Sinking cities: How land subsidence is affecting Arizona
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The Grand Canyon State's cities may not have any of George Strait's prized "ocean front property in Arizona," but they do have one thing in common with coastal cities around the world: The cities are sinking. In fact, the whole state is.
A recent study published in the journal Nature has shown that the world's coastal cities are falling prey to subsidence in addition to the already-documented rising sea levels.
Land subsidence is a geological term for the sinking or settling of the Earth's surface. Subsidence can be caused by a variety of factors, but in most cases it's accelerated by the extraction of groundwater.
Arizona, of course, doesn't have rising sea levels to contend with — but that doesn't mean land subsidence is a non-issue.
According to the Arizona Geological Survey, over 3,000 square miles of the state are affected by subsidence, and it's increasing in urban areas.
The land sinking isn't the only problem — subsidence is often the cause of fissures, which can lead to cracked and collapsing roads, broken pipes and utility lines, and in extreme cases, human injury or death.
Edward Kavazanjian, a professor of geotechnical engineering at Arizona State University, says that subsidence can be stopped or slowed, but not reversed.
The "settlement" of the soil means the ground itself will no longer be able to absorb water the same way it did before groundwater was extracted.
"When they have surplus water and sometimes with treated wastewater, they pump it back into the ground to try and restore the aquifer," Kavazanjian said. "That'll halt settlement, but it won't erase it."
The best way to halt subsidence or at least slow it down is to stop pumping groundwater, Kavazanjian said, but that would lead to Arizonans needing to find a new source of water. One would be recycling it for direct reuse, a process some local breweries are already doing due to a partnership with Scottsdale Water. It's the only water utility in the state currently authorized for direct potable reuse.
Another way, said Kavazanjian, is to more effectively regulate groundwater management areas.
"There are large parts of the state that are not considered groundwater management areas, where there are very few restrictions on pumping," he said. He hopes that groundwater management areas will expand in the coming years.
What to do if you notice a new fissure on or near your Arizona property
- Keep children, pets, and livestock away from the fissure.
- Email the AZGS at [email protected] and contact the municipal or county emergency manager's office.
- Prevent runoff water from flood or irrigation from entering the fissure if possible. The erosion caused by the water can cause the fissure to widen rapidly.
- Consult a geotechnician regarding the extent of fissuring and how to minimize damage to your home and property.
