Rivers.run - River Levels

This app just gets better every year 👍

Update: sadly, now seems dead. I hope it will be revived. This free app is the simplest, cleanest and quickest way to check USGS stream data: flow, temperature, precipitation, whatever the stream gauges collect. The interface isn’t the most intuitive, but after a few minutes use it’s a snap. Excellent. I hope the developer will allow higher resolution maps for offline usage, as modern devices have plenty of storage to accommodate that data.

This app is specifically written for whitewater rivers. It includes a map with a pin for every river gage in US and Canada. Whatever you want in a whitewater river app, it probably already exists in this app. And there is a link for each river for you to submit suggestions to the developer.