There is no online gauge
There is a painted gauge on the river right/upstream side of the put in bridge abutment.
Minimum (boney) Level is 1' 6" on the painted gauge or to the top of the numerous 5 inch dia holes in the bridge abutment.
My recommended minimum level is 2' on the painted gauge.
Above 3' on the painted gauge is pushy and eddies start to disappear. Consider it Class IV, above 3'.
The highest I have run it is at 3.5'. At this level the run takes 25 minutes if you do not have to portage any strainers.