Global Terrestrial Network for River Discharge (GTN-R)
Shapefile for watersheds based on the entire basin-358.
This was the source:
http://grdc.bafg.de/servlet/is/6701/
Quoted on that page is the projection:
"All ESRI-Shape-files provided below are in geographic coordinates
(GCS_WGS_1984)"
Here is the description of how these basin boundaries were derived.
http://grdc.bafg.de/servlet/is/6746/
Files: GIS/Basin
Retrieved: 20041216