Controls on spatial variability in mean concentrations and export
patterns of river chemistry across the Australian continent
Abstract
The state and dynamics of river chemistry are influenced by both
anthropogenic and natural catchment characteristics. However,
understanding key controls on catchment mean concentrations and export
patterns comprehensively across a wide range of climate zones is still
lacking, as most of this research is focused on temperate regions. In
this study, we investigate the catchment controls on mean concentrations
and export patterns (concentration–discharge relationship,
C–Q slope) of river chemistry, using a long-term data set of up
to 507 sites spanning five climate zones (i.e., arid,
Mediterranean, temperate, subtropical, tropical) across the Australian
continent. We use Bayesian model averaging (BMA) and hierarchical
modelling (BHM) approaches to predict the mean concentrations and export
patterns and compare the relative importance of 26 catchment
characteristics (e.g., topography, climate, land use, land cover,
soil properties and hydrology). Our results demonstrate that mean
concentrations result from the interaction of catchment intrinsic and
anthropogenic factors (i.e., land use, topography and soil),
while export patterns are more influenced by catchment intrinsic
characteristics only (i.e., topography). We also found that
incorporating the effects of climate zones in a BHM framework improved
the predictability of both mean concentrations and C–Q slopes,
suggesting the importance of climatic controls on hydrological and
biogeochemical processes. Our study provides insights into the
contrasting effects of catchment controls across different climate
zones. Investigating those controls can inform sustainable water quality
management strategies that consider the potential changes in river
chemistry state and export behaviour.