Hi, my name is Mike Freeman and I'm a hydrologic technician with the USGS office here in Salt
Lake City, Utah.
I would like to take a few minutes to talk about using SWAMI to make a weir discharge
measurement.
From the 'Site Information' page, select 'Tasks', 'Discharge Measurement' and then select 'New
Channel' to begin your measurement.
In the "Channel Information" page you will enter the channel name, and for the Qm method
select 'Weir' from the drop down menu.
As you've noticed the 'Deployment Method' was automatically populated with 'Other'.
After you have populated all of the fields click 'Measure' to go the 'Measurement' page.
In the 'Measurement' page, the measurement is noted as a 'Flume Measurement'.
Disregard the title of this page.
The measurement will be documented as a 'Weir Measurement' in SWAMI and in SiteVisit.
After you have taken your head readings at the weir, record the head readings in the
'Head' box by entering the reading directly or clicking the calculator and entering the
value with the appropriate numbers.
Next assign a measurement time to the head reading by clicking the blue 'Time' button.
This will assign a time to the head reading to the nearest minute.
If you would like to assign a head reading to the nearest second, click the calculator
next to the time box.
By clicking the 'Now' button you will assign a time value to the nearest second.
Click 'Done' to return to the measurement screen.
Once time and head readings have been recorded, click 'Add' to populate the reading.
You may need to make multiple readings to determine the mean head reading to determine
the discharge at the weir.
For this example we will enter 4 head readings.
After the 4 head readings have been added, SWAMI will determine the 'Mean Head' for the
measurement.
To do this, simply click the boxes next to head measurements you wish to use.
For this example, we will use all head readings with a reading of 2.68 ft.
After you have checked the boxes, enter the correlated flow from the mean head reading
from the assigned weir rating for your station.
For this example, the correlated flow for a head reading of 2.68 ft has a discharge
of 1.35 cfs.
After the correlated flow has been entered, click 'Done' to end the weir measurement.
A dialog box will appear asking if you want to end the measurement.
Click 'Yes' to end the measurement.
The next page is 'Channel Summary' page, where you can document channel conditions and the
measurement location.
The drop downs make documenting channel conditions pretty easy.
In this example our Section Location was 'At the Gage'.
You will notice that the measurement distance is automatically entered as 0.
Horizontal Flow was 'Even'.
For Channel Conditions the material was 'artificial, Stability was 'firm' and the Channel Material
was 'even'.
Velocity Description, the velocity was distributed 'standard', and 'steady'.
Once you have finished the Channel Description click 'Done' which will return you to the
'Channel Summary' page.
Click 'Done' to return to the 'Discharge Measurement' page.
From the 'Discharge Measurement" page you can add another channel to the measurement,
or if you are done, you can enter your gage height information to compare the measured
flow to the rated flow.
For this example our stage is 2.68 ft.
If the weir is the control of the gaging station, the percent difference will be 0 as you entered
the corresponding discharge from the rating table as observed in this example.
To verify the weir rating, a discharge measurement using an alternative method should be done
a couple times each year.
When your measurement is complete, click 'Done'.
You will be asked if you want to end the discharge measurement.
Simply click 'Yes' to end the measurement.
Your last task is to fill out the measurement summary page.
Typically, I enter the measurement number.
If the measurement number is unknown, you can select the auto sequence for the measurement
number which will assign the next measurement number in SiteVisit.
Rate your measurement, determine the base flow conditions, fill out the gage height
information and populate the start and end times.
Lastly include any measurement remarks.
If the weir is the control of the gage, be sure to mention the conditions of the weir,
documenting if the weir is level or the upstream velocity conditions approach the weir.
Once you have populated all fields in the 'Measurement Summary', click 'Done' to end
the measurement.
Now, your measurement is complete.
If you have questions on completing a weir measurement in SWAMI, please contact the SWAMI
help group at the email address shown or visit the FCIS webpage at the address shown.