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[[File:Stream.jpg|thumb|Figure 1. A flowing mountain stream.]]


Flow is the total volume of a fluid that flows past a fixed point in a river or stream over time. It is comparable to the speed at which a volume of fluid travels as seen in Figure 1. Volumetric flow rates can be measured in various volume/time units such as:


[[File:Stream.jpg|Figure One: A flowing mountaian stream|thumb|300px|right]]
* Liters per second (L/s)
* Cubic feet per second (ft³/s)
* Gallons per minute (gal/min)
* Cubic meters per second (m³/s)


Household tools or specialized meters can be used to find flow rates for pipes, sewage systems, and household appliances. People use flow data for [[microhydro]] systems, [[wastewater]] systems, [[rainwater]] catchment, [[water auditing]], settling rates, water table statistics, and other [[water]] related information. To find the flow of larger water bodies such major rivers or behind dams, meters are used.<ref name="Flow Rate">Engineers Edge. (2000). Fluid Volumetric Flow Rate - Fluid Flow. Retrieved October 28, 2009, from Engineer's Edge website: http://www.engineersedge.com</ref>


The purpose of this page is to focus on using low technology hand methods to find the flow of streams and small rivers.  Flow can also be found for pipes, sewage systems, and household appliances. People use flow data for [[Microhydro]] systems, waste-water information, settling rates, water table statistics, etc. To find the flow of larger water bodies such as dams or major rivers, high technology is used such as meters. Meters are described briefly in this page.
This page describes low-tech methods to determine flow of small streams and rivers, as well as other tools that can be used for this purpose.
==Flow ==
Flow is the total volume of a fluid that flows past a fixed point in a river or stream over time. It is comparable to the speed at which a volume of fluid travels as seen in Figure One. Volumetric flow rates can be measured in various units such as:
*liters/sec
*cubic feet/sec (cfs)
*gallons/min (gpm)
*cubic meters/sec <ref name="Flow Rate"> Engineers Edge. (2000). Fluid Volumetric Flow Rate - Fluid Flow. Retrieved October 28, 2009, from Engineer's Edge website: http://www.engineersedge.com/fluid_flow/volumeetric_flow_rate.htm</ref>


==Measuring Flow==
== Method 1: Bucket method ==
There are numerous ways to measure flow rate which include:  
=== Bucket method ===


The Bucket method is a simple way to measure the flow rate using household items. It requires a stopwatch, a large bucket, and two to three people.
[[File:BucketMethod.jpg|thumb|Figure 2. Finding the flow rate using a bucket.]]


#Measure the volume of the bucket or container.  
The Bucket method is a simple way to measure the flow rate using household items. It requires a stopwatch, a large bucket, and preferably two to three people. To measure the flow rate using the bucket method:
#Find a location along the stream that has a waterfall. If none can be found, a waterfall can be constructed using a weir (see Figure Four).  
 
#With a stopwatch, time how long it takes the waterfall to fill the bucket with water. Start the stopwatch simultaneously with the start of the bucket being filled and stop the stopwatch when the bucket fills. The bucket should not be filled by holding it below the surface of the stream because it is not the true flow rate.  
# Measure the volume of the bucket or container. Keep in mind that a typical 5 gallon bucket is often actually less than 5 gallons.
#Record the time it takes to fill the bucket.  
# Find a location along the stream that has a waterfall. If none can be found, a waterfall can be constructed using a weir (see Figure 4).
#Repeat steps two and three about six or seven times and take the average. It is a good idea to do a few trial runs before recording any data so that one can get a feel for the timing and measurements required.  
# With a stopwatch, time how long it takes the waterfall to fill the bucket with water. Start the stopwatch simultaneously with the start of the bucket being filled and stop the stopwatch when the bucket fills. The bucket should not be filled by holding it below the surface of the stream because it is not the true flow rate.
#Only eliminate data if major problems arise such as debris from the stream interfering with the flow.  
# Record the time it takes to fill the bucket.
#The flow rate is the volume of the bucket divided by the average time it took to fill the bucket. <ref name="Water Flow"> Trimmer, W.L. (1994 September). Estimating Water Flow. Retrieved October 29, 2009, from Oregon State University website: http://extension.oregonstate.edu/catalog/pdf/ec/ec1369.pdf</ref>
# Repeat steps two and three about six or seven times and take the average. It is a good idea to do a few trial runs before recording any data so that one can get a feel for the timing and measurements required.
# Only eliminate data if major problems arise such as debris from the stream interfering with the flow.
# The flow rate is the volume of the bucket divided by the average time it took to fill the bucket.<ref name="Water Flow">Trimmer, W.L. (1994 September). Estimating Water Flow. Retrieved October 29, 2009, from Oregon State University website: [https://web.archive.org/web/20091122100921/http://extension.oregonstate.edu:80/catalog/pdf/ec/ec1369.pdf http://web.archive.org/web/20091122100921/http://extension.oregonstate.edu:80/catalog/pdf/ec/ec1369.pdf]</ref>
 
