Over the years man's use of the river has diminished in an industrial context being replaced by a large number of recreational users.  This in itself can only be seen as a good thing as users of sailing, rowing and power boats wish to travel on a clean water way free from pollution and waste. 
As is only too obvious a huge increase in recreational users would have a negative impact on natural habitats especially during breading seasons.  Thankfully well marked wake zones and traffic channels minimise potential harm.