The River Thames rises at Thames Head (near Kemble / Cirencester map) or Seven Springs (near Cheltenham map), depending on who you talk to.

It flows through Lechlade, Oxford, Abingdon, Wallingford, Reading, Henley-on-Thames, Marlow, Maidenhead, Windsor, Eton, Staines and Weybridge, before entering the Greater London area.

Non Tidal Thames Progress

• Thames Head to Lechlade: (no progress)
• Lechlade to Standlake: Main flow done, smaller flows missing
• Standlake to Eynsham: 50% of main flow done, smaller flows missing
• Eynsham to Oxford Ring Road: 50% of main flow done, smaller flows missing
• Oxford, except centre: Main flow done, some smaller flows done, some missing
• Central Oxford: Main flows done, some of the smaller ones still to do
• Oxford Ring Road to Abingdon: Main flow done most of the way to Abingdon, smaller flows missing
• Abingdon to Wallingford: ?
• Wallingford to Reading: ?
• Reading to Henley-on-Thames: Mostly complete
• Henley-on-Thames to Marlow: ?
• Marlow to Maidenhead: ?
• Maidenhead to Windsor: ?
• Windsor to Eton: ?
• Eton to Staines: Main flow done (mainly from Landsat)
• Staines to Chertsey: Main flow done (mainly from Landsat)
• Chertsey to Kingston: Main flow done (from landsat and riverbank footpaths)
• Kingston to Tidal Thames: ?mostly done?

Tidal Thames

• Tidal up to Teddington Lock - between Richmond and Kingston. map
• Through London (and Central London)
• ...and out to sea. map

The tidal section of the river was initially brought in by the coastline imports, and then people tracing from landsat. These days it can be corrected by tracing more accurately from Yahoo! Aerial Imagery.

It's still a little unclear actually what the tagging should be. Tag:waterway=riverbank nails it down, except that it's not clear when it becomes coastline. Proposed features/Tidal Rivers discussion is not finalised, and currently we are using BOTH waterway=riverbank and natural=coastline throughout central London.