|IPA Factsheet - River Wye / Afon Gwy|
Site Description The Wye, on the border of England and Wales, is a large lowland river with the fourth largest flow of any river in England and Wales. From its source to its confluence the main channel is 250kms long, drains a catchment of 4136km2 and has the fourth largest flow of any river in England and Wales. Rising at an altitude of 680m on Pumlumon Fawr in Powys, the Wye meanders down through Wales, Herefordshire and Gloucestershire, finally entering the Severn Estuary at Chepstow. The River covers approximately 2234.89 hectares. Together the River Wye (Lower Wye) and the River Wye (Upper Wye) SSSIs and several of their tributaries represent a large, linear ecosystem which acts as an important wildlife corridor, an essential migration route, and a key breeding area for many nationally and internationally important species.
Botanical Significance There is a varied water-crowfoot Ranunculus flora; stream water-crowfoot R. penicillatus ssp. pseudofluitans is abundant, with other Ranunculus species – including the uncommon river water-crowfoot R. fluitans – found locally. Other species characteristic of the lowland habitats include flowering-rush Butomus umbellatus, lesser water-parsnip Berula erecta and curled pondweed Potamogeton crispus. There is an exceptional range of aquatic flora in the catchment including river jelly-lichen Collema dichotum. The river channel is largely unmodified and includes some excellent gorges, as well as significant areas of associated woodland. In its upper and middle reaches the river channel is dominated by submerged flowering plants such as spiked water milfoil (Myriophyllum spicatum) and beds of water crowfoot (Ranunculus fluitans). Other common plants include rigid hornwort (Ceratophyllum demersum) and perfoliate pondweed (Potamogeton perfoliatus). Rare aquatic species include whorled water milfoil (Myriophyllum verticillatum). In the lower reaches of river through the Wye Gorge, the calcium and nutrient content of the water increases. Here, aquatic vegetation is mainly comprised of pondweed species such as fennel pondweed (Potamogeton pectinatus) and curled pondweed (P crispus). Aquatic macrophytes disappear below the tidal limit at Brockweir and marginal vegetation is often absent or much reduced below this point due to tidal scour. However, some species thrive along the transition zone between brackish and freshwater conditions where large areas of mud are exposed at low tide. Marginal vegetation often consists of reed canary-grass (Phalaris arundinacea) and branched bur-reed (Sparganium erectum). Other marginal plants such as amphibious water bistort (Polygonum amphibium), brooklime (Veronica beccabunga), yellow-cress (Rorripa spp.) and water forget-me-not (Myosotis scorpioides) are widespread and frequent. (The nationally scarce horse-tail (Equisetum x litorale) is found growing along the margins of the river in its upper section). Below Brockweir the upper mud banks of the river are colonised by salt-marsh species such as sea aster (Aster tripolium), saltmarsh-grass (Puccinellia spp.) and sea-milkwort (Glaux maritima). Characteristic bankside plants include stinging nettle (Urtica dioica), great willowherb (Epilobium hirsutum) and reed canary-grass (Phalaris arundinacea).
General Habitat Description Habitat types include: Tidal rivers, Estuaries, Mud flats, Sand flats, Lagoons (including saltwork basins) and Salt marshes, Salt pastures and Salt steppes. It has a geologically mixed catchment, including shales and sandstones, and there is a clear transition between the upland reaches, with characteristic bryophyte-dominated vegetation, and the lower reaches, with extensive Ranunculus beds.
Conservation Issues Diffuse pollution and siltation from agriculture in the catchment. Water quality impacts arising from changing agricultural land-use within the catchment are having direct and indirect effects on the SAC interests through effects of diffuse pollution such as nutrient run-off and increased siltation. English Nature and the Countryside Council for Wales are seeking to address such issues through improved targeting of existing and new agri-environment schemes and through improvements in compliance with agricultural Codes of Practice.