| The hyporheic zone is the porous region surrounding the streambed where surface water (SW) and groundwater (GW) interact. The vertical heat advection and conduction (VHAC) model is used to process streambed temperature data and predict SW downwelling and GW upwelling rates and previous work has primarily evaluated model performance in sand-dominated substrates. In high permeability bed forms, longitudinal flow paths connect downwelling and upwelling zones and potentially violate the VHAC model assumption of vertical-only flux. We attempted to determine whether the VHAC model can accurately predict the vertical component of flux observed from independent tests in a highly permeable pool-riffle system. This research used laboratory flume and computational fluid dynamics (CFD) models to test the predictive accuracy of the VHAC model in a gravel bed pool-riffle system, where hydraulic theory predicts SW downwelling along the pool glide, longitudinal flow beneath the riffle, and GW upwelling along the pool run. Research results modify previous VHAC model application guidelines and indicate the model can accurately predict flux for seepage rates in the range of ±5.0E-02 m/s.;Keywords: hyporheic exchange, vertical heat advection and conduction model, CFD, flume. |
