The Wye river forms the boundary between England and Wales for part of its length. It is 215 km long. The River Dee forms the boundary between England and Wales for part of its length. It is 110 km long. But forming the boundary is separating England and Wales, not joining them.
The Severn river rises in the Cambrian Mountains of Powys, Wales then flows across the border and into England, then flows through Shropshire, Gloucestershire, and Herefordshire before forming an estuary between England and Wales. Does that count as joining the two countries? Taking the river as ending and the estuary beginning at Severn Beach, South Gloucestershire, the Severn is 354 km long.
You have to ask whether any river joins England and Wales. It is the sovereignty of the British Crown that joins them, and the authority of the Westminster Parliament.
The River Vyrnwy is a river in Wales and England. It is 40 miles long.
River Severn is 220 miles long and flows through England and Wales River Thames is 215 miles long and flows through England. River Trent is 185 miles long and flows through England. River Great Ouse is 143 miles long and flows through England. River Wye is 135 miles long and flows through England and Wales River Tay is 117 miles long and flows through Scotland River Towy is 68 miles long and flows through Wales
The longest river in Britain is the Severn closely followed by the Thames.
The River Soar is approximately 32 miles (51 kilometers) long. It flows through Leicestershire and joins the River Trent near the town of Loughborough in the East Midlands, England.
The shortest river in Britain is Scotland's River Scavaig which runs from Loch Coriusk in the centre of the Black Cuillin of Skye to the sea in a mere 250 yards :)
it is 700ft
The River Cleddau that consists of the Eastern and Western Cleddau rivers in Pembrokeshire, west Wales. They unite to form the Daugleddau estuary, which forms the important harbour of Milford Haven.
It is 64 km/40 mi long,
The River Avon is a 85 mile long river in England. The River Aire is a 71 mile long river in Yorkshire, England.
The River Wharfe is a river in Yorkshire, England and is 60 miles long.
A tributary is a river or stream that joins the main river. Viewing a map of the River Severn shows it has many tributaries on its long journey from its source in Plynlimon, Wales to the Severn Estuary.
The river that is southwest of Savannah is the Oconee River. The Oconee River is 220 miles long. It starts in Hall County, Georgia and terminates when it joins the Ocmulgee River.