Send the basics and any useful source links. If you only know the river, start there. The fastest requests to add are the ones with a clear put-in, take-out, and matching USGS gauge.
Request form
What to send
A route name or river name, state, and enough context to understand the stretch. If you can give us the put-in, take-out, and a USGS gauge link, it is usually very easy for us to review and add.
Best-case request: route name, state, put-in, take-out, and the exact USGS gauge that should drive the call. DNR, park, or club links help too.