LuvtheFish I am not sure why a question about understanding the water gage readings must be so secretive. That seems like the exact type of question and information that should be shared on a discussion board.
So here is my experience:
-- If the flow reaches 150 cfm and is increasing Walnut is very difficult to fish. I usually do not fish when the gage is that high.
-- At about 125 cfm and decreasing the fishing can be very good.
-- For me the sweet spot is 60-100 cfm. You get a good drift and the water is not muddy or clear. Usually just right.
-- Below 50cfm, the water is is clearing and by 30 cfm the water is clear and the flow is not great for drifting your presentation.
In all the cases if the fish are there you can catch them. You just need to adjust how you fish.