<center>


[[Image:BucketMethod.jpg|thumb|Figure Two: An example of the Bucket Method|300px|right]]
<br>Here is an example using data found for the flow rate of the Jolly Giant Creek on [http://humboldt.edu/ Humboldt State University]grounds:
{| class="wikitable"
{| class="wikitable"
|-
|+ Bucket method data for flow (example)
! Trial Number
! Trial Number
! Time (seconds)
! Time (seconds)
! Bucket Volume (gallons)
! Bucket Volume (gallons)
|-
|-
| 1
| 1
| 13.2
| 13.2
| 5
| 5
|-
|-
| 2
| 2
| 14
| 14
| 5
| 5
|-
|-
| 3
| 3
| 14.5
| 14.5
| 5
| 5
|-
|-
| 4
| 4
| 13
| 13
| 5
| 5
|-
|-
| 5
| 5
| 13.4
| 13.4
| 5
| 5
|-
|-
| 6
| 6
| 13.1
| 13.1
| 5
| 5
|}
|}
Using this data, the volumetric flow rate (Q) is equal to the volume of the bucket (v) divided by the average time (t).<br>
 
</center>
Here is an example using data found for the flow rate of the Jolly Giant Creek on [[Cal Poly Humboldt]] grounds: Using this data, the volumetric flow rate (Q) is equal to the volume of the bucket (V) divided by the average time (t).
 
<center>
 
<math>Q=v/t</math><br>
<math>Q=v/t</math><br>
where <math>t=(13.2+14+14.5+13+13.4+13.1)sec/6 trials</math> <br>
so t=13.5 seconds
<br>and v= 5 gallons
<br><br>
<math>Q=5 gallons/ 13.5 seconds</math><br>
The flow rate Q= 0.37 gallons per second<br>
or 22.2 gallons per minute


===Float method===
where <math>t=\frac{13.2s+14s+14.5s+13s+13.4s+13.1s}{6 trials}=13.5 seconds</math>
[[File:Float Method.jpg|thumb|Figure Three: Finding the flow rate using a float and a meter stick.|400px|right]]
 
so <math>t = 13.5 seconds</math> and <math>V = 5 gallons</math>
 
<math>Q = \frac{V}{t}= \frac{5 gallons}{13.5 seconds} = 0.37 \frac{gallons}{second}</math>
 
So the flow rate is 0.37 gallons/second or Q = 0.37 gal/sec * 60 sec/min = 22.2 gallons/minute.
 
Therefore the '''flowrate (Q) is 22.2 GPM'''.
 
</center>
 
== Method 2: Float method ==
 
[[File:Float Method.jpg|thumb|Figure 3. Finding the flow rate using a float and a meter stick.]]
 
