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Virtual Groundwater Model Activity 15 points Name _____________________________________ Introduction:: Even though groundwater only makes up an estimated 0.61% of the water on Earth, it accounts for 98% of the freshwater available for our use (Fetter, 1999). In many parts of the world (including the arid American Southwest) water is the primary resource that limits the amount of living organisms that can inhabit the surrounding ecosystems. Despite the central role of groundwater's importance to human society, few people understand even the basics of groundwater flow. In this activity, we will explore the basics of groundwater movement, the effects of pumping wells, and groundwater contamination using an online version of a groundwater model that looks somewhat like an ant farm. (Note: If we were in the classroom, you would get to play with the actual models. It's a bit more fun than the virtual model.) Goals and Objectives: The groundwater model provides a hands-on experience that allows you to observe and manipulate a miniature hydrologic system. You will be able to see the results of changing recharge, pumping wells, and surface contamination. Specifically, you will: a) Observe the saturated and unsaturated zones of the aquifer in the model a) Manipulate and observe variations in recharge and discharge b) Observe, record, and explain what causes groundwater to flow. c) Observe the connections between surface water and groundwater using dyes. d) Examine the effect of pumping water from a well on groundwater flow. You are asked to generate predictions about groundwater flow and then will be able to test your hypotheses using the model. Instructions: Watch the introductory video (https://vimeo.com/398697315). This shows you how to use the virtual model. The groundwater model is at https://pvw.kitware.com/sandtank/. You can explore the model on your own, using directions in the website's manual (https://www.hydroframe.org/sand-tank-user-manual). At the bottom of the page, after the explanation of the various controls, you can find instructions for a basic run. Feel free to experiment with it before starting this activity. In this activity, every line with bullets (dots) gives you instructions for things to do. Every line with numbers asks questions that you need to answer to get credit for the lab. The number of points for each item is given in parentheses at the beginning of the question. You should answer any question that starts with "prediction" before you do the next group of instructions - you are making a hypothesis about what you think will happen. The "prediction" questions will receive full credit as long as you answer them. The "observation" questions ask about things that happen when you run the model. The "generalization" questions deal with broader concepts beyond the model. Part 1: Observing Groundwater Flow Figure 1. Screen capture of the basic groundwater model on the hydroframe website. · Click on the hydraulic head slider (the top of the blue column on the left side of the model). Raise it until the number at the bottom reads 40.00. · Set the Lake/River toggle to "Lake." · Run the model by clicking the button that says "RUN" in the upper right corner of the window. 1.1. Observation: The top of the blue area on the model represents the water table. Which direction does the water table slope? 1.2. Observation: Describe the difference in the height of the water level in the wells on the left side of the model versus the water level in the wells on the right side of the model. 1.3. Observation: Layers above the water table are unsaturated. Which of the layers is unsaturated? 1.4. Observation: Layers below the water table are saturated. Which of the layers are saturated? 1.5. Observation: The two dark-colored layers have a lower permeability (hydraulic conductivity) than the other layers. Permeable layers that are entirely underneath a lower permeability layer (aquitard) are known as "confined aquifers." In this model, which layers are confined aquifers? 1.6. Prediction: when you run the model, which direction will the water flow? · Using the red (down) arrow, inject 2 units of dye into Well D (fourth well from the left, the shallowest well). · Click "run" once. You should see a large red splotch appear at the bottom of the well. · Click "run" a second time. 1.7. Observation: Which direction does the red dye move? 1.8. Generalization: Is that the same direction as the water table slopes, or the opposite direction from the slope of the water table? 1.9. Prediction: If the slope of the water table were reversed, in which direction the dye moves? · Change the right hydraulic head slider to 45, and the left hydraulic head slider to 28. · Click "Run" four times in a row. 1.10. Observation: What direction did the dye move when the slope of the water table was reversed? 1.11. Generalization: What controls the direction that water (and pollutants) move below the water table? 1.12. Generalization: Imagine that you couldn't see the water table (because it is hidden underground), but you can drill wells. How could you use the water level in the wells to figure out the direction that groundwater would move? Part 2: Impacts of Pumping Water from a Well · Click "Reset" then "Run." The model should now be back to its original condition. · Raise the left hydraulic head slider to 45. Click "Run." 2.1. Prediction: what should happen to the shape of the water table if you pump water out of the fourth well from the left (the same well you've been using)? · Click the blue (up) arrow above Well D (the fourth well from the left) until the number below it reads "-20". · Click "Run." 2.2. Observation: What happens to the shape of the water table near the pumping well? · Click "Run" several more times. 2.3. Observation: What happens to the shape of the water table after you stop pumping water out of the well? · Inject 5 units of dye into Well J (second from the right side of the model). · Click "Run." 2.4. Prediction: If you pumped water out of Well K (the well on the right side of the model), what should happen to the dye that you injected into Well J? · Click the blue (up) arrow to pump 20 units of water (-20) out of Well K (right side of the model). Click "Run". · Pump 20 more units of water out of Well K. Click "Run" again. 2.5. Observation: What happened to the red dye from Well J? 2.6. Generalization: If Well K were your well, and the red dye was a pollutant, what would happen to the water quality from your well? Part 3: Confined Aquifers · Raise the left hydraulic head slider to 45. Click "Run." · Pump 5 units into Well B (2nd from left). Run (5 times) 3.1. Prediction: Would the dye go into Well E? · Pump 20 units from Well E (5th from left) 3.2. Observation: did the dye go into Well E? 3.3. Prediction: if you pump from Well F (next well to the right of Well E), would the dye go into Well F? · Pump 20 units from Well F (6th from left) 3.4. Observation: did the dye go into Well F? 3.5. Generalization: how does the confining layer affect the ability of water and pollutants to travel upward into shallower wells?