Mr. Fitzgerald does something very handy in his opinion piece. He very roughly estimates the volume of water the State Board’s new Delta flow recommendations would keep in the Delta, which illuminates something crucial. His ballpark estimate is that the flow requirements to maintain native fish populations in the Delta would translate to about 7.5 MAF more water that has to make it to the Delta and flow west. The important thing that I want everyone to see is that I am so fucking right. We can convert this in our heads by now.
7.5MAF of in-Delta water * (1 acre of ag land/3 AF water) = 2.5 million acres of ag land out of production.
This is all extremely rough, with lots of factors in both directions.
For ag:
There’s no way Delta fish are going to get all those flows.
Some of the flows can do double or triple duty, go through the Delta and get used again.
Maybe some of that water would come out of urban, not ag. (I crack myself up.)
Against ag:
This is just the Delta. Imagine if we had real instream flow requirements for all the rivers in the state.
We’re going to have less water in general, falling in a form we don’t have capacity to catch.
I’m telling you. California ag is going to decline from 9 million acres to 6 million acres in the next few decades. If you are in ag and do not have the among the safest two-thirds of the ag water supply, your farm will not have water in 2040 and later. Do not plant orchards. No vines! If your self-identity requires farming, sell your land while someone might still buy it and buy farmland on the east side or the Sac Valley. If you are with the Farm Bureau or the Farm Water Coalition, you should be playing on the image of family farmers to extract the best transition terms from the rest of the state for that bottom third of farming*. Fighting to keep the third of farmers with the least secure water supply in business is fighting against the inexorable forces of climate change, population growth, and rising energy costs. I know you hate the liberal hippie scientists and big government, but they’re not the source of farming’s problems. They’re the messengers, reporting that the physical world is changing in ways that will make a good chunk of the farming that we do now in California impossible.
*In their ten year drought, Australia went from 14,000 farmers in the Murray-Darling Basin to 5,000 to 7,000 farmers. They lost more than half their farmers. I’m predicting that we’ll only lose a third of the farmed acreage in California by mid-century. Faster if the drought happens sooner.
On the public record 
I wonder if losing half the farmers translates to losing half the acreage. 80% of the farmers might work 20% of the acreage, or if bought out, it could represent zero acreage loss.
What could ag water conservation save? Can you get down to 2 AF/acre with drier crops, less evaporation, etc?
Hey Scott! Wow, it has been a while. It is so nice to see you.
I think of 3af/a as a floor; that’s already pretty well managed. Below that and you’re talking about different types of crops, ones that evolved for very low water requirements.
ET includes evaporation and transpiration. You don’t usually see those two separated out. Theoretically, you only need the transpiration part (that goes through the plant), but in real life, some of the water is exposed to the air (on the soil or plant leaves) and it gets evaporated. The best you can do would be to only apply the amount for transpiration, but the technology to do that (subsurface drip) isn’t always possible or cost effective.
(In the olden days, like the 80’s and 90’s, it was real common to see 5-7ft of water applied. 14 feet on rice. Seeing 3.5ft on row crops and 5 feet on rice is already pretty good.)
“The best you can do would be to only apply the amount for transpiration, but the technology to do that (subsurface drip) isn’t always possible or cost effective.”
…Whoa. What does that do to the rest of the soil?
Dries it out and salts it. I was skipping the salt flushing requirement, but I can see that y’all are too savvy for that.