Monthly Archives: December 2008

Happy New Years!

The next few posts were written to be read from the top down.  Hope you like them.

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Field and basin efficiency in general.

The junkies among you can read a more technical description of field and basin efficiency here, or see a sketch of a description in this slide show (which only makes sense if you already know the topic).

The reason I don’t like to talk about field and basin efficiency is that ag advocates are known to do a sorta bullshit sleight of hand, saying that their “efficiency” is some amazingly high number (anything higher than 90%) and so they don’t need to listen to any more of this talk about new irrigation practices. If they are talking basin efficiencies, that means that for some large boundary, perhaps their water district or a watershed, the amount of water they collectively apply is only barely more than collective crop demand, and presto! Everyone in that area is a very good irrigator. Except they don’t really say “basin efficiency”. They say “efficiency” or “district-wide efficiency”, and hope that you will be suckered into thinking that they mean the average of every single grower’s field efficiency.

Field efficiency comes from matching irrigation water to crop demand on a single field or small farm. This is the realm that individual farmers can influence, with the type of techniques that the Pacific Institute talks about (irrigation scheduling, crop shifting). If every single grower had an field efficiency in the 90s and you averaged them to get some average field efficiency in the 90s, that would indeed mean that you are talking to very skilled irrigators who don’t need any advice from you. But having a basin efficiency in the 90s doesn’t mean everyone is doing a good job applying a precise amount of water. It just means that water gets used again and again within the big boundary area.

I kinda resent giving the idea of basin efficiency much credence, because some advocates use it in a sneaky way to imply that all their irrigators are doing a good job. I also don’t like that some advocates use the idea of basin efficiency to say that there is no good reason to improve their practices on the smaller field scale. This isn’t true, as both the irrigation professors and the Pacific Institute report point out. What high basin efficiency can look like in practice is that growers overapply water at the top of the basin and other growers use it again, as tailwater with pesticides or fertilizers or salts in it. Or it sinks into the ground and other growers pump it out. Or it returns to the river, salty and warm, and gets diverted again. You could still have high basinwide efficiencies, but you pay costs in water quality or pump energy or crop yield. Taking more water than you need (because it will return soon enough or so that it can percolate into groundwater) hurts the rivers it was diverted from; fish would like to live in that clean cold water until the very last second before it gets used. So yeah. There are real problems with using high basin efficiencies to give yourself a free pass.

On the other hand, there is no denying that it exists. A lot of diverted water gets used several times. It is a cheap way to move water, or at least a way to move water that externalizes some of the costs. Further, people have been living in this connected system for two generations now. I have to think they have roughly optimized their positions and come to rely upon them. Getting someone else’s water after it ran off the field may not be a good way for the system to work, but at this point, I’m inclined to think it is the best bet for that second grower. They’ve had forty years to debate sinking a well or digging a pipe directly to the river. If they thought those were better for them than taking tailwater, I think they’d have done it. Disrupting that system (like, if you had the grower at the top really cinch down on irrigation efficiency) will probably put downstream growers in a worse position. To the extent that it means that they’re internalizing their environmental costs, I’m fine with it. But as much as they perceive it to damage their interests, they’ll fight that.

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Field and basin efficiency in the Pacific Institute report.

Yeah. They missed the ball on this one. I mean, they talk about field and basin efficiency on pages 14-16, but didn’t follow through. If water is used several times in a basin, then the amounts you could save by practices that make each field more efficient aren’t additive. If you improve the top field from 70% efficient to 85% efficient, all the downstream users have also had a chunk taken out of their supply. If they applied management and money to adjust for that missing chunk, their efficiencies would all move upward some small percent. If they don’t adjust their field efficiencies up, they’ll go get more real water from somewhere. Either way, you can’t add up all the yields from improving field efficiencies as if they were separate. Shit. This is hard to explain. Ummm…

The potential for wringing water out of California agriculture is NOT:

(new improved field efficiency – old sloppy field efficiency)(annual applied water) = bonus water for fish AND cities AND still plenty for ag!

It would be like that if all of the farmwater were completely independent. Then you could add each efficiency improvement up separately the way the Pacific Institute report does.

