Transient acid surges in an upland stream

This paper examines the hydrological and chemical processes controlling transient acid surges in a small, upland catchment in the Cairngorm Mountains of Scotland. The major episodes of increased acidity are produced by preferential elution of pollutants from snow at the onset of melt and by heavy autumn rainstorms when the catchment is saturated or frozen. Records of flow and water quality over a 3 yr period have been used to calibrate a lumped conceptual hydrochemical model. Using this model it is shown that concentration and distribution of input pollution by hydrological processes is the major control on episodic variations of stream water quality in this catchment.