Hydrology and Earth System Sciences | 2019
Anthropogenic and catchment characteristic signatures in the water quality of Swiss rivers: a quantitative assessment
Abstract
Abstract. The hydrological and biogeochemical response of rivers carries information\nabout solute sources, pathways, and transformations in the catchment. We\ninvestigate long-term water quality data of 11 Swiss catchments with the\nobjective to discern the influence of major catchment characteristics and\nanthropic activities on delivery of solutes in stream water. Magnitude,\ntrends, and seasonality of water quality samplings of different solutes are\nevaluated and compared across catchments. Subsequently, the empirical\ndependence between concentration and discharge is used to classify the\nsolute behaviors. While the anthropogenic impacts are clearly detectable in the concentration\nof certain solutes (i.e., Na+ , Cl− , NO3 , DRP), the influence\nof single catchment characteristics such as geology (e.g., on Ca2+ and\n H4SiO4 ), topography (e.g., on DOC, TOC, and\xa0TP), and size (e.g., on\nDOC and TOC) is only sometimes visible, which is also because of the limited sample\nsize and the spatial heterogeneity within catchments. Solute variability in\ntime is generally smaller than discharge variability and the most\nsignificant trends in time are due to temporal variations of anthropogenic\nrather than natural forcing. The majority of solutes show dilution with\nincreasing discharge, especially geogenic species, while sediment-bonded\nsolutes (e.g.,\xa0total phosphorous and organic carbon species) show higher\nconcentrations with increasing discharge. Both natural and anthropogenic\nfactors affect the biogeochemical response of streams, and, while the\nmajority of solutes show identifiable behaviors in individual catchments,\nonly a minority of behaviors can be generalized across the 11\xa0catchments\nthat exhibit different natural, climatic, and anthropogenic features.