The potential for wringing water out of California agriculture IS:

(new improved basin efficiency – old sloppy basin efficiency)(annual applied water) = not a whole hell of a lot.

Keeping in mind that I don’t like the concept of basin efficiency any more than you do (because people with an agenda use it for evil), when I hear estimates for basin efficiencies in CA, they’re on the order of 95%. Considering that groundwater levels are dropping drastically, I do not believe that there is a free 10% of inefficient water use sloshing around aggregate Great Valley agriculture. It is also worth remembering that is gets pretty expensive to go after the last few percents of efficiency. Your early gains are all big and cheap, but your last gains start to cost real money.

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Missed it by a lot.

Perhaps the most persuasive piece of the irrigation professors’ critique was this text box:

If so much water is being wasted as implied by the estimates of potential savings in the PacInst Paper, it would have to be going somewhere. That somewhere could only be into the ground or out through rivers. But we know that there is a huge groundwater overdraft (perhaps 2 million acrefeet/year) in the San Joaquin Valley and the San Joaquin River runs dry near Dos Palos in the summer.   (emphasis in the original)

It sounds facile, but it is true.  The Pacific Institute efficiency argument says, in effect, that 3.5 million acrefeet of water is sloshing around California agriculture, not being taken up by plants*.  If so, where is it? 


There aren’t many choices.  The Tule Lakebed doesn’t hold a three foot deep lake in August.  Excess irrigation water sure isn’t draining to the San Joaquin River. In fact, look. The western part of the San Joaquin Valley sends about 50,000 acrefeet/year of really gross water to the Grasslands Bypass Project (16,000 af this dry year). Fifty thousand acrefeet a year? Draining the better part of the west side of the San Joaquin Valley? You’ve got to show me a whole bunch more bypass projects to come up with the other 3.45* 1.65 million acrefeet the Pacific Institute says is loose water. Or you could show me rising groundwater levels, as the ground soaks up excess irrigation water. Except you can’t, cause they aren’t there.


The only explanation I can come up with for such a huge gap between building upward from models of field irrigation efficiency and working downward from a valley-wide water budget is double counting. I think the Pacific Institute method of adding up efficiency improvements from all those farms double (and multiple) counts the same chunk of water each time it gets re-used as if it were separate chunks of water from which you can extract 10% every time. That’s why I don’t think there is potential to get 3.5 maf of water from Great Valley agriculture and have ag stay at current levels.






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Which is why…

I think that a report that describes efficiency improvements that let ag farm happily while 10% of the water they use goes elsewhere is a false promise. It is balm for urban users and enviros, who would like to trade money for efficiency improvements for real wet water and still leave ag whole and happy. But that isn’t realistic.  I think ag would contract sharply if big pieces of water weren’t available to them*. If we’re honest, that is the discussion we should be having. Of course water for the uses Californians value will come out of ag water use. It is that, new dams**, or tapping Wild and Scenic Rivers, and all the hippie urban votes will come down against ag. I think we should be planning a managed retreat for agriculture. I don’t think ag should be fighting to protect the acreage they’re farming now. They should be fighting to protect whatever core they value and to extort as much exit money out of the Californian collective as they can.

The rough estimates I talked about a couple days ago can give us an idea of scale. Six million acrefeet of lost snowpack storage? Cities and rivers jonesing for another 3.5 million acrefeet? That’s three million acres of farmland, out of about nine million acres***. Some of that farmland will retire itself. About half a million acres on the west side of the San Joaquin Valley are saltifying (a process that will speed up as climate change makes the weather hotter, which means applying and evaporating even more slightly salty water). We’re gonna lose about 100,000 acres in the Delta as islands collapse. (Sweet graphic here. ) Urban encroachment will take out a bunch more acreage (although perhaps less, now that we have new urban planning legislation to discourage sprawl.). So, you know. Maybe 800,000 acres out of 3,000,000 acres will retire themselves.

The rest will involve choices. We could let it happen without planning, in which case ag will be eaten from the bottom up and by chance, with financially vulnerable farmers collapsing in a hodge-podge. We could institute a water market, which will arrive at an economically efficient outcome, regardless of whether we like an economically efficient outcome. A really fucking stupid way to do it would be based on order of seniority, with more recent farmers having to take the hit first and farmers that have been there a long time being protected until the end, no matter what they grow or how. That’d be unbelievably stupid.

