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PROVO — Rob Sowby says you can basically flip a coin when asking if someone in Utah is overwatering their lawn.
Sowby, a professor of civil and construction engineering at BYU, and his colleagues recently studied Utah lawns and found about half of homeowners overwater their lawns, which he says is unnecessary.
"You can still have a nice yard without wasting water," he said Tuesday, in a question and answer article for the university. "Water isn't the only thing that makes a lawn green; if you have a yard, you should make more effort to fertilize properly, consider the soil type you have and water according to local guidelines."
Sowby co-authored a study about efficient irrigation that was published in the journal Sustainability earlier this year. It found that irrigating lawns about 20 to 30 centimeters per month (about 7.8 to 11.8 inches) is about the maximum a lawn can benefit from watering. Anything beyond that "offers no benefit and results in less healthy vegetation," the researchers wrote.
They add that the urge to water more for green grass is "misguided" because overwatering may lead to yellowing. In fact, they found that parcels of land receiving 10 centimeters per month actually had better vegetation health than parcels receiving 60 centimeters.
Unless we have several years of sustained, improved precipitation, we will remain in a drought.
–Rob Sowby, BYU professor
The problem they found is that about 50-60% of lawns studied were beyond this threshold of 20 to 30 centimeters per month, indicating many people are overwatering their lawn.
This finding has major implications heading into the summer, Sowby says. It shows you can reduce water consumption and still have a healthy lawn.
Sowby says Utah is at a "turning point" in terms of water supply. About 72% of Utah is listed in an extreme drought but the severe drought conditions after another below-average snowpack this winter. That low snowpack mixed with severe drought conditions over the previous two years, and the 20-year megadrought, is why Utah's reservoirs are struggling.
Utah's reservoirs are at 63% of capacity, according to the Utah Department of Natural Resources. Lake Powell and the Great Salt Lake, which both hit all-time lows last year, have been hit particularly hard by the megadrought and it will take years for either to get back to normal, if that ever happens.
At the same time this happening, Utah is growing at the fastest rate in the nation, and more people equals more water consumption. Sowby argues that reducing landscape irrigation is one of the best ways to help conserve water because it's one of the least impactful water uses.
"We're no longer in a stage of 'Let's wait and see if things get better,'" he said. "The policy has to change and the behavior of institutions, landowners and people has to change."
He urges residents to follow the Utah Division of Water Resources' weekly watering guide, (available at conservewater.utah.gov) and consider investing in a smart irrigation controller to help be more efficient.
The BYU article was published a day after a major spring storm subsided, dumping over 4 inches of water across some parts of the Wasatch Front. But one storm — or even a few for that matter — hardly makes a difference given the deficits from the past few years, Sowby adds.
Take Salt Lake City, for example, which has the most data available to track of anywhere in Utah because the National Weather Service has documented its weather since 1874.
Utah's capital city received 0.86 inches of rain over this past weekend, but remains 3.56 inches below the 30-year normal precipitation rate heading into June this calendar year, according to weather service data. The past two calendar years were just as dismal, meaning Salt Lake City is still about 12.66 inches below normal from January 2020 to the end of May 2022. The deficit is actually more than what has been collected (via rain or snow) in either of the past two years.
Sowby says he understands Utahns have heard the same messages for three years now but this is why hydrologists and water managers preach caution — even after a big storm and following an above-average year. It's going to take many years to get back on track, to where water reservoirs are closer to 100% statewide.
"That message needs to be consistent, even in wet years, so residents take it to heart," he said. "Unless we have several years of sustained, improved precipitation, we will remain in a drought."
