The water beneath our soil is a valuable resource. Groundwater makes up about 98 percent of the usable fresh water on Earth (see References 6). Understanding how we pollute groundwater will help us protect it from contamination and ensure that it will remain available to future generations.
What is Groundwater?
Simply put, groundwater is moisture that is stored in the earth. It may have started out as rain, snow, hail or sleet that soaked into the ground and saturated the soil. The soil acts kind of like a giant sponge -- the groundwater occupies the spaces between the soil particles. Groundwater is important because we use it for drinking, as well as watering crops. An aquifer is an area that holds a great deal of water. It is easy to pump water from an aquifer for drinking, washing, bathing or watering crops. (See References 1) One of the most important U.S. aquifers is the Ogallala aquifer, which lies beneath 225,000 square miles of land in the Great Plains (see References 4).
The Water Cycle
Groundwater is not stationary -- it is part of the water cycle. The water cycle is a continuous loop. The sun drives the water cycle by heating the water in the Earth's oceans. Some of this water evaporates into air and forms into clouds. Clouds generate precipitation. Precipitation that falls onto land becomes surface runoff or soaks into the soil where it replenishes groundwater and aquifers. Some groundwater is close to the surface where it seeps back into lakes, rivers or streams. Other times, springs release groundwater or people pump it out of the ground. Unfortunately, this means that pollution can move through the water cycle, too. (See References 2)
How Groundwater Gets Polluted
Pollution reaches groundwater in several ways. Rainwater and runoff may contact contaminated soil while filtering down into groundwater. Some liquid hazardous substances, like fuel residues, solvents and other chemicals, can filter down through soil and rock and into groundwater as well. Some oily substances don't mix with the water but instead remain pooled on top, acting as a long-term contaminant. (See References 5) Natural substances can contaminate groundwater. Arsenic is a naturally occurring toxic metal that sometimes gets into wells and makes the water unsafe to drink (see References 3).
How to Clean Up Groundwater Pollution
Groundwater contaminants may go undetected for years. When scientists discover pollution, they assess the risk. If the danger to human health and the environment is high, people may attempt to clean up or contain the pollution. Cleanup strategies may include pumping the water from the soil and treating it to remove the contaminants, and then pumping it back into the ground. Sometimes people try to contain the pollution instead, using biological, chemical and physical processes to treat the water while it is still in the ground. A badly polluted aquifer may be abandoned and the users may have to find a new source of water. (See References 3, 5)
Ways to Prevent Water Pollution
You can help prevent groundwater pollution. Look around your house for old materials that could seep into the ground, such as used oil, paint, solvents and other chemicals. Make sure they go to an appropriate disposal facility instead of into the garbage. Never pour any chemicals down the drain, and try to use natural, biodegradable products. Minimize the use of chemicals on your lawn; for example, help pull weeds instead of spraying them. (See Resources 1, Kids Can Protect Groundwater Too!)
- The Groundwater Foundation: What Is Groundwater?
- U.S. Geological Survey: The Water Cycle
- Water Encyclopedia: Groundwater Pollution
- Iowa State University; Ogallala Aquifer Depletion; Michael Glantz; 1989
- U.S. Environmental Protection Agency: Superfund for Students and Teachers: Groundwater Contamination
- National Ground Water Association; Ground Water Introduction and Demonstration; Kimberly Mullen
Based in the Midwest, Bethany Wieman has been writing articles about gardening, DIY, finance, travel and sustainability for more than 10 years. She was featured in the book "The Complete Guide to Growing Vegetables, Flowers, and Herbs from Containers." Wieman's professional background is in marketing, working with such brands as Swiss Army, Timberland and Callaway Golf. She holds a Bachelor of Arts in English.
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