I like to start by namecalling.

I must say, the Pacific Institute has balls of steel. They do what everyone else is scared to do: they predict how much water could be saved by changing how agriculture uses water. They give estimates, say that efficiency measures could save 3.4 million acrefeet. This is important. Now we know that the Pacific Institute is talking about more water than new dams would yield. Even more audacious, the Pacific Institute says that agriculture can save a couple reservoirs worth of water just by using more sophisticated irrigation methods and crop shifting. It can still be ag! Better ag! It can be even better ag, and we can have another 3.4 million acrefeet of water!

There’s a reason everyone else is scared to do this. If you ask ag water experts how much water can be saved (or how much is wasted, the same question), the answer is a lot of hemming and hawing, until they collapse into “it’s complicated.” This makes everyone outside of ag crazy. How complicated can it be? Tell me how much your crop needs and tell me how much you put on. My brain tells me the difference is the amount you wasted. The ag expert says no, it isn’t like that. We don’t know very precisely how much water the crop needs. It changes! It changes with the weather and time of year and stage of growth of the plant and what you want the crop to be like and what you want next year’s crop to be like. But, if you insist, we can make a rough guess. You know what else we don’t know? How much water we put on! Hah! Take that, Mr. Fancy Subtractor! OK, there has been a lot of improvement here too and a lot of fields are measured now. If they exist, those measurements are probably good within ten or fifteen percent (pg 8). Now you’re subtracting a rough amount from a rough amount, and the range is pretty big, maybe twenty or thirty percent of your totals. In fact, that range is just about the swing between inefficient water use and efficient water use.

That’s OK, say people who are determined to chase this down. We’ve worked in complicated systems before. Everyone thinks their system is complicated. Tell me, is there anywhere else the wasted water could have gone. Yes! Three places. Two of them are invisible! It could go into the air, through the plant or just off the ground, both of which are hard to measure! It could go underground, which you can’t see and lags by days, months or years and you need permission to measure, which you probably can’t get, and is different in the next soil lens over! It might also run off the end of my field. In that case, it might go to the next grower, who also irrigates his crops with it. Or it goes into a drainage canal, which is the last pitiful remnant of habitat left in the county. Or it goes back to a river, hot and full of pesticides. That might happen three or four times. So tell me, Mr. How Hard Can This Be, is it wasted? Remember, whatever you calculate for this field can’t be extrapolated to another crop type on a different soil type or different location in the region.

The problem is genuinely difficult and most people retreat about now. But the Pacific Institute is not afraid. They made rough guesses, well qualified, and give enough of their methods and calculations to be critiqued. Like all sensible modelers, they aren’t vested in any precise output of their model, but think it offers useful ballpark information. This is entirely respectable and their report just radically stretched the boundaries of the conversation about ag water use in the direction of efficiency and conservation. This is great. Sadly, I find the critiques of the model to be pretty persuasive. I think their rough guesses are too broad. I do not think 3.4 million acrefeet of water can be saved in the ag sector without substantially shrinking California ag.