Wansbeck Riverside Park slipway

Wansbeck Barrage, built in 1975 near the coast, impounded this stretch of the river into a non-tidal lake four kilometres long and up to 200 metres wide, giving it its own navigation lock. The impoundment runs from the barrage downstream to Sheepwash Weir upstream, the boundary the Environment Agency uses when describing this reach.

The surrounding country park holds Local Nature Reserve status, gained by Castle Island in 2003 and extended to the wider 112-hectare site, which includes the ancient woodland of Blackclose Dene, in 2007. Herons, kingfishers, mallard and geese are recorded on the water, and the banks support red squirrels and roe deer. The river is also one of the country's significant strongholds for the native white-clawed crayfish, with a population the Environment Agency describes as one of the most abundant of the species in Europe.

Silt is accumulating on the lake bed behind the barrage, which the Environment Agency says is affecting both future recreational use and water quality. The water body's most recently published classification, from 2019, rates its overall ecological status as Moderate, with mercury and polybrominated diphenyl ethers (PBDEs) both failing on chemical status.