A Comparison of Two Streams

Transcription

1 A Comparison of Two Streams Subject/target grade: Grade 9-12 Ecology, Earth/Environmental Science, Biology, Chemistry Duration: Three 50-minute class periods; one 2-hour field trip (depending on location and availability of suitable stream) Setting: Classroom, outdoors Materials and Equipment Needed: Computer with Microsoft PowerPoint, internet access, audio, and projector Water-quality testing kit Bucket for storage of used chemicals Knee-high rubber boots Cameras Plant identification field guide Macroinvertebrate net and identification guide (optional) Learning Objectives: Identify common human-caused impairments to a stream on sight Describe pathways of pollutants to streams Explain relationships between human landuse decisions and impacts to water quality Perform chemical analyses of water Lesson Overview This lesson is intended as a follow-up to Lesson #3, Exploration of an Impaired Stream. In this lesson, students will repeat stream-assessment procedures for a stream that has been minimally-impacted by human activities. Students are expected to recognize the range of differences between this stream and the impaired one previously examined. By observing the impaired stream first, students should complete these lessons with a clear understanding of what a healthy stream should look like. Students will again enjoy the hands-on outdoor activities and learn how land-use decisions can have far-reaching ecological consequences. As the key exercise following data collection, students will apply the scientific method to compare and contrast the two streams. Together, activities in these two lessons are also intended to serve as an ideal project to describe in a scientific poster. Note: This lesson requires the local availability an impaired stream. This lesson makes numerous references to the Coles Creek, a small stream in the Houghton, Michigan area. Lesson Sequence Day 1: Introduction to key concepts (PowerPoint), handouts Day 2: Field activity at stream Day 3: Data analysis and scientific method exercise Day 4: Wrap-up, assessment Lesson Core The Guiding Question: How do the health of these two streams compare? Safety precautions: Students must exercise caution when walking through wet areas and near steep banks. 1

2 Michigan Content Expectations: Biology B1.1A Generate new questions that can be investigated in the laboratory or field. B1.1C Conduct scientific investigations using appropriate tools and techniques (e.g., selecting an instrument that measures the desired quantity length, volume, weight, time interval, temperature with the appropriate level of precision). B1.1D Identify patterns in data and relate them to theoretical models. B1.1E Describe a reason for a given conclusion using evidence from an investigation. B1.1g Use empirical evidence to explain and critique the reasoning used to draw a scientific conclusion or explanation. B1.1h Design and conduct a systematic scientific investigation that tests a hypothesis. Draw conclusions from data presented in charts or tables. B3.4C Examine the negative impact of human activities. B3.5E Recognize that and describe how the physical or chemical environment may influence the rate, extent, and nature of population dynamics within ecosystems. Earth Science E4.p1B Analyze the flow of water between the elements of a watershed, including surface features (lakes, streams, rivers, wetlands) and groundwater E4.p1D Explain the types, processes, and beneficial functions of wetlands. E4.1C Explain how water quality (groundwater and surface) is impacted by land use decisions. Social Studies CG.2 Explain the changes over the past 50 years in the use, distribution, and importance of natural resources on human life, settlement, and interactions C Evaluate, take, and defend positions about the formation and implementation of a current public policy issue; examine ways to participate in the decision-making process about the issue. Advanced Preparation: Prepare all worksheets for students. Visit the web links included throughout this lesson to find suitable resources for classroom use. Ensure adequate supply (and correct sizes) of rubber boots for students to wear for field work. Identify suitable stream site to study in advance of field trip, becoming familiar with general features and access points. Prepare chemical water-testing equipment and ensure adequate supplies of all materials. Background Information for Teachers: There are three categories of indicators generally used to assess the ecological health of streams. The stream s physical condition can be inferred by making simple observations described in this lesson worksheet (and accompanying PowerPoint). Many human modifications of streams are quite obvious, such as engineered channels or banks, removal of stream-side vegetation or wetlands, straightening or re-locating of the stream, and so forth. Chemical tests of water quality can indicate pollutants from runoff or other sources. For many chemicals, their mere presence in the water can indicate problems capable of limiting the biological health of the stream. With the proper testing equipment, chemical analyses of water can be a simple and enjoyable hands-on activity for students. Biological health of the stream can be assessed by sampling macroinvertebrates from the stream, many of which cannot tolerate impaired conditions from pollutants. For this lesson, students will be introduced to simple physical and chemical assessments. Biological assessments would serve as an ideal extension of the lesson. Materials helpful in the design of a biological assessment lesson are referenced in the Additional resources section of this lesson. 2