The float method (also known as the cross-sectional method) is used to measure the flow rate for larger streams and rivers. It is found by multiplying a cross sectional area of the stream by the velocity of the water. To measure the flow rate using the float method:


The float method (also known as the cross-sectional method) is used to measure the flow rate for larger streams and rivers. It is found by multiplying a cross sectional area of the stream by the velocity of the water.
# Locate a spot in the stream that will act as the cross section of the stream.
# Locate a spot in the stream that will act as the cross section of the stream.
# Using a meter stick, or some other means of measurement, measure the depth of the stream at equal intervals along the width of the stream (see Figure Three). This method is similar to hand calculating a [http://en.wikipedia.org/wiki/Riemann_sum Riemann sum]for the width of the river.
# Using a meter stick, or some other means of measurement, measure the depth of the stream at equal intervals along the width of the stream (see Figure 3). This method is similar to hand calculating a [https://en.wikipedia.org/wiki/Riemann_sum Riemann sum] for the width of the river.
# Once this data is gathered, multiply each depth by the interval it was taken in and add all the amounts together. This calculation is the area of a cross section of the stream.
# Once this data is gathered, multiply each depth by the interval it was taken in and add all the amounts together. This calculation is the area of a cross section of the stream.
# Decide on a length of the stream, typically longer than the width of the river, to send a floating object down (oranges work great).
# Decide on a length of the stream, typically longer than the width of the river, to send a floating object down (oranges work great).<ref name="Stream Flow">Wikipedia. (2009, October). Streamflow. Retrieved October 28, 2009, from Wikipedia website: [https://en.wikipedia.org/wiki/Streamflow http://en.wikipedia.org/wiki/Streamflow]</ref>
# Using a stopwatch, measure the time it takes the float to travel down the length of stream from step 4.
# Using a stopwatch, measure the time it takes the float to travel down the length of stream from step 4.
# Repeat step five 5-6 times and determine the average time taken for the float to travel the stream.
# Repeat step five 5-10 times and determine the average time taken for the float to travel the stream. Throw the float into the water at different distances from the shoreline in order to gain a more accurate average.
# Divide the stream length found in step 4 by the average time in step 6 to determine the average velocity of the stream.
# Divide the stream length found in step 4 by the average time in step 6 to determine the average velocity of the stream.
# The velocity found in step 7 must be multiplied by a friction correction factor. Since the top of a stream flows faster than the bottom due to friction against the stream bed, the friction correction factor evens out the flow. For rough or rocky bottoms, multiply the velocity by 0.8. For smooth, muddy, sandy, or smooth bedrock conditions, multiply the velocity by a correction factor of 0.9.  
# The velocity found in step 7 must be multiplied by a friction correction factor. Since the top of a stream flows faster than the bottom due to friction against the stream bed, the friction correction factor evens out the flow. For rough or rocky bottoms, multiply the velocity by 0.85. For smooth, muddy, sandy, or smooth bedrock conditions, multiply the velocity by a correction factor of 0.9.
# The corrected velocity multiplied by the cross sectional area yields the flow rate in volume/time. (Be sure to keep consistent units of length/distance when measuring the cross section and the velocity eg. meters, feet)<ref name="Stream Flow"> Wikipedia. (2009, October). Streamflow. Retrieved October 28, 2009, from Wikipedia website: http://en.wikipedia.org/wiki/Streamflow</ref>
# The corrected velocity multiplied by the cross sectional area yields the flow rate in volume/time. (Be sure to keep consistent units of length/distance when measuring the cross section and the velocity e.g. meters, feet)
 
== Method 3: Weirs ==
 
Weirs are small dams that can be used in measuring flow rate for small to medium sized streams (a few meters or wider). They allow overflow of the stream to pour over the top of the weir, creating a waterfall, as seen in Figure 4. Weirs increase the change in elevation making the streamflow more consistent which makes flow rate measurements more precise. However, it is very important that all the water in the stream be directed into the weir for it to accurately represent the stream flow. It is also important to keep sediment from building up behind the weir. Sharp crested weirs work best. There are many different types of weirs which include broad crested weirs, sharp crested weirs, combination weirs, V-notch weirs and minimum energy loss weirs.


