Emergent archetype patterns of coupled hydrologic and biogeochemical responses in catchments

Abstract

Abstract Relationships between in‐stream dissolved solute concentrations ( C ) and discharge ( Q ) are useful indicators of catchment‐scale processes. We combine a synthesis of observational records with a parsimonious stochastic modeling approach to test how C ‐ Q relationships arise from spatial heterogeneity in catchment solute sources coupled with different timescales of reactions. Our model indicates that the dominant driver of emergent archetypical dilution, enrichment, and constant C ‐ Q patterns was structured heterogeneity of solute sources implemented as correlation of source concentration to travel time. Regardless of the C ‐ Q pattern, with weak correlation between solute‐source concentration and travel time, we consistently find lower variability in C than in Q , such that the predominant solute export regime is chemostatic. Consequently, the variance in exported loads is determined primarily by variance of Q . Efforts to improve stream water quality and ecological integrity in intensely managed catchments should lead away from landscape homogenization by introducing structured source heterogeneity.