Thursday, December 03, 2009, 4:30PM - 5:30PM
Full title: "Understanding the hydrologic factors affecting the growth of the nuisance diatom Didymosphenia geminata in rivers and the potential for using managed flood releases to control future growth."
Didymosphenia geminata is a nuisance diatom species impacting many mountain streams in Colorado and the western US. In recent years there has been an apparent increase in the tendency to bloom in traditional habitats as well as spreading to new watersheds. The most significant impact being the invasion of rivers in New Zealand where it has been identified as a threat to the sustainability of stream ecosystems. D. geminata appears to be more common in regulated streams downstream of reservoirs and lakes. One of the few controlling factors on growth is the physical removal due to elevated shear stress and bed disturbance. This has resulted in the consideration of managed flood releases from reservoirs as a potential mitigation measure. The objective of this research is to investigate the role of spatial and temporal variations in shear stress and potential bed disturbance in the removal of D. geminata based primarily on a number of study sites in Boulder Creek, CO. Initial results indicate that high flow events are significant in the removal of D. geminata and that a critical threshold may exist based on the non dimensional Shield's stress which is associated with the potential for bed disturbance. The results of the study will be useful in determining the magnitude, duration and timing of flood events necessary to control the growth of D. geminata which can then be considered along the the many other competing demands for water from reservoirs in the western US.