Northern Shenandoah Valley Watershed Investigation
Hydrogeology Experiment on Surface-Groundwater Interactions:
How Do Our Actions Affect Water Quantity and Quality?
Teacher
Virginia Science SOLs: 6.1, 6.7, 6.9
Prepared for the Southwest Texas Educators Workshop Spring 2007. Developed by Jessica Gordon,
Graduate Research Assistant, Jackson School of Geosciences Outreach Programs, The University of Texas at Austin.
Modified by Blandy Experimental Farm Education Staff 2/2011
Learning Objective: Students will learn how different surfaces influence water runoff
and groundwater recharge and how pollution travels through creeks, streams, and
aquifers.
Key Concepts & Skills: Different surfaces affect the movement of water in various ways.
Students will make observations and predictions about surface runoff and groundwater.
Students will collect, record, and analyze data.
Investigative Question: What impacts do different surfaces have on surface water
runoff, groundwater recharge, and stream pollution?
Materials
Hydrogeology models
Beakers
Watering cans
Water
Buckets
Calculators
Graduated cylinders
Stopwatches
Student Worksheets
Vocabulary
Runoff
Aquifer
Recharge
Groundwater
Stormwater
Watershed
Impervious surface
Pervious surface
Permeable
Background Information: Water is an essential resource for all living things. Half of the
drinking water in the United States comes from groundwater sources, water stored
underground in cracks and spaces in soil and rocks. Groundwater needs to be restored
to provide freshwater and this occurs through precipitation. Ideally, most precipitation
would go into recharging (i.e. replenishing or restoring) the groundwater supply and to
plant up-take. However, runoff occurs when precipitation cannot infiltrate the soil. This
occurs when there is a lot of precipitation but also happens today due to anthropogenic
(human) causes such as impervious (impenetrable) surfaces. When there is an excess of
precipitation, much of the water runs off land and becomes stormwater. Stormwater
runoff is generated when precipitation from rain and snowmelt events flows over land
or impervious surfaces and does not seep into the ground.
An aquifer is a geologic formation made of a layer of permeable rock (fluids can pass
through) that has large pockets of water. Water can enter an aquifer through faults,
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Northern Shenandoah Valley Watershed Investigation
fractures, sinkholes, or seep through the soil in a process called recharge. How we live
on our watershed (the area of land that drains into a body of water) can impact water
quantity and quality. It is important to maintain the quantity and quality of
groundwater in order to be able to continue to use this resource.
Post-experiment question ideas:
1. Which surface had the most run-off? Why do you think this happened?
2. What does impervious mean?
3. What commonly sits on concrete? [cars] Do you ever see any liquid leaking
from a parked car? [oil] Where will this oil eventually go?
4. Which surface had the most water recharge? [bare soil]
5. What did the water look like? [dirty] What’s in the water? [dirt]
6. What do we call that process when soil funs off with water? [erosion]
7. Did the recharge water from the plant surfaces look different from the bare soil
surface? [yes; little or no soil] Why do you think this happened? [roots keep the
soil from eroding]
8. Lots more potential questions to ask your students!
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Northern Shenandoah Valley Watershed Investigation
9. Hydrogeology Experiment: Use the hydrogeology models to determine how
surface type affects runoff and groundwater recharge. Then, design an
experiment that produces the least amount of runoff and the greatest amount of
recharge.
Hydrogeology Model: The Effect of Groundcover on Surface Runoff and Groundwater
Recharge
For this investigation, hydrogeology models have been built to demonstrate how
impervious and pervious surfaces (concrete, soil, non-native grass, and native plants)
influence surface runoff and groundwater recharge. Discuss the features of the
different surfaces.
Type of Surface
Examples of this type of surface
Concrete
Sidewalks, parking lots, roads, roofs
Soil
Grass
Bare soil at construction sites, disturbed areas of
land in a lawn, dirt roads, livestock loafing areas
Lawns, fields
Native Plants
Woods, native plant gardens, native wetlands.
Use the table below to predict how water will move through the different surfaces.
Check the appropriate box.
Which surface will have the
most water runoff?
The least water runoff?
Which surface will have the
most water recharge?
The least water recharge?
Concrete
x
Soil
Grass
Native Plants
x
x
x
Based on your predictions above, write a hypothesis.
