Water supply outlook above average, Carson City group told

After a dry winter, area water supply got a boost from a wet and cool March.

“It was second to 1991 in terms of water supply recovery,” Tim Bardsley, senior service hydrologist, National Weather Service, told the audience on Wednesday at the Carson Water Subconservancy District’s two-day 2018 Carson River Watershed Forum at the Community Center.

Snowpack recovered nearly 11 inches in the month and the water supply outlook is trending above average. At the Carson River’s Carson City gauge, for example, water supply was 120 percent above normal on Wednesday, a rolling snapshot based on current streamflow and a few days forecast. Thursday it was 114 percent above normal.

“It is quite dynamic,” said Bardsley. “It’s a huge improvement, though, slightly above average.”

Bardsley said there should be unsettled weather for the next two weeks, possibly snow and cooler temperatures delaying snowmelt. A drying trend is forecast to hit at the end of the month into early May, when the snowmelt should kick in.

But barring a big snow event in May or June, Bardsley said flooding isn’t a big concern.

“There is not that much snowpack out there,” he said.

A bigger worry is wildfires in June through September due to a growth in vegetation carried over from last year’s wet winter and the precipitation this past March.

A wet summer would mitigate that, said Bardsley, but that’s unpredictable.

“Will we have a wet summer?” he said. “That’s eight ball-type stuff.”

Much longer term, the outlook is for increasingly earlier snowmelt due to rising temperatures, said Wesley Kitlasten, hydrologist, U.S. Geological Survey, who spoke on Thursday.

“You cannot build a legitimate climate model that does not show this warming, resulting in shift of timing of hydrograph,” Kitlasten said.

In 50 years, runoff could occur in mid-March rather than mid-May, he said.

That would result in a decrease of surface water delivered to water rights holders throughout the watershed because the water is passing through the system before it can be used for irrigation.

The most affected would be early priority water rights holders, those with rights from 1860, because they get more water than most so their percentages would drop the most. And more water would end up in Lahontan due to the early snowmelt, said Kiltasten.

During a question and answer period, an attendee asked if higher temperatures would also shift the growing season earlier, helping to mitigate the effect of early runoff.

Kiltasten said it can’t be moved up much because of short daylight hours earlier in the year.