12 May 2015

A thought on pricing water for evaporation

JD emails:
As I was contemplating data in a water conservation plan, it dawned on me that it should be possible to charge more for water used for irrigating landscape. As since it is actually lost to the atmosphere, consumptively used (in large part), and therefore not (locally) recyclable like most indoor water use is, it does pose a higher cost on the local water supply. Higher costs could also be attributed to salinization, since consumptive water drives that problem.

Accounting for outdoor use could happen with separate landscape meters, or wet weather billings ["winter use"] to establish the indoor baseline above which use is considered irrigation. In fact, separate metering may not even be needed, as remote sensing can measure consumptive use down to the square meter (with drone technology these days).

So, given that the base water rates must remain non-tiered (i.e., constitutional), this surcharge would apply to all in theory, but practically only on large consumptive users.

Of course the drone replacement cost (as people shoot them down) will need to be figured J
I agree with JD's ideas: California ALL utilities can apply a scarcity surcharge based on outdoor water use (use above baseline set in winter) to reflect the "cost" of water lost to evaporation that cannot be collected and recycled.


JD said...

I liked your conceptually similar example of Singapore where they charge more for water leaving on ships based on the fact that it too will not be locally recyclable.

I also understand Australia also applied this idea to export crops during the depths of their severe drought...ie water was too valuable to export.

Of course the next step is perhaps those that benefit from the evaporation may wish to subsidize such use...ie Colarado River Basin from California....in which case we better have figured out a system that allows appropriate price signals to develop.

JD said...

It sould also be noted that my musing was in the context of the court ruling that simple tiered pricing (w/o a nexus to actual cost) is prohibited by the CA Constitution.

Jim said...

We measure the volume of potable water going into the residence. Couldn't we also measure the volume of sewage leaving the residence. The difference would be a direct measure of the consumptive use.

JD said...

Where possible that would work. Hard (costly to do reliably) to measure sewage flow at the house level, but most muni systems can do it for each sewer "watershed" area as pump stations / treatment plants have meters.

The remote monitoring technology can cover the State (to sub acre level) about weekly and drone or aircraft can bring it down to square meters of resolution. The remote monitoring technology wouild also pick up evaporation loss from un-irrigated plants, such as trees, that are tapping the groundwater directly, or from rain barrel irrigated plants, that would be missed by the meter in and out method.

Not that I am against trees, or rain barrels, but their draw on the resource needs to be considered in the full management picture. (Much of rain barrel water has a downstream use....unless you're located near terminal drainage, ie the coast.)

David Zetland said...

That's done in some places. I argue in my book that it's not really worthwhile b/c water that leaves the property "saves money" on treatment while water that's collected can be reused. Thus, it's a bit of a wash in terms of cost to the utility. THAT said, you may want to price one if quality is more/less important than quantity.

Jim said...

Water that does not get back into the sewer system can not be reclaimed and sold again. In Southern California, water that leaves the system might, in the not-to-distant future, be a loss to ratepayers instead of a savings.

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