9 Feb 2012

Water rights: diversion or consumption?

One of the first complications we run into when discussing water rights is how to quantify them.*

Consider an example of an irrigation canal that carries 100 units of water shared among 10 farmers. If each farmer gets an equal share towards diverting that water, then each farmer can take 10 units from the canal.** But these diversions are not the same as consumption. Irrigation with 10 units of water does not mean that the crops will consume 10 units. Consumption varies with irrigation technology. Drip irrigation may use 95 percent of the water (with the rest evaporating or sinking into the soil); flood irrigation may only result in 20 percent consumptive use -- most of the water flows off the land and back into the canal. These return or tailwater flows mean that 100 units of diversion will not result in 100 units of use; excess tailwaters flow downstream. Farmers who do not like this "waste" tend to allocate water in terms of consumption, so that a farmer with 10 units of consumptive use (and 66 percent irrigation efficiency) may divert 15 units of water to use 10 units. Farmers allocating 100 units of consumptive water will not leave any "waste" to their neighbors (or the environment).

Those are the facts. The interesting question, now, is how best to encourage efficiency among those farmers.***

We can create an incentive to use less water by raising the price per unit of water diverted to the farmer, allowing farmers with a right to 10 units of consumption to sell some of that consumption, or by imposing an assumed "efficiency parameter" on a farmer, i.e., assuming that a farmer with 10 units of consumption rights only needs 12 units of diversion to get 10 units of consumption.

Each of these solutions (individually or together) suffers from an important flaw -- the need to track water consumption. Such tracking is important when a farmer claims he is only using eight units of water and wants to sell the other two or only pay for eight units. It's also a problem when the farmer uses more water than assumed by the efficiency parameter (11 of 12 units, for example).

It thus seems easier to speak in terms of a farmer's water diversion -- something that's easier to measure -- and then ignore the amount of water the farmer uses. Thus, we can have 10 farmers taking 10 units each and ignore their return flows, assuming that anything that makes it downstream is a bonus.**** Such a system would be easier to administer. Efficiency would rise if farmers found ways to increase consumption for each diverted unit (reducing their payments for diversions) or sold their "unused" tailwater to others. Sales of diversion-based water rights outside of the area would tend to cause problems downstream by removing all return flows; such an event could be avoided by quantifying sales/export in terms of consumption, but that number would require measurements of consumption that was not tracked in the past.

These are just some thoughts on how to measure rights for markets or administrative purposes.

Please add your own thoughts, corrections and questions.

* It's worth noting that the word "right" can create emotions out of proportion to their function. It may be better to call them entitlements or licenses, to make it easier to retire "paper water" that will never be allocated with wet water or to facilitate trades by reducing the emotional burden of selling one's "right" (see my discussion in my paper on All-in-Auctions).

** We ignore "head water" flows in the canal that keep the canal wet and make it possible to carry 10 units to each farmer.

*** We are ignoring environmental flows, which are either taken care of separately from the farmers' decisions or are augmented by purchases from farmers who use less.

**** Mike Young, while discussing this point, indicated that downstream users (farmers or environmentalists) would count on these flows as rights. They would object to a decrease in flows that might result from greater efficiency (more use) by the 10 farmers.


Joan said...

Often criticized, area-based irrigation pricing schemes (farmers pay for hectares of irrigated area) may be a better way to account for real consumption then volumetric pricing (based on diverted flow). Crop types are generally quite homogeneous within an irrigation scheme so roughly speaking consumption is also in the same range, if under the same irrigation practices.

Major flaw of course is that this pricing mechanism doesn´t give the farmers any incentive to invest in techniques that reduce the non-beneficial consumption, i.e soil evaporation. So they will continue to use flood irrigaiton instead of drip, f.e. But maybe this could be accounted for in the pricing mechanism, charging farmers more when they use non-efficient techniques. It´s relatively easy to check for their irrigation infrastructure.

Bottom line: pricing of irrigation should be based on beneficial consumption. Volumetric pricing does not take into account the basic principles of hydrology (evapotranspiration and return flows)

Eric said...

