Area: 96.4 hectares, 238.2 acres.

Most of the site is leased to the Royal Society for the Protection of Birds and managed as a nature reserve. Site area increased.

Reasons for Notification:

The former estuary of the River Wey, this site comprises a variety of wetland habitats of great importance for birds as a breeding, wintering and passage site. The lake and reed beds have formed since the exclusion of tidal water in the 1920s, though areas of relict saltmarsh remain. Scrub is an important additional habitat and wet grassland on alluvium over Oxford Clay is also present.

Extensive beds of reed Phragmites australis have developed both as young and vigorous pure stands and, on slightly higher land, in a mixture with other marsh species including reed canary grassPhalaris arundinaceapond sedgeCarex riparia and rushes Juncus spp. Patches of saltmarsh – probably originally islands in the estuary – are an interesting feature and present greater botanical diversity. There is a coarse turf dominated by creeping bentAgrostis stolonifera and red fescueFestuca rubra, in which the rushes Juncus maritimus and J. gerardii are frequent. Sea club rushScirpus maritimussea asterAster tripolium and sea milkwortGlaux maritima are also typical of this saltmarsh element. 

The northern and western fringes of the site have most scrub, with blackthorn Prunus spinosahawthorn Crataegus monogyna and sallow Salix caprea being the principal species. The river edge and flood meadows support various wetland–marsh plants. 

More than 50 bird species breed at this site, including a very large population of reed warblerAcrocephalus scirpaceus and rare species such as Cetti’s warbler Cettia cettibearded titPanurus biarmicus and nightingale Luscinia megarhyncos.

The roadbeds support important pre-migration roosts of sand martinRiparia ripariahouse martinDelichon urbicaswallow Hirundo rusticaand yellow wagtailMotacilla flava. There is also a very large passage of sedge warblerAcrocephalus schoenobaenus in early autumn. The site is  important for wintering wildfowl with the regular flock of shoveler Anas clypeata of particular note. 

Radipole Lake is also rich in invertebrates. Butterflies and dragonflies are well represented, and more than 450 species of moths have been recorded. The spider Argiope bruenichii is locally frequent.