This category leads to websites about the River Mersey deriving its name from the  Anglo-Saxon for "boundary river":,

corresponding to Mercia and Northumbria, later between the historic counties of  Lancashire and  Cheshire.

In 1974 the areas on both banks of the lower reaches of the Mersey Estuary and marine mouth, were absorbed into the

metropolitan county of  Merseyside.

The River Mersey is formed with the confluence of the Rivers Goyt and Tame,

now under the M60 and the Peel Centre in  Stockport.

The river winds south of  Manchester, often forming the boundary of this city;  Gatley a suburban area

in the  Metropolitan Borough of Stockport, Greater Manchester, south of  Didsbury

then west of  Chorlton-cum-Hardy,  Sale before entering the  Manchester Ship Canal at  Irlam, then briefly

representing the boundary between  Salford City and  Trafford Borough at  Urmston, Carrinton and  Partington,

and crossed by a bridge at Warburton, to join the A57 to  Warrington in Cheshire,

where the canal is sluiced for the river to flow through the town centre before flowing west where it

becomes estuarine between  Runcorn and  Widnes.

Here the Mersey is spanned by A533 road bridge known as the Mersey Gateway.

A shorter span is west, the A533, Silver Jubilee Bridge, paired with a rail bridge at Runcorn Gap.

At this point the Manchester Ship Canal is still south of the estuary, and between the two road bridges, a lock

serves as transit at high tide, but the main entrance is further west, north west of  Ellesmere Port at locks

in the Merseyside parish of  Eastham.

North of Eastham the mouth of the Mersey forms the metropolitan district boundary between  Liverpool city

and the  Wirral Peninsula.

This category is for geographical websites devoted to the longest river in the UK, with its source above the Hafren Forest in North Wales, flowing through the English Midlands and flowing through Gloucestershire, with its tidal bore at its mouth, to the Bristol Channel between England and Wales, spanned by the Severn Suspension Bridge at Cheptow, and the Second Severn Crossing, at Caldicot, where the railway tunnel also emerges.

Websites about the river forming the border between Devon and Cornwall for much of its length to Plymouth Sound,

and incorporating Tamar Valley Area of Outstading Natural Beauty.

The most northerly point is the catchment to the man-made Upper Tamar Lake, which the county boundary dissects

between the parishes of  Bradworthy and  Kilkhampton.

Upper Tamar Lake is only five miles from the west coast, and ground water in Kilkhampton flows to the west, so

although the Tamar forms the boundary flowing south, is not regarded as the Tamar Valley.

More tributaries come from the parish of Bradsworthy, although the River Walden through Bradsworthy flows east,

and joins the River Torridge, eventually flowing north into the Barnstaple Bay.

Lower Tamar Lake is entirely within Devon, and from Bradsworthy parish the Tamar flows through Pancrasweek parish,

then again forms the county boundary with Launcells, but then the Tamar is entirely within  Bridgerule,

before separating Whitstone and Pyworthy.

At North Tamerton, the Tamar is joined by the River Deer from Holsworthy, again dividing the counties at

Tetcott, Luffincott, Northcott and St Giles on the Heath in the  Torridge District of Devon.

South of North Tamerton the parishes on the west bank of the Tamar are Boyton and Werrington before  Launceston.

The Tamar remains the county boundary for the West Devon parishes of Lifton, Bradstone, Dunterton,  Milton Abbot, 

Sydenham Damerel, then Gulworthy,  Bere Alston,  Bere Ferrers, where the River Tavy joins the tidal estuary,

with Plymouth on the east bank.  Here bridges span the Tamar to  Saltash.

Upstream from Saltash on the west bank are the Cornish parishes of Botusfleming, Landulph, Pillaton,

St Dominick, Calstock (represented by  Gunnislake), Stoke Climsland, Lezant & Lawhitton, south of Launceston.

The River Thames is most noted as flowing tbrough the capital of the United Kingdom, London.

By this point, the river is tidal, and known as the Tidestream of the Thames, which stretches east beyond the

Thames Barrier and Dartford Crossing, becoming Sea Reach east of  Tilbury and  Gravesend.

This region, and the area of sea east to the Dutch coast, separating the North Sea from the  English Channel,

is represented by the  Thames Estuary category.

Before London there are many tributaries flowing into the Thames, but perhaps the most significant is below  Dorchester, Oxfordshire, where the River Thame joins the River Isis.

West of this confluence, despite the name, the Isis is considered as the Thames, with its source at springs north of  Kemble, Gloucestershire.

This category is for geographical websites devoted to the River Wye, ranking fifth-longest river in the UK.

The source in North Wales, with the first tributary, Afon Tarennig, at its first bridge, the A44, Pont Rhydgaled.

The first major settlement is ar  Llangurig, where the Wye flows south with the A470 on its east bank.

Then at Rhadader (Rhaeadr Gwy), Llanwrthwl, Newbury-on-Wye, to  Builth Wells (Llanfair-ym-Muallt),

where the A470 crosses and continues south on the west bank.

A bridge leaves the A470, north of Erwood to join the B4594 to Painscastle, or north back to Aberedw,

where the tributary, the River Edw joins the Wye from the east.

A bridge also leaves the A470 between Boughrood and Llyswen, where the Wye the flows northwest,

bridged by the A468 at Glasbury, onwards to  Hay-on-Wye, before leaving Powys for Herfordshire.

The River Wye continues east flowing through  Hereford, meandering south to  Ross-on-Wye, where its

is crossed by the A40, which follows the west bank, as the Wye meanders south west, north west of the 

Forest of Dean, to  Goodrich, and  Monmouth flowing south, forming the border with England, to its mouth

at  Chepstow, into the mouth of the Severn, where it is spanned by the Severn Suspension Bridge at  Sedbury.