Yes, for the US this project is based upon NHDPlus, which is the authoritative national source for the US, and saved us many man-years of effort. Huge thanks to the NHDPlus project team.
And for the international services big thanks to Bernhard Lehner and World Wildlife Fund for their work to build HydroSHEDS.
We are accepting contributions through the Community Maps program for higher resolution authoritative hydrologic content for additional areas.