LAS VEGAS (KLAS) — A study released by the Desert Research Institute (DRI) suggests that there’s a middle-ground to water savings that could influence landscaping decisions in Las Vegas and other desert communities.
The research, led by Rubab Saher, Ph.D., looked at different approaches to water savings and landscapes that reduce heat around buildings. The study found that “oasis” landscapes accomplish both water savings and cooling.
In an interview with 8 News Now, Saher compared the benefits of oasis landscaping to efficiency offered by a hybrid car. By balancing water savings and the need for cooling, the study points to alternatives to xeriscapes — desert landscaping that tends to add more heat.
“The simple take-home message from what we learned was that xeric (desert) landscaping is not the best long-term solution and neither is mesic (tree-turf),” Saher said. “An ‘oasis’ style landscape, which contains trees like Acacia or ghost gum, and shrubs like dwarf poinciana, requiring light irrigation, are the best solution, because it conserves water but also contributes to cooling through the evapotranspiration of the plants.”
The Southern Nevada Water Authority (SNWA) offers landscape planning tools and examples of how to use different kinds of landscaping for variety.
An email newsletter titled “A Water Update” from SNWA today summarizes the current water situation and conservation measures that are either in place or under consideration. See SNWA’s summary, including information on golf course “water budgets,” ornamental water features, evaporative cooling systems and pool size limits.
Another element of SNWA’s conservation initiatives will further outlaw grass and sprinklers. “While local development codes have prohibited decorative grass at new commercial properties, residential property owners have been able to install sprinkler irrigation and grass in up to 50 percent of their backyards. The SNWA and its member agencies are implementing changes that prohibit all grass and sprinklers at new residential properties.”
SNWA emphasizes the importance of following seasonal watering restrictions because outdoor water consumption accounts for 60% of the water used in Southern Nevada.
“Southern Nevada’s commitment to conservation has resulted in a 48 percent decline in per person water use per day since 2002, despite the addition of more than 750,000 new residents,” according to the newsletter.
But SNWA isn’t stopping there. A new water conservation goal of 86 gallons per capita per day by 2035 was approved last year.
Efficient use of water is woven into Saher’s personal and academic lives. A native of Pakistan, she grew up in the Sindh province, which has a climate similar to the Mojave Desert. Her undergrad degree in civil and environmental engineering led to work for her master’s degree in hydrology, irrigation and drainage. At UNLV, she earned her Ph.D. while working on the study for DRI.
The 23-year drought in the Southwest U.S. has focused attention on water savings, particularly with outdoor water use for landscaping. But Saher’s research included attention to how different landscape choices can still provide cooling while reducing water use. There are good alternatives to grass and big trees that guzzle water.
DRI, Arizona State University and UNLV teamed on the new study, which compared air temperatures and water use in the three types of landscapes. The study was released this month.
If you just want to save water, xeriscaping is the best choice because it delivers only the water that’s absolutely necessary for plants to survive.
The trade-off is temperature, and Saher’s research showed an oasis landscape can achieve surprising levels of cooling. She described the “dual personality” of the oasis landscape, mitigating heat and saving water.