ERDC/TN APCRP-EA-07, "Modeling the Impacts of Suspended Sediment Concentration and Current Velocity on Submersed Vegetation in an Illinois River Pool, USA

PURPOSE: This technical note uses a modeling approach to examine the impacts of suspended sediment concentrations and current velocity on the persistence of submersed macrophytes in a shallow aquatic system. Studies were conducted on Peoria Lake, Illinois, spanning historical times when a meadow-forming species (Vallisneria americana) successively thrived and disappeared, and current times when the return of submersed canopy-forming (Potamogeton pectinatus) and meadow-forming species is anticipated. Canopy-forming plants concentrate their shoot biomass at the water surface, and meadow-formers just above the hydrosoil. In turbid conditions canopy-forming plants are expected to colonize earlier and persist longer than meadow-forming plants. Hydrodynamic, sediment transport, and aquatic plant viability models have been used to evaluate the key environmental conditions in which submersed aquatic vegetation would persist. Simulation results of the various models formed the basis for mapping historical, current, and potential (future) habitat suitability for submersed vegetation under various model scenarios. Several model results illustrated situations in which plant persistence was better at deeper sites than at shallow sites. The latter is contrary to common opinion where biomass production of submersed plants is thought to decrease with increasing water depth and increase with increasing light availability. Thus, simulations generated new insights in habitat quality for submersed vegetation. Information obtained from this study may be used to modify river management practices, and to implement operational scenarios aimed at maintaining/optimizing aquatic vegetation habitat.