Editing Ouse Washes (section)

==Water control==
{{Ouse washes map}}
The Ouse Washes are part of the system for controlling the flow of the [[River Great Ouse|Great Ouse]] when water levels in the river are high. In normal conditions, the waters of the Great Ouse run through the New Bedford River (or Hundred Foot Drain) to join the tidal stretch of the river at Welmore Lake Sluice, where another automatic system controls outflow. High water levels open the automatic [[sluice]] at Earith, thereby releasing water to the Old Bedford River, which eventually overflows onto the [[washland]] between the Bedford rivers, with the Welmore automatic sluice controlling outflow. When levels drop, the washes drain back into the Old Bedford River.<ref name=AEDA/> 

The [[Environment Agency]] sets the trigger level for the sluices, allowing higher levels in the Great Ouse in summer than in winter.The enclosed area of washland runs from Earith northeast to Downham Market where it links via the New Bedford River to the tidal Great Ouse and hence to the sea. At capacity, the site can accommodate {{convert|90000000|m3}}, although it only completely filled in 1947.<ref name= BB115>{{cite journal | last1 = Taylor| first1 = John| title = Great bird reserves: The Ouse Washes| journal = British Birds| volume = 115 | issue =8 | pages = 421–480 | year =2022 }}</ref> 

The washland area between the rivers is {{convert|32|km}} long and about {{convert|1|km}} wide and acts as a [[floodplain]] during the winter and, increasingly, also in the summer. The area between the outer barrier banks of the two artificial rivers covers about {{convert|1900|ha}}. As the [[peat]] underlying the Fens has dried out through drainage, it has shrunk and lowered the level of the washlands, making flooding more frequent.<ref name=AEDA/> The Washes and its banks have a total area of {{convert|2400|ha}}, and newly created wet grasslands adjacent to the washes increase the total area to {{convert|2750|ha}}. About 10% of the area is open water, but most of the habitat is grassland with [[Phalaris arundinacea|reed canary-grass]] in the wettest locations, transitioning through [[Glyceria maxima|reed sweet-grass]] to the [[Agrostis stolonifera|creeping bent]] that dominates in the drier areas.<ref name= BB115/>