[3] From this point the river flows south to collect the Allerhope Burn at the edge of the forest, continuing through a steep sided valley before reaching Clennell Hall.

The fourteen year record shows that the catchment of 28 square kilometres (11 sq mi) to the gauging station yielded an average flow of 0.57 cubic metres per second (20 cu ft/s).

[1][4] The catchment upstream of the station has an average annual rainfall of 1,003 millimetres (39.5 in) and a maximum altitude of 615 metres (2,018 ft) at Cushat Law.

[5] The River Alwin has been classed as having good ecological quality under the Water Framework Directive.

This is one of the upper bands in the five part framework scale, which ranges from high, good, and moderate, through to poor and finally bad.