Why Care About Contaminants in Groundwater? Subject/ target grade: Middle School (8 th grade) Earth Science Duration: Two 50 minute periods Setting: Classroom Materials and Equipment Needed: Per class Computers with projector Per group 8 oz. clear plastic cup ½ cup gravel ½ cup clay ½ cup sand Dropper 4 oz. clean water Learning Objectives: Describe how groundwater is connected to surface water. Describe how various land use activities can contaminate groundwater or reduce groundwater availability and how groundwater contamination can be prevented. Michigan Content Expectations: E4.1C. Explain how water quality in both groundwater and surface systems is impacted by land use decisions. Lesson Overview: This lesson will review what constitutes groundwater and where students may find groundwater in their local watershed. Lessons in the Watershed Connections unit discussed groundwater and how land use decisions may affect groundwater quality. Here students will learn more detail about the location and source of groundwater in their local watershed. Students will focus on learning about potential contaminants in their groundwater and how these contaminants may spread in the groundwater. This will set the students up with the background knowledge they will need to complete the Fruitvale activity in upcoming lessons. Lesson materials are adapted from the Michigan Environmental Education Curriculum Support Water Quality Lesson 5: Why Care About Groundwater?. Lesson Core The Guiding Question: Why should we be concerned with contamination of our groundwater? Safety precautions: None. Advanced Preparation: Prepare a short presentation to describe and define the important terms outlined below. Background Information for Teachers: Groundwater is one of the nation s most valuable natural resources. It is the source of about 40 percent of the water used for all purposes in the United States, exclusive of hydropower generation and electric power plant cooling. There is approximately 40 times more groundwater than surface water. Groundwater occupies the cracks and spaces between rocks and mineral grains (Figure 1). The saturated zone is where all of the pore spaces between soil or rock particles are 1
filled with water. In contrast, all of the pore spaces in the unsaturated zone are not filled with water. The imaginary line separating the unsaturated upper layer from the saturated lower layer is called the water table. Rain, snowmelt, and surface waters (lakes and streams) seep downward from the ground surface to replenish or recharge groundwater supplies. Porosity is a measure of the waterbearing capacity of subsurface rock, due to the openings or pore spaces between earth particles, similar to the tiny spaces in a sponge. Porosity may be up to 40 percent of an earth material s volume, as in beach sand, or less than 10 percent in bedrock composed of basalt. Permeability is how quickly water moves through the interconnected spaces between the particles of earth materials. (See Porosity and Permeability of Earth Materials transparency.) Groundwater flow is very slow compared to surface water movement. An approximate average rate used for natural flow in an aquifer is one foot per day. This rate of flow is thousands of times slower than river flow (typically measured in feet per second). This means that a parcel of groundwater takes over a decade to move a mile and about a century to cross beneath a township. Aquifers are large underground waterbearing formations capable of storing (high porosity) and transmitting (high permeability) sufficient quantities of water to meet people s needs. Sand, gravel, and sandstone make the best aquifers because of their moderate to high porosity and permeability. Groundwater Quantity in Michigan More than one-third of U.S. residents and one-half of Michigan s residents get their drinking water from groundwater; the remainder get their drinking water from surface water sources the Great Lakes and rivers. Urbanization can alter groundwater recharge. Groundwater supplies are being impacted as lands that had served as groundwater recharge areas wetlands, meadows, and forests are paved for development. Impervious surfaces do not allow rain and snow melt to seep into the ground to replenish (recharge) aquifers that supply public and private drinking water systems and other uses. Instead, rainwater runs off into surface water bodies, carrying pollutants. In Michigan (and other parts of the United States), groundwater pumping from one well can affect the water available from a nearby well. As groundwater is removed by a pumping well a cone of depression forms around the well. As the rate and duration of pumping increases, the cone of depression extends deeper, and its outer boundary moves farther away from the well. A high capacity well has a larger cone of depression than a small capacity well of the same depth and withdraws groundwater from a larger area of the aquifer. When the cones of depression of two or more wells overlap, the result is called well interference. If the well interference is significant, the well users no longer have a sufficient supply of water to satisfy their needs. Groundwater can seep upward to replenish rivers, lakes, and wetlands. Likewise, surface water can move downward into the groundwater. Surface water is almost always connected to groundwater, and vice versa. An example in which an understanding of this interconnection is critical is the nature of stream flow during drier times of the year. When precipitation is low or absent, the majority of flows in many streams come from groundwater seeping into the bed of the stream. Thus, if significant quantities of groundwater are removed by pumping near the stream, the flow in the stream can be reduced to the point of impacting the stream s ecosystem. Michigan is at the center of the Great Lakes, the largest source of clean, freshwater in our country. Michigan s freshwater is an 2
