Students will build an aquifer with wells for pumping and monitoring. Students will see that too much pumping dries up the well and contamination is persistent.
Main Curriculum Tie:
Science - 4th Grade
Standard 1 Objective 2
Describe the water cycle.
- environmental scientist
pint jars (one per group)
lotion pumps (craft store?)
1/4" vinyl tubing
bucket for wastewater
Background For Teachers:
Groundwater makes up 27% of the world's fresh water and 52% of Americans rely on groundwater.
Aquifers are composed of gravel, sand, etc with water filling the voids between grains (a sandstone is ~30% voids). The water table is the boundary that separates saturated rock or sediment from unsaturated rock/sediment. The saturated zone contains water and rock/sediment only. The unsaturated zone also contains air.
Monitoring wells are used to check the water table height. If a well is drilled into a static aquifer, the height of water rising up into the well represents the water table. Production wells are generally larger diameter and have submersible pumps that remove up to 100's of gallons a minute. If the aquifer is pumped faster than recharge, the water table will drop and the well will eventually run dry. The bottom of the well must be within the saturated zone to be able to pump water.
Student Prior Knowledge:
Groundwater is part of the water cycle.
Intended Learning Outcomes:
1. Use science process and thinking skills.
2. Manifest science interests and attitudes.
3. Understand important science concepts and principles.
4. Communicate effectively using science language and reasoning.
5. Demonstrate awareness of the social and historical aspects of science.
6. Understand the nature of science.
Ahead of time:
Cut straws in half to fit in the jars.
Using electrical tape, attach 9" pieces of 1/4" tubing to the lotion pumps.
Start with a refresher on groundwater.
Water is stored within the voids in rocks, the water table is the top of the saturated zone, water flows underground and discharges into streams, lakes, and springs. That water can be intercepted by pumping wells.
Discuss the importance of groundwater:
15.3 million km^3 of groundwater but that is only 1% of the Earth's water. However that is 27% of fresh water with 72% being ice and the remaining 1% is split between rivers, lakes, streams and the atmosphere. 52% of Americans rely on groundwater (100% if you count agriculture). Salt Lake City pumps 160 million cubic yards of water per year (that's 32 billion gallons).
- Production: biggest of the well types and have pumps attached (100s of gallons a minute).
- Monitoring: used to check the water table and collect samples by scientists
- Artesian: free flowing (high pressure at depth, no pump required)
- Oil: deep and expensive up to $20 million per well
Building the model:
As the students begin pumping (into a small cup), the water coming out will be murky and look unclean. Tell them that all wells need to be "developed" to remove the fine sediments.
- Tape a short straw vertically to the inside of the jar (close to the bottom, this is your monitoring well).
- Add an inch of pebbles
- Set the lotion pump in place, centered in the jar.
- Add a few inches of gravel so the well is 1/2 to 2/3rds buried.
- Add water just short of the top of the gravel.
- Before you begin pumping, check the water table with the monitoring well and mark it on the jar.
It will be your job to come around and give the students a small amount of water. Tell them that when it rains, only 10% of the water makes it to groundwater, the rest runs off or evaporates.
Once the wells are developed (a few little cups), start playing out different scenarios:
- What if there was a leak in the sewer line and contaminated water seeped into the aquifer (put a drop of food dye in their waste water cup and tell them to dump it back into their jar). How much pumping does it take to remove the dye? If this was your well, what would you do in the meantime (get water from your neighbor, drill a well elsewhere?
- After the sewer leak is mostly removed, a gasoline truck crashes next to your well and leaks gasoline into the subsurface (add 3 drops food dye to the pebbles). How long does it take to remove the dye? If you pump 3 oz a year, how many years does it take to clean up? Where do you get water in the meantime? Is it safe to drink water that is contaminated with gasoline?
- Contaminate one group's model but not the others. If they want clean water, they will need to share with the other students. All but one well could be contaminated and everyone will have to share from one well. Not a lot of water is it?
- Other scenarios can be played out with droughts and contamination.
EPA Water Sourcebook: Grades 3-5 "Well, Well, Well"
Created Date :
Nov 16 2010 09:11 AM