Groundwater

Photo of slightly polluted water that will be absorbed by the ground below. — Water rises just above the surface in Caroline County, Maryland. (Photo by Chesapeake Bay Program)

FAQ

What is groundwater?

Groundwater is water that can be found under the earth’s surface, stored in the cracks and spaces between particles of soil, sand and rock. Groundwater comes to the earth’s surface when it flows through a spring or into rivers, streams and lakes. Scientists with the U.S. Geological Survey (USGS) have found that in an average year, almost 27 of the 50 billion gallons of streamflow that enter the Chesapeake Bay come from groundwater.

How does groundwater become polluted?

Groundwater can become contaminated when pollutants on the land seep into underground aquifers. A number of human activities can pose a threat to groundwater, including leaking or damaged storage tanks of gasoline or oil; abandoned containers or uncontrolled spills of hazardous waste; fertilizers, pesticides or road salts applied to lawns, fields and roads; and leaking landfills and septic systems.

How does polluted groundwater affect the Chesapeake Bay?

Contaminated groundwater can push pollutants into the Chesapeake Bay. The slow movement of polluted groundwater into the Bay can lengthen the “lag-time” between the adoption of a pollution-reducing practice and the positive effect of that practice on a particular river or stream. This means slow-moving groundwater could push nutrient pollution into the Bay even after we have lowered the amount of nutrients we put on the land.

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Terms

Aquifer

A body of permeable rock that can contain or transmit groundwater.

Bedrock

Solid rock underlying the earth’s surface.

Groundwater

Water that is stored under the earth’s surface, in the cracks and spaces between particles of soil, sand and rock.

Lag-time

The span of time between the adoption of a pollution-reducing practice and the visible effects of that practice on a particular waterway.

Nutrients

Chemicals that plants and animals need to grow and survive but, in excess amounts, can harm aquatic environments. Elevated levels of the nutrients nitrogen and phosphorous are the main cause of poor water quality in the Chesapeake Bay.

Pesticides

A general term that describes the chemical substances used to destroy or control insect or plant pests. Many pesticides are manufactured and do not occur naturally in the environment. Others are natural toxins that are extracted from plants and animals.

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