27 Jul 2011

Do turf removal programs save water cheaply?

A lot of water managers offer rebates to customers who remove lawns or replace old appliances.

These rebates are wasted when they pay customers who are going to take those actions anyway, but let's assume that they really DO motivate customers to change their potential demand for water.

So my question is this: What's the cost per acre-foot (or cubic meter) of these programs?

Let's examine the most famous program: The Southern Nevada Water Authority (of Las Vegas) will pay $1.50 per square foot to remove turf (and replace it with "desert landscaping"), for up to 5,000 square feet (464 m^2). Let's assume new landscaping uses zero water and that efficiently irrigated turf uses 62 gallons per square foot per year (source below).

Let's do the calculations: One acre foot of water contains 325,851 gallons, so 5,255 square feet of turf need to be removed to reduce water demand by one acre foot. How much will that cost SNWA? About $7,900. Of course, that's a one time payment and saving will occur over many years. If we use a 10% discount rate (turf removal reduces water use for ten years), then that's $790 per acre foot saved.

Is that a lot or a little? Farmers in Palo Verde Irrigation District (just down the Colorado River) pay about $4 per acre-foot for untreated water. The cost of desalinated water is roughly $1,000 per acre foot. So turf removal may be economical but probably isn't. For example, it's definitely not cost-effective when the payment goes to homeowners who already want to remove their turf or when owners who "feel good" about saving water use more (the rebound effect).

For more on not effective, read "Cash for grass" (on this page), where a landscape expert discusses three other programs and suggests six ways to reduce landscape water use that may be more efficient.

Bottom Line: Payment for lawn removal may be an easy program to administer, but it's probably not cost-effective in saving water or economically-efficient in finding the cheapest way to reduce water use. A direct incentive to use less water (raise prices!) would not only be more efficient (some people would remove turf; others would take shorter showers) -- it would also generate revenue.

Addendum: The author of the paper ("Sylvan Addink, PhD. Certified Professional Agronomist") has patents for managing water use on landscaping and a company that "provides environmentally enhanced landscaping irrigation." Seems that we have a biased source, but --luckily -- I wasn't relying on his numbers/arguments.


PM said...

Your per acre-foot price comparisons were hardly apples to apples. $4/AF for leasing untreated drinking water is one thing, conserving an AF of treated and delivered water is another. The conservation savings should be compared against the utility's cost to obtain, treat, and deliver that AF of water, not against what a farmer can lease it for.

$1,000 per AF for desal water? Who in the US is producing desal water that cheaply? Certainly not Tampa Bay Water - with one of the largest and newest desal plants around. My understanding is that actual costs of desal have proven to be in the neighborhood of $10,000 - $20,000 per AF once all costs are considered, maybe even more.

Turf removal and other conservation measures might look like more attractive options when compared against the real costs of obtaining, treating, and delivering water.

Emily Green said...

If in fact the point of this is that more emphasis should be put on the cost of water as a conservation tool, then I applaud that sentiment. However the rest is shoddy. Met, the SNWA etc didn't undertake cash for grass programs because they were more expensive than developing new water, if, in fact, that new water was available -- a big if. Debra Mann has presented figures on contrasting costs repeatedly at Met board meetings. The outdoor conservation programs supported by the Met have included more efficient irrigation techniques. The linked study is clearly the work of someone who is biologically illiterate and appears to be working on behalf of a well-funded turf grass industry.

benjaminpink said...

Hi David, a couple things. First, you said assume efficiently irrigated turf used 62 gallons per square foot per year. In the paper, the guy says that the irrigation requirement for SNWA turf is 79 gal/sqft/yr. The savings is 62 gallons when compared with Xeriscape. Second, to assume that people water their turf efficiently is a big assumption. In my experience in San Jose, people typically over irrigate their turf a lot (it varies widely). Third, most if not all conservation programs have some element of free ridership. In Santa Clara County, the program has many rules in order to reduce this. Fourth, the program is definitely not "easy" to administer. It is in fact rather complex to administer. The SCVWD is not doing the program because it is easy. I'm going to do a cost benefit analysis on our program and post my results in another comment. I have several problems with the author's sections about the "negative environmental impacts from the removal of turf". "Turf is low cost" give me a break. As for the problems with drip irrigation losing efficiency over time, sure yes, but ALL irrigation systems must be maintained for efficiency, not just drip. His recommendation for WBIC programs is outdated: most agencies, at least in the bay area, have found that WBIC programs are not all they were touted to be. I have more criticisms of this paper but I'll stop now.

David Zetland said...

@PM -- your comment only supports the wide range of costs for "new water" and turf removal is NOT at one extreme (i.e., no brainer)

@Emily -- so why did thye undertake cash for grass? I read EVERYWHERE that it's about reducing water demand (equivalent to "add more supply). Interesting comment on the study -- I don't have the chops to know good from bad on grass botany, but it does NOT seem to be a hack's work in favor of turf.

@Benjamin -- "62 gals" included waste (see paper), but your point is good. Agree with your other points. What's a WBIC program?

David Zetland said...

@all -- see addendum to OP wrt the cited paper. Author runs an irrigation business in Riverside. I sent an email asking him to defend his "findings."

benjaminpink said...

David, WBIC is Weather Based Irrigation Controller ("smart controllers"). WBIC programs have shown not to produce as much savings as people had hoped they would. Smart controllers still need to be programmed properly and in some cases they actually cause the user to water more than they were previously watering. There are many factors that go into whether a smart controller actually will save you water.

David Layden said...

It's interesting that SNWA is willing to implement such a program as cash for grass and other rebate programs: pool covers, irrigation controllers and rain sensors. Yet their water rates are comparable or even less than rates charged in the Pacific Northwest.

It seems that more aggressive pricing by water districts that have extensive and sometimes controversial rebate or cash back programs might lessen their own administrative costs quite a bit and still achieve their water demand goals.

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