Chapter 10-How Water Behaves in the Ground

Overview:Although we each use between 120 and 200 gallons of water each day, we seldom have a full understanding of where our water comes from, how it is stored and delivered to us, or what can happen when it is not respected. In the United States, most water used for domestic purposes comes from surface systems (lakes, rivers, streams, reservoirs) or groundwater (wells or springs). Desalinization of ocean water (a surface water system) produces fresh water in only a few coastal areas. Most of us are aware that our actions on land have an impact on surface systems. We can read almost daily about pollution of our major rivers, lakes and oceans. We do not, however, often hear about groundwater systems; yet, in the United States, nearly 50 percent of the people rely on groundwater as their primary source of water. A recent study of well water (not only in Montana but throughout the United States) showed that nearly 50 percent of the well water samples tested were contaminated with bacteria.
     With these facts in mind, we must understand groundwater systems how and why groundwater systems exist, how they are affected by land surface activities, and how we can effectively use them.

Materials Needed:

• Copy of Montana State University Extension Service video, "Preventing Groundwater Contamination"
• Video projector (VCR)
• Television or monitor for viewing video

Procedure: When class begins, ask the students to recall the previous lesson about groundwater contamination. They will recall that layers or zones of rocks and gravel saturated with water underlay the earth's surface soil. In many places, the pores and spaces between the rocks and gravel are of sufficient numbers, volume and size that the water in the pores can be pumped. Therefore, these layers (aquifers) serve as large storage reservoirs. They should also recall that under equilibrium conditions, we can pump most of the rain water entering these aquifers. They should also recall that aquifers of different materials (i.e., amounts and sizes of gravel and rocks) produce different amounts of water upon pumping. Once an aquifer is contaminated, it takes quite a bit of pumping to remove the contaminant. Also, when a contaminant is spilled on a wet soil, not much water is required to move the contaminant to groundwater.
     One way to have the students gain an understanding of the groundwater idea is to have them draw a picture of the hydrologic cycle. Replace the earth with the model pumping well. Another activity is to design a crossword puzzle using the key words of this lesson. After you have discussed the idea of groundwater, the process of groundwater pumping, and the idea of aquifers, ask the students if there are any questions they would like to have addressed.
     Point out to the students that these examples are just a few of the ways that groundwater can become contaminated. Anyway, it usually takes a long time to see the effects of groundwater contamination, although little water may be necessary to cause contamination. Producers used models, videos, and time lapse photography to show other ways groundwater becomes contaminated. Ask students to think of other ways in which groundwater becomes contaminated. List these on the board.
     After the discussion, have the students watch the MSU Extension Service video "Preventing Ground Water Contamination." Following the video, discuss additional groundwater ideas with the students.

Lessons Learned: We have explored the ideas of groundwater recharge and contamination. During these lessons, the students will have gained an understanding of aquifers, aquifer recharge, and well pumping. They will also see how wells work. They should have a better understanding of the value of storage and protection that groundwater provides. They should understand how wells work, and how easily groundwater systems can become contaminated. They should also realize the difficulty of cleaning a contaminated aquifer. By watching the video and discussing the ideas presented, they should understand the relationship between groundwater and surface water systems, and how contaminants move within groundwater systems and from one well or aquifer to another. They should also understand that it sometimes takes a long time for a contaminant to move from its point of entry to detectable levels in well water or a surface water supply.
     Because of the activities in this lesson, students should be aware of the following ideas:

1. groundwater behavior and aquifers
2. aquifer recharge and contamination
3. pumping wells
4. relationship between groundwater and surface water supplies
5. complexities of groundwater contamination and clean up

The lesson above was adapted from "What is Water Quality? A Resource Guide for 4-H Leaders and Teachers," 80 pages of activities and experiments related to water quality. ($5.00) Order from the Montana 4-H Program at Montana State University-Bozeman. Phone 406-994-3501.

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