In a fresh study in the journal Hydrology, a team of scientists from DRI, Arizona State University (ASU), and the University of Nevada, NEVADA (UNLV), examined the irrigation water requirements of three common forms of urban landscapes. Then, they compared air temperature, surface temperature, and wind speed round the three sites to understand how differences in landscape types impact their surrounding environment.
The three landscape types analyzed in the analysis were a “mesic” tree and turf-grass landscape with water-intensive plants; a “xeric” landscape consisting primarily of desert plants on drip irrigation; and an intermediate “oasis” landscape type with a variety of high-and low water use plants. The websites were located around buildings within an experimental study area at ASU in Phoenix.
Needlessly to say, the mesic (tree and turf-grass) landscape showed the best water consumption rate. However, the mesic site also had the cheapest surface and air temperatures, both in the daytime and nighttime, thus creating better conditions for outdoor thermal comfort.
The website with xeric (desert) landscaping had the cheapest irrigation water requirement however the highest temperatures. Air temperatures in the xeric landscape plot averaged 3oC (5.4oF) greater than in another two landscape types.
The oasis landscape, with a variety of high- and low-water use plants, provided the very best of both worldslower irrigation water requirements compared to the mesic site but more daytime cooling compared to the xeric landscape.
“The easy take-home message from what we learned was that xeric (desert) landscaping isn’t the very best long-term solution and neither is mesic (tree-turf),” said the study’s lead author Rubab Saher, Ph.D., Maki postdoctoral research associate at DRI. “An ‘oasis’ style landscape, which contains trees like Acacia or ghost gum, and shrubs like dwarf poinciana, requiring light irrigation, will be the best solution, since it conserves water but additionally plays a part in cooling through the evapotranspiration of the plants.”
The analysis also examined the role of buildings and open sky to comprehend the result of shade on the landscape. They discovered that shade in the narrow space between buildings created shade of comparable temperature compared to that under a tree in a mesic landscape and so are thinking about doing follow-up studies for more information concerning the impact of creating orientation on maximizing summer shade.
“I became thinking about this topic because urban irrigation and water efficient landscaping are actually important issues in the Western U.S., but haven’t been studied very thoroughly,” said Saher. “Folks have been applying options for calculating irrigation from agricultural fields, but cities have become different landscapes, and the techniques homeowners irrigate have become unpredictable.”
The authors hope that their findings are beneficial to homeowners, city planners, or anyone attempting to help conserve water but prevent warming temperatures in arid urban regions.
“Removing turf grass from the landscape is a great approach for saving water, but if we remove all of the turf grass, the temperature will rise,” Saher said. “For each and every acre of turf grass removed, we should also plant native and/or rainfed trees to create arid cities livable over time.”
More info: Rubab Saher et al, Assessing the Microclimate Effects and Irrigation Water Requirements of Mesic, Oasis, and Xeric Landscapes, Hydrology (2022). DOI: 10.3390/hydrology9060104
Citation: Removing turf-grass saves water. But does it increase urban heat? (2022, September 14) retrieved 14 September 2022 from https://phys.org/news/2022-09-turf-grass-urban.html
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