Objectives:
Students will:
- investigate changing groundwater levels and why they change.
- offer suggestions to keep groundwater levels from rapid decline.
- determine how different
rock layers affect groundwater levels.
Materials:
- Soda bottle with the ends cut off (used in "Getting the Groundwater Picture")
- glass or cup
- Cup of sand
- Cup of gravel
- Cup of water
- Pump (like a hand lotion pump)
- A piece of cheesecloth or pantyhose
Note: If you did "Getting the Groundwater Picture", you should already have this setup ready.
Procedure:
- Review the activity "Getting the Groundwater Picture".
- Discuss wells with the students and have them predict what will happen to their aquifer when they begin to use the pump on their well to draw water from the ground.
- Put a small piece of pantyhose on the bottom of the pump tube so it does not suck in soil or sand. Tape the pump to the side of the bottle so the pump is above and pointing out of the cut end of the bottle. Fill the soda bottle one-half full of small gravel and pour sand on top of that.
- Have a student fill the bottle about half full of water. Have the students locate the top of the aquifer or water table.
- Have a student begin pumping water from the aquifer into a glass. At certain intervals, have the students locate the top of the water table. Note the changes. Discuss the reasons.
- How does the water get back into the well after it has been pumped up? (rain, snowmelt, surface water returning to the soil, water can seep in from other aquifers, etc.) Discuss recharge.
- Have the students discuss how different substrata would affect the pump. Would it ever bring up mucky water? Would certain rock types mean you would have to put the pump deeper to get water? Would it be easier to get water from shale or limestone? What if the well were to go through a cave?
-
Imagine
you are in a farming community. Will irrigation have an affect on your
well? What about use of fertilizers or pesticides? Will you always be
able to get water at the depth you first drilled to? Would a drought
effect your water supply? How would the balance in the water table be
maintained? Will other wells from the surrounding area (farms or cities)
impact your water supply? - Consider the following: Will affects of local industrial practices affect your water quality? What about dumping oil into the ground, dumping chemicals into nearby rivers? What effect would dumping waste directly into old wells?
- Discuss that the water table is not level, so all wells will not be at the same depth even if they are close to each other. The water table will mimic the surface above, having hills and valleys. Water can dip where the land above does, or it can dip where a well has been pumping water out. In the experiment with the pump, as water was pumped out, the water level dropped. Water drops more rapidly near the well than away from it. Often the replacement water cannot return as quickly as water is being taken out. Most rainfall is evaporated or used by plants, some goes into rivers or streams and only about 1% of water returns to the water table directly.
- What are some of the problems with getting water from a well? What is the cost of installing a well? (Depth of water, hard rock to break through to get it, cost, chance of well drying if not deep enough, etc).
- Does the placement of the well matter? Have the students guess, thinking of their own homes, how far a well should be from the following: septic tank, livestock yards, silos, septic leach fields, petroleum tanks, manure storage, pesticide and fertilizer storage and handling. Soil is a filter, but it can only clean so much. After the students have made their guesses, tell them a well should be at least 25 feet from a septic tank; 50 feet from a livestock yard, silos, and septic leach fields; 100 feet from petroleum tanks, manure storage, pesticide and fertilizer storage, and handling; 250 feet from manure piles. If a well is not carefully placed or is misused, anything from the surface can get directly into the water supply without ever passing through the ground.
- If two wells were placed close together, could this cause a problem? What if one of the wells was contaminated? What if one well connected two aquifers could there be positive effects? How about negative effects? (Wells generally have casings, like a straw around your pump tube, which would not allow water from another aquifer travel down the hole for your pump and pollute the new well or aquifer. However if these casings don't go down far enough, polluted water can enter your new aquifer. State laws vary on how deep these casings have to be. What if the length the law requires is not far enough to protect your well?) Considering all of these factors, how would you decide where is the best place to put your well?
This activity is available as an Adobe PDF.
Groundwater