Spatial and temporal variability of the stream water chemistry of an alpine/sub-alpine catchment in the Coast Mountains of British Columbia

The focus of this study is the hydrochemical variability of runoff events in two nested alpine/sub-alpine basins. More specifically, the aim is to link hydrograph interpretations to results of hydrochemistry during rain storms in order to understand better short term hydrochemical fluxes and variability in solute sources. Hydrograph separation was undertaken by using four hydrological tracers; electrical conductivity, concentration of silica, and the stable environmental isotopes oxygen-18 and deuterium. The different methods predicted consistent high pre-storm water contribution for the lower station at peak flow (60%-90%) but less consistent results were found at the upper basin outlet (25%-90%). The chemical characteristics of the stream water have been analyzed using three different approaches, namely; statistical, mass balance, and thermodynamic. Linear correlation was used to investigate the statistical association between discharge and the individual chemical species. The mass balance approach was used to correlate stoichiometry of the bedrock mineralogy to dissolved constituents in the stream water. Finally, a thermodynamic technique was used to evaluate to what extent the stream water could be represented as an equilibrium system and how this changed over the course of the storm. The results from these methods showed that the stream water variability was caused almost entirely by dilution from rain water input.Arts, Faculty ofGeography, Department ofGraduat