Responses of macroinvertebrate drift, benthic assemblages, and trout foraging to hydropeaking

Abstract

We utilized both hydropeaking and experimental flows to quantify responses of macroinvertebrate drift, benthic assemblages, and fish consumption to double-peak release patterns. Our results suggest that changes in discharge may have a greater impact on macroinvertebrate drift than absolute flow levels, such that mean daily drift biomass was significantly higher during double-peaking; however, drift increases were sustained for only 30–60 days despite ongoing hydropeaking. Drift increases were proportional to peak magnitude, with drift biomass peaking during the rising limb of the hydrograph and declining prior to the cessation of peak flows. Both within- and among-day drift hysteresis appeared related to patterns in vegetative export, principally Cladophora and Amblystegium. Increases in macroinvertebrate drift were not associated with detectable reductions in benthic densities, while we observed inconsistent and modest taxa richness reductions. Lastly, gut fullness for both brown and rainbow trout increased significantly following periods of hydropeaking, suggesting that the effects of double-peaking can propagate through tail-water food webs.

Macroinvertebrate drift response to hydropeaking: An experimental approach to assess the effect of varying ramping velocities

“…Allowing hydropower operators to increase flow to an unlimited extend is considered to negatively impact stream biota (Marty et al, ; Smokorowski et al, ). If the increase of flow occurs gradually, macroinvertebrates may be able to find shelter in the hyporheic zone, resulting in lower drift densities (Armanini et al, ; Miller & Judson, ; Timusk et al, ). Our results partly go in line with this argumentation and support the hypothesis of lower drift proportions, when ramping velocities are low.…”

“…The existing studies indicate that if the increase of flow occurs gradually, macroinvertebrates may be able to find shelter in the hyporheic zone resulting in lower drift densities (Armanini et al, ; Miller & Judson, ; Timusk, Smokorowski, & Jones, ). Miller and Judson () even suggest that changes in discharge may have higher impact on macroinvertebrate communities than the flow magnitude itself. Consequently, measures aiming to reduce ramping velocities may mitigate the negative effects associated with storage operated hydropower plants (Smokorowski et al, ; Tonolla et al, ).…”

Causes and consequences of invertebrate drift in running waters: from individuals to populations and trophic fluxes

“…A key consequence of this conceptual model is that the absolute magnitude of hydraulic stress may be less important than its direction and rate of change in determining the response of invertebrate drift to flow variation (Imbert and Perry 2000). Empirical support for this model comes from drift observations during hydropeaking in regulated rivers, where differences in drift concentration between ascending and descending points along a hydrograph are regularly observed (Perry and Perry 1986;Patterson and Smokorowski 2011;Miller and Judson 2014).…”

Responses of benthic invertebrates to repeated hydropeaking in semi‐natural flume simulations

“…Few studies have examined the response of macroinvertebrate drift to repeated hydropeaking events over short‐time periods, which may lead to an additive effect on the benthic community that is not detected in a single event alone (Troelstrup and Hergenrader, ; Zimmerman et al ., ; Smokorowski et al ., ; Miller and Judson, ). The difficulties in monitoring the impact of altered flows, which may be confounded by other factors (i.e.…”