3 Students may not recognize the ecological values provided by smaller streams, or may perceive greater values with the economic development (urbanization or agriculture) that typically drives stream modification. Students will be introduced to the difficulty of making values decisions (e.g., is a strip-mall or farm field more valuable than a small stream?). As an option, students can be introduced to the evolution of laws and policies that have resulted in the water resource management strategies in place today. Important Terms: Ecosystem Habitat Community Population Species Biodiversity Hydrology Watershed Ecological restoration Sediment ph Total dissolved solids (TDS) Dissolved oxygen (DO) Nitrates Phosphates Hardness Parts per million (ppm) Introductory Classroom Lesson (Day 1) Engage: Teacher should begin lesson by polling students to review the impaired stream previously examined and ask what they think a healthy stream should look like. Ask students to share their knowledge of any streams in the area they consider particularly healthy. This lesson uses Coles Creek (Houghton, MI) as the case-study stream. As part of the in-class activities, be sure to ask students to again describe what makes streams valuable. For instance, you may wish to ask: How are streams important to plants and animals? How do healthy streams benefit humans? Should we put greater emphasis on stream protection? Because students already have experience assessing a stream, the in-class lesson should be fairly short and allow abundant opportunities for discussion. Before ending the lesson, provide students a preview of the ensuing field activities and make them aware of the ensuing application of the scientific method to compare and contrast the two streams. Building on prior knowledge: The important terms listed above have likely been explored in previous class readings and activities. This lesson will provide students real-world examples of how the chemical concepts listed above are critical measures of water quality. Pre-teaching: Students should be wellprepared for field activities from their previous experiences with Lesson #3 as well as its PowerPoint presentation and worksheets. Additional pre-teaching, if desired, can include materials from the many sources listed under Additional resources. Numerous federal, state, and local agencies make available materials to help citizens become familiar with basic concepts related to stream assessment. Otherwise, students can simply follow the instructions on the attached worksheet as well as instructions that accompany the selected chemical water-testing equipment (under guidance of the teacher). 3

4 Additional activities: Teacher may wish to include film clips demonstrating stream assessment procedures. Many of the sources listed under Additional resources contain information about video tutorials, although many require purchase. Advanced preparation for field activities: At the conclusion of the classroom lesson, teacher should briefly introduce the procedures, safety precautions, and learning objectives for the ensuing field work. Students should try on boots before leaving the classroom. Students should be reminded of the sensitive nature of streams and be instructed to not behave in an environmentally-harmful manner. Students should also be reminded that no garbage gets left at the site. Students will need copies of Field worksheet (provided at the end of this lesson), which is the same as the worksheets from Lesson #3. The worksheet asks students to document their visual observations and record waterquality data. Copies of a suitable plant identification guide will be necessary if the teacher wishes to incorporate this component of the lesson. Students should be encouraged to take many site photographs. Field Lesson: Day 2 Explore (repeated from Lesson #3): Upon arriving at the case-study stream, select suitable locations for water-quality tests. Break the class into small groups: some will perform chemical tests and others will record observations of the stream s physical characteristics (as guided by the field worksheet). Perform water-quality tests and numerous locations to allow student groups to rotate between chemical testing and physical assessments. Lead the observation students on a brief tour of the stream and assist as necessary; otherwise the worksheet questions they are asked should be relatively easy for all students to answer. Encourage students to the stream upstream and downstream and look for as many physical indicators as possible. Explain: The teacher should draw attention to noteworthy features while touring the site. The teacher will likely be needed to help identify the first sightings of stream modifications as students fine-tune their observational skills. The teacher may also need to help student identify plant species (if this activity is included). The teacher may also need to help students characterize the overall topographic features of the site to help characterize hydrologic flow patterns near the stream. The teacher will also need to ensure that consistent data-collection techniques are being used by students. At some point during this lesson, the teacher may wish to conduct a brief review of the steps of the scientific method. Elaborate: The teacher will need to conduct field exercises with a high level of enthusiasm, making every effort to point out the ecological importance of streams and encouraging students to identify natural features that provide ecological benefits (e.g., the importance of pools as habitat for aquatic organisms). Throughout observations, the teacher should help students identify examples of easily-observable physical differences between the two streams. Students should continuously be encouraged to think about connections between the stream and its surroundings. Wrap-up Lessons (Days 3 and 4) Back in the classroom, students should first share their observations as a group. Teacher should lead discussion of findings from the site, eliciting responses from all questions on the worksheets, to ensure that all students are able to provide answers to all questions on worksheets. Teacher should assemble photographs taken from each site to visually 4

