Times report points to flaws in Florida's aquifer water flow model

01/28/13 Seán Kinane
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The model that Florida regulators use to issue water pumping permits is likely to severely underestimate the rate of water flow in the aquifer because of a type of geology called 'karst.'

According to an article in Monday's Tampa Bay Times by reporter Craig Pittman, that could be contributing to pollution and low flow of springs in the state.

The story is called ‘Aquifer models full of holes.’

"A lot of the water that we drink and use to water our lawns and so forth in Florida comes from underground. It comes from the aquifer which is this sort of big river that flows under the ground where we can't see it. And since it's hard to monitor something that you can't see the state uses computer models of the flow of the water in order to determine whether sinking another well was going to alter that flow so much that it's going to hurt the nearby wetlands and springs and lakes and other well owners in the vacinity. The problem is then, what I wrote about is that the computer models that the states been using apparently since the 1970's are all based on the assumption that what's down there that the water is flowing through is what they call a porous medium, sand and gravel. When in fact when you're around the states springs which is most of the northern end of the state from about here up what you're dealing with is what's known as karst. It's limestone full of these big holes, little holes, all kinds of holes that serve as sort of a super highway for water so that instead of flowing in a sort of steady state through sand and gravel it shoots through there like it's being sprayed out through a firehose and obviously that means the travel time for the water is very different."

So the effect of that is that they could be letting people take water when there's not enough water in the aquifer or at least maybe it can be having an effect on nearby wells or nearby aquifers and also pollution can travel more quickly, is that right?

"Yes and that's very much the concern and the folks who've been studying this and doing dye hits where they drop florescent dye into sinkholes and wells in order to see how quickly it migrates have been finding some pretty startling differences between what's really happening versus what the computer models show. The one I specifically cite in the story. These folks were studying pollution around Silver Springs and dropped florescent dye into the aquifer and the computer model said 'okay, if it's here it's going to take two years to travel this distance. If it's here it's going to take ten years, here it's going to take a hundred years.' And it just shot through that area. It zoomed across half the hundred year distance in six months. It was traveling a mile a month. So obviously the model was very, very wrong."

So the model they're using is wrong, does that mean there's no model possible to model how water moves through karst?

"That's sort of the argument that the folks in charge are making. They contend that doing a model that is based on the assumption of a karst landscape is too difficult, too expensive and they'd have to do all kinds of dye testing, use ground penetrating radar, consult the cave divers and so forth. The problem is that, as I found, Coca Cola actually commissioned such a computer model and got one. It took them four years and $400,000 but they did come up with a model that they say works in a karst landscape and accurately reflects what's going on down there and they tried to give it to the state for free and they said 'no thank you.' "

And finally Craig Pittman, reporter with the Tampa Bay Times, you kind of postulate in your article that there might be a reason behind the fact that they are not that concerned that the models are bad, how does this have to do with development and water rights?

"Well, it wasn't me that was postulating it was the people I was interviewing, the guy who did the computer model for Coca Cola that was turned down by the state. He said, you know, they don't want to have any impediment to permit issuance. Current computer models let them continue to keep cranking out water use permits so why would they want to mess with that?"

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