Stream-Subsurface Exchange and Hyporheic Zone Influence on Reach-scale Water Budgets within a Boreal Shield Catchment of Quebec, Canada

Mass loss of solute and gross channel water losses and gains were quantified to understand the influence of hyporheic exchange on water budgets of boreal shield catchments. Six series of tracer injections were performed on 9 reaches of a stream network within a subwatershed of Gatineau Park, Quebec from July to November, 2011. Solute loss was substantial and increased throughout the summer baseflow recession to a maximum of 88% at reach 4. High solute exchange exists for all reaches despite most exhibiting slight positive net discharge values, resulting in minimum gross channel water loss no less than 34% during low flow conditions. Strong power law relationships for most reaches (R2 >0.9) suggest discharge as the most important variable on the magnitude of mass loss. Although inter-reach variability in mass loss could implicate watershed-scale controls on exchange potential, there was no correlation between LiDAR DEM-derived watershed morphometrics and mass loss.