===Weirs===
[[File:Weir.jpg|thumb|center|Figure 4: An example of a V-notch weir.]]
[[File:Weir.jpg|400px|left|thumb|Figure Four: An example of a V-notch weir]]


Weirs are small dams that can be used in measuring flow rate for small to medium sized streams (a few meters or wider). They allow overflow of the stream to pour over the top of the weir, creating a waterfall, as seen in Figure Four. Weirs increase the change in elevation making the streamflow more consistent which makes flow rate measurements more precise. However, it is very important that all the water in the stream be directed into the weir for it to accurately represent the stream flow. It is also important to keep sediment from building up behind the weir. Sharp crested weirs work best. <ref name="Microhydropower"> Klunne, Wim Jonker. (2009, June). Hydropower Basics: Measurement of Flow. Retrieved November 4, 2009, from Microhydropower website: http://microhydropower.net/basics/flow.php</ref>
== Method 4: Meters ==
There are many different types of weirs which include broad crested weirs, sharp crested weirs, combination weirs, V-notch weirs and minimum energy loss weirs. <ref name="Weir"> Wikipedia. (2009, October). Weir. Retrieved November 4, 2009, from Wikipedia website: http://en.wikipedia.org/wiki/Weir</ref>
<br /><br />


===Meters===
Meters are devices that measure the stream flow by directly measuring the current. There are many different types of meters but the most common are the Pygmy meter, the vortex meter, the flow probe, and the current meter, described below:
Meters are devices that measure the stream flow by directly measuring the current. There are many different types of meters by the most common is the Pygmy meter, the vortex meter, the flow probe, and the current meter: They are briefly described.


<gallery>
<center>
File:PygmyMeter.jpg|'''Pygmy meter''': a wheel is rotated by water flow and the rate of the rotation signifies the water velocity. It is primarily used in measuring discharge. <ref name="Meters"> Geo-Scientific Ltd. (2001). Flow and Current Meters. Retrieved November 7, 2009, from Geo-Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/index.html</ref>
<gallery heights=170>
File:PygmyMeter.jpg|'''Pygmy meter''': a wheel is rotated by water flow and the rate of the rotation signifies the water velocity. It is primarily used in measuring discharge.<ref name="Meters">Geo-Scientific Ltd. (2001). Flow and Current Meters. Retrieved November 7, 2009, from Geo-Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/index.html</ref>
File:VORTEXmeter.JPG|'''Vortex meter''': velocity is proportional to the downstream frequency of the vortex flow and is read on a digital readout. It is used for measuring flow in pipes.<ref name="Flow Meters">Cahner Publishing Company. (1984, November 21). Liquid Flowmeters. Retrieved October 28, 2009, from Omega Engineering website: http://web.archive.org/web/20170909023441/http://www.omega.com:80/techref/flowcontrol.html</ref>
File:FlowProbe.JPG|'''Flow probe''': the flow turns a propeller that sends the water velocity data to a digital readout display in ft/s or m/s<ref name="Flow Probe">Geo Scientific Ltd. (2001). Global Flow Probe. Retrieved November 7, 2009, from Geo Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/Flow_Probe.html</ref>
File:CurrentMeter.jpg|'''Current meter''': electronic pulses determine water velocity. Can be used in large bodies of water like oceans to measure the current.<ref name="Current Meter">Geo Scientific Ltd. (2001). Swoffer Current Meter. Retrieved November 4, 2009, from Geo Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/Swoffer2100_CurrentMeter.html</ref>
</gallery></center>


File:VORTEXmeter.JPG|'''Vortex meter''': velocity is proportional to the downstream frequency of the vortex flow and is read on a digital readout. It is used for measuring flow in pipes. <ref name="Flow Meters"> Cahner Publishing Company. (1984, November 21). Liquid Flowmeters. Retrieved October 28, 2009, from Omega Engineering website: http://www.omega.com/techref/flowcontrol.html</ref>
== Further reading ==


File:FlowProbe.JPG|'''Flow probe''': the flow turns a propeller that sends the water velocity data to a digital readout display in ft/s or m/s <ref name="Flow Probe"> Geo Scientific Ltd. (2001). Global Flow Probe. Retrieved November 7, 2009, from Geo Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/Flow_Probe.html</ref>
{{Rainbook}}


File:CurrentMeter.jpg|'''Current meter''': electronic pulses determine water velocity. Can be used in large bodies of water like oceans to measure the current. <ref name="Current Meter"> Geo Scientific Ltd. (2001). Swoffer Current Meter. Retrieved November 4, 2009, from Geo Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/Swoffer2100_CurrentMeter.html</ref>
* [[Wikipedia:Volumetric flow rate]]
</gallery>
* [http://web.cecs.pdx.edu/~gerry/class/ME449/lectures/pdf/flowRateSlides_2up.pdf Volumetric Flow Rate Measurement]


