Print Close
IPA Factsheet - Ouse Washes
Site code
CountryUnited Kingdom
Administrative regionEast of England (Cambridgeshire)
Central co-ordinates52o 29' N / 0o 13' E map
Altitude-3 - 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 itís 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.

 General Habitat Description The washes (about a third of the IPA) are dominated by extensively grazed, wet grassland, the remainder by arable land; however the botanical interest is associated with the ditch systems of both the washes and the adjacent land, and the gravel pots in the Block Fen area. The ditches of Block Fen carry clean waters into the Counterdrain (SAC) system and the main function of the ditches on the washes is as a system of wet fences to control stock.

Land use

Land use% CoverLevel
agriculture (animals)33Cover
nature conservation and research33Cover
water management33Cover
extraction (minerals)2Cover
agriculture (arable)65Cover

Threatened Species

Species NameIPA Assess.Species Assess.AbundanceData qualityCriteria

Botanical Richness

EUNIS level 2 code & nameIPA Assess.Habitat Assess.% of indicator speciesNo. SpeciesNational BiotopeData qualityCriteria
C1 Surface standing waters2007200700poorB

Threatened Habitats

IPA Habitat code & nameIPA Assess.Habitat Assess.AreaData qualityCriteria


DesignationProtected Area NameRelationship with IPAOverlap with IPA
Special Area of ConservationOuse Washesprotected area contained by IPA311
Site of Special Scientific InterestOuse Washesprotected area contained by IPA2403
Special Protection AreaOuse Washesprotected area contained by IPA2447
Ramsar Wetland SiteOuse Washesprotected area contained by IPA2469


TypeDescriptionYear startedYear finishes
Protected Area Management PlanSSSI Ouse Washes
Habitat Management PlanCoastal and Floodplain Grazing Marsh BAP1995
Other Management PlanWater level management plant1991
Species Action Plan (SAP)Sium latifolium (UK BAP)
Species Action Plan (SAP)Oenanthe fistulosa (UK BAP)2007
Species Action Plan (SAP)Alisma gramineum (UK BAP)
Species Action Plan (SAP)Tolypella prolifera (UKBAP)
Species Action Plan (SAP)Tolypella intricata (UKBAP)


agricultural intensification/expansion (arable)low
climate change/ sea level risemedium
water (management systems)high

 Conservation Issues Water flow and quality in the ditch systems feeding the site Water quality in the River Great Ouse Shift in flooding timing from Great Ouse to early summer resulting in excessive nutrient loading or submergence during main growth period Imperative to maintain the site as a flood storage structure

Contact Information

ContactContact Type
Tim PankhurstSite report compiler
Jon ReevesSite report compiler