Or, we could choose something. We could decide that we like certain farming practices and preserve the farm acreage that uses them. We could decide what we want six million acres of farmland to look like, on what soils and where and how big the farms should be, and design a system that supports those. We could choose to save the acreage on the best soils. We could choose to maintain the agriculture that supports rural communities. We could choose to retire the acreage that would make the best wildlife habitat when retired. We could decide it isn’t our responsibility to feed the whole country (which has perfectly good farmlands of its own if they weren’t growing corn and soybeans) at the expense of our own rivers. I don’t want to shock you or anything, but what I’m saying is that we could apply priorities to get the best possible outcome from a large, wrenching re-alignment.

But we will not face choices like that, or even admit that we have to make them, if we cling to the hope of efficiency gains that will let us carry on as usual. That’s my real gripe with the Pacific Institute report.





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That’s why I’m so disappointed with the outcome of the Ag Vision process. So much time and comment and thought went into crafting a vision for California agriculture in 2030. Truly, the transcripts of their public meetings are amazing and you should read them for firsthand accounts of what it is like to farm in California*. All that knowledge and expertise, and they came out with a bunch of platitudes? I mean, really? The framework reads like “we want a bunch of obvious good things”.  Well yeah.  I do too.  This is still bigger-pie territory, not facing-hard-trade-offs territory. Bummer.





*Hee. I am not just telling you that you should read government reports for fun. I’m directing you to read transcripts of public meetings for fun. Rock on.

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I will never explain the unit “acre-foot” on this blog.

I’ve been slow to finish up my review of the Pacific Institute report, because that will mean that I have to get into the concepts of field and basin efficiency and I dread that.    I don’t mean to be a tease; I know how badly you’ve been craving more of this series.  I’ll put some peripheral thoughts here,  so we can have a clean discussion of field and basin efficiency and the core conclusion of the Pacific Institute report without them buzzing around and plaguing us.

A thought:

I agreed with the technical critiques in the irrigation professors’ report, which isn’t too surprising, since one of them trained me.  If you have any technical questions about anything in those reports, I’d be happy to take my best shot at answering it.  As much as those critiques cast doubt on whether the Pacific Institute report is identifying real potential for water savings, I’m also a doubter.

Another thought:

I said that I’d critique the Ag Water Management Council’s report.  Here goes.  This is self-reporting by a self-selected group of the most progressive ag water districts.  I don’t think the claims are very impressive; there’s a lot of hedging about how far along the districts are in adopting Efficient Water Management Practices.  That said, these leading districts are alert to the practices and implementing them at some rate unspecified by the report.  I don’t take this report as proof that ag is doing everything it can.  It is more like the best likely spin you could put on ag’s water use practices.  Also, man.  Love the pictures. 

Yet more thought:

For your sense of scale, here are some recent rough numbers.

3.5 million acre-feet/year – the Pacific Institute report thinks this is the amount ag could yield without hurting, or maybe even while doing better.

31.5 million acre-feet/year – this is roughly how much ag applies overall.  Am I really doubtful that irrigated ag could give up 10% of its applied water without hurting?  Are they really so tight that there isn’t 10% slack in the system?  Yeah, I really am doubtful, and I’ll tell you why when I tackle the field and basin efficiency talk.  But OH LOOK!

6 million acre-feet/year – this is how much warmer winters will cost CA in snow storage of water by mid-century.  That’s twice the amount we’re wrangling about in the Pacific Institute report, so as much as the Pacific Institute report seemed to be making bold claims, this should be twice as dramatic.

I’ll give you three more numbers that I find really handy.

10 million acres – the rounded-up area of irrigated ag in California.  It is closer to 9 million acres these days, but 10 million acres is easier to use.

California is about 100 million acres. 

As a very, very rough estimate, one irrigated acre uses about three acre-feet of irrigation water a year.  (This goes neatly with the 10 million acres and 31.5 million acre-feet/year.)

These are the numbers I use to get a gut sense of things*, decide whether a claim is big or little or ridiculous.  You may use them too.





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