There a USGS gauge below Osborne Canyon near the take-out. There is also a USBR gauge Crooked River at Smith Rocks. Flows of 1400 - 4600 cfs represents the range of acceptable flow although kayaks can enjoy the run down to 800 cfs. 1500 cfs is about the lower limit for rafts and above 2000 cfs is considered a good flow. As flows increase to 4000 cfs, sections of the run approach class V and you definitely want to bring your A game. Check out the teacup diagram to determine the status of reservoirs upstream.