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 about solute sources, pathways, and transformations in the catchment. We investigate long-term water quality data of 11 Swiss catchments with the objective to discern the influence of major catchment characteristics and anthropic activities on delivery of solutes in stream water. Magnitude, trends, and seasonality of water quality samplings of different solutes are evaluated and compared across catchments. Subsequently, the empirical dependence between concentration and discharge is used to classify the solute behaviors. While the anthropogenic impacts are clearly detectable in the concentration of certain solutes (i.e., Na+, Cl−, NO3, DRP), the influence of single catchment characteristics such as geology (e.g., on Ca2+ and H4SiO4), topography (e.g., on DOC, TOC, and TP), and size (e.g., on DOC and TOC) is only sometimes visible, which is also because of the limited sample size and the spatial heterogeneity within catchments. Solute variability in time is generally smaller than discharge variability and the most significant trends in time are due to temporal variations of anthropogenic rather than natural forcing. The majority of solutes show dilution with increasing discharge, especially geogenic species, while sediment-bonded solutes (e.g., total phosphorous and organic carbon species) show higher concentrations with increasing discharge. Both natural and anthropogenic factors affect the biogeochemical response of streams, and, while the majority of solutes show identifiable behaviors in individual catchments, only a minority of behaviors can be generalized across the 11 catchments that exhibit different natural, climatic, and anthropogenic features.

Spatial variability in specific discharge and streamwater chemistry during low flows: Results from snapshot sampling campaigns in eleven Swiss catchments

“…Previous studies have related landscape characteristics, such as catchment size, mean slope, drainage density (e.g., Asano et al, ; Likens & Buso, ; Wolock, Fan, & Lawrence, ), geology, or land use (e.g., Bluth & Kump, ; Botter, Burlando, & Fatichi, ) to streamwater EC and ion concentrations during low‐flow conditions. However, we could not find strong relationships between landscape characteristics and EC that were valid across multiple catchments within a region (Figure ).…”

Technical note: A two-sided affine power scaling relationship to represent the concentration–discharge relationship

“…In comparison with the logarithmic transformation, the additional degree of freedom offered by n allows for a range of transformations, from the untransformed variable (n = 1) to the logarithmic transformation (n → ∞). This "progressive" property was underlined long ago by Box and Cox (1964): when n takes high values, Eq. 3converges toward the one-sided power scaling relationship (power law) (Eq.…”

“…As a progressive alternative to the one-sided power scaling relationship (power law), we propose to use a twosided affine power scaling (2S-APS) relationship as shown in Eq. 3 (Box and Cox, 1964;Howarth and Earle, 1979).…”

“…From a numerical point of view, the relationship presented in Eq. 3is equivalent to first transforming the dependent (C) and independent (Q) variables using a so-called Box-Cox transformation (Box and Cox, 1964), and then adjusting a linear model. In comparison with the logarithmic transformation, the additional degree of freedom offered by n allows for a range of transformations, from the untransformed variable (n = 1) to the logarithmic transformation (n → ∞).…”

Technical Note: A two-sided affine power scaling relationship to represent the concentration–discharge relationship

“…It would be impossible to list here all the articles that have addressed this subject, and we refer our readers to the most recent reviews (e.g., Bieroza et al, 2018;Botter et al, 2019;Moatar et al, 2017) for an updated view of the ongoing research on C-Q relationships.…”