2019 Pinal Groundwater model released

The “2019 Pinal Model and 100-year Assured Water Supply Projection Technical Memorandum” — an analysis of the Pinal County area’s groundwater conditions, performed by the Arizona Department of Water Resources,  is now complete and available for viewing.

The model can be viewed here.

 

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Groundwater flow model of Willcox Basin completed

drill rig

As a result of continuing observations of groundwater level declines in the Willcox Basin, the Arizona Department of Water Resources (ADWR) initiated development of a numerical groundwater flow model in late 2015.

The Willcox Basin covers an area of approximately 1,911 square miles in southeastern Arizona and is essentially a closed basin.

That modelling has been completed. Major findings of the modelling include:

• The three-year ADWR modelling project finds high rates of groundwater pumping in Willcox Basin altering the groundwater flow system “to a significant extent.”

• Evidence of the amount of groundwater removed from storage between 1940 and 2015 ranged from 4.9 million to 6.2 million acre-feet (an acre-foot equals 325,851 gallons of water, or the amount of water needed to cover an acre of land a foot deep).

• Projecting forward to simulate a period of time between 1940 and 2115, the modelling concluded a net “change in storage” – meaning, in this case, a reduction in storage – ranging from 19.8 million acre-feet to 24 million acre-feet.

• Going forward to 2115, the modelling simulated long-term “draw down” in various portions of the aquifer range from a minimum of 354 feet (in the aquifer system north of the Willcox Playa) to as much as 917 feet (in the aquifer system near Kansas Settlement).

• Both data and modelling indicate that significant declines in regional groundwater levels continue to occur.

• Based on the Willcox Model results, pre-development estimates of groundwater in storage circa 1940 ranged from 80 to 97 million acre-feet. Recent estimates of groundwater in storage (2015) range from 73 to 92 million acre-feet. Projection estimates of remaining groundwater in storage range from 57 to 77 million acre-feet. However it must be noted that a significant portion of the remaining groundwater in storage is found at considerable depth and may not practical to remove.

The Groundwater Flow Model of the Willcox Basin may be found here

An Executive Summary of the results of the Flow Model may be found here

For more information regarding this matter, please contact Sally Stewart Lee, Public Information Officer at sslee@azwater.gov  or (602) 771-8530.

Groundwater documentary and discussion in downtown Prescott on Wednesday

Kathy Ferris

Groundwater expert and documentarian Kathleen Ferris, discussing her film on the creation of the 1980 Groundwater Management Act

It is always helpful to have a solid appreciation for the past before making big decisions about the future. Especially when the subject is water.

Prescott and surrounding northern Arizona communities are hard at work right now attempting to accurately analyze their water future. In March, the high country community, along with Salt River Project, agreed to conduct a refined groundwater-flow model for the Big Chino Sub-basin, which Prescott anticipates will be an important future water supply. The plan is to accurately assess the hydrogeologic connection of the Big Chino aquifer with the Upper Verde River.

The analysis is expected to be completed in 2020.

On Wednesday, meanwhile, the producers of a much-acclaimed documentary on the history of Arizona’s landmark groundwater-protection act — the Groundwater Management Act of 1980 — have scheduled a viewing of their film in downtown Prescott this week.

Kathleen Ferris, Senior Research Fellow at the Kyl Center for Water Policy at Arizona State University, and her movie-making partner, film producer Michael Schiffer, will host the presentation at the Elks Theater at 117 E. Gurley Street in Prescott on Wednesday evening.

Immediately following the 26-minute viewing, Ferris will host a panel discussion on the present-day issues facing Arizona’s water supply — including a discussion of what steps, if any, the Arizona Legislature ought to take to update the 37-year-old Groundwater Code.

The six-person panel will include Tom Buschatzke, director of the Arizona Department of Water Resources. Joining Buschatzke will be Greg Kornrumph of SRP, Sarah Porter of the Kyl Center, Yavapai County Supervisor Thomas Thurman, town of Clarkdale Mayor Doug Von Gausig, as well as Schiffer.

