Little Don River

The Little Don River also known as the Porter, is a tributary of the River Don in South Yorkshire, England. Arising on the Langsett Moors in the northern Peak District, the Little Don River feeds the Langsett and Underbank Reservoirs. It runs through the town of Stocksbridge before joining the River Don.

A 2.7-acre (1.1-hectare) section of the river has been designated as a site of special scientific interest since 1977. The site is of considerable importance as it is a proposed reference example for various subdivisions of the Carboniferous.^[1] It is one of 35 sites of special scientific interest in South Yorkshire.

The Little Don rises as a large number of streams flowing northwards from Howden Edge, close to the 1,640-foot (500 m) contour, on Rushbed Moor and Harden Moor, which unite and then flow eastwards. It is soon joined by Loftwshaw Brook, which similarly starts as a number of streams on Rushbed Moor, but slightly further to the west, and follows a more northerly route before joining the Little Don. It is joined by Mickleden Beck and Haslingshaw, both of which flow northwards and join the right bank. Long Moor Beck flows eastwards and joins as the Little Don enters Swinden Plantation, and the moorland scenery gives way to woodland. The river loops to the north, where it is joined by Great Grain, and passes over a weir to enter Langsett Reservoir.^[2]

El embalse fue construido como una empresa conjunta por las corporaciones de Sheffield, Doncaster, Rotherham y Barnsley. La Corporación de Sheffield compró el sitio en 1898 (o 1889, las fuentes varían) a la familia Pilkington, y también compró varias granjas locales que luego fueron abandonadas, para evitar la contaminación del suministro de agua. Las obras para la construcción de la presa, y las presas de los embalses de Midhope y Underbank, más abajo, comenzaron simultáneamente, y el embalse de Langsett se completó en 1904. Fue inaugurado oficialmente el 17 de octubre y contenía el mayor volumen de agua de las presas construidas en el área de Sheffield. ^{[ 3 ]} El transporte de materiales para la construcción fue facilitado por el ferrocarril de la Corporación de Sheffield, que recorría la orilla norte del río desde Stocksbridge. ^{[ 4 ]} La presa cruzaba el valle en el extremo este del embalse, y Midhope Cliff Lane corría por la parte superior del mismo. Se construyeron una planta de tratamiento y filtros debajo de la presa, y un aliviadero para mantener el flujo en el río se extendía desde el borde norte de la presa. ^{[ 5 ]} La propiedad del embalse pasó a la Autoridad de Aguas de Yorkshire en 1974, y tras la aprobación de la Ley de Aguas de 1989 y la privatización de las compañías de agua, ha sido propiedad de Yorkshire Water. El embalse cubre 124 acres (50 ha) , el terraplén de tierra que forma la presa tiene 1037 pies (316 m) de largo y un máximo de 115 pies (35 m) de alto, ^{[ 6 ]} y almacena más de 1400 millones de galones imperiales (6400 Ml) de agua. ^{[ 7 ]} Una nueva planta de tratamiento para reemplazar las de Langsett y Midhope se construyó entre 1983 y 1985, y puede tratar 60 megalitros de agua por día. Suministra agua potable al suroeste de Barnsley y al noroeste de Sheffield. ^{[ 6 ]}     

A little further downstream, the Little Don is joined by Hagg Brook, a small stream that is fed by the overflow from Midhope Reservoir. There is another weir in the Little Don at Midhopestones, just before Midhopestones Bridge.^[2] This small bridge carried Mortimer Road over the river, and is constructed of coursed gritstone blocks. It has three arches, a large one in the centre and a smaller one at either side. It dates from 1788 and is grade II listed.^[8] Underbank Reservoir begins immediately below the bridge. While Langsett and Midhope reservoirs are used for water supply, Underbank provides compensation water for the Little Don and the Don. The volumes of water released were thought to be too high in 2017, as they had historically supplied the many industrial sites further down the Don.^[9] There is a spillway from the southern edge of the dam with a weir at the bottom, after which the river is crossed by Unsliven Bridge.^[2] A bridge was mentioned at this location in a charter which pre-dates 1290. The bridge that now stands there was erected around 1730, with a main arch and a smaller arch in the north abutment. It formed part of the route between Bradfield and Wakefield, on which traffic increased significantly during the industrial revolution. It was widened twice in the 18th century, and by 1796 was twice as wide as it had been. The northern approach was realigned in 1805, when the bridge became part of the Langsett, Wadsley, and Sheffield Turnpike. A toll bar was erected near the bridge, but was removed in 1838 when the Turnpike was repealed by Act of Parliament. The road to the north of the bridge was realigned as part of the work to build the reservoir dam. It has only been used by local traffic since the Manchester Road was moved further to the north.^[10]

