Flow Rate Of a River

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100315-1919 EST

Ham:

Do a Google search with the words
detroit river flow rate
Note: the rate is estimated at 190,000 cubic-feet per second. 30 MPH is 44 ft/sec. Velocities in the Detroit river vary from about 0.05 to 2.0 ft/sec. Assume 1 ft/sec, 3 MPH, then an area of 190,000 sq-ft is moving per second. Average width is 2400 ft, about 1/2 mile. This would seem to make average depth 80 ft.


One result is
http://mi.water.usgs.gov/progproj/mi08900.html

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You need to do water flow measurements at different locations across the river. A draft tube with paddles inside or dye dropped on water at a point location timed until it reaches another monitoring point with known distance from the drop point can approximate water velocity at certain points.

Take note that the water velocities are different at different location across the river flow. Velocities will be lower at the sides (friction at the river shores) and river bottoms, greater at deeper locations and fastest at river flow center.

Just like in integral calculus, you will get an area strip (depth X test spacing) then multiply the calculated "water area" by the average velocity that you can come up with at both test points. You now have a "strip flow" value.
(sq. ft. X ft/sec = cu. ft./sec, which is volumetric flow!
Add all these "strip flows" and voila! you come up with the approximate volumetric flow of the river!

Hope this helps.
 
gar said:
100315-1919 EST

Ham:

Do a Google search with the words
detroit river flow rate
Note: the rate is estimated at 190,000 cubic-feet per second. 30 MPH is 44 ft/sec. Velocities in the Detroit river vary from about 0.05 to 2.0 ft/sec. Assume 1 ft/sec, 3 MPH, then an area of 190,000 sq-ft is moving per second. Average width is 2400 ft, about 1/2 mile. This would seem to make average depth 80 ft.


One result is
http://mi.water.usgs.gov/progproj/mi08900.html

.
Click to expand...

That is a heap of water. The Roanoke River at 10,000 cfs will just barely stay in the banks.
 
There are gauge stations installed in many locations. They essentially measure the height of the flowing water. Based on a detailed calibration, utilizing all of the above mentioned factors and sometimes few additional, a chart is prepared for that location giving the flow rate at any water level for that particular location. Some are manually operated measuring tapes suspended from bridges, others use a hydraulic connection in what looks like a well off to one side of the water course. These can be manual or automatic with recording and/or telemetering. In all cases, not a trivial exercise. Measuring velocity itself is a bit easier, just need to drop a floating object in the water and time it over a known distance.
 
100316-1251 EST

The long term average flow rate of the Niagara River is 205,000 cubic feet per second. Thus there was a net addition from the Lake Erie area of about 15,000 cubic feet per second. Note: the Detroit River is the summation of Lake Michigan, Lake Superior, Lake Huron, and Lake St Clair.

At Quebec City this has increased to about 434,000 cubic feet per second if my calculations are correct.

The Hudson River rate is about 32,000 cubic feet per second at times. See http://www.appliedcoastal.com/pdf/01-13_rpt.pdf

Ham, have we given you enough reading for now?

In 1951 the USS Wisconsin was anchored in the Hudson River in the morning with low steam pressure and the anchor slipped. The ship moved on to the New Jersey mud banks. A very large number of tug boats from New York harbor were used to restrain the Wisconsin from going further on the mud. The Wisconsin horsepower rating was about 200,000 and I believe tugs are about 5000 HP.

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