Influences on Hyporheic Exchange in a Small Coastal British Columbia Suburban Stream

Abstract

This study examined how discharge, streambed topography, and channel planform influence hyporheic exchange in a coastal suburban stream in B.C. Tracer experiments were carried out in four reaches of Hoy Creek in Coquitlam using sodium chloride, and piezometers were installed to determine the vertical hydraulic gradient (VHG). The tracer data were used in OTIS, a transient storage model, to determine the following parameters: cross-sectional area of the stream and storage zone, dispersion, and the storage zone exchange coefficient (α). For the lower reaches, there was no significant relation between α and discharge; however, there was a significant positive relation between α and discharge for the upper reaches. Dispersion and the cross-sectional area of the storage zone did not change with discharge. VHG and streambed tracer breakthrough curves/data showed predominantly upwelling conditions. Hyporheic flow occurred mainly through meander bends, step-pool systems, and riffles.