Chicago River Field Trip Activity Summary Students will calculate flow rate and stream flow of a local river. Background Flow rate measures the speed at which water in a river is travelling down the river (often reported in feet/second). Stream flow measures the volume of water moving down the river over a given time period (often reported in cubic feet/second). When flow rate increases, water has a greaterr ability to erode its channel and banks. More and heavier sediment can be carried by the river. This can increasee the river s turbidity (decrease its clarity). Sunlight will be unable to penetratee as deeply into the river, and aquatic plants and algae can suffer. Because the United States Geologic Survey (USGS) (https://waterwatch.usgs.gov/) has been monitoring stream flow for decades and continues to do so today, it is possible to look at changes in stream flow over time, the response of stream flow to a rainstorm (called a stream hydrograph), and to compare the stream flow calculated at the riverr to data from other places and times. More urban rivers tend to be flashier, meaning that after a storm stream flow increases rapidly and dramatically. This creates high erosion rates. It also makes it difficult for stream bank vegetation to establish itself because stream banks are often very steep (due to high erosion) and are either well above the water line or completely inundatedd with water during highh rain periods. Grade Level: 6 th 12 th Duration: 50-60 minutes Objectives: 1. Students use math and graphing skills to understand and calculate flow rate and stream flow. Materials: Copies of Stream Flow Calculation sheet (one per small group of students) Stop watches (5) Meter (or yard) sticks (5) Waders (15) Long tape measure at least 100 meters (or feet) Oranges, or preferably sticks or leaves (5) Masking tape Standards: 11.A..3c, 11.A.4c, 11.A.5e, 11.A..3f, 11.A.4f, 11.A.3g, 12.D..5a, 12.E.3b NGSS: MS-ETS1-3, HS-ETS1-2, HS-ETS1-3, RST.11-12.9, MS-ETS1-2, SL.8.5, MS-ESS2-2 Procedure Information on planning and organizing a field trip can be found at www.chicagoriver.org/education, then click on field trips. Safety tips for your trip are here as well. p. 1
Before the field trip you may want to have students study stream flow data from the United States Geologic Survey (https://waterwatch.usgs.gov/). Alternatively, you can have studentss compare their data to USGS dataa once they return from the field trip. As always, students on field trips should be divided into small groups. No more than 15 students are needed for this activity, although it can be done with as few as three. There are six different tasks in the activity. Split the 15 students into groups of three (depending on how many boots you have). Assign students in each group the following roles: (1) timer / measurer, (1) object dropper / data recorder, and (1) object catcher. Have students follow instruction sheets to calculate stream flow. Depending on your students, it may be helpful to review procedures in the classroom before the field trip. You will also need to decide on the number of data points you want students to take acrosss the river. Ten is usual; three is a good minimum. The more data points, the more accurate the students calculations will be. Extensions Students can take their depth measurements and graph the profile of the stream bottom. Students can look up stream flow data from the USGSS to determine if the flow they found is high, low or average. If there has been a recent storm, students can look up the data from a nearby USGS stream monitoring site from the weeks before and after the storm to understand how stream flow in the river responds to storms. Below is a list of Chicago River stream sites monitored by the USGS: USGS Code River Name 0553500 Skokie River 05535070 Skokie River 05535500 West Branch of Chicago River 05536000 North Branch of Chicago River 05534500 North Branch of Chicago River 05536995 Chicago Sanitary & Ship Canal 05536290 Little Calumet 05536290 Little Calumet 05536270 North 05536275 Thorn 05536210 Thorn 05536210 Thorn 05536255 Butterfield 05536235 Deer Gage Location Lake Forest Highland Park Dates Available 1951-1999 1967-2000 Northbrook 1952-2000 Niles 1950-2000 Deerfield 1952-2000 Romeoville 1984-2000 South Holland 1947-2000 Harvey 1916-1933 Lansing Thornton Glenwood 1949-2000 Chicago Heights 1964-1979 Flossmoor Chicago Heights You can also choose to extend their stream flow studies using the classroom lesson What Does Stream Flow Tell Us from Friends of the Chicago River. This lesson explores the changes in peak stream flow over the last decade in the Chicago region. p. 2
