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At what point does the River Severn start being completely freshwater?

There is no such "point". The mind conceives of things as having sharp defining lines: here/there, tadpole/frog, fresh/salt. The universe, on the other hand, deals in processes - travel, metamorphosis, tides and diffusion. This is known as the Sorites paradox, named after the Greek philosopher who asked the prototypical question: 'How many beans make a heap?' One obviously doesn't, nor does two, but keep adding beans and you get a heap. But where is the "point" where before adding a bean you didn't have a heap, and now you do? Obviously, there isn't one. So the question is meaningless. The river becomes more and more salty until it reaches the sea. You could specify a concentration of salt, but even that would vary during the course of a day.

Alan Hamilton, Telford Shropshire

At it's source in the Welsh mountains! As rivers are generally believed to flow downhill towards the sea all rivers start out being completely freshwater, becoming brackish only in their tidal reaches.

James Ellaway, Sydney Australia

I guess that it starts being completely freshwater at its source.It stays as fresh water until it reaches Gloucester when it spills over the weir into the tidal section.The locking system ensures that saltwater is always at the lowest level.

Jack Hill, St Albans England UK

As the tide rises and falls in estuaries a "salt wedge" (a layer of heavy salt water which sits on the river bed as it is denser than freshwater)travels up and down the river. There is a fairly sharp divide between the salt and freshwater, (and not a gradual gradient as you travel down river as suggested above)although there is some mixing at the interface between the two. This divide will travel up and down with the salt wedge, presumably as far as the weir that Jack Hill mentions, although I have no local knowledge of the area.

Adam Cooper, Swansea Wales

The weir is at Maisemore. When the incoming Severn Bore reaches the weir it is reflected giving the unusual sight of a tidal wave moving downstream.

Michael Parry, Holywood, Northern Ireland

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At what point does the River Severn start being completely freshwater? | Notes and Queries | guardian.co.uk

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THIS SCEPTRED ISLE At what point does the River Severn start being completely freshwater? There is no such "point". The mind conceives of things as having sharp defining lines: here/there, tadpole/frog, fresh/salt. The universe, on the other hand, deals in processes - travel, metamorphosis, tides and diffusion.

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it starts being completely freshwater at its source.It stays as fresh water until it reaches Gloucester when it spills over the weir into the tidal section.The locking system ensures that saltwater is always at the lowest level.

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Lobsters and crayfish are both crustaceans and invertebrates who shed their tough exoskeleton many times over the course of their lives.