The River Severn is the longest river in Britain, from source to tidal waters and it is about one hundred and eighty miles (that is 290km) long. The River Severn estuary adds about another forty miles (64km) to the river’s total length. The River Severn rises near the River Wye around the northeastern slopes of Plynlimon, Wales and it follows a semicircular course mainly southward to the Atlantic Ocean and the Bristol Channel. The River Severn drains an area of about 4350 square miles (which is about 11,266 square kilometers) with an average release of 2170 cubic feet (that is 61.5 cubic meter) per second at Bewdley.
The river starts its journey southeasterly and descends from an elevation of 2000 feet (600 meters) at its source to about 500 feet at the Welsh town of Llanidloes. From there, it turns stridently northeastward and follows the Vale of Powys, passing through Welshpool and Newton. The River Severn joins River Vyrnwy at Llanymynech where the headwaters are stemmed to form the reservoir of the Lake of Vyrnwy. From here the drinking water of Liverpool is supplied. The Severn turns eastward above a plain where it circles around the old town of Shrewsbury. The river continues flowing eastward and joins the River Dee. However, its course was blocked here by ice during the period of Pleistocene Epoch and so the water found its way around to the southeast at Ironbridge.
The flowing current of the river through the gorge at Ironbridge was very important to the iron industry of Coalbrookdale at the time. The River Severn then continues to flow from this point southward until it joins with the River Stour at Stourport and goes through Worcester. Worcester Cathedral can be seen standing on a cliff that rises from the steep left bank of the river. The Severn becomes tidal at Gloucester and it wanders to the sea. It becomes difficult to navigate on this particular section and therefore the river is bypassed by a ship canal that was opened in 1827. There are other canals that join the river, connecting it with the River Thames and with the Midlands region of England. Between Somerset and South Wales, the estuary widens progressively and finally becomes the well known Bristol Channel.