Crimple Beck
[2][3] Beyond Spofforth its course continues to Blackstones where it is measured, joining the River Nidd midway between Little Ribston and Walshford.[3] The flow of the beck is measured by two gauging stations, the first near Burn Bridge in its upper reaches has operated since 1972, the second near to the confluence with the Nidd, at Blackstones since 1991.[6][7] The upper gauge at Burn Bridge, with a catchment of 8.1 square kilometres (3.1 sq mi) yields an average flow of 0.11 cubic metres per second (3.9 cu ft/s).[8] The much larger catchment area of 76.8 square kilometres (29.7 sq mi) to the lower Blackstones gauge, recorded a correspondingly higher average flow of 1.02 cubic metres per second (36 cu ft/s).[10] The catchment upstream of the station has an average annual rainfall of 752 millimetres (29.6 in) and a maximum altitude of 243 metres (797 ft) on Stainburn Moor near the source of the beck.