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Monsoon rains improve drought, but long term drought continues

Posted at 7:22 PM, Sep 16, 2021
and last updated 2021-09-16 22:22:07-04

TUCSON, Ariz. (KGUN) — Earlier this year, most of Arizona was in the throes of exceptional or D-4 drought, which is the highest category according to the Arizona Drought Monitor. After a productive monsoon with record rainfall, about 47 percent of the state is in one of the lowest categories of drought, or D-1.

Michael Bogan, an assistant professor at the University of Arizona's School of Natural Resources and the Environment, said the monsoon rain was a huge improvement from last year's dry summer.

"Last monsoon, some people called it a non-soon, there was no rain," Bogan said. "And last winter there was only one rain storm and that's not enough."

This improvement doesn't mean that the drought is over.

"The bigger drought that we are in is going on 21 or 22 years where most of those years we’ve had below average precipitation," Bogan said.

University of Arizona Associate Professor Gregg Garfin said the winter snowpack -- slow melting packed snow -- is the key.

“If we have a dry winter, then all of that stuff dries out and that makes it easier for if there are ignitions and for fires to spread next spring,” Garfin said.

Short term vs long term drought

There's two different types of drought: long term and short term. According to the National Integrated Drought Information System, short term drought is six or less months of very little rain. Long term drought, which is defined as more than six months of a rain deficit, deals mainly with reservoirs and snowpack. To improve long term drought, consistent rainfall particularly in the winter is critical as the summer rain doesn't help fill those reservoirs.

The drought brought water levels in Lake Mead and Lake Powell to historic lows. Cities like Tucson rely largely on water from the Colorado River Basin System, which is replenished with snowpack, Garfin said.

But last year, the snow fall was poor, Garfin said. "A lot of the snowpack either melted off or it was sucked into really thirsty soils and didn't do a whole lot of replenishing the supplies in those big Colorado River Reservoirs like Lake Powell or Lake Mead," Garfin said.

La Niña Winter

Climate experts like Garfin and Bogan expect this winter to be another La Niña winter.

"La Niña brings southern Arizona really dry winter conditions," Garfin said. "It's really rare for us to have wet La Niña winter."

But, Garfin said in the northern parts of the United States, La Niña brings moisture.

"It's possible that the upper Colorado River Basin will get good precipitation this winter and that would be good for our overall water supply – there's no guarantee there," Garfin said.

While other factors like temperature are important in monitoring and predicting drought conditions, Garfin said it's critical to continue to keep watch over the water supply.

"Probably one of the most important things for those of us in Tucson is thinking about our water supply," Garfin said. "We have to be vigilant about our water use."