Calculating Stream Flow You are your group are going to measuring steam width, steam depth and stream velocity and then using this data to calculate stream flow (or the volume of water going down the river over a given time period, usually one second). Roles Timer / Measurer: (1) measure the depth of the river (2) hold the stopwatch and time how long it takes the objects to travel one meter. Object Dropper / Data Recorder: (1) drop the objects when timing the velocity (2) record all width, depth and velocity readings. Object Catcher: catch the object when timing the velocity. Directions If your teacher has not already done so, choose a location to measuree stream flow. Choose somewhere that represents the average conditions of your site. The river must be safe to enter and no deeper than the boots. Everyonee should gather the equipment they need and anyone wading into the river should put on hip waders and find a meter stick or long stick to use to feel the bottom of the river ahead of where they are walking. Step 1: WIDTH The first task is to stretch a long tape measure across the river, securing it so thatt it is held taut above the water. Measure the width of the river and record it on your data sheet. Decide how many sections you d like to divide the river into for sampling. Ten is usual; three is a good minimum. The more dataa points, the more accurate the students calculations will be; however, it will also take longer. Step 2: DEPTH Now divide the stream width by n+1 (n being the number of sampling points). Place a piece of masking tape at each sampling point across the river. For example, if the river is 55 meters wide and you wish to sample 10 points, you end up with a sampling interval of 5 meters, like so: p. 3
riverbank river midpoint riverbank 5 5 5 Record the sampling interval on your data sheet. Each group should walk along the measuring tape being held taut across the river. Be sure to take a measuring stick and an orange/ /stick/leaves with you. With your measuring stick, measure the depth of the water at each sampling point (marked b the tape). Be careful not to push the stick into the sediment. Record each on your data sheet. Calculate the average depth of the river. Step 3: VELOCITY Hold the meter stick just above the water s surface and parallel to the river s flow so that one end is just below the tape measure and the other is one meter upstream. The Object Dropper should be upstream and the Object Catcher should be downstream, like so: Object Catcher Direction of flow Timer / Measurer Object Dropper / Data Recorder Make sure everyone is ready. Gently drop / place the object into the river, upstream of the measuring tape. Time how long it takes for the object to float one meter. If the object gets caught up or was not floating for the entire meter, redo that trial. Measure the time (in seconds) that it takes the object to float one meter at each sampling interval and record it on your data sheet. Calculate the average velocity of the river. Calculate stream flow. Multiply the measured stream width by the average stream depth (measured in the same units as the width). Multiply the result by the average stream velocity (measured in the same units as the width and depth). These calculations be done at the river or back in class. p. 4
Stream Flow Monitoring Data Sheet Site: Date: Weather today: Weather over the past 48 hours: Description of flow: Be consistent with units. Our class will measure stream flow in meters 3 /sec feet 3 /sec # of data points desired (n), so n + 1 = Stream Width: Sampling Interval: Edge* 1 2 3 4 5 6 7 8 9 10 Depth 0 cm (or inches) Time 0 sec * Why do we include the edge in the calculation of Average Depth and Average Velocity? Becausee river depth and velocity drop to zero at the edge, by definition, and the edge is part of the stream, so you must include a zero in the calculation of the two averages. Averag e # Depth Time meters (or feet) seconds # Be sure to convert centimeters to meters (or inches to feet) when calculating average depth. Averagee Velocity the distance the object was floated (1 meter, or other?) = Average Time (sec) Average Velocity meters (or feet) / second Stream Flow = Stream Width x Averagee Depth x Average Velocity Stream Flow = meters 3 /sec feet 3 /sec p. 5