# flow rates



## benjaminrogers (Jul 11, 2011)

How can a flow rate be at 700 CFS when the depth is only 2ft? Are we talking pure white water? It's the gauge on the Mad at Springfield. But further up at West Liberty it's on 65 CFS in 3 ft. of water?


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## riverKing (Jan 26, 2007)

that simply means that where they took the measurements for the flow the water may have been in a riffle in springfield, and in a deep pool in west liberty. I would not worry about the gauge depth, only the flow. also, just because the gauge reads 1 ft or 70ft doesn't mean the water is that deep there, some gauges are based at elevation, so they may read 1021ft at the gauge, but the stream is still fishable.
btw, the mad is fishable throughout the river right now. Look for 300fs and down at the Urbana gauge to fish Below st rt 29 to the county line. The upper river (above 29) is fishable if the west liberty gauge is below 100 cfs. The river usually takes less than 48 hours to clear after a rain, but if it is a major rain event look for the bell curve on the graph to begin to level out. Sometimes on the mad the water can actually be to high to fish and still have 4-5ft of clarity, it is the only river in ohio that I have seen this happen.


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## Andrew S (Jul 7, 2011)

It has to do with the width. A very large, wide river can be moving along very slowly but have a very, very high CFS value.


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## copperdon (Jun 3, 2011)

Andrew S said:


> It has to do with the width. A very large, wide river can be moving along very slowly but have a very, very high CFS value.


I've seen that on the Colorado river.

The section of river southwest of Glenwood Springs has an average flow rate of around 2800 - 4500 CFS, and while that may sound high to those of us who fish these little Ohio, WV and PA creeks, that's actually in the prime fishable range on that stretch of the Colorado because it's wide. High flow rates, but much of that stretch is quite calm.
I've fished it and although it does run deep, it's a beautiful stretch of river.
I had one of my best fishing days ever on this stretch - 13 cuthroats and 4 browns, all averaging around 14 - 18" using a #18 BWO.












Although, if you get into Glenwood Springs where the Colorado meets the Roaring Fork River and it starts to look like this: LOL


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## Andrew S (Jul 7, 2011)

That's a good example.

Flow rate, in CFS, is not the same thing as the "speed" of the water. It's how much, i.e. total volume, of water passing a point on the river over a given time.

It's the cross-sectional area of the entire river (square feet) times the velocity of the water (feet per second). When you multiply square feet by "single" feet, you get cubic feet...all divided by, or "per", second.

A river 20 feet wide and 2 feet deep has a cross section area of 40 square feet. So would a deep channel 10 feet deep and 4 feet deep. The two would have the same stream flow if the velocity of the water was the same.

So, you can't really know how to interpret the CFS values you read on-line unless you know both the width and depth of the river you're checking out. And in reality, of course, you want to know from seeing it first hand, or reading, what ideal flow rates are for a given stretch.

The Mad is a smaller river up north, and it's picking up more water as it goes down, so it's not surprising that you'd see very high streamflows lower. But this doesn't mean the water down there is moving faster, and in fact could be moving much slower, since the river is wider.


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