9641 - Laserfiche WebLink

Home Browse Search

. . adequate to effect substantial recruitment because large numbers of razorback sucker larvae must be transported from the river into the wetlands. In contrast to single breach wetlands, entrainment rates of beads, water, and presumably fish larvae were relatively high in flow-through wetlands. Entrainment of beads and water increased with higher flows in the river; although entrainment rates (beads entrained per volume of flow entrained) were not always highest at the highest flow (this was true at Thunder Ranch in 2006, but not at Thunder Ranch in 2005 or Stewart Lake in 2006). We suspect that entrainment of drift material would continue to increase as flow levels increased over those we observed. Bead and flow entrainment rates in flow-through wetlands were similar on the ascending and descending limbs of the hydrograph. In wetlands with multiple breaches (e.g., Thunder Ranch), the upstream breach captured more beads than downstream breaches. This was especially true as flows increased and the upstream breach became more effective at entraining beads, thereby leaving fewer beads available to become entrained downstream. These data collectively suggest that higher spring peak flows may be beneficial to connect flood plain wetlands with the river and enhance entrainment of razorback sucker larvae. However, timing spring peaks to coincide with production of larvae is critical, as is the need to provide overwinter habitat for fish in wetlands. A primary recommendation is to synthesize entrainment data with other physical and biological data collected in the middle Green River, so that a cohesive strategy for flood plain management and recovery of razorback suckers can be achieved. Other direct recommendations from the results of this study include determining whether alterations to breach configuration are necessary (including single breach wetlands) to maximize entrainment and exploring the trade- . . . . . . . . Xl .