In order to calculate discharge we need to know two things. First, the area of a cross section of the river and, second, the velocity of water moving past that cross section. The video above shows how we measure the cross sectional area. I used the lab quest to graph this data and find the area under the curve (you could also split the cross section into rectangles for younger students). I included this graph as an image. To find velocity we used the stream flow probe to get several velocities from different points along our cross section. I used the LabQuest to average these points to find an average water velocity. Finally, we multiplied our cross sectional area (m2) by the average water velocity (m/s) to get discharge (m3/s). The calculated discharge for the Portneuf at the Lava site was 9.78 m3/s.
This is some good stuff! Thanks for explaining the mathematical manipulations. Do you know where someone can get their hands on LabQuest software? Have you used the software for anything else?
You can borrow LabQuest devices from the learning library (ask Dr. Rosemary Smith, smitrose@isu.edu for more information). There is also a LabQuest emulator you can download from Vernier for free. I'm not sure how it works as I only have experience with the device.
I'm not sure that the river would be that high when you would be measuring it. I looked at a few different water years and June is one of the highest discharge months (I've attached some graphs from the USGS gauge just downstream of this location). Other options would be to choose a different site (we measured city creek and didn't even get our feet wet) or to have an adult measure but have students record data. Discharge is also a more difficult parameter to measure so you may just choose to omit that measurment completely.
Dischagre is how much water passes by a cross section per some amount of time.
Discharge data is helpful when determining flood stages and where water is coming from. For example, we know that most of the Portneuf is diverted into Marsh Creek during the growing season and that water coming back into the Portneuf from Marsh Creek is significantly lower quality than when it was diverted in the first place. This tells us that if we want to improve the water quality of the Portneuf then efforts in Marsh Creek would give a lot of bang for the buck. This information is also used when determining how much water to hold in reservoirs or when to release water strategically to avoid flooding. Check out this water balance map by the Bureau of Reclamation.
Dischage data is also continuously collected by the USGS (in cfs, cubic feet per second) and tells if a section of river is at the right level for boating or fishing.
Comments
Video
Looks like a great day. Way to share a video with a measuring lesson.
Video
Velda, are you ready to plan a trip for our students?
Data from Stream Flow Measurements
In order to calculate discharge we need to know two things. First, the area of a cross section of the river and, second, the velocity of water moving past that cross section. The video above shows how we measure the cross sectional area. I used the lab quest to graph this data and find the area under the curve (you could also split the cross section into rectangles for younger students). I included this graph as an image. To find velocity we used the stream flow probe to get several velocities from different points along our cross section. I used the LabQuest to average these points to find an average water velocity. Finally, we multiplied our cross sectional area (m2) by the average water velocity (m/s) to get discharge (m3/s). The calculated discharge for the Portneuf at the Lava site was 9.78 m3/s.
Good Stuff!
Emily,
This is some good stuff! Thanks for explaining the mathematical manipulations. Do you know where someone can get their hands on LabQuest software? Have you used the software for anything else?
LabQuest Software
You can borrow LabQuest devices from the learning library (ask Dr. Rosemary Smith, smitrose@isu.edu for more information). There is also a LabQuest emulator you can download from Vernier for free. I'm not sure how it works as I only have experience with the device.
How easy do you think this
How easy do you think this would be for students to do? I am not sure I want them waist deep in the river!
Measuring Flow with Students
I'm not sure that the river would be that high when you would be measuring it. I looked at a few different water years and June is one of the highest discharge months (I've attached some graphs from the USGS gauge just downstream of this location). Other options would be to choose a different site (we measured city creek and didn't even get our feet wet) or to have an adult measure but have students record data. Discharge is also a more difficult parameter to measure so you may just choose to omit that measurment completely.
Calculating
Thanks for explaining how the measurements are taken. What does the data tell you? Why is it so important?
Discharge Data
Dischagre is how much water passes by a cross section per some amount of time.
Discharge data is helpful when determining flood stages and where water is coming from. For example, we know that most of the Portneuf is diverted into Marsh Creek during the growing season and that water coming back into the Portneuf from Marsh Creek is significantly lower quality than when it was diverted in the first place. This tells us that if we want to improve the water quality of the Portneuf then efforts in Marsh Creek would give a lot of bang for the buck. This information is also used when determining how much water to hold in reservoirs or when to release water strategically to avoid flooding. Check out this water balance map by the Bureau of Reclamation.
Dischage data is also continuously collected by the USGS (in cfs, cubic feet per second) and tells if a section of river is at the right level for boating or fishing.
This looks great!
Thanks for the information. I cannot wait to do this with my students next year.