Site Code
Country: United Kingdom
Central coordinates: 52.48333333o [52o 28' 59" North], 0.21666667o [0o 13' 0" East]
Administrative region: East of England (Cambridgeshire)
Area: 2479 ha
Altitude: 0 - 9
Site Description
The Ouse Washes is a very large flood control structure designed to contain flood waters coming down the Great Ouse river. It has a complex structure being a very extensive washland lying between two rivers at different levels. The washlands themselves are divided into hundreds of fields by a complex ditch system which is fed from the main river. There is also a counter washland which runs alongside the main system and which has it’s own water sources, including waters pumped in from the adjacent Block Fen, an intensively cultivated arable area overlying an extensive deposit of river terrace gravels.
Botanical Significance
*(Some species at the bottom)
The IPA supports an extensive array of aquatic and marginal plants associated with the extensive ditch systems and localised clean water sources. Most notable are the critically endangered stoneworts Tolypella prolifera and T. intricata and the water-plantain Alisma gramineum, but there are also scattered stands of BAP plants Hydrocharis morsus-ranae and Oenanthe fistulosa aswell as a large population of Sium latifolium.
Tolypella prolifera, rare, <50 individuals, Decreasing, 10% national population
Chara aspera
Tolypella intricata, rare, <50 individuals, Fluctuating, 8% national population
Chara hispida
Alisma gramineum, rare, Fluctuating
Chara virgata
Sium latifolium, frequent, c. 550 individuals, stable
Chara vulgaris
Myosurus minimus, frequent, stable
Nitella flexilis agg.
Myriophyllum verticillatum, rare
Tolypella glomerata, scarce
Oenanthe fistulosa, rare, <50 individuals
Hydrocharis morsus-ranae, rare, <50, increasing
The botanical interest of the site is under threat from the influence of hypereutrophic waters entering the ditch systems either from the main river (Hundred foot river) or from agricultural land drains away from the buffering influence of the Block Fen gravels. This both affects plants directly, by making the waters they rely upon unsuitable, and indirectly, by favouring more competitive species at the expense of those which are less competitive.
Management guidance notes
This IPA contains all of that washland feature known as the Ouse Washes plus the Counter Washes on the north-east side, an area known as Block Fen outside the washes but to which it is hydrologically linked and an area of extensive pasture to the south of Mepal to which it is ecologically allied.
Notes
Most of the IPA is under SSSI designation and subject to management plans (most of which are overseen by conservation bodies). However, those areas outside the SSSi are not so subject and indeed are subject to commercial exploitation in the form of gravel abstraction and commercial farming