Into The Outdoors

Advanced Overview

Have you ever toured a cave? They are dark, maze-like, and some of the most interesting natural geologic features possible to explore. To many spelunking explorers, they represent Earth’s final frontier. Scientists estimate that only 8-10% of all caves on the planet have ever been explored. So where are all the others hiding?

Depending on where you live, caves might lie under your feet. A decent chunk of the United States consists of karst topography. Many caves that form in this type of landscape don’t have visible entrances large enough for people to explore. Unlike humans, water only needs a tiny crevice to penetrate fractured limestone and flow downward towards an aquifer.

Wells that tap into groundwater within the bedrock still provide a sizable percentage of citizens with their drinking water. And if these wells are located in areas with karst topography, those same citizens run the risk drinking contaminated water. Not to frighten you. Just trying to enlighten you with the science of karst country. Salmonella, dangerous protozoa, and harmful chemicals may be present in any given aquifer located in an area with karst topography. And people have no control over where karst topography exists. So what are some of the solutions to water pollution in these places?

The solution involves ensuring that as few as possible harmful materials get spread on and pass through the ground in karst regions. Sinkholes are one of the main pathways to the underground that often connect with aquifers. Sinkholes form when rock over cavities or caves weakens and eventually collapses. This forms a kind of vacuum that carries soil down into the Earth. A cone-shaped depression forms and, oftentimes, the bottom of a sinkhole becomes a cave entrance. Water, and anything else that it carries, is then able to reach aquifers without any filtration through layers of soil.

Many landowners don’t understand the connection between sinkholes and their groundwater, and unwittingly use sinkholes as trash dumps. Kitchen appliances, animal carcasses, car batteries, and cars themselves have all been removed during sinkhole cleanup projects. Makes you wonder, why would anyone dump trash in such a place? The shape of sinkholes hides garbage from view and maybe the landowners are thinking, “Out of sight, out of mind”. However, these landowners risk unknowingly contaminating their water and possibly the water an entire community relies on.

The bottom of sinkholes sometimes plug with rock or soil, creating ponds or lakes. If these bodies of water are located in a pasture, livestock enters them to drink… and you guessed it, go to the bathroom. Just because the sinkhole is plugged enough to create a pond, doesn’t mean that nothing permeates down into the groundwater. Manure can wash down and carry harmful bacteria into local drinking water supplies.

That’s why farmers should prevent cattle and other livestock from accessing sinkholes and other known “karst windows”. Karst windows get their name because they serve as direct openings into the underground. Because underground streams and rivers can flow for miles in areas of karst topography, even a few fences around major sinkholes make a big difference when it comes to preventing contaminants from entering groundwater.

Education offers one of the single best solutions to water pollution prevention in karst topography regions. Caves and springs have attracted people for thousands of years due to their interesting formations, eerie darkness, and the ways that they can be used for people. Caves serve as refrigerators, churches, places to gather food, and even graveyards. People in many rural areas of the world depend on springs from cave systems for their drinking water. And understanding the connection between the surface and groundwater reduces pollution in many karst topography regions.

One example from Texas illustrates yet another form of karst topography protection. The Edwards Plateau, a thick band of limestone in central Texas, sits over a large aquifer. Several species of blind salamanders call that aquifer home and live nowhere else. These blind, colorless amphibians feed on small insects and perform the role of top predator in this rare ecosystem. In other words, if they go, the ecosystem in the aquifer will collapse. And, for many years, people expected them to go.

The cities of San Antonio and Austin sit directly over the Edwards Plateau. The millions of people that live in those places use lots of water. They were sucking so much water out of the aquifer that it was getting dramatically lower. The more people moved to these fast-growing cities, the more pollution came into the picture. As more pollution entered an aquifer with less and less water in it, concentrations of pollution increased. And he salamanders couldn’t take it.

A few species were lost. But their extinctions spurred people into action. Beginning in the 1980’s and 1990’s, huge battles between the Texas government and citizens concerned about drinking water exploded. Many salamander species were listed on the Endangered Species Act and this affected what people could and could not do in the Edwards Plateau. It cost some developers a lot of money to protect the salamander but there have been no extinctions since these battles began. The salamanders, without ever knowing it, kept the drinking water of central Texas safe for years to come.

How do you know if you live in an area of karst topography? All states with even a small amount of karst have programs where karst features, like sinkholes and caves, are reported. You can check the websites of these programs or call their offices to find out if you are vulnerable to the problems of karst topography pollution. If you are, maybe you will feel empowered to volunteer with groups working to clean up sinkholes or caves. Who knows…you might even play a role in inventing a whole new solution to karst topography pollution!