Figure 1.
Images of (A) water diversion pipes located in the lower Sacramento River, California, USA and (B) green sturgeon swimming in the flume with a green sturgeon drawn (entrained) into the water diversion pipe during an experiment, recorded with an underwater camera positioned 2.1 m downstream of the pipe.
Figure 2.
Mean ± SE number of green sturgeon entrained through the unscreened diversion pipe at sweeping velocities of 0.15, 0.38 and 0.61 m/s and water diversion rates of 0.28, 0.42 and 0.57 m3/s.
Significant differences in the number of fish entrained at different flow combinations are marked with different letters (P≤0.011 for all significant pairwise comparisons).
Figure 3.
Mean ± SE number of fish that successfully passed the diversion pipe (A) or became entrained into the pipe (B) calculated in 10-min intervals at 0.15, 0.38 and 0.61 m/s sweeping velocities and a 0.42 m3/s water diversion rate.
Figure 4.
Mean ± SE number of fish that successfully passed the diversion pipe (A) or became entrained into the pipe (B) calculated in 10-min intervals at 0.15, 0.38 and 0.61 m/s sweeping velocities and a 0.57 m3/s water diversion rate.
Figure 5.
Mean ± SE number of green sturgeon that successfully passed the unscreened diversion pipe at sweeping velocities of 0.15, 0.38 and 0.61 m/s and water diversion rates of 0.28, 0.42 and 0.57 m3/s.
Significant differences in the number of successful pipe passages at different flow combinations are marked with different letters (P≤0.039 for all significant pairwise comparisons).
Figure 6.
Calculated mean ± SE entrainment risk per pipe passage at sweeping velocities of 0.15, 0.38 and 0.61 m/s and water diversion rates of 0.28, 0.42 and 0.57 m3/s.
Significant differences in the number of fish entrained among water diversion rates are marked with different letters (P≤0.006); fish entrainment did not significantly differ among sweeping velocities and there was no interaction.
Figure 7.
Laboratory-determined estimates of the percentage of juvenile green sturgeon lost to entrainment when repeatedly encountering (passing within 1.5 m of) unscreened pipes diverting 0.28 (▪), 0.42 (), or 0.57 (◊) m3/s of water at a 0.15 m/s river (sweeping) velocity, calculated from entrainment risk per pipe passage values (Fig. 4).
Table 1.
Flume discharge rates at experimental sweeping velocities and diversion rates.