economic asset more valuable than oil is to Saudi Arabia or timber is to Canada. Groundwater Quality in Michigan The quality of groundwater and surface water also is interconnected. If either is contaminated, it is likely the other will become contaminated. Land use activities including farming, lawn care, livestock production, mining, residential septic systems, landfills, hazardous waste disposal, gas stations, industry, and urban stormwater runoff can introduce fertilizers (nitrates), pesticides, animal wastes, toxic materials, human wastes, petroleum products, pet wastes, and salts to surface water or groundwater, and be transferred between the two. Important Terms: groundwater permeability aquifer water table saturated unsaturated porosity The water quality of public water supplies is regulated by the U.S. Environmental Protection Agency and the Michigan Department of Environmental Quality. Public water supply system operators are required to conduct regular testing of 80 federally and state-regulated contaminants and issue an annual Water Quality Consumer Confidence Report. Contaminants that may be present in groundwater include microbes, pesticides, fertilizers, radioactive materials, petroleum products, and other industrial chemicals or wastes. It is recommended that owners of private drinking water wells bring their drinking water samples to their local health department for water quality testing every one or two years. Protecting the quality and quantity of groundwater supplies is important for protecting the health and welfare of Michigan s citizens. Business, industry, and agriculture all require high quality groundwater for sustainable economic development. Tourism, an important economic activity in Michigan, demands high quality groundwater since it replenishes the streams, rivers, and lakes that residents and tourists enjoy. 3
Unsaturated Zone Water Table Saturated Zone Fractured Rock Groundwater Surface water Gravel Groundwater fills the spaces between soil particles and fractured rock underground. Figure 1. The relationship between surface water and groundwater sources. Source: The Groundwater Foundation (www.groundwater.org). 4
Engage: How can groundwater become contaminated? Building on prior knowledge: Where do you get your drinking water? Do you think more people get their drinking water from surface water or groundwater? How does the type of sediment affect groundwater quality? What are some ways that land uses could affect groundwater quality? Who should be concerned about groundwater quality? Who should be in charge of managing groundwater? In what places in Michigan do you think have the most polluted groundwater? Pre-teaching: Review with students the concept of groundwater and how they use it in their everyday life. Review questions listed in the Building on prior knowledge section. Have students list the important terms in their notebook. During this time, ask them to complete the definitions to the best of their ability. Explore: Review with students the PowerPoint presentation Groundwater and Contaminants. Discuss the questions posed in the presentation regarding the potential contaminants that may impact their drinking water sources. Pay close attention to understanding the discussion of concentration as students will use this information to complete the Fruitvale groundwater investigation in later lessons. Explain: At the end of the period, have each student share what they have learned about groundwater in their neighborhood. Elaboration: This experiment could easily be expanded to encompass a larger geographic area. Students could be tasked with examining threats to groundwater in another geographic area (e.g., desert or mountainous area). This would allow for a greater understanding outside of their native region. This could be done using mapping software such as Google Earth or a similar program. Evaluate: Students will be evaluated based on their participation in class discussions. Every student should answer at least one question from the Lesson Closure section below throughout the experiment and evaluation. Lesson Closure: Why should we worry about contamination of groundwater? Who should be in charge of monitoring groundwater quality? Who should clean up groundwater contamination? What are some major threats to groundwater health? What are some examples of dangerous contamination levels in groundwater? Lesson Extension Additional Resources: United States Geological Survey (USGS) and Michigan State University (MSU) map viewer gives geographic data on water sources and contamination sites in Michigan (http://gwmap.rsgis.msu.edu/viewer.ht m). 5
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