5 review relevant observations. Teacher should assess student learning with simple discussion questions such as: How might these observations indicate a healthy stream? What ecological and human benefits does this stream provide? Does its condition hamper those benefits? Without comparing datasets from the two streams, which do we suspect is healthier? The teacher should collect data sheets with all results of the chemical analyses and compile findings into a single spreadsheet. A brief review of the scientific method may be in order before proceeding with the scientific method worksheet. Students should consider possible relationships between the visual observations of the stream s physical condition and the results of the chemical analyses. Teacher may also need to help interpret the results of chemical tests, to help students realize what the findings could indicate, why they matter, and what sources could be influencing the results. Evaluate: Several evaluation items can be included with this lesson: 1. A worksheet on the films or readings that accompanied the introductory classroom lessons 2. Field worksheets with observations and data collected at the stream site 3. Completion of the scientific method worksheet 4. An optional quiz after all lessons and field exercises have been completed, encompassing the central points of the lesson be able to identify numerous differences in their observations of the two streams. Ask students to explain how the site observations may or may not be related to results of the chemical analyses. Students should share their personal perspectives on the value of restoring and protecting streams in Michigan. Students should complete the lessons with an enhanced understanding of the ecological importance of streams in their area and additional practice at a real-world application of the scientific method. Lesson Extension Conduct a biological assessment of the stream from materials available from the additional resources listed below. If GIS capabilities are present, have students analyze land-use factors from digital datasets that may confirm their observations from the field. For example, students should be able to identify the relatively-impacted land cover that surrounds the healthy stream compared to the human development surrounding the impaired stream. Have students create a poster that illustrates their findings and describes the differences between the health of these two streams. Bring garbage bags and encourage students to collect any garbage they encounter as they explore the stream. Assign a garbage bag to each group and offer a prize to the group that collects the most. However, be careful to allow garbage-hunting interfere with the tasks of the exercise! Lesson closure: Teacher should ask students to summarize how human land-use activities at this stream may or may not be affecting the health of the stream. Students should readily 5

6 Additional Resources: Michigan Environmental Education Curriculum Support webpage, featuring information for obtaining water-quality lesson ideas. The MEECS Water-Quality Lesson #7 ( How healthy is this stream? ) offers similar lesson ideas to the one presented on these pages. Visit: _3580_ ,00.html Michigan Department of Environmental Quality (MDEQ) water homepage: ,00.html (Photo: Kozich) Michigan Environmental Education Curriculum web module: stakeastreamtour.htm EPA Rivers and Streams webpage: EPA National Rivers and Streams Assessment webpage: rssurvey/riverssurvey_index.cfm USDA Natural Resource Conservation Service homepage: ain/national/home NRCS stream assessment guide: ms.pdf 6

7 A Comparison of Two Streams Name Field worksheet Observation group: Examine the stream at various locations and answer the following questions to describe how natural the stream appears. Use general observations. For each of these questions, do not just answer yes or no. Describe what you see and take many pictures. 1. Does the stream meander or does it tend to be mostly straight? 2. Do the banks look like they are made of natural materials? 3. Are there places where the banks are steep, or are they mostly gradual? 4. Is any stream-bank erosion noticeable? 5. What examples of human development do you see near the stream? 7

8 6. Is the stream visibly polluted? 7. Are there wetland areas alongside the stream? 8. Does the vegetation near the stream appear natural? Are there places where the vegetation looks oddly sparse? Water quality group: Conduct the following chemical tests on the stream water and record your data in the table below. Sample site 1 Sample site 2 Sample site 3 Temperature ( C) ph Hardness (mg/l CaCO 3 ) Total Dissolved Solids (ppm) Dissolved oxygen (ppm) Nitrates (ppm) Phosphates (ppm) 8

