Based on previous studies of the Arbuckle-Simpson Aquifer, researchers might have decided that there was nothing else to discover.

But a research team from Oklahoma State University has found that the aquifer still holds many secrets.

Experts know more about the aquifer now than they did in the past, but they still have a lot to learn, said Dr. Todd Halihan, a professor of hydrogeophysics at OSU.

“I think the system is far better understood than it was a decade ago, but that there’s pieces that are still pretty mysterious,” Halihan told the Ada Water Resources Board on Tuesday. “Not out of the range of understanding, but just that are a little tougher answers to get.”

Halihan and his students recently finished studying the hydrogeological features of the aquifer, which is the source of several important regional springs. Among then is Byrd’s Mill Spring, which is Ada’s main source of drinking water.

Halihan’s students have already built a three-dimensional geological model of the aquifer, which is a useful tool for checking to see if large structures can be located near a certain area, Halihan said. The students have also studied the aquifer’s epikarst zone, a relatively thick area of bedrock that extends from the base of the soil zone and is characterized by extensive fracturing.

The rock that makes up the aquifer basin boosts its ability to transmit and store groundwater, making it a key source of water for municipal and rural users.

The Arbuckle-Simpson is unusual because its characteristics do not change as the basin gets deeper, Halihan said.

“With its thickness, you would expect lots of interesting variability,” he said. “This is really interesting in that it doesn’t, which tells you exactly how it’s functioning because if it was normal, it should have lots of variation with depth.

“But it doesn’t, and that tells you that this thing is pretty well mixed vertically.”

Halihan said the Arbuckle-Simpson defies expectations in several ways. For example, he said most geologists who are unfamiliar with Oklahoma would not expect Byrd’s Mill Spring to be the state’s largest spring.

“Most of the Missouri classic springs or Florida springs, you’d look at a geology map and go,‘Well, of course that’s where the big flow is going to be,’” he said. “You look at a map of the Arbuckle-Simpson and you go, ‘Where’s the biggest spring coming out?’ If you just have the map and have no knowledge of Oklahoma, I don’t think any geologist would pick Byrd’s Mill Spring as your big one. It doesn’t look like it should be.”

Student Kyle Spears focused his research on Byrd’s Mill Spring because he wanted to understand where the water originates and how it gets to the spring. That information could help the city identify the best sites for wells in the area.

The spring produces 8,300 gallons of water each minute, or about 12 million gallons a day, Spears said. He said the city does a good job of protecting water from the spring, but officials may want to consider extending that protection into other areas.

“The question that we’re looking at is, should we really just be protecting over here, or should we be looking all around? Should we be looking several miles away?” he said. “So these are some questions that have come up.”

Spears said the evidence indicates that the water comes from several sources and converges in a single location, creating the spring.

Halihan said as researchers collect more evidence of how the Arbuckle-Simpson works, they may be able to provide officials with information about which sections of the aquifer need extra protection.

“Right now, that answer’s a bit tricky,” he said.

Guy Sewell, an Ada City Councilman who serves on the Water Resource Board, said the presentation offered good news about the amount of water in the aquifer. But he said the information also raised questions about the recharge area in Byrd’s Mill Spring.

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