Resource Cards
What is groundwater?
Water that occurs below the Earth's surface is called groundwater. You find it within the pores of sand and gravel or the cracks of fractured rock beneath the land. Groundwater exists in these openings in the subsurface environment like water exists within a sponge. Some of it can be removed from the ground and used for things like drinking, watering crops, and in the Columbia Basin, cleaning potatoes in factories before they are made into french fries.
Where does groundwater come from?
Water enters the ground from many sources. In the Mid-Columbia Basin this might include rainfall and melting snow, water from irrigated lawns and farm fields, leakage from rivers high in the mountains, or irrigation canals. If the water from these sources does not evaporate or get used up by plants it seeps into the ground and eventually fills the cracks in the rock or the spaces between the soil particles and becomes groundwater.
How does groundwater move?
Gravity is the main force that makes groundwater move. Water that seeps into the ground at high elevations is pulled downward by gravity. Because of this, groundwater generally moves downhill toward rivers or lakes at the bottom of valleys. In the Tri-Cities area, rain and snow that falls high on the hills and water put on crops to make them grow seeps into the ground and moves downhill to drain into the Columbia River. The water generally must move through the small spaces between rock particles and through small cracks in rocks, so it travels very slowly. It may take many years for rain that falls this year to become groundwater and then make its way into the Columbia River.
Why is groundwater important?
Groundwater provides 97% of the Earth's drinkable water. Farms, cities, and factories often rely on groundwater. Groundwater stays at the same temperature all year so it can be used to heat houses in winter and cool them in summer. In some areas, groundwater has become increasingly important as a source of heat for "heat pumps." In some parts of the world where little rain falls, groundwater is the only source of water. Without it no one could live in those places, and no plants would grow.
Why do scientists study groundwater?
Because of water quality's importance to the health of humans and ecosystems, federal and state governments and water users have focused attention in recent years on cleaning up polluted groundwater. Groundwater has been polluted in urban and rural areas by such things as industrial and municipal wastes; leaking sewers and septic tanks; animal feedlots; and lawn and crop fertilizers, pesticides, and herbicides. Scientists study how groundwater is polluted, including how below-ground differences in chemical composition as well as biological and chemical reactions affect the pollution. They look for levels of materials such as chromium, lead, mercury and arsenic - harmful in certain amounts - and how the pollutants might move with water below ground.
"Science is constructed of facts as a house is of stones. But a collection of facts is no more a science than a heap of stones is a house." Henri Poincare
Keep in mind this fact sheet is intended to be used only as background information to support your effort to encourage inquiry-based science, which parallels the way scientists uncover knowledge and solve problems.
See if you can find groundwater.
Here's how: Groundwater exists near the Earth's surface along rivers, lakes, and the seashore. At the beach begin digging, and before you go very far water will begin to pool in the bottom of the hole. You have uncovered groundwater. Does the water quickly fill the hole when you scoop it out, or does it take a long time?
Questions a scientist might ask: How quickly does the water fill the hole? Does the water seem to be moving toward the ocean, river, or lake or away from it? What is the water temperature? Is it warmer or colder than the water in a nearby lake or river?
Find out how fast water moves through different kinds of soil.
Here's how: Put cheesecloth over the end of two tubes that are at least 2 inches in diameter and 10 inches long. Fill one tube with fine sand or clay and the other with fine (pea) gravel. Pour water into each tube, and see how long it takes for the water to come out the bottom. Use a stopwatch to record the times. Does it take more or less time if the sand is wet when you start the experiment?
Questions a scientist might ask: How long does it take for water to travel through the material in the tube? How much water remains in the soil after it stops draining? If you needed to get water from the ground, would you want to put your well in a layer of fine sand or in a layer of fine (pea) gravel?
Write a brief description about what you learned about groundwater from experimenting with it.
- Environmental Education Pre K-8 Activity Guide, Project Learning Tree, 1993, American Forest Foundation, Washington, D.C.
- Full Option Science System (FOSS), Lawrence Hall of Science, University of California, Berkeley, California. Water (Grades 3-4, Landforms (Grades 5-6).
- Great Explorations in Math and Science (GEMS), Lawrence Hall of Science, University of California, Berkeley, California. Liquid Explorations (Grades K-6), River Cutters (Grades 6-9).
- National Science Resource Center: Science and Technology for Children (STC), National Academy of Sciences, 1996, Washington D.C. Land and Water (Grade 4), Soils (Grade 4).
- The Magic School Bus at the Waterworks, Joanna Cole, 1986, Scholastic, New York.
- Earth's Water: Groundwater - http://ga.water.usgs.gov/edu/earthgw.html
- Rivers Project Home Page - http://www.siue.edu/OSME/river/Whatisriversproject/Whatisriverproj.htm
- The Groundwater Foundation - http://www.groundwater.org/
- USGS Groundwater Information Pages http://water.usgs.gov/ogw/
- What is Groundwater - http://www.groundwater.org/kc/whatis.html
Initial development and printing was funded by the Partnership for Arid Lands Stewardship. Written by: Bob Bryce, Pacific Northwest National Laboratory. Series Editor: Georganne O'Connor; Design: WinSome Design; Printing: Eagle Printing and Graphic Design. First Printing: June 1998.