9 A Comparison of Two Streams Background information for water-quality testing Temperature. Often (but not always), temperature can be in indicator of conditions of the water. Warm water usually supports more biological activity, which could lead to higher concentrations of total dissolved solids and lower concentrations of dissolved oxygen. However, the size of the stream and the time of year could result in temperature variations that are totally natural. ph. The acidity/alkalinity of the water is measured on the scale of 0-14 (see below). Sometimes acidic pollutants can lower the water s ph and serve as an indicator of trouble. In other cases, natural sources of acidic materials make soils and water naturally acidic. For example, streams in areas with conifer trees (pines, spruces, hemlocks, cedar, etc.) can have acidic water from the natural acid in the trees needles. And needles fall to the ground. Also, ph can be buffered (made less acidic) by several natural factors, mostly involving the geology of the area. Acid ph scale Base Neutral Hardness: Hardness is a measure of the mineral content of the water. The most common minerals causing hard water are calcium and magnesium. Hard water is more difficult to lather up, but according to most sources, it does not pose health risks to humans. Water in much of the U.S. is naturally hard. Therefore hardness is not really an indicator of quality. It simply helps us better understand the chemistry of the water we re testing. Hardness scale: 0-60 mg/l = soft mg/l = medium mg/l = hard Over 180 mg/l = very hard Total dissolved solids (TDS): Total dissolved solids include the sum of all tiny particles of solids (less than 2 micrometers) contained in the water. These particles can represent a wide range of naturallyoccurring materials in addition to pollutants such as runoff from farms, parking lots, sewage facilities, and so forth. Thus, TDS is can be a good indicator of the overall water quality. Healthy water, especially for drinking, will ideally have low TDS concentrations. 9

10 Dissolved oxygen (DO): Dissolved oxygen concentration can indicate the health of water. DO is necessary for aquatic life. Just like us, organisms in the water need oxygen to breathe. Dissolved oxygen is also needed for the decomposition of organic matter. Many organisms cannot tolerate oxygen-poor conditions. Think about fish kills that sometimes happen in lakes the fish die (and float to the surface) because the water s DO concentration sinks too low. Therefore, healthy water will ideally have high DO concentrations. Nitrates: Nitrate concentration is in excellent indicator of water quality. These pollutants typically originate from sources such as fertilizers or human wastes (sewage) that run off into the water body. High nitrate concentrations may indicate the presence of other contaminants that are harmful, including disease-causing organisms such as e coli. Because of these risks, the EPA puts a limit of 10mg/l of nitrates for drinking water. Therefore, healthy water will ideally have low nitrate concentrations. Phosphates: Like nitrates, high levels of phosphates indicate pollution from fertilizers, sewage, detergents, or other sources. Healthy water will ideally have low phosphate concentrations. See the graph below. Quality index refers to the health of the water. Note that the highest quality index score is where phosphate levels are the lowest. Source: 10

11 A Comparison of Two Streams Name Scientific method worksheet Like all scientific experiments, this method serves as the guide to our exercise. Think about the steps we ve conducted so far and answer the questions below. Step 1: Define the question. What were we trying to determine with this experiment? What do we want to figure out? Form a simple question and write it below. Question: Step 2: Make observations. What did we look at when we were at the two streams? Summarize the observations we described on our worksheet (not the chemical analyses). Based on observations, state which stream appeared healthier. Observations: 11

12 Step 3: Form a hypothesis. The hypothesis should be based on the observations, and should try to explain what we saw without the benefit of testing. Make a prediction that we can test. Hypotheses should be as short as possible and should be stated very clearly. Hypothesis: Step 4: Test the hypothesis. This step involves the collection of data, which we did when we performed chemical tests at each stream. In many cases results can be expressed simply in a table or chart. We ll present our results that way. In the table below, insert the results from the water-quality tests at both sites. Look at the data tables from the previous worksheets. The figures in the table below should be the averaged values from each sample location at each stream. Ask you teacher for help if you do not know how to do this. Test results: Huron Creek Coles Creek Temperature ( C) ph Hardness (mg/l CaCO 3 ) Total Dissolved Solids (ppm) Dissolved oxygen (ppm) Nitrates (ppm) Phosphates (ppm) 12

13 Step 5: Draw conclusions. Do the results of the tests support the hypothesis? In other words, are the test results consistent with our visual observations? Explain the conclusion in a paragraph. Make sure to explain what the results mean (read the background information to interpret the test results. Explain how the findings are connected to the observation and hypothesis. The conclusion should answer the question defined in step 1. Conclusions: 13