I would like a discussion of 'rights' that quantitatively included all the externalities. You can measure water sent to a farmer or a private lawn or an apartment building or a public park. Then what?
If an entity uses water, it is not consumed in the sense of burning a log. Almost all of it passes through the entity to be available to some other entity downstream. Downstream can be an aquifer that recharges slowly, a cornfield three hundred miles downwind, a mountain snow pack, an aluminum smelter, or a salt marsh. That entity then passes almost all of the water it gets downstream. Each entity needs its water to survive. Many upstream entities can waste water by causing it to evaporate more than normal or causing it to reenter the ground through leaky pipes.
All these wastes or diversions are connected through the fact that water molecules are seldom actually consumed. They are just passed along.
Please discuss these quantitative connected externalities in some comprehensive plan that is more global than 'put a water meter in every farm.'


Joan said...

@ Eric, I think your line of thought is similar as mine and David´s. Indeed, proper water accounting should be done, based on consumption, and volumetric pricing (´put a water meter in every farm´ as you say) is too simple and does not easily lead to increased water productivity.
Just one comment on what you state as ´water molecules are seldom consumed´: indeed they do not disappear from the system, but when they start being in the gas phase (evapotranspiration) they can be considered as lost or consumed from the perspective of the irrigation district or basin. They will of course condense in some cloud but most probably far away. In many basins in the world, all the water molecules falling by precipitation on the basin are consumed (by evapotranspiration) before they can reach the sea, which means that almost no or zero flow enters the sea.

Eric said...

@ Joan, The reason that I put in the cornfield downwind was to allude to evapotranspiration. A key place where evapotranspiration is critical is in a rainforest. If I remember correctly, in the rainforest of the Amazon, the water that falls in the Andes cycles into clouds, rain, clouds ... twenty times between falling in the Andes and reaching the Atlantic. Without this cycle, there is not rainforest.
How should such things be incorporated into a viable model of water management?

Mr. Kurtz said...

Some of this stuff has been adjudicated, but I will defer to someone with a legal background and/or a professional water manager to comment on issues like what constitutes beneficial use as opposed to waste. At least in California, conserved water can be sold without threat to one's water rights. Assuming the sales price is adequate, that alone is a big incentive to invest in conservation projects.
Let me throw one more thing into the mix: "carriage" water. That's the water needed to carry any volume in a ditch of a given size. For instance, if a canal or pipe is designed to carry 60 second-feet, and the upstream users (who hold, for example, the rights to 50 of those second feet) have installed drip systems that eliminated all their run-off, the guy at the end of the pipe who is supposed to get the remaining ten feet gets just a little piddle which never makes it out the end. He'd need another 10 feet of "carriage" water to get the ten he is entitled to. That remaining ten feet goes on its merry way to the ocean or the next guy.
BTW furrow irrigation can be extremely efficient depending on soil types and leveling. It is essential to manage salts (even in drip fields), and uses far less energy (and plastic) than other systems.

Eric said...

Is there a wiki or something even more flexible someplace where these issues can be laid out and discussed in a longer and more nonlinear format than seems to fit into a blog?
I use wiki-like sites for discussions of complex topics. Two current ones that I run are on entrepreneurship in Los Alamos, NM and on the scientific and theological aspects of the Shroud of Turin. For the Shroud of Turin, there are many complex, interrelated issues that all must be digested and then put back together in order to have a credible answer to 'What is the Shroud of Turin and how do we know?'

It feels that a thorough discussion of water issues is at least as complex.


Jay said...

* I agree that the word "right" is emotionally loaded. As property it seems that water rights have the potential to have been awarded suboptimally. Demand for water has exploded in many watersheds. Values have changed since rights were established with environmental flows better understood and now valued more highly now than in the past.

Allocation of electromagnetic spectrum may have similar issues with award of water rights. Reallocation of spectrum has the potential improve efficieny and encourage new technologies and new uses. Are there mechanisms to reallocate water rights that would encourage improvements in efficiency and assure environmental flows?

DC said...

The issue is even more complicated. (Of course it is, this is water.)

Suppose in Year 1, Person X establishes a right to divert 100 units from the previously untapped Virgin River. Under that right, Person X then puts the water to a reasonable and beneficial use (as locally defined), and then disposes of the non-consumptively used portion of that water back into the Virgin River (cleaned up per local treatment rules). Further suppose that by year 10, (after the right has been fully developed) the return flow is 50 units.

Suppose that in Year 10, Person Y establishes a right to divert 50 units of water from the Virgin River, and with that right the river is deemed fully appropriated. Person Y also puts the water to a reasonable and beneficial use, and returns 25 units into the Virgin River. Essentially, Person Y has established a right to divert Person X’s return flow.

