Snowpack impact: Water usage affected
California’s reliance on Colorado River lessened
While building a snowman in Yuma might not be a possibility, the wintry precipitation elsewhere actually does have an impact here in the desert southwest.
That’s because this season’s increased snowpack in Northern California will run off into water systems used by population-dense Southern California, reducing their reliance on Colorado River water, says Chuck Cullom, the Colorado River programs manager for the Central Arizona Project.
Cullom spoke at the second and final day of the Southwest Ag Summit Thursday morning, saying that the Colorado River Aqueduct, which flows from Parker Dam toward Los Angeles, is usually greatly needed by Southern California.
However, due to the increased snowpack in Northern California, they’ll be able to draw more from the Bay-Delta system (both the Sacramento-San Joaquin Rivers Delta and the San Francisco Bay) and the Los Angeles Aqueduct.
“Our water supply (in Arizona) is linked to climate and water use in Northern California,” he said. “The Northern California system is improved, so (Metropolitan Water District of Southern California’s) use of
the Colorado River is reduced.”
Increased snowpack in the Upper Colorado River Basin is an especially good reason for optimism.
With more water trickling into the system as snow melts this summer — and less stress put on it from California — Lake Mead, Lake Powell, the Flaming Gorge Reservoir and Green River’s Fontenelle Reservoir will all rise.
Cullom jokingly said this will “reset the doomsday clock for about four years.” More seriously, he means it’s a temporary alleviation to common water shortages in the region.
Snowpack and runoff years like the 2016-17 season happen infrequently, he said, but they aren’t completely unusual.
“This is the greatest snowpack of this century,” he joked, noting that it is indeed one of the best seasons in the past 20 years or so. He mentioned 2011, 1992-94 and 1982-84 as other historically notable years for heavy snowpack and runoff in the Upper Colorado River Basin.
In mid-November 2016, the amount of snowpack there was actually trending lower than usual. Come mid-December, there was a significant increase.
“We’ve been getting storm after storm after storm, increasing the snowpack,” Cullom said. “We hit the seasonal average on Jan. 1.”
The snowpack is starting to normalize now, but even if it didn’t snow for the rest of the season, which usually lasts until sometime in April, the amount this year would still be at least 120 percent of the seasonal average.
Since the snowfall and snowpack season typically is between October and April, that means runoff in April, May, June and July will heighten fairly dramatically — and again, that’s even if it doesn’t snow anymore this season.
Right now, Flaming Gorge, the largest reservoir upstream of Lake Powell on the Utah-Wyoming border, is at 82 percent full and snow hasn’t even melted yet, meaning it will almost certainly end up at more than 100 percent full.
“That bad boy’s going to fill — and spill down to Lake Powell, which is good news for us,” Cullom said.
Lake Powell, meanwhile, is at 46 percent full now and estimates show that it will be around 60 percent full after runoff at the end of the summer. Through all of this, Lake Mead’s water elevation will grow by 25 feet, he said.
Bruce Gwynn, executive director of the Yuma Fresh Vegetable Association, host of the Ag Summit, said the added water in the system doesn’t necessarily affect Yuma directly, but it does indirectly by alleviating stresses on the system.
“Yuma has the oldest water rights in Arizona. We have plenty of water and we are well protected for a long, long time,” he said. “But what (snowpack) does — it puts water in the system at Lake Mead, takes the pressure off the CAP (Central Arizona Project), takes the pressure off everybody else (and) gives us three, four (or) five years of … better efficiencies.
“It’s a good thing. If it happens again next year — even better.”