Department of Infrastructure Engineering
The University of Melbourne
Unravelling the Mechanics of Hyporheic Exchange
Introduction
The hyporheic zone connects streams to aquifers
and their surroundings more generally. Exchange
within the hyporheic zone occurs at a range of
scales both in terms of orientation (lateral and
vertical) and spatially (ranging form reach to
catchment scales). The reach scale has been
studied in most detail, with a multitude of flume
experiments examining the mass transport
characteristics
across
the
sediment-water
interface. These studies use effective diffusivity to
parameterize exchange, yet the physical basis of
the exchange process is only in part diffusive.
Environmental conditions such as bedforms are known to
increase rates of hyporheic exchange (Packman et al., 2004), but
also affect roughness, to which hyporheic exchange also scales
(Grant et al, in press).
Figure 1: parameterization of bedforms
(1)
(2)
Research Problem
There are 3 approaches in describing
hyporheic exchange:
Hypothesis: Hyporheic exchange is driven by three different
mechanisms, which can be represented to each form their
constitutive parts of effective diffusion.
Research Objectives
This research project will address the following questions:
•What are the dominant processes of hyporheic exchange?
•Under which conditions do these mechanisms dominate?
•How are these processes temporally and spatially distributed?
The project will be experimental, combining a range of techniques to
simultaneously measure processes in a fume.
References
1.
Effective diffusivity (Deff) modelled with Fick’s
First Law (Eq. 1)
2.
Exchange driven by fluctuating dynamic head
(DDH) according to the “pumping” model (eq.
2) (Elliott and Brooks, 1997)
3.
Coherent turbulent penetration (DTP) (Fig.2)
If each of these mechanism are represented by
a constitutive effective diffusion coefficient
then the different mechanisms can be
represented in eq. 3.
Elliott, A. H., and N. H. Brooks (1997), Transfer of nonsorbing solutes to a streambed with bed forms: Theory, Water
Resour. Res., 33(1), 123-136.
Grant, S. B., and I. Marusic (2011), Crossing Turbulent Boundaries: Interfacial Flux in Environmental Flows, Environmental
Science & Technology, 45(17), 7107–7113.
Grant, S. B., M. J. Stewardson, and I. Marusic (in press), Effective difusivity and mass flux across the sediment-water
interface in streams, Water Resources Research, xx(xx).
Packman, A. I., M. Salehin, and M. Zaramella (2004), Hyporheic Exchange with Gravel Beds: Basic Hydrodynamic
Interactions and Bedform-Induced Advective Flows, Journal of Hydraulic Engineering, 130(7), 647-656.
Rempfer, D. (2003), Low-Dimentional Modeling and Numerical Simulation of Trnansition in Simple Shear Flows, Annual
Review of Fluid Mechanics, 35(1), 229-265.
For more information:
Figure 2: Coherent turbulent structures [a. Grant et al., 2011,
b. Rempfer(2003) c. www.hrenya.colorado.edu]
Discipline: Environmental Engineering
Alexander Heinrich McCluskey
PhD Candidate
(3)
amccluskey@unimelb.edu.au
D417 – Environmental Hydrology and Water Resources
Webpage:
http://www.ie.unimelb.edu.au/people/rhd.html#McCluskey
Supervisors:
Dr. Michael Stewardson & Prof. Stanley Grant