Variations in the natural chemical concentration of river water during flood flows, and the lag effect: Some further comments

Abstract

Following upon the recent paper by Glover and Johnson (1974), the authors briefly present results from several Devon catchments which demonstrate the complexity of variations in the chemical concentration of river water during flood flows. Certain solute species increase rather than decrease in concentration during storm events and the “chemographs” of those species which exhibit dilution are often complicated by a “flushing effect”. Some solutes may exhibit variable response, evidencing increased and decreased concentrations during different events. Even in small catchments, the “chemograph” response can lag behind the stream-flow response and examples of where the trough precedes the stream-flow peak have also been documented. Values of “chemograph” lag between zero and 14.5 h have been found at a gauging station on a Devon river and the variation can be tentatively explained in terms of catchment moisture status. Any attempt to account for the nature and timing of “chemograph” response must consider processes operating over the entire catchment in addition to those in the channel.