The Word of the Day is Karst

There are a lot of words I don't use very often that are still pretty important. Consider, for example, the word karst. It turns out that karst refers to terrain that started out as (relatively) solid rock - usually limestone or dolomite - and portions of which, over time, have become riddled with holes.

In some cases, these holes are small, giving the rock the ability to hold water like a sponge (without the squishiness, of course). In the U.S. this is the case frequently enough that 40% of our drinking water comes from karst aquifers. (There’s another word for another day.)

The void spaces in karst can also be pretty large. Ever been to Mammoth Cave National Park in Kentucky? Or perhaps you’ve visited Marvel Cave at Silver Dollar City (included in the park’s admission price) in Branson, Mo. It turns out both were formed from karst, although they represent different aquifers. (As an aside, my wife and I visited Luray Caverns in Virginia on our honeymoon a few years back. It’s hard to determine from the USGS map whether they’re in a karst formation, but it was a nice place to visit anyway.)

I learned about karst last week as I was writing about a project that consists of surgically inserting a deep, new cutoff wall into the Wolf Creek Dam, in south-central Kentucky. It turns out the dam was built on a karstic formation and has had seepage issues ever since it was completed, which was the same year that I was born. A little leakiness here and there is no big deal. I've heard water dripping in every cave I've ever visited. But when it’s dissolving away the very foundation of the dam, it does become more of a concern.

(original construction photo, from the Corps' Fast Facts brochure ) 

Suffice it to say, experts in foundation engineering are working with the Army Corps of Engineers and this wall, when it’s completed in the middle of next year, should do the trick. At that point Nashville, some 200 odd miles down the river, and all the smaller river towns in between should be able to rest a little easier.

Also once the project is completed, the Corps expects to be able to let Lake Cumberland to fill up again, which will make a lot of marina owners, etc. (to say nothing of the 4.9 million visitors who show up every year with boats and fishing rods), very happy to get their shoreline back up where it’s supposed to be. After all, Lake Cumberland is the largest manmade reservoir east of the Mississippi and the ninth largest in the U.S.

Another interesting feature: one of the reasons the dam was built in the first place was to generate hydroelectric power. Ordinarily the pool elevation behind the dam is 720 above mean sea level. However, for most of the time since March 2005 it has been at about 680 feet, which seriously reduces how much electricity can be produced. For an interesting example, check out this TVA schedule. (When it was going full blast, electricity generation at the Wolf Creek Dam was bringing in $77 million a year.)

So yes, Virginia, or Kentucky, or whomever is asking, there is a word called “karst” and it’s pretty interesting stuff.

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The Corps of Engineers' Fast Facts brochure is available online at http://www.lrn.usace.army.mil/wolfcreek/pdf/Wolf%20Creek%20Dam%20Brochure.pdf

Here are some additional related websites, if you’re interested in pursuing more information.

http://heartoflakecumberland.com/lake-cumberland/history/

http://www.lakecumberland.com

http://www.lrn.usace.army.mil/wolfcreek/

Katie Couric video segment about living just downstream from the dam, from August 2007: http://www.youtube.com/watch?v=2gn5nTyUXbc&feature=topics 

Corps video about the project: http://wn.com/WOLF_CREEK_DAM,_KY