Whitewater Map shows realtime data about the water level of different sections of whitewater. All of the data comes from AmericanWhitewater.org. You should give them a donation.
In the future, my goal is to add filters to limit the displayed locations, and to improve what is shown when you click on a river.
If you encounter anything that confuses you, or see any bugs, please email me at firstname.lastname@example.org. Feedback really helps - user feedback is the reason whitewatermap.com is what it is today.