The following is taken from “Cash for Grass” – A Cost Effective Method to Conserve Landscape Water? by Sylvan Addink, PhD, Certified Professional Agronomist, originally published in the Jan/Feb 2005 Turf News, a publication of Turfgrass Producers International.
The full article with a list of references can be seen at http://ucrturf.ucr.edu/topics/Cash-for-Grass.pdf.
Water districts, municipalities, and states are increasingly confronted with the challenge of finding enough water to sustain their growing and thirsty populations. In the midst of a drought, the importance of allocating and saving water is of even greater importance. In the search for methods to achieve this goal, a variety of alternatives have been pursued, some more successfully than others.
One of the methods used has been “Cash for Grass” programs. Four of these programs were conducted in North Marin, CA; Las Vegas, NV; Albuquerque, NM, and El Paso, TX. In examining these programs, the following observations were noted:
- The average calculated cost per acre foot of water saved was $899. This was based on a 15 year life and a 25% erosion factor. As indicated below, the 25% erosion factor is likely to be higher, causing an increase in the cost for each acre foot saved.
- Each program required the installation of xeriscape plant material, which is generally watered with a drip irrigation system. A newly installed drip irrigation system can use 20% less water than an in-ground sprinkler system. However, after several years, the drip irrigation system will lose some of its efficiency advantage over the sprinkler system. In Arizona, a check of several older drip systems revealed an average uniformity of less than 20%. The short-term results reported for the “Cash for Grass” programs did not consider this factor.
- The programs required xeriscape density of 50% at maturity. The coverage and water needs of the xeriscape canopy would increase over time as the plants matured, resulting in further erosion of water savings. The short-term results reported for the “Cash for Grass” programs did not consider these factors.
- In addition, visual observations at some sites revealed that the early xeriscape plant coverage was 10% or less and would never achieve 50% coverage by maturity. This increased the early reported water savings at the expense of visually unappealing neighborhoods and golf courses.
- Three of the programs required installation of a new irrigation system to qualify for the rebate while the El Paso program did not. The higher cost per acre foot of water saved for the El Paso program ($1,834) is an indicator that much of the water savings can be attributed to the installation of more efficient irrigation systems, not the removal of turf.
- Based on water application rates on tall fescue plantings in Las Vegas, a water savings of 28% could have been achieved by applying only the amount of water required by the tall fescue plants. The Southern Nevada Water authority, in their summer 2004 Waterwise publication, stated that, “On average, residents use 40 percent more water on their grass than most turf requires.”
- The conclusion that the majority of savings came from emphasis on proper irrigation rather than conversion of turf to xeriscape is supported by a water conservation program established by the Irvine Ranch Water District (IRWD). There was a 50% reduction in water use on non-residential landscapes and “most of the reductions in water use were attributable to improvements in irrigation technology and management, rather than changes in landscape composition.”
Conclusions from examination of “Cash for Grass” Programs:
- There is doubt about the cost effectiveness of “Cash for Grass” programs due to the high cost per acre foot of water saved and low acceptance rate among consumers.
- The reported short-term results of the programs did not consider important long-term factors such as decreasing efficiency of drip systems over time and higher water use due to growth of the xeriscape plant material.
- Three of the programs examined did not separate the water savings for the irrigation system change from the water savings due to conversion of turf to xeriscape. This critical oversight can only be addressed with additional research in order to conclude the relative water saving benefits of each component.