High-water levels may be caused by upstream rains or water released through a dam. High water usually means swifter currents. Stay out of swift currents unless you are sure you can paddle through safely. If you planned only a leisurely trip, high water can be hazardous.
Low-water levels can cause you to run aground or scrape submerged objects such as rocks. Stay in deeper channels when possible.
Be aware of seasonal changes in water levels.