Here’s what an emerging megadrought means for the Southwest — AZBigMedia.com #ColoradoRiver #COriver #aridification

Graphic credit: Western Water Assessment

From The Cronkite News via AZBigMedia.com:

What sets this emerging megadrought apart from others, such as those recorded in the 1200s and 1500s, is that human activity is increasing the severity. Although past megadroughts had natural causes, the report found this natural phenomenon has been made worse by humans…

It’s important to understand the difference between deserts and droughts, said Kathy Jacobs, the director of the Center for Climate Adaptation Science and Solutions at the University of Arizona.

“I think making a distinction between sort of living in a desert where it’s hot and dry, and understanding that we could be entering into decades long shortage situations that really throw all of our water supply projections for a loop is a really important distinction,” Jacobs said.

To make that distinction, Williams and his team employed methods first used by researchers at the University of Arizona, in 1937 who discovered the width of the annual growth rings in tree trunks corresponded to moisture availabilities, or soil moisture.

“Our measurement of drought is really a combination of tree ring records that come up to 1900,” Williams said. “And then that, stitched together with our climate derived estimates of soil moisture, brings us up to 2018.”

He said a megadrought isn’t a multidecade period in which every year is dry, but instead an extended period when the occasional wet years don’t come close to making up for the predominance of dry years.

If the concept of an emerging megadrought seems abstract, there’s a reason. Williams said people might not immediately feel the impact of water sources depleting due to groundwater pumping in California, Arizona and other states…

Brad Udall: “…latest version of my 4-Panel plot thru Water Year (Oct-Sep) of 2019 of the #coriver big reservoirs, natural flows, precipitation, and temperature. Data goes back or 1906 (or 1935 for reservoirs.) This updates previous work with
@GreatLakesPeck

The Colorado River is one example of decreasing water resources. Arizona, California, Colorado, Nevada, Utah, Wyoming and New Mexico depend on the river for water, but the amount of water each state is promised has been consistently overallocated…

“The fact that the normal average year is actually getting drier and is projected to keep getting drier in the Colorado River means that we’re probably going to have to revise how much each state is allocated on the Colorado River substantially,” Williams said.

Beyond that, Jacobs stresses the need to elect representatives to the Arizona Legislature who care about the environment and to reach out to current legislators so they know how important tighter water regulations are to Arizonans and the state’s economy…

“The stakes for humans are higher than they’ve ever been before,” Williams said. “And as we change the climate, one of the things that is most predictable is that the distribution of water is going to change. Trying to figure that out before it really becomes a crisis, I think, is one of the most valuable things we can do.”

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