The site includes the flood-plain of the Warta river, where it meets the Odra river, and the lower course of the Postomia river. There are unregulated stretches of river, oxbow lakes, old drainage channels, small lakes, periodically flooded meadows, and pastures. The area floods almost every year, with annual fluctuations in water-level of up to 3.5 m. Highest levels are in March and April. In some years the whole area is underwater all year, in others for only a few months or not at all. Accordingly, the vegetation varies in different years. During heavy floods water-fringe vegetation predominates, mainly reed Phragmites and especially reed-grass Glyceria and canary-grass Phalaris, occupying a few hundred hectares. Large areas that have recently emerged from water are occupied by ruderal herbs Polygonum/Bidens. When the flood is limited or does not occur, such vegetation dies and is replaced by dry-ground vegetation and willow Salix bushes.
A very important area for moulting, staging, wintering and roosting waterbirds, mainly wildfowl. Up to 33,000 duck (Anatidae) stage here during spring migration, with up to 78,000 in autumn. Over 240 species have been recorded, including 160 breeding species. Data in table are for 1991-1996 unless otherwise stated
Pressure/threats to key biodiversity
Threats include a lack of water in some years (due to management of water-levels primarily for human uses), overgrazing by domestic geese and cattle, strong expansion of willow Salix scrub (partly due to abandonment of agriculture), disturbance of birds, river dredging, and recreation, tourism and hunting.
National High International High4,244 ha of IBA covered by Nature Reserve (S³oñsk, 4,244 ha). 4,244 ha of IBA covered by Landscape Park (Ujcie Warty, 28,000 ha). 4,244 ha of IBA covered by Ramsar Site (S³oñsk, 4,244 ha).