Red Screes forms part of the main watershed of the Lake District, which runs in an east-west direction across the summit and the two adjacent cols. All streams to the north eventually flow into the Solway Firth, and those to the south flow into Morecambe Bay. The boundaries of Red Screes are formed by the four streams in the adjacent valleys. To the south, Scandale Beck drains the western slopes and Stock Ghyll the eastern ones. These both join the River Rothay a few yards apart just to the west of Ambleside. To the north, Caiston Beck drains the western slopes and Kirkstone Beck the eastern ones, and these join where they reach more level ground at the end of the ridge. Thus the boundaries of Red Screes are formed symmetrically by four valleys, with the fell between them, rather than rising at the head of any one of them.