Aquatic Sciences Meeting, Albuquerque 2001

SS01 Submerged Aquatic Vegetation and the Water Column (Environmental Connections)

Date: Tuesday, February 13, 2001, Time: 11:15:00 AM

Location: Galisteo

Sturman, J, J, Environmental Science, Murdoch University, Murdoch, WA 6150, Australia, sturman@essun1.murdoch.edu.au

Oldham, C, E, Centre for Water Research, University of Western Australia, Nedlands, WA 6907, Australia, oldham@cwr.uwa.edu.au

THE EFFECT OF EMERGENT VEGETATION ON CONVECTIVE FLUSHING IN SHALLOWS WETLANDS

Many wetlands around the world are characterised by shallow water, dense vegetation in the littoral zones, no riverine inflow and minimal circulation. Recent research on the hydrodynamics of such wetlands, has identified convective circulation as being important in maintaining oxygen levels in the deeper waters and also in flushing the littoral zones. The flushing caused by convective circulation has previously been predicted for water bodies with no vegetation. We have extended that research and incorporated a term to predict the effect of emergent vegetation on the discharge velocities and therefore on the flushing. Previous work by other researchers has investigated the effect of vegetation on relatively high Reynolds number flows, however the wetlands described above typically have very low Reynolds number flows. We have therefore used a parameterisation of the drag coefficient, taken from porous media flow, in our model for convective discharge velocities. Laboratory and field experiments were then used to test the model’s capability to predict discharge velocities. Finally a comparison of flushing timescales with typical oxygen uptake timescales highlights the importance of this mechanism for shallow wetlands.

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Aquatic Sciences Meeting, Albuquerque 2001

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