During my water chat with Joe Berg of MWDOC, we discussed his studies of water conservation for landscaping in urban areas.

Although he discussed some on-going studies (where only 30 percent of homeowners given access to $3,000 credits towards installation of high-efficiency irrigation controllers actually opted into the program; 70 percent did nothing), he also told me about a completed study [PDF] where MWDOC and partners compared the impacts of three interventions on water waste (runoff):

The… retrofit group… used ET controller technology and public education. The… education group… received educational materials, but did not receive controllers. The… control group…received neither ET controllers nor educational materials.

[snip]

The R3 Study showed that weather-based irrigation controllers, which provide proper landscape water management, resulted in water savings of 41 gpd in typical residential settings and 545 gpd for larger dedicated landscape irrigation accounts. The observed reduction in runoff from the retrofit test area was 50 percent when comparing preintervention and post- intervention periods and 71 percent in comparison to the control group. The education group saw reductions in water use of 28 gpd, and a reduction in runoff of 21 percent in comparison to the control group.

How “economic” was the intervention? Unfortunately, the cost of fitting ET controllers ($150) and paying for the signal ($48/year) was only accompanied by annual savings of $14/customer. So — although 44 percent of retrofit customers and 23 percent of education customers reported reductions in their water bills — the program is not cost effective.

There are two conclusions to draw from this study:

1. More-expensive bills for excessive use (landscaping) would make these programs more economically attractive.
2. Larger landscapers would benefit from them. (This was the finding of a related study [pdf] of large landscapers, where water savings (=avoided use) cost only $165/AF.)

Bottom Line: Lawns in deserts are luxuries that suck precious water. Charge more to have them, and people will forgo them — or irrigate them more efficiently.