This river is a major tributary of the Yarlung Tsangpo (aka the Brahmaputra). It seemed that the road (track?) we were travelling on, visible on the right, must be regularly impassable due to high water.
Please have a look at my other photoblog at http://www.nomadlens.com where I post daily images of the South West of England (where I live). I really appreciate your comments on both of them.