Report on the Karst Workshop with
Dr. Kevin Rudolfo
June 11, 2011
Do you know what an aquifer is? How about karst geology? Area residents learned how both are critical to understanding our drinking water at Saturday’s geology presentation and field trip, hosted by the Soldiers Grove Library and the Crawford Stewardship Project.
Geology professor Kelvin Rodolfo explained that an aquifer is underground rock or sediment saturated with water, like a sponge. Most people think that well water comes from underground pools, but this is rarely true. Our main aquifer is the Jordan sandstone, and it is replenished from precipitation on the surface, and not, as Rodolfo pointed out, from Lake Superior water traveling underground (a myth he has encountered many times). In fact, most groundwater is collected from rain and snow within a 5-mile radius.
Karst refers to limestone and dolomite bedrock that develops vertical and horizontal cracks because surface and groundwater is naturally slightly acidic, and it slowly dissolves such rocks, enlarging the cracks over time. It is responsible for our stunning local scenery of fissured cliffs and coulees. The process was first described in the Kars (or Karst) Plateau in Italy and Slovenia that has similar rocks. Features in karst terrain include underground caves, and sinkholes produced when they collapse. Other karst features are “blind” valleys where streams disappear below the surface to run in underground channels. Some water emerges as cold springs, keeping our streams at the low temperatures favored by trout.
Our aquifers are replenished by water traveling rapidly through these networks of cracks. Once the water enters a sandstone aquifer, though, it can travel only very slowly between the pores in the sand.That’s why karstic areas are particularly vulnerable to groundwater pollution. And Rodolfo says that pollution of our Jordan sandstone aquifer is “forever.”
In a Vernon County Karst Pilot Study, Rodolfo examined hundreds of well-drilling logs, and found that the area is riddled with karst. He says that landfills and impoundments of any sort are doomed to fail in such terrain because caves and crevices in the underlying rocks eventually collapse under the pressures exerted on them by the impounded fluids. This concept is evidenced by the numerous sinkholes studding the countryside.
A proponent of having your water tested, Rodolfo emphasized that nitrates in well water are responsible not only for the well-known “blue baby syndrome,” but also are carcinogens that pose a risk to everyone. The Valley Stewardship Network in Viroqua (608-637-3615) can tell you how to get your well tested. He recommends anyone whose well water contains more than ten parts per million of nitrate to install a reverse osmosis filtration system.