Quality as well as quantity of aquifer water important

• We have an abundance of fresh, high-quality groundwater, but what if that quality diminishes?

There has been much discussion on the usage of Memphis aquifer water by TVA as cooling water.

Memphians are very aware, obviously, of this great natural resource beneath our feet and share in ensuring its availability for future generations.

When TVA announced its plans to drill its own production wells into the Memphis aquifer, concerns of unwarranted depletion quickly boiled to the surface. TVA anticipates using 3.5 million gallons per day (mgd) maximum.

Yet up to two years ago, Cargill Sweeteners on Presidents Island across from TVA used upwards of 6 mgd before leaving Memphis.

Is 3.5 mgd for cooling wasteful? I pose a few more questions.

How often do we see landscaping sprinklers going while it’s raining? Is water constantly running while we brush our teeth, shave or rinse dishes? Does water flowing down the curb on a hot summer day suggest we have overwatered our lawn?

I have estimated that we have approximately 57 trillion gallons of Memphis aquifer water beneath Shelby County. It can be argued that 3.5 mgd is a drop in the bucket, but we must never forget that our resource is finite and that individually we can be good stewards of our groundwater.

I suggest we consider looking at the withdrawal of Memphis aquifer water outside the context of who’s pumping it. We have an abundance of fresh, high-quality groundwater, but what benefit does that serve us as consumers or those industry partners the Chamber of Commerce is enticing to come to Memphis if that quality diminishes, if the groundwater becomes contaminated?

Memphis aquifer water primarily originates from rainfall in Fayette County to the east of Shelby County. It moves very slowly through the sand grains westward toward Memphis.

Similar to dating fossils of dinosaurs, we can determine the age of our groundwater. Beneath Downtown Memphis, the age of the Memphis aquifer water is between 2000-3000 years old.

But in two Memphis Light, Gas and Water Division well fields near TVA and Presidents Island, we see water as young as 23 years old. How is that possible and what does it tell us?

Young water (50 years old) originating from a shallow aquifer is moving through naturally occurring holes in the protective clay layer that sits between the Memphis aquifer and shallow aquifer. As the shallow aquifer is not protected by any clay, it is more prone to contamination and that contamination can migrate into the Memphis through these holes. (And no, the holes cannot be plugged.)

TVA groundwater pumping can contaminate Memphis Aquifer

So regardless of what industries are sitting off the bluff in Southwest Memphis and who’s pumping how much, it is the threat of contamination to the Memphis aquifer that I draw attention to.

Historical records as far back as 1765 indicate that the Mississippi River migrated back and forth across that area well before the U.S. Army Corps of Engineers tamed the river with levees.

We know holes in the protective clay layer exist in that area because we see young water. Are there are more holes than what we have mapped? Likely, and research would help here.

Evidence indicates that these holes are usually old river meander scars. So it’s not so much that TVA is wishing to pump 3.5 mgd from the Memphis aquifer, it’s just not the best place for anyone to pump from the Memphis aquifer.

It is easy for us to take for granted that which is plentiful and readily available. We should be good stewards of our groundwater, both to its quantity and quality.

U of M will allow employee's article on aquifer

Brian Waldron is director of Center for Applied Earth Science and Engineering Research (CAESER), Herff College of Engineering, University of Memphis. These are his views and do not reflect the opinion of the U of M.