| dc.description.abstract | The aim of this research is to gain more understanding on the parameters that affect hyporheic
exchange. Hyporheic exchange is a diverse process, in which many different parameters
affect the hyporheic flow paths and residence times. Literature research has showed that
hyporheic exchange is in most cases mainly dependant on the channel morphology, the
sediment characteristics of hyporheic zone and the flow velocity of the stream. Many other
factors also affect hyporheic exchange, such as lateral groundwater inflows and natural
obstructions. The diversity of all of these factors makes it hard to predict hyporheic exchange
through models. The advective pumping model has shown that it is able to predict exchange
due to bedforms well. This contributed to different studies, which allowed the prediction of
vertical hyporheic exchange fluxes. But lateral hyporheic exchange fluxes still can not be
predicted.
Flume experiments were conducted at the Quesnel River Research Centre (QRRC) in Likely,
BC, Canada, to provide more insight on the pattern of hyporheic exchange. EC-meters were
placed inside a flat gravel bed with a d50 of 25.28 mm for the top layer, and 22.90 mm for the
bottom layer. Experiments were performed with different flow velocities and water levels.
These experiments showed the irregularities in hyporheic exchange in a heterogeneous gravel
bed and provided some insight in the pattern of hyporheic exchange. To further investigate
some of the unknown variables, an advection-diffusion model was made. By means of this
model, the effects of variations in flow velocity and water level were studied.
The following conclusions were made:
· An increase in flow velocity results in smaller residence times, and an increase in
water level results in larger residence times.
· Water level has a relatively large impact on the reach of the hyporheic exchange into a
flat gravel bed. | |
