Key regional water resource back on line - SanTan Sun News SanTan Sun News

Key regional water resource back on line

June 6th, 2021 development
Key regional water resource back on line


One of the Southeast Valley’s priceless water-storage facilities is up and running again after more than a year.

Reactivation of the Granite Reef Underground Storage Project (GRUSP) comes just as Arizona braces for cutbacks in its supply of Colorado River water – the first time in history that such restrictions will have been imposed.

GRUSP is owned by Salt River Project, which has supplied water and electricity to the region for more than a century, and by several cities – Chandler, Gilbert, Mesa and Tempe among them.

The facility sits in the Salt River bed about four miles downstream from the Granite Reef Diversion dam.

It is designed to channel water – mostly from the Colorado River via the Central Arizona Project – to large surface ponds. From there, the water trickles through porous materials to an aquifer for storage.

The ponds went dry more than a year ago. Ironically, it was water that caused the problem when storms washed out the GRUSP delivery channel. With repairs complete, water began flowing to them again this month.

GRUSP is one of the biggest water-recharging projects of its kind in the country. Completed in 1994, it has stored more than 1 million acre-feet of water from the CAP and SRP systems.

That, according to an SRP press release, is 17 times the water that typically is stored in Saguaro Lake.

The project was designed for just such an eventuality as now appears imminent in the Colorado River basin – a prolonged drought leading to reduced water allocations.

The situation has been building for years.

Although there have been occasional wet winters, climatologists say the West has been in a drought since around 2000.

If anything, the situation has worsened over the past year. The hottest summer in Arizona history was followed by an anemic winter that brought little rain or snow.

Almost all of Arizona, as well as portions of neighboring states, is currently listed as experiencing extreme or “exceptional” drought.

As of late May, the Salt and Verde river reservoirs operated by SRP were 72 percent full, compared with 97 percent at the same time a year ago.

Even so, that number represents more than 1.6 million acre-feet of water, which means the Valley is in no danger of going dry anytime soon.

The bigger picture, encompassing the vast Colorado River system, is far grimmer.

Lake Mead, the biggest reservoir on the Colorado, has been receding for 20-plus years. In in late May it contained only 37 percent of the water it was designed for.

Mead is nearing the level at which Arizona would be forced to accept less Colorado River water than in the past. If the cuts come in 2022 as expected, the first to be affected would be agricultural customers, many of them in Pinal County.

The anticipated cuts would see farmers lose half their CAP water in 2022, and all of it in 2023 and thereafter, if the Colorado River does not recover.

Arizona water officials plan to deal with that by pumping groundwater. But because needed infrastructure is not in place, there’s a good chance that 20 to 30 percent of Pinal County farmland will go dry, according to some estimates.

Southeast Valley cities are expected to receive their share of Colorado River water for at least the next several years. But as Western states’ populations continue to boom amid a megadrought that shows no signs of easing, that could change.

Under agreements reached with the six other states that draw water from the Colorado, Arizona is first in line to suffer cutbacks as needed.

In such a case, the water now being saved at GRUSP and SRP’s other underground storage facilities could prove vital to the Southeast Valley.


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