Hydrology of Pesticides in a Chalk Catchment: Surface Waters

Abstract In an extensive study of pesticides in a Chalk catchment, twenty pesticides were selected for study; and this paper reports the findings of an eighteen‐month programme of river and rainwater sampling. The results of periodic samples and an intensive river monitoring programme over the duration of a flood event are described. Both rain and river water within the catchment were found to contain significant numbers of pesticides at varying concentrations. The paper describes the values and temporal variations which were discovered. Higher concentrations and greater numbers of pesticides appeared to be brought down by floods and high river flows; however, even during low flows, some pesticides were persistently found in the river.