Groundwater Pollution

OWLS™ Water Education: Why Groundwater Pollution Occurs

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MOTHER NATURE NETWORK in depth look at what causes ground water pollution follows the Groundwater Contamination Infographic

ground water polution Infographic

Water education by Mother Nature Network.
Farms, freeways and front yards are flooding underground aquifers with dangerous toxins, slowly poisoning many communities’ water supplies. But how can this happen?

Copyright © 2013 MNN Holdings, LLC. / used as educational material only.

Russell McLendon / Nov 09 2009 / Farming & Agriculture /Toxins & Chemicals / Water Pollution

Click on right image to view animated infographic.

Farms, freeways and front yards are flooding underground aquifers with dangerous toxins, slowly poisoning many communities’ water supplies. But how can this happen?

For a planet where water covers 70 percent of the surface, Earth certainly makes its residents work hard for a drink. Aside from fish and other saltwater-sipping sea life, most of us have to share what little freshwater we can find on land.

And that’s no small task. Only 3 percent of all water on Earth is freshwater, more than two-thirds of which is locked up in glaciers and ice caps. Of the other third, barely a trickle collects on the surface — lakes, rivers, streams and swamps represent less than 0.5 percent of all freshwater worldwide.

So where’s the rest of it? An estimated 2.5 million cubic miles of freshwater are neither frozen, floating nor flowing on the surface, yet they account for at least 30 percent of total freshwater on the planet. Don’t bother looking on the planet for all that water, though; it’s actually in the planet. And while such a hidden location usually makes this underground ocean of freshwater safer to drink, it can also make it more dangerous — something the EPA recently acknowledged when it announced plans to crack down on the country’s biggest water polluters.

This can happen around big farms and animal-feeding operations, where fertilizers, pesticides, and manure often exist in large concentrations. When farm runoff drifts down into the ground, it can sometimes overload the soil’s filtration system and taint groundwater below. Some of the most dangerous agricultural pollutants include:


In estuaries and coastal waters, fertilizers often create algae blooms and dead zones. In groundwater, they can lead to the buildup of nitrates, which are carcinogenic. They can also impede infants’ ability to transport oxygen in their blood, leading to “blue baby syndrome.”


Leaky or overflowing sewers and septic tanks can release bacteria-laden human waste into surface water and soil, potentially contaminating drinking-water sources. But concentrated animal feeding operations (CAFOs) often deal in even larger amounts of waste. Farmers spread manure across fields as fertilizer, and many let it collect in wastewater lagoons lined with plastic to stop it from seeping into groundwater. Soil normally would filter out harmful bacteria anyway, but large enough concentrations can make it through and contaminate an aquifer. Such incidents are rarely scientifically proven, however, given the difficulty of tracing an individual illness back to bacteria deep in the soil. The EPA regulates livestock operations with more than 700 cows, but the New York Times reported in September that those regulations are rarely enforced and farmers often aren’t required to turn in paperwork. EPA Administrator Lisa Jackson has since responded by announcing that the agency will overhaul the way it enforces the 1972 Clean Water Act.


DDT famously washed into U.S. waterways in the 1960s and ’70s, moving up the food chain into fish and eventually into bald eagles — the synthetic pesticide soon began thinning out bald eagles’ eggshells so much it pushed the national bird to the brink of extinction. Not all pesticides bioaccumulate this way, and the most toxic era of pesticide use (copper and chlorine compounds, for example) is long behind us. But large crop fields, as well as private lawns and golf courses, are still sprayed with many EPA-regulated insecticides, fungicides and herbicides. Studies have linked one common weed killer, atrazine, to birth defects, cancer and low sperm counts in humans, and the EPA recently announced it will re-examine its previous findings that the chemical is harmless to human health.


Cattle, hogs and other livestock in CAFOs are often given a regimen of pre-emptive antibiotics, warding off the bacterial diseases that would normally flourish in such an environment. While many livestock industries have come to rely on such drugs, they may also be helping make some bacteria more drug-resistant. Overexposure to antibiotics can help bacteria evolve an immunity to the drugs, weeding out the weaker individuals and leaving more hardy ones alive to reproduce. In theory, this phenomenon can eventually create “superbugs,” or drug-resistant strains of bacteria and viruses. In July, the Obama administration announced it was seeking a ban on unnecessary antibiotics in livestock, although similar attempts have been shot down before by the agribusiness lobby.

Other Sources

City and farm runoff aren’t the only sources of groundwater pollution. Here are four other substantial threats to clean groundwater supplies:

Natural Gas Drilling:

A process known as hydraulic fracturing, or “fracking,” is often used to drill for natural gas. A blend of chemicals is mixed with water and blasted deep into cracks in the ground, opening them up to make the gas more accessible. EPA scientists are currently conducting an investigation into whether natural gas drilling is contaminating groundwater sources in some Western states — many houses have been abandoned after methane seeped into the water, and at least one house exploded in 2003, killing three people inside.

Mining: Mad rushes for gold, silver, mercury and other metals left a toxic legacy throughout many Western states during the 1800s and early 1900s, paralleled by current and former coal mines in the East and Midwest. Toxins such as lead and arsenic were used in 19th-century mining, and often persist today in abandoned mine shafts. A recent study by the U.S. Geological Survey found nearly every inland freshwater fish species is contaminated to some degree with mercury, a combination of mine runoff and emissions from burning fossil fuels, namely coal.

Military Bases:

Some U.S. military facilities have been criticized over the years for polluting local water sources, although the Defense Department has worked recently to lessen its environmental impact. But many bases are still plagued by contamination from long ago — the Associated Press reported earlier this month that the U.S. Army Corps of Engineers has spent $116 million cleaning up 58 Cold War-era nuclear missile sites that were contaminated with trichloroethylene (TCE), a chemical that was used to clean and maintain warheads but has since drifted into some groundwater supplies. TCE is believed to damage the human nervous system, lungs and liver, and can cause abnormal heartbeat, coma or even death. It’s also “reasonably anticipated” to cause cancer in humans, according to the National Toxicology Program, and the total nationwide cleanup may cost $400 million before it’s finished.

Saltwater intrusion:

By overpumping an aquifer near the coast, people are in danger of creating a vacuum that can quickly be filled with salty seawater. Known as “saltwater intrusion,” this phenomenon can make a water supply undrinkable and useless for irrigation, effectively rubbing saltwater in the wound of already-low water levels.

For more information about water pollution and water conservation, see these related articles on MNN:

Brighter Living: Conserving water indoors
How can I be smart about watering my lawn and garden?
Lax oversight creates toxic water supply
What is the Gulf of Mexico dead zone?
What happened to the Everglades?
EPA to evaluate whether common weed killer harms more than weeds
EPA: Chemicals found in Wyo. drinking water might be from fracking
Levels of Indian groundwater have dropped dramatically, study says
As Las Vegas spreads into the desert, water gets even more scarce
School drinking water contains toxins, AP investigation finds

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