Hydrological Considerations

Abstract

Hydrology is important in acidification and liming studies since it is evident from many investigations that changes (both short and long term) in surface water quality are related to stream flow or lake turnover. This reflects the pathways by which rain reaches surface waters, contributions of groundwater and intercepted fog and mist, and the dynamics and kinds of chemical and biological reactions that occur during this transfer. Since groundwater usually has a long residence time within underlying mineral materials in a catchment, it has higher conductivity and alkalinity. Thus, when atmospheric input is low (drought) the hydrological base flow reflects groundwater composition, rather than rain composition. Conversely, following heavy rains or snow melt, the base flow contributes little to the total, and acidity deposited from the atmosphere, or mobilised during heavy runoff from upper soil layers, will predominate.