Hypothesis: _____________________________________________________________
________________________________________________________________________
________________________________________________________________________
Independent variable (what you will be changing): ___Type of Surface
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Northern Shenandoah Valley Watershed Investigation
Dependent variables (what will respond to the change): ___Amount of Water in surface
runoff and groundwater recharge______
Controlled or constant variables (what must remain the same/be held constant):
______speed of rainfall, amount of water______________________________________
Directions
Student A-Fill the beaker with 1000 mL of water.
Student B- Beginning with the cement model, pour the water slowly and evenly over the
surface.
Student C -Transfer the runoff and recharge water from the large buckets into two
beakers.
Student D- Record runoff and recharge on the data sheet.
Rotating students, repeat the above with the other three models. Fill in the table below
as you conduct the experiment.
Table 1 (Example data) Measurements are in milliliters (mL).
Concrete
Runoff
Recharge
Soil
Runoff
Recharge
Grass
Runoff Recharge
Native Plants
Runoff Recharge
Trial 1
1000
0
550
150
118
800
10
900
Trial 2
910
62
700
215
150
850
0
950
Trial 3
950
40
750
155
300
650
22
950
Total
2860
102
2000
520
568
2300
32
2800
953
34
666
173
189
767
11
933
Average
(Mean)
Calculate the average percent of runoff and recharge for each groundcover.
Table 2 (Example data)
Type of
% Runoff
% Recharge
(average runoff)/(1,000 mL)*(100)
(average recharge)/(1,000 mL)*(100)
Surface
Concrete
95%
3%
Soil
66%
17%
Grass
22%
76%
Native Plants
1%
93%
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Northern Shenandoah Valley Watershed Investigation
Discussion
1. What is the importance of doing multiple trials?
Only doing one trial leaves doubt as to whether the experiment was conducted
correctly. Replication, multiple trials increases the validity of the data.
2. Do you think that conducting three trials was enough or should more trials be
conducted? Why?
Answers may vary. In general, more replication gives more data. With more data,
outliers (unexpected data) do not skew or distort the data as much.
3. How could you design a system that would decrease or reduce the amount of
runoff from an impervious surface?
Multiple ways to do this. Plant roots stabilize soil, so more plants equals less soil erosion
and more water going into recharge the groundwater! Designing a system to lower or
reduce the amount of runoff could be an extension activity.
Conclusions (restate the research question, provide important data from your chart as
supporting evidence for what you learned, and state any problems that you
encountered). Be prepared to present your findings.
Answers will vary.
Table 3 (Example data)
Surface
Concrete
Type of Pollution
Heat, sediment, oils, any
runoff
Soil
Sediment, fertilizers
Grass
Fertilizers
Native Plants
Fertilizers, if used
Potential surface locations?
Sidewalks, parking lots,
rooftops, dumping oil down
storm drain
Construction areas, bare soil
areas
Home lawns, agricultural areas
Meadows, woods, wetland
areas, gardens
1. We have examined how surface type influences surface water runoff and
groundwater recharge, but how do our actions affect water quality? What are
some potential sources of pollution you have identified for each type of surface?
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Northern Shenandoah Valley Watershed Investigation
Answers will vary.
2. How has this activity changed the way you think about surface runoff,
groundwater recharge, and how decisions you make can influence water
quantity and quality?
Answers will vary.
3. What is the most interesting thing that you learned? Did anything surprise you?
Answers will vary.
4. What are the benefits and limitations of this model? What would you change to
make the model better?
Prompts for discussion:
How are the models different from real life?
Actual rainfall varies in amount of water falling in a particular event. Flood conditions
versus a slow steady soaking rain for example.
Precipitation varies; it is not as simple as the water coming out of the water container in
this experiment.
The experiment is a simulation. Is this the same as collecting actual data from four
areas? Why is this model useful? (Can’t go into the groundwater recharge in real life and
measure it.)
Recharge is not immediate.
5. What can you do to help keep our creeks, rivers, and aquifers clean?
Plant gardens, encourage community to plant plants instead of leaving bare ground.
Proper disposal of waste, use less fertilizers, use organic fertilizers, or use fertilizers
properly.
Extension Activity for the classroom:
a. Look at aerial photographs of your town. Identify the amount of different types
of groundcover, potential sources of pollution, and what kind of impact each
type of groundcover has on the water cycle. How has this changed overtime?
b. Design a hydrogeology system that reduces runoff (see Discussion #3)
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