Paradox Valley Unit: Earthquakes yes, but less saline water in the #ColoradoRiver

Here’s an in-depth report from Stephen Elliott writing for The Watch. Click through and read the whole thing. Here’s an excerpt:

Nestled in an unassuming corner of Paradox Valley along the banks of the muddy Dolores, the work done at the Paradox Valley Unit, a facility operated by the United States Bureau of Reclamation, has enormous implications for the water supply of major cities in the Lower Basin of the Colorado River, including Las Vegas, Phoenix and Los Angeles.

The project is also having a literal impact closer to home, in the form of seismic activity; since injection began at the site in 1991, seismic monitors have recorded around 6,000 “seismic events,” or earthquakes, within 16 kilometers of the injection well.

It is known beyond any reasonable doubt that the earthquakes are the result of the brine injections.

“The injection history and seismicity history correlate pretty well in both the spatial and temporal extent. It’s generally accepted that the seismic activities in Paradox Valley are induced by injection,” said Shemin Ge, a hydrogeology professor at the University of Colorado.
“Yes, we induce small earthquakes,” said Andy Nicholas, facility operations specialist at the Paradox Valley Unit. “They knew from the beginning that there was the likelihood to do that.”[…]

When it comes to water quality in the western U.S., the importance of the Paradox Valley Unit cannot be overstated. If the salt wasn’t extracted from beneath the Dolores in Paradox Valley, it would end up not only in Lake Powell and Lake Mead, but also in treatment facilities for major urban Lower Basin water-user cities.

At the Paradox Valley facility, extraction wells between 40 and 70 feet deep along the Dolores pull brine out of the groundwater beneath the river, process it and pump it three miles across the valley to the injection well. The injection well then shoots the brine more than 2.5 miles down into the Mississippian Leadville Formation, beneath the Paradox salt formation that serves as a barrier preventing the brine from ascending back upwards.

Prior to the Bureau of Reclamation’s extraction-and-injection process, which began in the early 1990s, the Dolores River picked up roughly 185,000 metric tons of salt each year as it flowed across Paradox Valley. (Unlike most river valleys, which are created by erosion, this one was formed by the collapse of a salt-cored geological fold, instead of the flow of a river. Indeed, paradoxically, the Dolores River cuts across this span instead of paralleling it, giving the Paradox Valley its name.)
Between 2008 and 2012, the average injection rate at the Paradox Valley Unit was 190 gallons of brine per minute. As of last month, the PVU well had injected just over two million tons of brine beneath the muddy Dolores riverbed during its 24 years of operation.

The total tonnage of salt removed from the Colorado River system by the PVU is impressive, but the significance of the facility depends on the valley’s status as a so-called point source of salinity. A majority of the salt that flows into the Colorado River system does so through non-point sources such as large agricultural areas, where a tract thousands of acres in size might contribute a relatively small amount of salt to the river. At Paradox Valley, however, all of the salt enters the river system in a comparably small area, and can be more easily extracted and quantified than at non-point sources.

At non-point sources — say, a large agricultural valley where irrigation runoff pushes salt into a river — the best the Bureau of Reclamation and its partner agencies can do is offer canal-lining projects, which prevent some salt in the soil from flowing with excess irrigation water into rivers, and provide education for farmers about more efficient irrigation practices.

At the PVU, on the other hand, the Bureau of Reclamation can physically extract salt from the groundwater and quantify it, making it the only such location in the Colorado River Basin where salinity control impacts are 100 percent known. (There is a point source of salinity near Glenwood Springs that is perhaps more significant than the one at Paradox Valley, but no salt extraction is done there.)

All told, 10 percent of the salt taken out of the entire Colorado River system by the Colorado River Basin Salinity Control Program is extracted at the Paradox Valley site.

“It’s the only place where we’re removing salt in a physically measurable way. We’re measuring the quantity of salt, so we’re certain that we got that pumped out of the river,” said Steve Miller, a water resource specialist with the Colorado Water Conservation Board. “[The PVU] gives us a chance to really grab a large amount of salt in a very controlled fashion. The project is really important to the Lower Basin [states], but not so important to Colorado. In terms of the total amount of salt reaching Lake Powell it’s very important, because in Paradox we can get a lot of salt out in one fell swoop.”

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