CASA GRANDE — Groundwater is essential for the survival of Arizona and its growing economy.
For decades, water management professionals have stockpiled water underground as agricultural producers shifted to using surface water from the Colorado River.
This extreme planning might just save the day as water gets harder to find.
Underground aquifers have been strengthened by pumping water into them and large underground storage facilities have been constructed.
Under the federal Drought Contingency Plan, Pinal County farmers stand to lose two-thirds of the irrigation water they have been receiving from the Colorado River.
The DCP is an effort to keep the Colorado River’s major reservoirs from reaching catastrophically low levels and starts to go into effect when levels in Lake Mead hit a low level of 1090 mean sea level, or MSL. Lake Mead is currently at 1083.05 MSL, meaning Arizona will likely lose some of its Colorado River allocations in 2020 if dry conditions continue.
If Lake Mead gets below 1075 MSL, the DCP is triggered and 192,000 acre-feet will be lost.
When surface water flows are impacted by the DCP, ag producers will pump water from underground to irrigate, which is expensive but necessary to grow crops and raise livestock.
With the “banked” water under the cities, populations and growth will not be impacted as badly, and the cities still have their required 100-year assured water supply.
The Arizona Water Banking Authority stores water at two types of facilities: Underground Storage Facility and Groundwater Savings Facility.
A USF is a facility that physically stores water in the aquifer through direct recharge. The most common type of recharge project uses infiltration, or spreading, basins in which water is spread out over a large surface area and water infiltrates or seeps into the alluvial material, eventually reaching the aquifer.
Another type of recharge project involves the use of injection, or recharge, wells where water is forced directly into the aquifer through the borehole of the well. This recharge method is less common than infiltration basins because of its higher operational expense.
The other type of USF is called a Managed USF, where water is discharged into a stream bed and allowed to flow naturally down the channel without the assistance of any construction. Water infiltrates, or percolates, into the aquifer below the stream channel.
The water bank partners with farmers and irrigation districts that would have been pumping groundwater to grow a crop.
The water bank was established in 1996 to increase utilization of the state’s Colorado River entitlement and develop long-term storage credits for the state. AWBA stores unused Colorado River water to be used in times of shortage for Arizona.
In the Valley about 2.4 million acre-feet of banked water has been stored underground by the Arizona Municipal Water Users Association. That is enough water to meet the needs of the metropolitan Phoenix area for about three years.
The stored water will ease pressure on ag producers if shortages occur.
Jake Lenderking, director of water resources for Global Water, said ag producers have groundwater rights and are pumping some water from underground for irrigation.
“They have been using groundwater and will in the future,” Lenderking said. “Are they going to be using more? I don’t know. Under DCP cuts, it was envisioned that they would be if that occurs. The lake levels are up higher.”
Lenderking said the water year ahead looks to be in good shape. Water is plentiful this year as lots of moisture fell in the upper basin of the Colorado River.
“Lake Powell had a lot of runoff and that triggers additional water to Lake Mead. Basically that means we won’t go into a Tier One shortage,” he said. “I think the increase of shortage is really low. It would take a pretty dry year. Last year’s runoff into the Colorado River gave us a little bit of relief. We are not out of the drought yet. We still have to do due diligence in the future, through weeks, months and years.”