Wetlands have widely recognized functions of water quality improvement. For example, floodplain wetlands can trap sediment and phosphorus in streams. Recent studies show that many wetlands altered by humans were drained to support agricultural use. Indirect impacts from pollutants, urban runoff, and non-ntaive species invasion continue to degrade wetlands. While the value of wetland restoration to improve streamwater quality are recognized, our understanding and estimate of potential benefits of floodplain wetlands restoration are still limited. We are interested in studying the effects of vegetation characteristics (density, distribution, submerged and emergent vegetation) on surface water and sediment processes. We are also developing a coupled wetland hydrodynamic and sediment model that can simulate floodplain inundation and sediment transport. Detailed flow field and sediments concentrations in wetlands are used to calibrate the developing model. The wetland model would allow us to evaluate the benefit of floodplain wetlands restoration. From the other aspect, accurate and efficient mapping of vegetation and subbottom conditions in shallow waters can provide a valuable monitoring tool for reclaiming lakes, rivers, streams, and wetlands. To better understand and restore aquatic habitats, persistent mapping and monitoring is necessary to record changes and mark possible improvement. Traditional methods of aquatic vegetation mapping rely heavily on taking vegetation samples and visually determining the extent of submerged and emergent vegetation. Manual sampling of submerged plant species can be destructive to the habitat, time consuming and limited by the clarity of the water and the number of samples necessary to adequately evaluate the condition of a large area. We are currently developing a combined mapping method using ground penetrating radar (GPR), side scanning sonar (SSS), and subbottom profiler (SBP) to quickly and noninvasively determine the presence of vegetation in target areas (e.g. wetland restoration project at Cherokee Marsh).
Two alternative states exist in shallow lakes: one with clear water, characterized with abundant submerged macrophytes, and the other with turbid eutrophic water, dominated by phytoplankton. Aquatic macrophytes are usually acted to substantially stabilize sediments bed and increase bed consolidation, yielding the reduction of suspended sediments in the water column to have better water clarity. Once sediment resuspension decreases and water quality improves, higher light availability can promote macrophytes growth. On the other hand, aquatic macrophytes may change aquatic environment and reduce sediment resuspension through their developments. Nevetheless it is unclear if two alternative states for an intermediate-depth lake (2.5 m ~ 5 m) still hold. If macrophytes can grow in the deeper regions of an intermediate-depth lake, sediment resuspension would reduce and the eutrophic state would change back to a clear water state. Our research questsions are: What is the role of turbulence on sediment resuspension in vegetated/unvegetated and carp/without-carp areas areas? What are the differences of wave-current and turbulence in vegetated and unvegetated areas, and how are their interactions to sediment resuspension? Better answer these research questions would be critical for the ongoing Lake Wingra restoration project.
Sponsor : NSF-North Temperate Lakes Long-Term
Ecological
Research
City
of Madison,
WI
Dane
County Land and Water Resources
Department
Hilldale
Undergraduate/Faculty Research Fellowships
Wisconsin Department of Natural
Resources
Student Investigators:
Khurran Khan (PhD), John Reimer (PhD), Kevin Lin (PhD)
Hoi-Lai Tseung (MS), Nathan Wells (MS)
Abby Wedig (Undegraduate)
Graduated: Henry Yuan (Ph.D.)
Openings
Collabarators:
Dr. Richard "Dick" Lathrop at Center of Limnology and WDNR, UW-Madison
Mr. Russ Hefty, Conservation Resource Supervisor, City of Madison
Professor Anita Thopmson at Biological Systems Engineering, UW-Madison
- Yuan, H.L., Lathrop, R.C., Carpenter, S.R., and Wu, C.H., Wind-driven circulation in a small shallow lake: Roles of weak stratification and littoral-zone vegetation, to be submitted, 2012.
- Yuan, H.L. and Wu, C.H.,Numerical investigation of
vegetation effects on flow motions using a non-hydrostatic model with a
generic two-equation turbulence closure, to be submitted, 2012.
- Wu, C.H., Young, C.C., and Yuan, H.L., Non-hydrostatic modeling of vegetation effects on wave and flow motions, 10th Estuarine and Coastal Modeling, 304-321, 2008.
Submerge vegetation
Floating
vegetation
Emergent
vegetation
Two
alternative states of shallow lakes
