Monsoon rains are finally putting a dent in Arizona’s epic drought — but so far it’s an itsy, bitsy divot.
It will take a lot more rain and snow in both winter and summer to bring the state out of the historic 20-year drought that has stressed forests and drained reservoirs, say Arizona officials.
In the meantime, Lake Mead and Lake Powell have hit record-low levels, with water rationing looming for the state.
Still — just halfway through the monsoon season — rainfall totals have already dwarfed last year. A series of storms dumping rain imported from the Gulf of Mexico and the Gulf of California have doused the state’s wildfires, salvaged stressed forests and bolstered reservoir levels – at the cost of widespread, sometimes lethal flooding.
Moreover, the weather service predicts more thunderstorms and rain this weekend and on into next week — especially in the White Mountains. Show Low has a 20% to 50% chance of rain every day from Saturday to Wednesday.
Officially, the monsoon season stretches from June 30 to September 30, according to the US Weather Service. In most areas of Northern Arizona, we’ve had two to four times as much rain so far this year as in the whole of the monsoon season last year.
Show Low has received 8.11 inches of rain since June 15, compared to 2.2 inches for the entire three-month monsoon season last year, according to the Weather Service.
Other areas have also seen a dramatic increase.
• Payson went from 3.6 inches in the 2020 monsoon season to 7 inches so far this year.
• St. Johns went from 1.25 inches to 3.44 inches.
• Snowflake went from 1.75 inches to 5.66 inches.
• Flagstaff went from 1.78 inches to 6 inches.
• Sedona went from 0.41 inches last year to 4.86 so far this year.
The intermittent cloudbursts have sent floodwaters crashing down many streams in the White Mountains and Rim Country. Even on Wednesday with several days of only scattered rain, the Salt River at Roosevelt was flowing at 263% of normal and Tonto Creek at Roosevelt was flowing at 3,700 times normal. The Verde flows were 2,000 times normal — thanks to the runoff from the weekend storms still moving through the system.
Lake Roosevelt has risen slightly — to 67% full.
Meanwhile, C.C. Cragin Reservoir has risen to 27% full. The reservoir started the summer so empty the Salt River Project didn’t bother pumping water out for Payson or its downstream reservoirs.
Nonetheless, drought retains its grip on the entire region. Virtually all of Arizona remains in extreme or exceptional drought, although some areas like Gila County and Northern Apache County have moved from “exceptional” to merely “extreme.”
On the other hand, areas without the grace of the monsoon — like Nevada, California and Utah — have moved further into the “exceptional” category, with a resulting increase in wildfires.
The wild swing from last year’s “nonsoon” to what’s shaping up to be one of the wettest monsoon seasons in years accords with recent research.
Arizona’s vital monsoon will likely become increasingly intense in coming years, according to a recent study by the US Department of Agriculture’s research arm. (https://journals.ametsoc.org/view/journals/apme/56/9/jamc-d-16-0358.1.xml)
Since the 1970s, monsoon rainfall intensity has increased by 6-11% and the number of rain events annually has increased by 15%. However, the storms aren’t becoming larger — just more intense.
In many desert areas, the monsoon accounts for 60% of annual rainfall. In the White Mountains and Rim Country, most of the rainfall comes in the form of winter storms.
The researchers attribute the increasing intensity of monsoon storms to the steady increase in average temperatures — amounting to about one degree every 14 years. That’s one reason Arizona set a series of heat records before the vigorous monsoon set in.
The Climate Assessment for the Southwest produced by researchers from the University of Arizona suggests the increase in average temperatures will have profound impact on rainfall patterns in Arizona. The rising temperatures will increase the number and intensity of drought years, decrease streamflow and reservoir levels and produce a more intense — but less predictable — monsoon season.
So enjoy the rain — but also don’t drive across any flooded washes.
Because there’s no telling what’ll happen next.