Time goes on. Person X wants to do more water using activities, but as the Virgin River is now fully appropriated, Person X invests in water use efficiency projects and then puts the conserved water to a reasonable and beneficial use. So, Person X is still diverting 100 units, but now by being both more efficient in use and expanding use, is returning only 25 units into the Virgin River.

What happens to Person Y? In the absence of some legal intervention to readjust Y’s right to divert (which is not a given), Person Y will continue to divert 50 units per Y’s rights. The Virgin River would thereby be over appropriated by 25 units.

One option would be to condition rights to divert on some minimum return flow, essentially shifting to a quantified right to consumptive use. This would require meters on both the intake and outfall, and is at least technically feasible (politically feasibility is a different question). And, it wouldn’t upset the basic rule of allowing transfers of truly conserved water.

But what about groundwater? Measuring deep percolation by each groundwater user would be challenging at best, and efforts to regularly and rigorously quantify consumptive use have been less effective than desired, at least so far.

Don’t know if this helps or not

JD said...

Your post sparked interest when I saw it this morning as its connected to things like rain water capture, recycled water rights etc... heck we have a client who doesn’t want us to use the word “loss” to describe leaks in their distribution system as some board member thinks that may affect their water rights…..

Ron Griffin said...

The academic literature tells us that a single instrument (diversions v. consumption) is inadequate in the water case due to social issues about instream flow quantities. Consumption seems most important overall, yet diversions do reduce instream flows over some stream segment until such point that return flow might reenter or otherwise become available for downstream reuse. Hence, both are uniquely relevant in many situations. Unfortunately, whereas diversions can be readily measured, consumption must be modeled due to its diffuse nature, much like a nonpoint pollutant.

CC said...

Things to consider/think about such as "carriage water" and how water sales might impact other farmers' water rights, ie, when someone sells their water rights upstream, whats happening with the carriage water (maybe what you refer to as "headwater").

We always need to keep in mind that a farmers "waste water" has beneficial uses, one its either somebody's water supply, groundwater recharge, or may be helping maintain wetlands or other environmental uses. Farmers would like to get credit for return flows and if they are charged based on diversion, then they should credited imo. Also when there is water right sale off the farmland to M&I, when farm water is curtailed, is the sale water right also being curtailed?, it should be, imo.

I think its important to not make "farmer efficiency" the main goal, because there may be unintended consequences/impacts. Is efficiency about producing more food/diversion unit or is it about the overall water use? then you need to consider what is happening with the "waste water".

I believe farmers want to be efficient, esp. if they are paying for diversion, they are running a business. However becoming more efficient may require upfront money they may not have to invest and the returns may not be worth it.

CH said...

Re water rights under western U.S. appropriations doctrine: a new water right (never used before) is specified in terms of DIVERSION rate at a particular site for a particular "beneficial use" use, e.g. ag . Through use over time, the period of use (e.g. May-Sept) and total consumptive use are established. When a transfer is proposed, the typical practice is to allow the consumptive volume per season to be diverted at the new point of use, at the original rate of diversion. In the new use and in any subsequent uses stemming from future transfers, the total consumptive volume may be "used to extinction", i.e. totally consumed.
That's the way I understand it anyway I'll admit it leaves particular situations a bit unclear. That's why water lawyers do so well!!

Jay said...

A couple of thoughts occur to me.

River flows can vary by ORDERS of magnitude during each year and between years.

Precision in calculating comsumptive uses versus other uses seems misguided. In an analogy to financial markets precision is no substiute for accuracy. When randomness is large, trying to calculate second or third order affects leads to adverse outcomes illustrated by the Long Term Capital debacle that confused correlation and causation. Another example of this kind of thinking is the high ratings on subprime mortgage pools prior to the mortgage market collapse.

As a bridge designer I am well aware that low probability floods seems to occur at frequencies far above those predicted by historic models. I suspect low flows also demonstrate more extreme behavior than predicted for some of the same reasons.

Bottom Line: Precision in calculating available water rights may leave no factor of safety. Sustainability requires an adequate factor of safety in the face of uncertainty.

Eric said...


Could someone explain how this work fits into some coherent overall picture?


chris corbin said...

I'm all for developing appropriate standards (e.g. 1 acre-foot per acre) and applying consumptive use. This help overcome the 'adverse effect" barrier to trade.

Here are some more thoughts on this topic



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