[wnissen]

The people consume only a fraction of the water and it's dishonest in the extreme to say that things would be "fine" without them. Each ton of alfalfa in California consumes more water than a family uses in a year and yet sells for $200. There were 13 million tons sold last year. If we got rid of the low-value forage crops, the people (who would pay a hell of a lot more than $200 a year) would have more than enough water.

[protomyth]

So, as an intellectual exercise, if the Los Angeles and San Francisco metroplexes simply vanished, would there be enough water?

[plorkyeran]

Agriculture is responsible for around 80% of California's water usage, so even if every person in the state vanished and the farming was done entirely by robots things wouldn't change much.

[thaumaturgy]

I don't know. Let's see.

LATimes has an article from last year on high and low residential per capita water usage (http://www.latimes.com/local/california/la-me-1105-californi...). Using that, let's estimate a .5kgal/person/day usage for San Diego and Orange counties, and a .05kgal/person/day usage for the San Francisco region. (The difference in those numbers was surprising.)

The most recent census numbers estimated the Orange County population to be ~3.1 million people, Los Angeles county to be ~10 million people, and San Diego county to be ~3.2 million. San Francisco county is about .8 million. Let's add in Contra Costa, San Mateo, Marin, Alameda, San Mateo, and Santa Clara counties at roughly the same per capita usage, with populations of ~1.1 million, ~.8 million, ~.3 million, ~1.6 million, ~.8 million, and ~1.9 million people respectively. At this point, we've accounted for ~23.6 million of California's ~38.3 million residents.

Crunching the numbers, this works out to ~8.2Mgal/day for the southern California region's residential water usage, and ~.4Mgal/day for the Bay Area region's residential water usage. (Check my math, but I don't think I screwed it up.)

According to an article from Slate (http://www.slate.com/articles/technology/future_tense/2014/0...), almond farming alone in California uses roughly 3Ggal (that's three giga-gallons, or three billion gallons) of water per day.

Or, to put it yet another way, if we decided instead that about 23.6 million people were worth some almond farms, we could balance their entire water usage by reducing California's almond farms by less than 1 percent.

So, no, there would not be enough water if those metroplexes simply vanished.

[Smushman]

It is hard to tell if you are trolling, a California farmer, or just being plain obtuse.

tl;dr - NO. It would not make a difference.

Google your question. The answer is below for you.

Source: KCET article. February 10, 2014.

California's water budget is skewed heavily toward agriculture. The conventional estimate is that 80 percent of the water used in California flows into the state's multi-billion-dollar agricultural sector.

[protomyth]

No, I'm actually asking the question since Wikipedia's quote is "In an average year, about 40% of California's water is used for agricultural purposes". Which makes me wonder about how far down California is that it is now 80%?

[whyenot]

The figures used in the Wikipedia article include "environmental" water use (water that flows to the sea in streams, etc. most other sources do not include this in their figures. Environmental "use" accounts for 50% of total water use in the state and why Wikipedia's 40% for Ag is everyone else's 80%.

[wnissen]

It depends on how you count, due to overlap, such as rice paddies that are flooded with water releases that eventually head downstream. That could be counted under environmental or ag. If you take out the environmental water, ag is 80%.

[no_dumbass]

No.

http://www.kcet.org/updaily/socal_focus/commentary/where-we-...

> The drought has changed all that. Now, management plans are being looked at with care as California nears a 2020 deadline to cut the state's overall water use by 20 percent. [which would move us close to sustainability]

> About 14 percent is poured into bathtubs, toilets, and washing machines or sprayed over residential lawns.

We'd need a residential population of -30% of California's current population.