California needs 11 trillion gallons of water to recover from ongoing drought


#1

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#2

Really? Only 42 cubic kilometers?

California’s area is 423,970 km². So dividing 42 km cubed by this number, we get .00009906 km, or 9.906 cm. That would say that we only need 3.9 inches of rain, on average, to end the drought! That can’t be right.

This is a typical problem we have with big numbers; they are meaningless unless put into perspective, and it helps to scale them. For example, to put government spending into perspective journalists should always give the number of dollars per person: if the US spends a billion dollars on something, that’s about $3/person. People can grasp $3, they can’t grasp a billion dollars.


#3

Yeah it’s totally meaningless to express it this way. They way they should have expressed it is in terms of average annual rainfall. For example we need the average rainfall to just keep everything where it was (more or less) and we’d need 10% more every year for ten years to replenish groundwater. Or something along those lines.


#4

Amazon!
(Not the river)

Drones could bring water from nearby lakes. Really.


#5

Aren’t they measuring the “water debt” to water table, not the amount of necessary rain? Quite a bit of rain doesn’t get absorbed and simply runs off. You would need substantially more than 3.9 inches of rain to get 3.9 inches into the water table.


#6

This is the storage deficit, not the total precipitation deficit. There’s about 40 million acre-feet of surface storage capacity, about 150 million acre-feet of groundwater storage capacity, and this number – 11 trillion – reflects about 32 m.a.f. You get on average about 200 million acre-feet of precipitation in California in a given, average year.

They mean we need to put 11 trillion gallons back into storage.


#7

I wonder if desalination techniques will ever become cheap and practical enough to meet needs like that. California has the whole Pacific Ocean right there - water, water everywhere…


#8

For urban use? Sure. It’s already done in parts of Australia. It’s providing enough water for agriculture that’s tricky.


#9

I wonder if we’ll ever have something akin to a “water grid” in the USA where we can shift resources when necessary? I mean, we can already do that somewhat with reservoirs and the like within certain boundaries - as well as the famous CA Aqueduct.
And in ever-more populated dry areas, we certainly need to look into better capture of rain. As a Southern CA resident, it’s sort of sad to watch the rain just run off into the ocean (No surfing for a couple days for my friends), though I know in the big picture the snow pack is the most important of our yearly storage as of now.


#10

Let’s not forget that you get more run off during a drought than you would normally get. Baked hard ground means you get flash floods during rainstorms rather than it going back into the ground or evaporating.


#11

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