Update on previous post

My last post included a feeble attempt at showing that there is some correlation between price and water usage.  The connection, I believe, still stands but a helpful reader made a suggestion that greatly improves the interpretation of the data.  So I switched the x and y axes and tried some other types of regression and came up with a pretty good fit using a power function.  Here's the new graph:

I'll spare myself the embarrassment of trying to explain power functions, but the equation listed on the graph (above the R-squared value) describes the curve and indicates a non-linear relationship between price and consumption.  As might be expected, demand drops off rapidly when price increases initially, indicating greater sensitivity to price at the high end of water usage, then drops off more slowly when you get down towards 50 gpcd, which would mostly be indoor water use (less discretionary).  That seems to make sense to me.

Also, the most recent update from Circle of Blue includes the data shown on the map in their previous update in table form.  And provides sources for the data as well!  Ask and ye shall receive.  The article also discusses the alarming phenomena of falling demand and rising prices that seems prevalent among water utilities recently.  This is an unintended consequence of some of the more progressive rate-setting policies (like increasing block rates) and has been occurring for several years here in Tucson.  It could be largely avoided, most easily by returning to single or seasonal rates for water but that would have other, unwanted consequences.  So until the standard formulas for cost recovery in water rates are changed it will continue to be a fact of life in many cities.

How strong is the connection between price and water use?

I get a weekly email with updates from the website Circle of Blue, that occasionally contains gems like this one that showed up recently. What I've really been impressed with on their site are some of the nifty things they do by combining data with mapping functions.*  So if you scroll down on the Circle of Blue page linked above you will see a Google map that has a bunch of data call out points on it. Click on any of those points and it will show you data on per capita residential water use and average costs for water in each of the cities shown.**

By way of background, I received an email from John Fleck last year where he asked if I knew of a source listing per capita water use that compared "apples to apples" - i.e. comparing only residential water use, not just taking some random total water use number and dividing it by population. This can be surprisingly hard to find.

So as I was looking at the water use data I got the idea that it might be interesting to try plotting the gpcd numbers against the average price numbers just to see how well they correlate. And this is what I came up with:

 If I remember my statistics, 0.3563 indicates pretty strong correlation, but obviously there are other factors present besides price.  You might notice that I pretty much cherry-picked the data I presented as well.  I tried to include data from Western cities that might have similar water use patterns so that price would be main variable being tested here.  Is the result fairly obvious - sure.  But that's often the point of statistics - to test something that appears obvious and try to figure out if it really is.

Oh, and there was one other nice bit of data in the call outs attached to the map - it says what type of rate structure each city uses.  I hope the Circle of Blue folks keep up the good work.

* My only quibble with data presented in this way is that they don't indicate a source for their numbers.  There's an email address for the person who put the graphic together, so I might have to email him and find out where he got all his data from and verify that it really is "apples to apples".

** The data for Fresno is pretty shocking, but when you consider that they charge a flat rate for water and I believe still don't meter most of their connections it seems pretty self-evident.  Also I was disappointed that there was no gpcd data for San Diego and Los Angeles - they're probably pretty tired of taking their lumps for residential water use.

Still here

Yeah, it's been awhile - I know. I hate it when the real job keeps me so busy I can't spend any time on my pretend job.

There are some things going on that I need to comment on, so I will try to get to it soon. First is the impending, near-complete destruction of the Arizona Department of Water Resources that now appears imminent as a result of our state budget crisis and the shameless way our state legislature and governor have dealt with the problem. This will have very serious and long-lasting ramifications for water management in Arizona.

Second, I still plan to get back to the discussion of water harvesting I started at the end of 2009.

And finally, there are some rumblings going on in Tucson about getting the next phase of our regional water resource sustainability discussion going later this year. Which should tie in nicely with some recent developments at the state level related to water resources (of course who will staff and pay for any such efforts will be a real question - see above).

It's gonna be a very weird and busy year. Should be fun.

on-going brouhaha over water policy in the Tucson area

Anyone who has followed this blog through most of its existence will be aware that I started it during the initial stages of a local water resources study initiated by the City of Tucson and Pima County - where I live. This was a 20 month, two-phase, multi-disciplinary, multi-agency effort to catalog our existing water resources, water and wastewater infrastructure, and existing policies for managing those resources; followed by a discussion of recommended policy changes that could help ensure sustainability of those resources as this area continues to grow. Those recommendations were contained in a Phase II report that was issued in December of last year.

On Jan. 12, the City Council and the County Board of Supervisors held a joint meeting where they considered a resolution to accept the Phase II report and commit to following through on its recommendations. At that time the county voted to endorse the report but the the city, expressing reservations about the content of the report and the process of its creation, voted to continue the comment period for another 30 days then revisit the resolution.

Last week the city council (the paper incorrectly reports that the council approved the study, but all they did was agree to reconsider the resolution next week) held a study session and a public hearing on the report, which were well attended by both proponents and opponents of the report findings. Some on the city council are very concerned about recent charges that city government is unresponsive to the needs of the business community and that posture is stifling economic growth in the city. They point to the current slump in the development industry as evidence of those charges and insist that loosening up some of the regulations on development would spur this industry and restore the sort of economic growth we experienced during the years immediately preceding this current slump. This argument is preposterous (in my opinion, but I think it's a well-supported opinion) because the city policies and regulations regarding development were pretty much the same during the go-go years as they are currently AND the city has been looking at suspending a number of fees during the current slow-down.

