Under your feet exists a world of darkness and mystery, where caverns are formed by flowing water, to create a distinctive landscape known as karst. Karst landscapes form in areas where soluble rock lies beneath the ground’s surface. The most common soluble bedrock that karst landscapes form in is limestone. Karst forms very slowly over thousands of years as slightly acidic water (known as carbonic acid) seeps into the ground and dissolves the soluble rock down below. Carbonic acid forms when water (H2O) mixes with carbon dioxide (CO2) that is naturally occurring in the atmosphere and soil. Eventually, as the soluble rock dissolves away, the connected features characteristic of a karst landscape are formed. These features include networks of sinkholes, springs, caves, underground rivers and aquifers.
A large portion of Kentucky is considered a karst landscape. Other places known for their karst environment include parts of Florida, Tennessee, Alabama, and Georgia, amongst many other states. Examples of international locations where karst landscapes are found include Slovenia, Italy, France, Germany, Belize, Jamaica, China, Australia, and the United Kingdom. In each of these places, the karst landscape plays an important role in the quantity and quality of each area’s water resources. Bowling Green, Kentucky is no exception! Because we live in a karst area our actions on the surface can directly impact the health and quality of the world that is situated below, so we must think differently about how we manage our water resources and what we do on the land surface.
Why should you care about karst?
Karst landscapes cover about 12% of the world's ice-free land surface, in areas where more than 25% of the world's population live. Karst aquifers supply 20-25% of the world's population with fresh drinking water. All of Bowling Green is situated on karst, which makes its groundwater highly vulnerable to contamination.
Why are karst landscapes vulnerable to groundwater pollution?
There are two main reasons why karst landscapes are vulnerable to groundwater pollution, and therefore why we have to be aware of how our actions on the surface impact what’s down below.
The surface and subsurface are more connected in karst areas than most other landscapes. Karst has natural openings on the surface and throughout the underground bedrock that can become connected networks of sinkholes, springs, caves, underground rivers and aquifers. After every rainfall, trash and chemicals on the surface can easily enter through natural and man-made openings in the ground and rapidly travel throughout these networks. In fact, water and pollutants which flow into injection wells, curb inlets, sinkholes, cave entrances, or other stormwater drains does not travel to water treatment facilities where harmful chemicals or trash can be removed. Instead, the water flows directly into natural underground voids and passageways without being cleaned, and then flows to caves, springs, or surface water bodies such as the Barren River. Therefore, human actions on the surface, such as over applying fertilizers/pesticides or disposing of trash into sinkholes, can quickly and easily pollute both the water resources flowing below ground and the water bodies on the surface.
The bedrock that karst forms in (often limestone) does not effectively filter pollution from water and allows water to travel quickly through karst landscapes. Surface water can quickly moves underground through the natural karst features (sinkholes, cave openings, or sinking streams) or man-made features (injection wells, curb inlets, stormwater drains), and then can continue to travel for long distances through underground rivers or small cracks in the rock. To picture how fast this water can travel below ground, think about how a surface stream or river flows since underground rivers and surface rivers often look very similar. This flowing underground water can carry pollutants over long distances throughout the entire karst system. Therefore, what we do on the surface can impact our groundwater supply almost immediately. Groundwater may be out of sight temporarily, but because we live on a karst landscape, it may eventually resurface with all of the pollution it has been carrying. This pollution could be trash, debris, or even harmful chemicals from agricultural fields, home lawns, and urban streets and parking lots.
How do we impact karst landscapes and groundwater?
In karst areas, avoidable human impacts to groundwater often occur because many people do not know they are living on a unique landscape or do not understand how their actions on the surface affect what's below ground! Here is a list of some common activities in Bowling Green that can damage the karst resources in the state. Help be the Solution to Stormwater Pollution!
Urban development, especially surfaces that block water from soaking into the ground, such as pavement and buildings, can cause stormwater flooding on the surface and prevent water from resupplying karst aquifers. Since stormwater from rainfall can quickly carry greases, chemicals, nutrients from pesticides, fertilizers, oils and other waste products to low-lying areas, stormwater is one of the primary causes of pollution in many urban karst areas, including Bowling Green. Try to prevent stormwater-related damage to our karst landscape by making sure storm drains, curb inlets, and injection wells are free of debris and trash. Remember, make sure you fix leaky vehicles because the leaks don’t just end up on your driveway.
Sinkholes and caves are often direct connections to groundwater, but they are commonly used as illegal garbage dumps. When sinkholes and caves are used as dumps, groundwater can easily become polluted as rainwater drains through the sinkhole or cave, pick up pollutants in the garbage, and then makes its way directly to groundwater supplies without any natural filtering. Often, in a karst landscape, this polluted groundwater will eventually make its way to a nearby surface water bodies. In Bowling Green and the surrounding area, the surface water body may be the Barren River, where our drinking water comes from, or another creek where you enjoy boating or fishing.
