

@mastersthesis {7228,
	title = {Surface-groundwater {Mixing} in {Rivers}},
	year = {2013},
	note = {3563687},
	school = {Northwestern University},
	type = {phdPh.{D}.},
	address = {Ann Arbor},
	abstract = {In river networks, exchange between the main channel and the subsurface is essential to biogeochemical processes. Residence times in the heterogeneous sediment are much longer than travel times in the main channel, introducing substantial delays in the downstream propagation of solutes. Streambed topography is fractal, inducing multi scale head gradients that drive fluxes in and out of the bed. Together, these processes contribute to anomalous downstream transport along river networks. This thesis details three key contributions that each elucidate an aspect of hyporheic exchange and anomalous transport in rivers. The first contribution presents a versatile stochastic model of reactive transport in river systems that allows for broad travel time distributions. The model incorporates the effects of river structure and local chemical and biological processes on whole-stream biogeochemistry. The water column flows relatively fast and is typically well aerated, but the benthic region flows slower and is colonised by autotrophic biofilms. The bed sediment harbour rich heterotrophic communities living in a heterogeneous but much slower flow field, where residence time distributions are broad. Because these very distinct reactive regions aggregate at the reach scale to produce compounded transport signatures, it is critical to account for them explicitly. The second contribution presents a physically based model that simulates solute transport in rivers and describe the scaling expected when water flows over alluvium. I use a particle tracking approach to solve transport equations in two dimensions and show that the presence of an underlying porous bed leads to ubiquitous anomalous downstream motion. Considering network scaling relationships, I am able to predict the transport scaling trends across river networks, from steep first order mountain streams to large rivers. Finally, I present experimental evidence that the fractal topography of a sand bed influences the scaling of solute transport. Riverbed topography is known to induce hyporheic exchange and influence transport dynamics along river networks. However, detailed datasets that include both topography and solute transport are lacking. In this last chapter, we provide such data and show that the fractal properties of the bed topography lead to the late time anomalous scaling of the solute data.},
	keywords = {0388:Hydrologic sciences, 0425:Biogeochemistry, 0484:Geomorphology, 0775:Environmental engineering, Applied sciences, Biogeochemistry, Earth sciences, Environmental engineering, Geomorphology, Groundwater, Hydrologic sciences, River networks, Riverbed topography, Solute transport, surface water},
	url = {http://search.proquest.com/docview/1400007243?accountid=14270},
	author = {Aubeneau, Antoine F.}
}