==Further reading==
== References ==
*http://en.wikipedia.org/wiki/Volumetric_flow_rate<br>
*http://web.cecs.pdx.edu/~gerry/class/ME449/lectures/pdf/flowRateSlides_2up.pdf
*http://www.stream.fs.fed.us/publications/PDFs/RM245E.PDF


==References==
<references />
<references />


==Beth's Comments==
{{Page data
* read through all the editing codes.
| keywords = measurement, flow rate, water, How tos, water, Microhydro
* Use this reference, as it explains the standard protocol http://www.stream.fs.fed.us/publications/PDFs/RM245E.PDF  Be sure to check the float method in this reference, as I think your description of the float method does not agree
| sdg = SDG06 Clean water and sanitation
* I think you should provide an example for the float method as well.  Your example idea is very helpful and clarifies the instructions.
| authors = User:Lonny, User:Mgn8, User:Adc37, User:Noh2
* Can you include an example calculation for a weir?
| published = 2009
 
| part-of = Engr115 Intro to Engineering, Engr305 Appropriate Technology
| organizations = Cal Poly Humboldt
}}


[[Category:Engr115 Intro to Engineering]]
[[Category:Water]]
[[Category:How tos]]
[[Category:Microhydro]]

Latest revision as of 19:12, 29 January 2024

Figure 1. A flowing mountain stream.

Flow is the total volume of a fluid that flows past a fixed point in a river or stream over time. It is comparable to the speed at which a volume of fluid travels as seen in Figure 1. Volumetric flow rates can be measured in various volume/time units such as:

  • Liters per second (L/s)
  • Cubic feet per second (ft³/s)
  • Gallons per minute (gal/min)
  • Cubic meters per second (m³/s)

Household tools or specialized meters can be used to find flow rates for pipes, sewage systems, and household appliances. People use flow data for microhydro systems, wastewater systems, rainwater catchment, water auditing, settling rates, water table statistics, and other water related information. To find the flow of larger water bodies such major rivers or behind dams, meters are used.[1]

This page describes low-tech methods to determine flow of small streams and rivers, as well as other tools that can be used for this purpose.

Method 1: Bucket method[edit | edit source]

Figure 2. Finding the flow rate using a bucket.

The Bucket method is a simple way to measure the flow rate using household items. It requires a stopwatch, a large bucket, and preferably two to three people. To measure the flow rate using the bucket method:

  1. Measure the volume of the bucket or container. Keep in mind that a typical 5 gallon bucket is often actually less than 5 gallons.
  2. Find a location along the stream that has a waterfall. If none can be found, a waterfall can be constructed using a weir (see Figure 4).
  3. With a stopwatch, time how long it takes the waterfall to fill the bucket with water. Start the stopwatch simultaneously with the start of the bucket being filled and stop the stopwatch when the bucket fills. The bucket should not be filled by holding it below the surface of the stream because it is not the true flow rate.
  4. Record the time it takes to fill the bucket.
  5. Repeat steps two and three about six or seven times and take the average. It is a good idea to do a few trial runs before recording any data so that one can get a feel for the timing and measurements required.
  6. Only eliminate data if major problems arise such as debris from the stream interfering with the flow.
  7. The flow rate is the volume of the bucket divided by the average time it took to fill the bucket.[2]
Bucket method data for flow (example)
Trial Number Time (seconds) Bucket Volume (gallons)
1 13.2 5
2 14 5
3 14.5 5
4 13 5
5 13.4 5
6 13.1 5

Here is an example using data found for the flow rate of the Jolly Giant Creek on Cal Poly Humboldt grounds: Using this data, the volumetric flow rate (Q) is equal to the volume of the bucket (V) divided by the average time (t).


where

so and

So the flow rate is 0.37 gallons/second or Q = 0.37 gal/sec * 60 sec/min = 22.2 gallons/minute.

Therefore the flowrate (Q) is 22.2 GPM.

