The River Irwell ( ) is a tributary of the River Mersey in north-west England. It rises at Irwell Springs on Deerplay Moor, approximately north of Bacup and flows southwards for to meet the Mersey near Irlam Locks. The Irwell marks the boundary between Manchester and Salford, and its lower reaches have been canalised and now form part of the Manchester Ship Canal.
In the 17th and 18th centuries, the Irwell's lower reaches were a trading route that became part of the Mersey and Irwell Navigation. In the late 19th century, the river's course downstream of Manchester was permanently altered by the construction of the Manchester Ship Canal which opened in 1896. The canal turned Manchester and Salford into a major inland seaport and led to the development of Trafford Park, which became the largest industrial estate in Europe. Further changes were made in the 20th and 21st centuries to prevent flooding in Manchester and Salford, including the construction of the Anaconda Cut in 1970 and the River Irwell Flood Defence Scheme in 2014.
The river became severely polluted by industrial waste during the Industrial Revolution, but in the second half of the 20th century a number of initiatives were implemented to improve water quality, restock it with fish and create a diverse environment for wildlife. Stretches of the river flowing through Manchester and Salford have attracted large-scale investment in business and residential developments, such as Salford Quays, and other parts have become important wildlife havens. The Irwell is used for recreational activities, such as pleasure cruising, rowing, racing, swimming and fishing.
Course From its source to the confluence with the River Mersey the Irwell is about long. Rising on the moors above Cliviger near the sources of the Lancashire River Calder and the Yorkshire River Calder, it flows south through Bacup, Rawtenstall, Ramsbottom and Bury before merging with the River Roch near Radcliffe. Turning west, it joins the River Croal near Farnworth before turning southeast through Kearsley, Clifton and the Agecroft area of Pendlebury. It then meanders around Lower Kersal and Lower Broughton. It bisects Salford and Manchester, joining the rivers Irk and Medlock, and then turns west toward Irlam, as part of the Manchester Ship Canal. Its course ends just beyond Irlam Locks, where it empties into the Mersey near Flixton.
Natural history
Until the early 19th century the Irwell was well-stocked with fish and other wildlife, with people living near Manchester Cathedral using its water for drinking and other domestic purposes. But during the Industrial Revolution, increasing levels of pollution caused by waste products discharged into the river by local industries proved fatal to wildlife, with fish stocks disappearing completely by about 1850. This situation abated somewhat during the 20th century, with a slow improvement in water quality leading to fresh populations of roach, bream and chub, and sightings of brown trout have become increasingly common.
Problems with water quality in some of the former Manchester Docks basins became apparent with the redevelopment of Salford Quays. Years of runoff from sewers and roads had accumulated in the slow running waters of this area and decomposition of organic matter was causing oxygen depletion. In 2001, a compressed air injection system was introduced. This raised the oxygen levels in the water by up to 300%, improving the water quality to such an extent that the number of invertebrate species present increased to more than 30, including freshwater shrimp. Spawning and growth rates of fish species such as roach and perch have also increased, and are now amongst the highest in England.
Two Sites of Special Scientific Interest (SSSIs) are located close to the banks of the Irwell, near to its confluence with the River Croal at Moses Gate Country Park near Bolton. The first is at Nob End, an 88 800 m2 site which has been designated because of its biological interest, based on the predominance of flora typical of limestone grassland including some nationally rare herbs and orchids. Nob End is also designated as a Local Nature Reserve (LNR). The second site is Ashclough, which is a site of geological interest. These two SSSIs are among the 21 found in Greater Manchester. In Salford the river flows through Clifton Country Park and Kersal Dale Country Park, both of which have been designated as LNRs.
Grey herons, cormorants, mute swans, kingfishers and many species of geese and ducks are regularly sighted on the river.Bullock, R The Salford Trail Retrieved on 23 October 2008 The Manchester Ship Canal near Salford Quays is one of the top ten sites in Britain for diving ducks, providing a winter home to approximately 3,000 common pochard and 2,000 tufted ducks.
Geology
From its source until shortly after its confluence with the River Croal, the river runs through a landscape formed from rocks of the late Carboniferous Coal Measures and the underlying (and therefore older) Millstone Grit, consisting mostly of a series of sandstone and shales. The lower sections of the river run through a landscape where the bedrock is of Permian and Triassic age, though alluvial and river terrace deposits often obscure the rock strata. The glaciers of the Pleistocene epoch radically re-shaped the landscape and then retreated, leaving behind deposits of sand, pebbles and boulder clay that formed the fluvioglacial ridges of the lower Irwell Valley. Ashclough, a site which comprises the steep banks of the river between Prestolee and Little Lever, has been designated an SSSI because of its geological interest, primarily because it is the best site in the area displaying the Ashclough marine band and its associated strata. Ashclough is a site of national importance for interpreting the coal measures palaeogeography of Great Britain.