The development folks are also pointing to a current policy (as I discussed here) recently enacted by the city to deny extension of water service to areas outside the current service area of the water utility unless there is a legal obligation to serve that area. They claim that there are many developments that would be moving forward if only the city would agree to provide water service. This is purely a bluff. There are other water providers in the area noted that could potentially provide water service (although there may be greater infrastructure needs for those utilities) if these development really were "shovel-ready", but I doubt they actually are.

This is basically a situation where our political leaders have to make a choice between serving the short-term economic needs of the community or caring for the long-term sustainability of the region. If you understand politics like I do, you'll understand why I'm worried about the prospects for full approval of the report. But they may yet surprise me. I'm hopeful that they will, but prepared to be at least a little disappointed.

Give us more water ... or the aquifer gets it!

This is just priceless.

A farmer from the Central Valley of California makes the argument, in an opinion piece for the Modesto Bee, that if only the Delta restrictions could be dropped, allowing more surface water to be delivered to farms, they could stop overpumping the aquifers - resulting in subsidence, diminished water quality, and wholesale dewatering of their insurance supply.

Come on guys. Are we really supposed to be sympathetic to your plight? OK, you're behaving rationally under the circumstances because the State of California has chosen (start at p. 8) not to govern in the case of groundwater use, but you could still choose to manage the resource more wisely by setting up local governance that actually collects some data on groundwater use, sets some pumping limits, and tries to avoid some of the external costs of over-pumping. But no, this is just another lame opportunity to whine about the Delta smelt and how the little fish is harming farmers.

Time to move on.

Once again, thanks to Aquafornia for bringing this to my attention.

LA Board of Public Works calling for on-site rainwater retention

There has apparently been much talk of low-impact development (LID) standards in the Los Angeles area recently and now their public works board is calling for a new requirement that 100% of runoff from a 3/4 inch storm must be contained on-site on all new developments and some redevelopments. The plans are detailed in an LA Times article here.

Tucson has a rainwater harvesting ordinance that is aimed primarily at collecting rainwater to replace use of potable water for on-site landscape irrigation, but also has incidental effects of reducing off-drainage of stormwater. The LA proposal is strictly aimed at realization of benefits from reduced runoff.

In some respects, the LA proposal is much stricter than Tucson's ordinance because it requires containment of all water produced by a 3/4 inch rainstorm, while the Tucson ordinance requires using on-site generated rainwater for at least 50% of on-site landscaping irrigation. Tucson does have regulations about managing runoff generated by property development - and these have resulted in a few recent developments around town that manage stormwater on-site to avoid costly mitigation of runoff effects - but in most cases there is infrastructure in place to handle some or most runoff from developed property.

If LA successfully implements this change it could prove difficult to comply with. As the story notes, in some locations getting the runoff to infiltrate into the soil will be a real challenge. And a 3/4 inch rain might occur over 30 minutes or over 36 hours - with the amount of runoff generated varying greatly between the two. This definitely changes the type of development you do - how much of a lot is built on, use of underground parking (if storage of runoff is necessary) - it could get costly. As this is just a proposal at this point it will undoubtedly undergo some changes before implementation. But should be interesting to keep an eye on it.

h/t to Aquafornia for bringing the Times article to my attention.

Some recent news from the Arizona water community

There were a few news items of note this week that I wanted to post on briefly.

First the good news. Kathy Jacobs of the University of Arizona (and formerly head of the Arizona Water Institute) was recently appointed to a new position in the White House (the one in Washington, D.C.) Office of Science and Technology Policy where she will work on climate change policy. Prof. Jacobs has pretty impressive credentials in that area and should be a real asset to the administration. Congratulations professor!

Second, the bad news. The latest issue of Southwest Hydrology showed up in my mailbox this week with a banner on the front indicating that it would be the last issue. This is a significant loss to the regional water resources community because SW Hydro has been a tremendous resource for disseminating new research and policy ideas in the management of water resources in arid and semi-arid hydrology. And they've been important to me because I have published a couple of short articles in the "On the Ground" section of the magazine. Betsy Woodhouse, who was the publisher has taken a new position at the University of Arizona and her colleague Gary Woodard gives the impression that they would like to bring the magazine back in the future if they can find a new funding source. But, their major source of funding - the National Science Foundation - has dried up for now. If anyone has ideas for keeping the magazine running send them to Gary Woodard (gwoodard@sahra.arizona.edu).

Finally, the final Phase II report on the Water & Wastewater Infrastructure, Supply and Planning Study (aka the Tucson/Pima County Water Study) has been released and can be downloaded from the study website - www.tucsonpimawaterstudy.com - of you're interested. The report will be formally presented to the local elected leaders of both jurisdictions in a special joint meeting next Tues., Jan. 12, at 9:00 am in the Pima County Administration Building, 130 W. Congress, 1st Floor, Board of Supervisors Hearing Room. Hope to see you there. If not, take a look at the report. It's no masterpiece but it provides a pretty good roadmap to a sustainable water future for this piece of dirt.