El siguiente puente río abajo lleva la carretera B6088 sobre el río. Más abajo, el curso solía serpentear por su llanura aluvial, pero luego se había rectificado al pasar por la planta de gas de Stocksbridge y la siderúrgica, donde alimentaba un pequeño embalse. ^{[ 11 ]} Para 1931, la siderúrgica se había extendido mucho más arriba del valle, ocupando el emplazamiento de la planta de gas, y el río había sido desviado a un nuevo cauce cerca de la carretera B6088. En algunas partes, se había entubado, ^{[ 12 ]} y a medida que la siderúrgica se ha expandido, se ha desviado más agua a través de alcantarillas. Las alcantarillas son largas y grandes, con algunos tramos cortos al aire libre, y son conocidas como 36DD por la comunidad de exploración urbana, probablemente porque tanto Samuel Fox, el creador de la siderúrgica, como la modelo Samantha Fox eran conocidos como Sam Fox. ^{[ 13 ]} También hay un pequeño tramo de alcantarilla debajo del centro comercial Fox Valley. Tras salir de nuevo a campo abierto, el río es cruzado por el ferrocarril de Stocksbridge , que va desde la estación de tren de Deepcar hasta la acería. Originalmente era una filial de Samuel Fox and Company, pero desde 1992 es propiedad de la acería. Se inauguró el 14 de abril de 1877 y los servicios de pasajeros, utilizados principalmente por los trabajadores de la acería y los alumnos de la escuela Penistone Grammar School, funcionaron hasta 1931. ^{[ 14 ]} El último puente lleva la A6102 hasta Deepcar , tras lo cual el río desemboca en la margen izquierda del río Don. ^{[ 2 ]}

La Agencia de Medio Ambiente mide la calidad del agua de los sistemas fluviales en Inglaterra. A cada uno se le asigna un estado ecológico general, que puede ser uno de cinco niveles: alto, bueno, moderado, malo y muy malo. Existen varios componentes que se utilizan para determinarlo, incluido el estado biológico, que analiza la cantidad y variedad de invertebrados , angiospermas y peces, y el estado químico, que compara las concentraciones de diversos productos químicos con las concentraciones seguras conocidas. El estado químico se clasifica como bueno o malo. ^{[ 15 ]}

La calidad del agua del sistema del río Little Don, que incluye el arroyo Hagg, era la siguiente en 2019.

The river system has not been classed as good quality because of sewage discharges and physical modification of the channel, which restricts the movement of fish. Like many rivers in the UK, the chemical status changed from good to fail in 2019, due to the presence of polybrominated diphenyl ethers (PBDE), perfluorooctane sulphonate (PFOS) and mercury compounds, none of which had previously been included in the assessment.

As well as barriers to the movement of fish, the river has also been affected by pollution from minewater and by the presence of the invasive species, the New Zealand mud snail. Pollution from minewater has been significantly reduced following the construction of a treatment plant by the Coal Authority. This is located between Langsett and Underbank reservoirs, and the minewater is pumped through it. There is a small amount of minewater which does not get processed by the plant, and a solution for this is being trialled by the Environment Agency, Yorkshire Water, and Highways England. In 2017, Yorkshire Water were assessing the amount of water discharged from the reservoirs into the river, with a view to altering them to more natural levels. Consideration has also been give to removing weirs, or providing fish passes where this is not reasonable. The provision of fish passes around the reservoir dams is not considered to be cost-effective, but installing one on a weir used for industrial water supply on the lower reaches of the river would increase the length of the Little Don accessible to fish from the Don twofold.^[17] Another fish pass, just above Langsett Reservoir, enables trout and other fish which were impounded within the reservoir to travel some 3.1 miles (5 km) further upstream.^[18] It allows them to negotiate the weir, which was installed to trap gravel before the Little Don entered the reservoir. The fish pass is of the Larinier type, and construction was completed on 19 April 2018.^[19]

Prior to the pass being constructed, Yorkshire Water funded a research project,^[20] which involved implanting passive integrated transponder tags into fish, and then using fixed telemetry equipment to detect the movement of fish both upstream and downstream across the weirs.^[21] Fish from the reservoir were tagged, as were fish from the upper Little Don and Thickwoods Brook. Migration in both tributaries was thought to be impeded, as both have a weir just upstream from the reservoir.^[22] In order to provide control data, similar monitoring was carried out at Grimwith Reservoir in North Yorkshire where there are two tributaries with no weirs. The study showed that there was no detectable movement from the reservoir into the tributaries, and less than expected in the downstream direction. This research informed the decision to construct the fish pass on the Little Don.^[23]