Understanding Sinkholes: Seeing the Water Beyond the Springs
Understanding Sinkholes: Seeing the Water Beyond the Springs The expedition team learns about the importance of protecting sinkholes in order to protect the aquifer.
By Peter Lane Taylor
Until recently, the disposal of human waste was governed by a simple, overarching principle: out of sight, out of mind. Earth's abundance of rivers, oceans, and holes in the ground offered early societies a nearly effortless way to make waste disappear.
Today, however, modern science has taught us better. We now know that planet Earth is a sealed system. Nothing we heave out of sight truly disappears, whether it's an old refrigerator dumped into a local stream or a tiny molecule of carbon monoxide released into the atmosphere from our tailpipes. Instead of going out of mind, these wastes remain in the system indefinitely and eventually come back to haunt us. In terms of the sinkholes of Florida, these ghosts have recently re-emerged with a vengeance, threatening not only the water quality of the springs, but also the very water we drink.
If sinkholes are indeed windows to the aquifer, we have good reason to be concerned about the view.
Like Florida's springs, sinkholes are rare and spectacular geologic formations, caused most often by the dissolution of the limestone aquifer near the surface or the collapse of an underground cave. Yet, like many things in nature, scientific descriptions cannot do justice to the intrinsic beauty of these unique natural phenomena. Many sinkholes, like Big Dismal sinkhole near Tallahassee, are portals to Florida's primeval past, offering us a brief glimpse of the unsullied wilderness once nourished here.
In terms of the overall health of the aquifer, sinkholes are also vital to water's journey from the sky to the springs. Recent dye-trace and radio telemetry experiments, such as the Rose Sink study near Ichetucknee Springs, have demonstrated that once these windows to the aquifer are open, they often provide direct access to the aquifer through which water flows from the recharge basin to the springs.
Dirty Windows to the Aquifer
Yet, if sinkholes are indeed windows to the aquifer, we have good reason to be concerned about the view. For over a hundred years, sinkholes throughout north Florida have been known as "go-away holes" and treated as little more than natural landfills for getting rid of unwanted trash and commercial debris. As a result, it's not uncommon to find the bottoms of sinkholes littered with the worst kind of human debris: construction material, anti-freeze containers, oil filters, industrial solvents and cleaners, and car batteries-occasionally still attached to the car.
For some municipalities, sinkholes have offered an easy and cost-effective way to get rid of ever-increasing volumes of stormwater. In one example, the city of Tampa in the early 1980s directed its runoff into 15 nearby sinkholes to prevent flooding and the direct discharge of stormwater into Tampa Bay. It didn't take long for officials to realize the mistake they had made. Within only a few years, one of the city's oldest and most revered swimming spots, Sulphur Spring, was closed to the public due to bacterial contamination, increased salination, nutrient loading, and decreased water flows. The closure was precipitated in part from the stormwater directed into the city's sinkholes.
Filling sinkholes for road building and to eliminate their attraction as landfills, as it turns out, isn't any healthier. Because of their importance as recharge conduits for the underground aquifer, backing up a dump-truck load of cement to plug a "nuisance" sink can have a significant impact on the water flow in the springs downstream, which in turn can seriously impact the springs fragile plant and animal communities.
Making matters worse, the sight of a sinkhole doesn't usually send people running for swimsuits and picnic baskets. While naturalists view these unique geologic formations with awe and fascination, sinkholes are often located on private land where they are considered by landowners to be more of a liability than an asset. As a result, sinkholes are rarely afforded any kind of protected status, nor are the activities around them managed in proportion to their value to the overall health of the aquifer.
Yet, as people are learning, it's impossible to protect Florida's magnificent springs without also protecting the sinkholes and other less-than-magnificent karst features that feed them. For the scientists, state park personnel, and various state and county government agencies charged with protecting the groundwater and the springs, this means protecting the sinkholes we'll probably never see in a book and never explore in a canoe. Though they may be out of sight, we must always keep them in the forefront of our minds.
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