A weekend storm dumped an inch of rain on Payson and turned the rodeo arena into a bog — but despite the wave of cloudbursts, the region has gotten only an average amount of rain since January.
Many Rim Country residents have been marveling at the intense green grass and the rain-swollen creeks, but that’s just because we’ve had our standards lowered by a decade of drought that still lingers throughout much of the Southwest.
Payson’s average annual rainfall total is 21.45 inches, which means the 15.25 inches the area has recorded since January is right on track. That reflects a near record January, a big record July — and dry months in between, said National Weather Service Meteorologist Andrew Latto.
So far in August, Payson has received 1.3 inches — compared to a normal average for the whole month of about 3 inches.
By contrast, in July Payson got a record 3.8 inches, compared to a long-term average of 2.7 inches.
A high-pressure area that has settled in above the Four Corners area has set up a great, slowly rotating pinwheel of air, which has been sucking warm, wet air in off the Gulf of Mexico to produce a chain of monsoon storms thundering through Arizona.
“We’re locked into a high pressure area for the next four or five days, so you’ll have a typical monsoon pattern. But Payson would need nearly two inches in the next week to hit the long-term average for August.
Still, the reservoirs on the Salt and Verde rivers have efficiently captured the runoff from the wet months.
That makes the region a temporary exception to the continued water woes that have plagued the rest of the Colorado River watershed. The big reservoirs along the Colorado River now hold only about half their full capacity after a disappointing spring runoff. Cities like Las Vegas, Phoenix and Tucson face a possible cutoff of their Colorado River water.
That makes the runoff from the Salt and Verde even more crucial. It also underscores the value to Payson of its Blue Ridge water supply, which will insulate it from mounting regional water shortages.
The chain of reservoirs along the Salt River remain 95 percent full, with most of that water in Roosevelt Lake — about 1.6 million acre-feet. All the other Salt and Verde river reservoirs combined hold one-third as much.
The huge shimmer of Roosevelt Lake loses about 338 acre-feet every day just from evaporation. That means every five days, enough water evaporates from Roosevelt to supply Payson for the year.
The flow of Tonto Creek where it merges with Roosevelt Lake totaled 32 cubic feet per second Monday — about twice normal and roughly equal to the amount of water SRP is putting into the East Verde from its Blue Ridge pipeline.
The flow of the Salt River on Monday was 227 cubic feet per second, about 30 percent below normal. The flow in the Verde River stood at 135 cubic feet per second, about one-third below normal.
The numbers reflect the degree to which the decade-long drought that at one point nearly dried up Roosevelt Lake has lifted locally in the past two years. The dry spell ranked as one of the most severe on record, but not as long as some other droughts recorded in tree ring measurements going back 1,500 years.
However, the drought continues unabated in the much more extensive and vital Colorado River drainage. Lake Mead, the biggest reservoir in the Colorado River system with 29 million acre-feet, has fallen to levels not seen since 1956. Many Colorado River water users may face rationing, which would hit Arizona users like Phoenix and Tucson first. Mead holds only 40 percent of its capacity and has dropped by 15 feet in the past five months.
Lake Powell has about 16 million acre-feet, about two-thirds of its normal capacity.
Las Vegas gets 90 percent of its water from Lake Mead, but could get cut off entirely if the reservoir’s water level drops below 1,000 feet. It now stands at just under 1,087 feet.
One study by researchers from the Scripps Institute of Oceanography predicted Mead had a 50 percent chance of running dry by 2021.
Such a water supply crash could have an immense effect on Arizona, despite the brimming reservoirs on the Salt River.
California water users have first call on Colorado River water in case of a drought, which means that Phoenix could begin to rapidly draw down Roosevelt Lake should it lose its share of Central Arizona Project water.
Some experts have predicted a furious scramble for water throughout the Southwest in the coming decades. For instance, eight climate studies completed in the past 10 years have predicted a decline in the snowpack in the Colorado River watershed of somewhere between 6 percent and 45 percent.
That will add to the plight of the Colorado River water users, since the division of the water rights among seven states by federal courts was based on stream flow measures during an unusually wet period. As a result, the courts essentially allocated 3 or 4 million-acre feet more than the Colorado River carries in an average year. For the past several years, water users have overdrawn the Colorado River system by at least 1.6 million acre-feet annually — an overdraft equivalent to the entire capacity of Roosevelt Lake.