Doors open at 6 p.m. More information is available online at https://www.facebook.com/GroundwaterFilmScreeningandDiscussion

 

Ebbing Away: Latest land “subsidence” monitoring report finds lower ground levels and fissures in some regions of Arizona

earth-fissures-pic

The problem of land subsidence in Arizona – the lowering in elevation of land-surface levels, largely the result of groundwater extraction – is a decidedly mixed bag, the Arizona Department of Water Resources is discovering.

Thanks to decreased groundwater pumping in the Phoenix and Tucson Active Management Areas, for example, subsidence rates in many areas of those AMAs have decreased between 25 and 90 percent compared to rates in the 1990s.

That is just one of the major findings of the department’s recent “Land Subsidence Monitoring Report No. 3,” released earlier this month.

And it’s the news from the happy side of the bag.

On the opposite side, land subsidence statewide is proving to be an increasingly serious challenge that is causing problems for infrastructure in some areas. And it is proving to be a headache even in certain parts of active-management areas.

 

Monitoring for subsidence

 

As the report describes, Water Resources first began monitoring for subsidence in the eastern areas of the Valley and around Luke Air Force Base in the west after numerous “non-exempt” wells – that is, wells that draw up groundwater at rates faster than 35 gallons per minute – were installed starting in 1997.

Historically, land levels in those areas have dropped at significant rates, the recent report finds.

The problems caused by land subsidence do not go away simply by fixing cracked foundations, reconnecting broken pipelines or repairing roadways.

Subsidence is caused by the collapse of open-pore spaces in subsurface aquifers, an unseen water-storage catastrophe in the making. When the open-pore spaces of aquifers fully collapse, they collapse permanently, in most cases.

“Land subsidence is a regional problem for some groundwater basins in the state and may continue to be an ongoing problem,” said Brian Conway, who prepared the report on behalf of Water Resources.

 

Arizona Department of Water Resources’s Brian Conway, Supervisor for the Geophysics/Surveying Unit

“Even if sustainable, safe-yield groundwater withdrawal occurred, residual land subsidence would continue until the groundwater levels recover — and/or the open pore-spaces in the sub-surface fully collapse.

As one would expect, the Water Resources report finds that subsidence is most active in regions outside the active-management areas – that is, in areas where groundwater pumping is unregulated.

Land subsidence has resulted in more than 160 miles of earth fissures. The Arizona Geological Survey maps all the earth fissures throughout the state. The Geological Survey analysts provide Water Resources with the data from their research.

The Geological Survey and Water Resources analysts have found that the Willcox Groundwater Basin in southeastern Arizona is the most active area for forming new earth fissures.

Southeastern Arizona is one of the regions most severely impacted by drought. The area also has seen substantial increases in farming operations that rely on mined groundwater.

 

Earth Fissure

 

The Willcox Basin is outside the reach of the state’s Groundwater Management Act of 1980, which regulates groundwater extraction in active-management areas. According to the report, new earth fissures in the area are impacting roads, highways, power lines and a pipeline.

The report observes that other non-AMA regions of the state also have seen considerable increases in their rates of earth subsidence, notably parts of the McMullen Valley Basin and the San Simon Valley Sub-basin. Both of those regions have seen increased agriculture activity in recent years that is reliant on mined groundwater

The subsidence mapping process employs the latest radar technology — known as “InSAR,” or satellite-based synthetic aperture radar.

The introduction of the InSAR technology has proved to be a game-changer in terms of the state’s ability to accurately track the development of subsidence over time.

Water Resources was awarded a $1.3 million grant from NASA in 2002 that kicked off a three-year effort to integrate the InSAR system into Arizona’s subsidence-monitoring programs.

The program now has 14 different partners in the effort whose financial support allows the department to fund the InSAR data collection.

The side-looking, self-illuminating, radar-imaging system has helped Water Resources develop an extensive library of scenes, covering an area greater than 150,000 square miles.

With the InSAR data, Water Resources has identified more than 26 individual land subsidence features around the state, collectively covering more than 3,400 square miles.

“The InSAR data is a huge part of our monitoring efforts now,” said Conway.

“We are able to cover large areas with the data and are able to see millimeter changes of deformation at a very high resolution.”