River Irwell catchment area The River Irwell catchment area extends from the moors above Bacup to the Manchester Ship Canal. The climate of the catchment area is wetter than the UK average, with rainfall of per annum compared to per annum, and the rivers quickly respond to rainfall. The topography varies considerably, with the upper reaches dominated by the Pennine moors at an altitude of between AODAbove Ordnance Datum (mean sea level) and the bottom of the catchment consisting of relatively flat land, which lies between AOD. The watercourses are characterised by steep narrow valleys, which contributes to high rates of run-off, as does the underlying solid geology. This comprises Lower Coal Measures overlying Millstone Grit, both of which are classified as minor aquifers which will only hold relatively small amounts of water. The surface deposits comprise thick peat in the upper reaches, with glacial boulder clay and glacial sand and gravel in the lower parts. The sand and gravel are also classified as a minor aquifer, whilst the boulder clay is a non-aquifer. The higher, steeper slopes of the upper part of the catchment provide a large source of erodible material and debris which is transported downstream to the lower, flatter parts of the catchment. Where the channel is constricted, this material is then deposited and can contribute to a reduction in channel capacity.
History Etymology
The origins of the name "Irwell" are uncertain but many accept the Anglo-Saxon origin, ere-well, meaning "hoar or white spring". The first part of the name may also be the Brittonic *ar, an ancient river-name element that implies horizontal motion, "flowing", "rising" or else "springing up".
Ancient history Flint scrapers, knives and other materials associated with the Neolithic period were discovered on Kersal Moor in the late 19th century and early 20th century. There have been isolated finds of artefacts characteristic of this period along the Irwell valley, and a possible hunting site was excavated at Prestwich Golf Course in 1982, which produced a quantity of Late Neolithic and Early Bronze Age flints. Neolithic tools have also been found in the River Roch near Bury and in Radcliffe, and Bronze Age burial sites have been found in Bury and Shuttleworth.
Celtic, Roman and Medieval The first recorded human settlements were those of the Celtic tribe, the Brigantes, who farmed the uplands and lower reaches of the river in the late Iron Age. In AD 79 the Roman Empire conquered these tribes, building forts at the confluences of the Irwell and the rivers Irk and Medlock and naming the town Mamucium. They also built a ford with rectangular stone blocks at Cornbrook, which is thought to be the first man-made structure to span the river. For four hundred years the Pax Romana brought peace, but their withdrawal in AD 410 left the tribes at the mercy of the Saxons, who renamed the town Manigceastre. The Danes later seized, and all-but destroyed Manigceastre, and absorbed what was left of the tribes. The Danelaw ruled until AD 920 when the Norsemen were expelled by Edward the Elder.
In the Middle Ages the town, which was now known as Manceastre (later to become Manchester), grew and prospered, and trading vessels plied along the river. The hamlet of Kersal, which now forms part of the City of Salford, was gifted to the Cluniac Priory of Lenton, near Nottingham, in 1142. The most important part of the gift was the fishing rights on the River Irwell, and even in the 18th century, the salmon rights on the rivers of Lancashire were let every year for many hundreds of pounds.see: Hansard 18 April 1950 vol 474 cc91-106
19th century During the Industrial Revolution factories, mills and terraced hovels grew up along the river banks. Joseph Corbett, the Borough Engineer of Salford, wrote in his 1907 book The River Irwell of his father Edward's experiences around 1819, of seeing "large shoals of fish, chiefly gudgeon but also other fish, rising to the flies" from a vantage point on New Bailey bridge, (now Albert Bridge) in Manchester. Local industry dumped toxic chemicals into the river, such as gas-tar, gas-lime and ammonia water, and by 1850 fish stocks had all but disappeared. In 1860 the Irwell was described as "almost proverbial for the foulness of its waters; receiving the refuse of cotton factories, coal mines, print works, bleach works, dye works, chemical works, paper works, almost every kind of industry." In 1862 the Scottish geologist Hugh Miller wrote about the Irwell, in his book First Impressions: The English People, describing it as: The hapless river—a pretty enough stream a few miles higher up, with trees overhanging its banks, and fringes of green sedge set thick along its edges—loses caste as it gets among the mills and the printworks. There are myriads of dirty things given it to wash, and whole waggon-loads of poisons from dye-houses and bleachyards thrown into it to carry away; steam-boilers discharge into it their seething contents, and drains and sewers their fetid impurities; till at length it rolls on—here between tall dingy walls, there under precipices of red sandstone—considerably less a river than a flood of liquid manure, in which all life dies, whether animal or vegetable, and which resembles nothing in nature, except, perhaps, the stream thrown out in eruption by some mud-volcano.