Our group consists of three international students and three Finnish students Leonie Debus (GER), Linwei Wang (CN) , Linjie Zhu (CN), Aleksi Kosonen (FIN), Kati Heinonen (FIN) and Tatu Santala (FIN). Leonie couldn't attend to this part of field work.
The measurements were done on 24th of September in pond Pieni-Valkeinen, Kuopio Finland. Task was to measure discharge of pond Pieni-Valkeinen's incoming and outgoing channels. Measurements were done using Thompson weir, volymetric method and current meter.
The measurements were done on 24th of September in pond Pieni-Valkeinen, Kuopio Finland. Task was to measure discharge of pond Pieni-Valkeinen's incoming and outgoing channels. Measurements were done using Thompson weir, volymetric method and current meter.
Pond Pieni-Valkeinen
Thompson Weir
Thompson weir is temporary dam which uses v-shaped metal plate that has measurement scale on it. The metal plate has a plastic sheet attached to it which is for guiding the streams water towards the dam.
Thompson weir. Here you can see some of the difficulties we encountered.
First we built it in the incoming channel. We searched for a good spot but we couldn't find one so we had to modify the stream to fit our Thompson weir. Water flow was so weak that we had to dig a place for the metal plate into the bottom of the stream so we could get enough water flowing through it. We tried to get the plastic sheet properly into the bottom, so water couldn't get through under it. But still some water got through (about 10 percent). After that we waited for the water to flow steadily and we read results from the metal plate.
The result was 2 cm.
Then we did the same thing in the outgoing channel and although the water flow was little bit better we still had to dig a place for the weir. Also in this phase water flow under the plastic sheet was also something around 10 percent. The result for this was 4 cm.
Volymetric method
This was challenging because there was not enough water going through the incoming channel. We had to use the Thompson weir again to get water into the bucket. We gathered water into the bucket for 20 seconds and did this 5 times.
Results was:
1l /20s
1,4l / 20s
1,6l / 20s
1,6l / 20s
1,7l / 20s
Because there was more water flowing in the outgoing channel we had to do this little bit differently. We used Thompson weir also in this but we had to measure the time it took to fill the bucket. Because it was hard to be exact with the position of the bucket and estimating when it was actually full, there is a little fluctuation in the results.
Results was:
1,9l / 4s
1,7l / 3s
1,9l / 3s
1,8l / 3s
2,0l/ 3s
We found that the incoming flow was 0.37 L/s and the outgoing flow was 3.10 L/s.
Because there was still some parts of water flowing below and the flow may have some differences by time it may not be so accurate.
Results of volymetric measurement.
Current Meter
We took measurements in incoming stream and outgoing stream, measuring the speed within a given time. However, because some measuring point flow velocity is large, some measuring point flow velocity is small. So we can take the average as the experimental result, and we can get a more accurate conclusion.
The tools we used are:
Measuring equipment SEBA mini current meter M1
stopwatch
roller measurement
note tool
The flow rate (m/s) is calculated per stratification point with the formula:
V =k ∙n +D
V = flow rate (m/s)
k = Wing Hydraulic Ascent (m)
n = Wing rpm (KRT/s)
D = Strainer constant
The flow equation is specific to the measurement unit and its odds (k = 0.2591 m) and (D = 0.005) are determined by the strainer calibration curve. The flow rate (m3/s) is calculated per stratification zone with the formula:
Q =V∙A
Q = Flow (m3/s) =Convert to unit L/s when presenting final results in report
V = flow rate (m/s)
A = surface area ("area of stratification area")
Results of current meter.
Errors
Differences in results between different measuring gadgets are explained with inexperience of users and user error. We didn't take all of the measurements from the same place, and there was quite a lot of water flow going under the Thompson weir. And because we took the volymetric measurements using the Thompson weir there was also bypass flow.
The result was 2 cm.
Measuring scale and the flow in the incoming channel
Then we did the same thing in the outgoing channel and although the water flow was little bit better we still had to dig a place for the weir. Also in this phase water flow under the plastic sheet was also something around 10 percent. The result for this was 4 cm.
On the left we are working hard. On the right is the flow of the outgoing channel.
Discharge results using Thompson weir.
Volymetric method
This was challenging because there was not enough water going through the incoming channel. We had to use the Thompson weir again to get water into the bucket. We gathered water into the bucket for 20 seconds and did this 5 times.
Results was:
1l /20s
1,4l / 20s
1,6l / 20s
1,6l / 20s
1,7l / 20s
Because there was more water flowing in the outgoing channel we had to do this little bit differently. We used Thompson weir also in this but we had to measure the time it took to fill the bucket. Because it was hard to be exact with the position of the bucket and estimating when it was actually full, there is a little fluctuation in the results.
Results was:
1,9l / 4s
1,7l / 3s
1,9l / 3s
1,8l / 3s
2,0l/ 3s
We found that the incoming flow was 0.37 L/s and the outgoing flow was 3.10 L/s.
Because there was still some parts of water flowing below and the flow may have some differences by time it may not be so accurate.
Bucket action!
Current Meter
We took measurements in incoming stream and outgoing stream, measuring the speed within a given time. However, because some measuring point flow velocity is large, some measuring point flow velocity is small. So we can take the average as the experimental result, and we can get a more accurate conclusion.
Intensive measuring
The tools we used are:
Measuring equipment SEBA mini current meter M1
stopwatch
roller measurement
note tool
SEBA mini current meter M1 at work
The flow rate (m/s) is calculated per stratification point with the formula:
V =k ∙n +D
V = flow rate (m/s)
k = Wing Hydraulic Ascent (m)
n = Wing rpm (KRT/s)
D = Strainer constant
The flow equation is specific to the measurement unit and its odds (k = 0.2591 m) and (D = 0.005) are determined by the strainer calibration curve. The flow rate (m3/s) is calculated per stratification zone with the formula:
Q =V∙A
Q = Flow (m3/s) =Convert to unit L/s when presenting final results in report
V = flow rate (m/s)
A = surface area ("area of stratification area")
Results of current meter.
Errors
Differences in results between different measuring gadgets are explained with inexperience of users and user error. We didn't take all of the measurements from the same place, and there was quite a lot of water flow going under the Thompson weir. And because we took the volymetric measurements using the Thompson weir there was also bypass flow.
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