The effects of the 1976 drought and autumn rainfall on stream solute levels

Operation of a previously existing sampling network during the 1976 drought has provided an opportunity to assess the effects of the drought and subsequent autumn rainfall on the water quality characteristics of a small catchment (9·3 km3) in East Devon. The availability of records for past years has enabled these data to be compared with longer-term response characteristics. Analysis indicates that the 1976 drought produced a unique solute response, with levels rising markedly during the autumn flush which resulted from the heavy rainfall following the drought period. Concentrations of several ions increased 3–4 times and NO3-N levels exhibited even greater increases of up to 50-fold. Some of the factors responsible for these increases and some implications are considered.