Method 2: Float method[edit | edit source]

Figure 3. Finding the flow rate using a float and a meter stick.

The float method (also known as the cross-sectional method) is used to measure the flow rate for larger streams and rivers. It is found by multiplying a cross sectional area of the stream by the velocity of the water. To measure the flow rate using the float method:

  1. Locate a spot in the stream that will act as the cross section of the stream.
  2. Using a meter stick, or some other means of measurement, measure the depth of the stream at equal intervals along the width of the stream (see Figure 3). This method is similar to hand calculating a Riemann sum for the width of the river.
  3. Once this data is gathered, multiply each depth by the interval it was taken in and add all the amounts together. This calculation is the area of a cross section of the stream.
  4. Decide on a length of the stream, typically longer than the width of the river, to send a floating object down (oranges work great).[3]
  5. Using a stopwatch, measure the time it takes the float to travel down the length of stream from step 4.
  6. Repeat step five 5-10 times and determine the average time taken for the float to travel the stream. Throw the float into the water at different distances from the shoreline in order to gain a more accurate average.
  7. Divide the stream length found in step 4 by the average time in step 6 to determine the average velocity of the stream.
  8. The velocity found in step 7 must be multiplied by a friction correction factor. Since the top of a stream flows faster than the bottom due to friction against the stream bed, the friction correction factor evens out the flow. For rough or rocky bottoms, multiply the velocity by 0.85. For smooth, muddy, sandy, or smooth bedrock conditions, multiply the velocity by a correction factor of 0.9.
  9. The corrected velocity multiplied by the cross sectional area yields the flow rate in volume/time. (Be sure to keep consistent units of length/distance when measuring the cross section and the velocity e.g. meters, feet)

Method 3: Weirs[edit | edit source]

Weirs are small dams that can be used in measuring flow rate for small to medium sized streams (a few meters or wider). They allow overflow of the stream to pour over the top of the weir, creating a waterfall, as seen in Figure 4. Weirs increase the change in elevation making the streamflow more consistent which makes flow rate measurements more precise. However, it is very important that all the water in the stream be directed into the weir for it to accurately represent the stream flow. It is also important to keep sediment from building up behind the weir. Sharp crested weirs work best. There are many different types of weirs which include broad crested weirs, sharp crested weirs, combination weirs, V-notch weirs and minimum energy loss weirs.

Figure 4: An example of a V-notch weir.

Method 4: Meters[edit | edit source]

Meters are devices that measure the stream flow by directly measuring the current. There are many different types of meters but the most common are the Pygmy meter, the vortex meter, the flow probe, and the current meter, described below:

Further reading[edit | edit source]

To Catch the Rain is the first book created from this much exclusive Appropedia content on rainwater. Thank you for making it happen! Get it digitally here or as paperback on Amazon.

References[edit | edit source]

  1. Engineers Edge. (2000). Fluid Volumetric Flow Rate - Fluid Flow. Retrieved October 28, 2009, from Engineer's Edge website: http://www.engineersedge.com
  2. Trimmer, W.L. (1994 September). Estimating Water Flow. Retrieved October 29, 2009, from Oregon State University website: http://web.archive.org/web/20091122100921/http://extension.oregonstate.edu:80/catalog/pdf/ec/ec1369.pdf
  3. Wikipedia. (2009, October). Streamflow. Retrieved October 28, 2009, from Wikipedia website: http://en.wikipedia.org/wiki/Streamflow
  4. Geo-Scientific Ltd. (2001). Flow and Current Meters. Retrieved November 7, 2009, from Geo-Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/index.html
  5. Cahner Publishing Company. (1984, November 21). Liquid Flowmeters. Retrieved October 28, 2009, from Omega Engineering website: http://web.archive.org/web/20170909023441/http://www.omega.com:80/techref/flowcontrol.html
  6. Geo Scientific Ltd. (2001). Global Flow Probe. Retrieved November 7, 2009, from Geo Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/Flow_Probe.html
  7. Geo Scientific Ltd. (2001). Swoffer Current Meter. Retrieved November 4, 2009, from Geo Scientific Ltd. website: http://www.geoscientific.com/flowcurrent/Swoffer2100_CurrentMeter.html
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