If farmers and homeowners don’t follow package instructions when applying pesticides and fertilizers, these concentrated chemicals can be easily washed into surface waters after a storm event or even soak through the soil and rock to the groundwater flowing below. Make sure you always follow application instructions and use pesticides and fertilizers only when necessary. Never apply these chemicals before a precipitation event such as rain or snow.
Septic tanks are common throughout Kentucky, including Bowling Green, but they can cause groundwater quality to decline if they are not properly constructed and maintained. A poorly maintained or constructed septic tank can allow pollutants in the tank to seep into the ground without undergoing any of the filtration process the tank system is build to provide. Do you know if your home has a septic tank and where it is on your property? How often do you have your septic tank inspected? A septic tank that never needs cleaning, is most likely broken! Be sure to have your tank inspected every 2 to 3 years. Is your house able to be hooked to a City sanitary sewer line? Sanitary sewer lines take wastewater to treatment plants so you don’t have to use the septic system.
Clogging natural cave entrances and sinkholes can prevent water from leaving the land surface and reaching the aquifer. Never fill in a cave or sinkhole entrance, and try to keep entrances free of debris! Keeping stormwater drains and curb inlets clear of debris is also important for preventing stormwater flooding and reducing water pollution.
Using more water than can be recharged by rainfall can eventually reduce the amount of water reaching the Barren River and being stored underground. This will decrease the amount of water available for our use and could cause springs to reduce their flow. Sinkholes can also develop as water-filled spaces in the aquifer are drained, leaving no support for the weight of the land surface. Conserve water whenever and wherever you can!
In a karst area, we have to be very careful of what we throw away and how we dispose of wastes. Be sure to pick up pet waste because any waste on the surface can be washed into our surface or groundwater supplies. Dispose of leftover paint by mixing it with kitty litter until solidified, then throw it away. Call hazardous waste disposal before tossing any hazardous chemicals from your house and garage! Never dispose of non-dispersible wipes down the toilet and minimize your use of the garbage disposal. Wipes in the toilet and food waste in the disposal can clog water lines and backup into your home or the karst groundwater. Lastly, there are no butts about it...Cigarettes on the ground, end up in our ground water. Never dispose of your cigarettes butts on the ground.
The City of Bowling Green's Stormwater Program is available to visit your classroom with a 40 to 50 minute long educational program. Our curriculum consists of information on our local water quality and the following:
Water Shed Model Display (where does water go).
Karst Landscape (definition and examples).
Strong focus on Bowling Green landmarks such as caves, springs and underground rivers.
Things that we can do to improve water quality.
How do pollutants and chemicals travel through our water?
Below is a list of other resources you can use to learn more about our local karst landscape, stormwater management, and groundwater supplies. Download and share these resources to Become Part of the Solution to Stormwater and Groundwater Pollution! Copyright is maintained by the Bowling Green Department of Public Works and its UnderBG Water Education campaign partners and should be indicated during any use of these materials.
What is Karst Infographic
Bowling Green Stormwater Complete 3-Panel
Bowling Green Stormwater Panel A (Stormwater Roadtrip)
Bowling Green Stormwater Panel B (Point and Non-point Source Pollution)
Bowling Green Stormwater Panel C (City Control Measures)
As part of our UnderBGKY.org Karst Groundwater Awareness Campaign, the Bowling Green Department of Public Works has participated in the Western Kentucky University “Red is Green” Tip of the Week Campaign to produce a series of short video clips about our local water.
The city has also been featured in a series of Spotlight on Bowling Green videos to discuss a selection of the programs and other initiatives available in the community.
According to the Environmental Protection Agency, the primary cause of water quality problems in the United States today is something called “nonpoint source pollution.” Nonpoint source pollution is runoff from rainfall, snowmelt, or irrigation that picks up soil and other contaminants as it runs over land before ending up in surface water bodies in underground rivers and aquifers. Because of our karst landscape, in Bowling Green stormwater runoff often seeps underground where it flows very quickly through cave streams until it reappears as springs. This runoff can have many negative impacts on plants, animals, and humans.
Sediment can cloud the water and make it difficult or impossible for aquatic plants to grow. Sediment can also destroy aquatic habitats.
Excess nutrients can cause algae blooms. When algae die, they sink to the bottom of the water body and decompose in a process that removes oxygen from the water. Fish and other aquatic organisms can’t live in water with low dissolved oxygen levels.
Bacteria and other pathogens can wash into swimming areas and create health hazards. Trash washed in waterbodies can choke, suffocate, or disable aquatic life such as ducks, fish, turtles, and birds.
Household hazardous wastes like insecticides, pesticides, paint, solvents, motor oil, and other auto fluids can poison aquatic and human life.
Polluted stormwater often affects drinking water sources. This, in turn, can affect human health and increase drinking water treatment costs. Barren River is the source of Bowling Green’s drinking water. The River is feed by stormwater runoff flowing along the surface and water that flows through the underground karst rivers before it resurfaces at springs along the River’s banks.
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