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Southern Utah Cities Are Encouraging ‘Time Of Day Watering,’ Though Early Research Says It May Not Matter



PROVO, Utah  – It’s been almost a month since Gov. Spencer Cox issued a state of emergency because of the drought in Utah. Now, municipalities across the state are introducing watering restrictions.

Some cities in Utah County are asking residents to not water their lawns until May. In St. George, the city implemented a “time of day” watering ordinance on Thursday. This kind of regulation is normal for the area, but Rene Fleming, a conservation coordinator with the city, said this year they’re implementing it early.

“The state’s in a drought, reservoir storage is low,” Fleming said at a St. George City Council meeting Thursday. “[We’re asking] our customers to water between 8 p.m. and 8 a.m. because that’s the coolest part of the day. More water will go into the soil rather than be evaporated.”

But Kelly Kopp, a professor of plants, soils and climate at Utah State University, is doing “mythbusting” research on time of day watering.

She said preliminary data is bringing the conventional wisdom of night time watering into question.

“When you consider all of the aspects of watering, including wind, temperature, all of it, and you look at the actual water applied and the water lost, there’s really not an advantage,” Kopp said.

The research she is part of still has another year to go — and needs to be peer-reviewed — but Kopp said it’s looking like the time of day watering principle “is going right out the window.”

Kopp said it’s more important for people to be aware of how much water their plants actually need and to wait later in the year to water.