There have been moments during the span of this newsletter where a story kind of falls into my lap that is just too good not to share with you all – and this is one of those moments.
CommonWx is a weather and climate newsletter, and while this story does have ties to those fields of study, it’s more about how our earth is so intricately connected – and how little we know about those connections.
This story begins in a field used for raising cows in Christiansburg in the New River Valley. In one corner of the property, surrounded by knee-high grass and plenty of… deposits from the residents here, sits a tiny shelter with a green door…
“So, this is kind of the innards of state observation well 019. This is the well casing – steel casing, I think it’s 11 inches in diameter,” Joel Maynard tells me as he leads me into the small structure. He’s a hydrogeologist with the Virginia Department of Environmental Quality’s Groundwater Characterization and Monitoring Program.
“Over on top of it is a shaft encoder that’s connected to a weighted float. So, this is an older style of measuring the water level because this one’s pretty shallow water – it’s usually within six feet of the surface.”
This well was first drilled in 1953 to supply water to the town of Christiansburg. In the late 60s, DEQ took it over to monitor groundwater levels in the area – which is still its primary purpose today.
“The data goes into this encoder, it goes through here into this box,” Maynard tells me as he lifts the lid. “This is a satlink logger and transmitter, it logs that data – most wells it’s every 15 minutes, but since this one has this property to it, we do it every five minutes. Then every hour it transmits out [of] that transmitter on the roof, hits a satellite and downloads to the U.S. Geologic Survey’s servers. Over time, what you get is this near continuous data stream, and you start to assemble what is the normal range, the normal water level that you expect in July at this well. Are you above that or below that? Because every time it gets dry out, somebody’s claiming this is the driest we’ve ever seen it. What you can pull up quickly is the actual data that gives you this unvarnished reality check that, ‘No, this is actually the normal range.’”
The Virginia Department of Environmental Quality uses that information – which comes from a network of wells across the state – to keep an eye on groundwater levels. That is one component – along with stream levels, reservoir levels and precipitation totals – that goes into how this state tracks drought conditions. If those four components fail to meet various thresholds, then Virginia will issue either a drought advisory or warning.
Once monitoring here began, it wasn’t long before the folks in charge of maintaining the well noticed something else going on when they came to collect the groundwater data…
“So, instead of having this encoder here – it was a drumroll of paper that would actually just continually monitor – like an old-style seismometer. You’d come out every month and pull this strip and you’d see these things on there and be like, ‘Yeah, this is weird,’” Maynard says.
Before the more modern setup, the paper he’s referring to would indicate rises and falls of the water within the well, which would sometimes happen rapidly. Those oscillations as they’re called are actually seismic waves. This particular well is able to pick up earthquake signals from around the globe, including the 8.8-magnitude one in Russia earlier this month.
The well is connected to a geologic structure known as the Elbrook Formation. That’s a section of fractured, water-bearing rocks – also known as aquifers. As seismic waves travel through the rock, water there is rapidly forced in and out of the well.
Now, there are other wells both in Virginia and across the country that are able to pick up seismic activity, but…
“Of all of the seismic wells that I’ve been watching, this one picks up the most by far of all I’ve been watching,” Rowan Johnson, a hydrologist at USGS’ Virginia and West Virginia Water Science Center tells me. “I’m not going to say that it is the most sensitive, but of the ones in Virginia that I monitor, it’s pretty sensitive.”
I asked Johnson, Maynard and Dave Nelms – who used to help maintain the well for USGS before retiring – about why the Christiansburg well is so sensitive… and it’s not exactly clear! Nelms says it may have something to do with what he calls “seismic permeability.”
“If it can transmit the seismic waves so readily, then it’s going to impact the water because the water is very sensitive to pressure changes.”
He adds that the rock structure with those fractured areas below the well may just be conducive to seeing the earthquake signatures.
“You don’t always see them in the coastal plain because it’s porous media down there – it’s sand and gravels – and so these signals can get squashed out. Another key to this well is that it’s affected by earth tides. So, you’ll see diurnal cycles, so that’s just the earth shrinking and swelling back up over the course of the day – and that’s putting the pressure on the fractures here.”
For context, an earth tide is kind of like ocean tides but for the solid earthen material beneath our feet (so water levels in the Christiansburg well rise and fall just like ocean tides).
And while this is the prevailing theory on how things work here, Maynard tells me he and his team are still digging wells across Virginia. The newest one in Luray also picks up seismic activity – kind of throwing that idea into doubt because that well is obviously in a different geological situation and environment.
“It’s hard to know what 10 feet out into the bedrock this way out in the aquifer what it’s doing. There can be faults and fractures rolling different ways. There’s a lot that’s just unknown.”
There are other mysteries about what exactly happens when seismic waves roll through here at the Christiansburg well, too.
“Not only does the water level oscillate, there’s slight variations in temperature and the chemistry down there.”
Part of solving those mysteries will come from being able to monitor the data from this well at regular intervals – which is why it logs that information every five minutes. That’s the most frequent pace in the country behind a well in Hawaii that logs every single minute.
“The higher frequency that you’re recording this data, potentially the more of these seismic events you’re going to see,” Johnson says. “If you take a data point, and then within that five minutes before the next data point is taken, if there’s a short seismic event but then it’s over by the time you get the next data point, you don’t see it.”
Maynard adds that a lot of the well network in Virginia is still periodic – meaning measurements are only taken every quarter.
That makes the Christiansburg well particularly important to both DEQ and USGS for data collection when it comes to both seismic activity and groundwater monitoring – a beautiful, scientific coincidence if you will...
“This well went in and it just happens to be really seismically sensitive because of essentially chance,” Johnson says. “It’s hitting these fractures and because of all of these other variables – so what else is happening in the earth? Like, how else is the earth responding to these faraway earthquakes that we don’t know just because we don’t have a well there? So, it’s just this neat peek into all these different ways that the earth is connected that we otherwise wouldn’t know about.”
You can read more about the monitoring efforts at the Christiansburg well site here, which also includes a list of the various different earthquakes across the globe that have been detected there. There's also a longer historical record here.
An early taste of fall?
The latest projection from NOAA's Climate Prediction Center shows cooler conditions on the way this week and into the first part of September.
Much of Virginia and the eastern part of the country are expected to see below-average temperatures over the coming days. To give some context, Blacksburg typically sees an average high temperature in the mid 70's and lower 80's during this time of year; Richmond is a touch warmer in the lower to mid 80's.
While the cooler weather is appreciated as college football comes back, we certainly could see summer-like conditions make a comeback. For example, the end of September and early October in 2019 brought extreme heat to parts of the Commonwealth before a more fall-like pattern set in.
Thanks for checking out this edition of CommonWx — the weather and climate newsletter from Radio IQ. Use this link to get the newsletter sent to your inbox.
