pressurizing the system to replace the gravity fed design it currently uses.

For a rough estimate for replacing agricultural uses too ~6x that urban figure at least then weep at the amount of pumps you'd need to bring that water up and inland to the farm lands from the coast. At least for replacing urban use most of the population lives on/near the coast where the water would be produced.

Re: The Los Angeles Aqueduct Is Wild

#93

Post by kenhwang »

vondur wrote: post #90
kenhwang wrote: post #57

Earlier quoted context omitted.

Owens valley, where LA "steals" water from, is on the eastern side of the Sierras. NorCal, including Sacramento, is on the western side of the Sierras. So unless they planned on pumping the water over/under the mountain range that surrounds it in every direction except for towards LA, that water was never available for any NorCal city to use.

Owens valley is basically dried up from the water that LA takes. It's interesting as you drive in the towns in the Valley and you see all the LA Department of Water and Power offices over 200 miles from Los Angeles. The courts had to force the LA DWP to quit taking too much water from the streams that feed Mono Lake as it was in danger of drying out.

Yep, Owens valley is basically an environmental disaster created by LA. So in the grand scheme of things, buying water from NorCal is better than stealing from the Owens valley through antiquated water rights.

But really, California (and really the entire Western US) needs a water rights governance overhaul. Right now the focus is all on urban water use, which is practically negligible compared to the agricultural water rights usage.

Re: The Los Angeles Aqueduct Is Wild

#95

Post by chrisrogers »

weaksauce wrote: post #49
hamdingers wrote: post #38

Earlier quoted context omitted.

There is no water scarcity in California, only misallocation. The vast majority of our water is heavily subsidized and used for agriculture, and a substantial amount of those crops are grown for export, yet agricultural exports makes up an insignificant part of California's economy. We could end all California water scarcity talk today, with no impact to food availability for Americans, by curtailing the internationa…

to put this to numbers... the exports are just about 0.5% of california's GDP. so yeah pretty much a rounding error.

0.5% is a far cry from a rounding error..

Re: The Los Angeles Aqueduct Is Wild

#97

Post by masklinn »

jonathonlui wrote: post #47
rimunroe wrote: post #13

I was surprised to find out it was largely uncovered, though I guess it probably makes it much cheaper to construct. I usually think of aqueducts as pipes or tunnels, like Persian qanāts. I wonder how much water is lost due to evaporation.

There's some testing to see how covering open irrigation canals with solar panels which would reduce evaporation and generate power > Their analysis found that putting solar panels over the 4,000 miles of California’s open canals could save up to 63 billion gallons of water annually https://www.universityofcalifornia.edu/news/solar-panel-cove...

> could save up to 63 billion gallons of water annually

To put it into perspective, 63 billion gallons is 193340 acre-feet, which is 0.5% of california's water use (a bit under 40 millions acre-feet). That's a tenth the water consumption of lawns, which is 1/15th the water consumption of agriculture.

Re: The Los Angeles Aqueduct Is Wild

#99

Post by kenhwang »

coryrc wrote: post #69
hamdingers wrote: post #38

Earlier quoted context omitted.

There is no water scarcity in California, only misallocation. The vast majority of our water is heavily subsidized and used for agriculture, and a substantial amount of those crops are grown for export, yet agricultural exports makes up an insignificant part of California's economy. We could end all California water scarcity talk today, with no impact to food availability for Americans, by curtailing the internationa…

Almonds are climate-appropriate product and valuable. Alfalfa can cheaply be grown off rainwater in the Midwest and it alone frees up sufficient water.

The problem is alfalfa is expensive to transport (heavy due to desired moisture content). So while it can be cheaply grown in the Midwest, it can't be cheaply transported from the Midwest to where buyers of alfalfa are (typically overseas).

Alfalfa is also a staple for crop rotation, so any farming operation will still grow some alfalfa to maintain rotation for good soil health (or during bad condition seasons since it's hardier to poor conditions and not a permanent crop).

If alfalfa cannot be exported (through policy or economic conditions), the low price attracts more livestock production in-state (which would be even worse for water use).

Those things makes it a hard crop to target for sustainability and export.

Re: The Los Angeles Aqueduct Is Wild

#100

Post by panzagl »

chrisrogers wrote: post #95
weaksauce wrote: post #49

Earlier quoted context omitted.

to put this to numbers... the exports are just about 0.5% of california's GDP. so yeah pretty much a rounding error.

0.5% is a far cry from a rounding error..

0.5% is like the literal definition of a rounding error.
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