channel, deep verses shallow water, gravel substrate verses sandy substrate) Evaluate: For grades 8 - 9: Calculate the velocity of the stream if the orange floats at a rate of 100 feet in 1.5 minutes. Calculate the flow rate of a muddy bottom stream if the average width is 5.5 ft and average depth is 17 inches and the orange floats at a rate of 67 ft in 2.4 minutes. What does the flow tell you about the watershed? What unit is flow measured in? When velocity increases in a stream, what happens? What factors contribute to an increase in water flow? For grades 9 - 12: If the average depth of the stream is 4 ft and width is 7.5 ft and it took the orange 10 seconds to travel the 10-foot length of the stream, what is the volume? If two streams drain equal sized and comparable watersheds, and one watershed is forested while the other is urban, which will have a greater discharge of water? Why? Extension: In the last step, the students compared their results and hypothesized what caused them to be different. As an extension, have the students investigate streams in their community noting changes that might have been made to them and how it has affected stream flow. Also have the students look at what are some of the consequences that occur as a result of those changes to the stream. Have students convert the various measurements to metric. Adapted from Georgia Adopt-A-Stream Educator’s Guide Based on Georgia Adopt-A-Stream Visual Stream Survey procedures. CALCULATING STREAM FLOW Flow = Area X Speed X Coefficient CALCULATE AREA Area = depth x width It is advisable to take multiple depth and width measurements always start at the waters edge with a first measurement of zero all data should be recorded in feet, with inches replaced by increments of 10 depth measurements 1. 2. 3. 4. 5. 6. 7. 8. sum 0 ft
average depth = sum of depth measurements number of measurements width measurements 1. 2. sum average width = sum of width measurements number of measurements Area = width X depth CALCULATE SPEED-measure the time it takes a float to travel a desired distance It is advisable to take at least 2 measurements of current speed take measurements from the stream run length in feet 20 feet is recommended time in seconds 1. 2. 3. 4. sum average time = sum of time measurements number of measurements Speed = length in feet average time in seconds CALCULATE STREAM FLOW Flow cfs = Area X Speed X Coefficient Flow in cubic feet per second .9 coefficient for muddy bottom stream .8 coefficient for rocky bottom stream Measuring Channel Cross-Section Objective: Students will document changes in stream-channel shape, or stream profile, by measuring the stream channel Location: Outdoors at local stream Time Needed: 60-90 minutes Subjects: Science, Math Alignment to NC Essential Standards for Science: 8.E.1 Een.2.3. section.
How Much Water Falls Here? Objective: Students will calculate the volume of water that falls onto an area of the school parking lot. Location: Indoors/Outdoors Time Needed: 90 minutes (can be divided into two class sessions) Subjects: Science, Math Alignment to NC Essential Standards for Science: 8.E.1 Een.2.3. EEn.2.4 Background: When it rains, where does the water go? Some of it is absorbed by the soil and plants, some is evaporated back into the air and some runs off the land. When it rains in areas with lots of impervious surface (parking lots, roofs, roads), water runs off to storm drains and drainage ditches, often at a fast rate because it is not absorbed into the ground. Urbanization and other development often adversely affect stream health by increasing the volume of surface runoff entering a local waterway. Urban stormwater runoff may contain sediment, debris, oil, gasoline, and heavy metals (nonpoint source pollution) that it has picked up after traveling over impervious surfaces. When potential pollutants are transported quickly from the land to a waterway, this can cause a phenomenon called “shock loading.” Shock loading is the overloading of water with nutrients, sediment, oil, etc, over a very short period of time giving the organisms little time to adapt to the changes in their environment. Shock loading can result in fish kills or algal blooms depending upon the type of pollutants in the runoff. For example, suspended materials in the runoff can also absorb and store heat that increases the water temperature. Materials: Yardstick Trundel wheel (optional) Writing materials Local rainfall data Tape measure Clipboards (optional) Graph paper Calculators Rulers Long piece of twine (meter and intervals) Preparation: Check online to find out the average annual rainfall for your area.