It rises on Tweedsmuir at Tweed's Well.
The River Tweed.
The Cheviot Hills
Surprise, surprise, Berwick-on-Tweed is on the River Tweed
The River Tweed is 97 miles long and, no it does not have mountains in it.
The Tweed River in Australia flows eastwards.
The River Till is a tributary of the River Tweed in England. It rises on Comb Fell. It meets the Tweed near Berwick-Upon-Tweed.
The town is called Berwick upon Tweed because it is "upon" the river Tweed.
the Tweed river is the border between NSW and Queensland
The Tweed River forms the border between Queensland and New South Wales at its mouth. The majority of the Tweed is in New South Wales. Though irrelevant to the question, there is also a Tweed River in the UK, and one in New Zealand.
north of Queensland
The Tweed River is about 149 km South of brisbane. or about 2 hours 15 minuters by car.
Freshwater.