The River Wallington curves and gently meanders west then south in south-east Hampshire. Rising at sources to north and south of Waterlooville these flow west around Portsdown Hill into a dammed section as the lake in the grounds of Southwick House to unite, then through the village of Southwick then, in that parish, to receive the Beck of similar flow from the north. The river turns south and runs past fields and past the large town Fareham, before entering Portsmouth Harbour, as its main natural watercourse inflow, at Wallington.