Effects of hydropower peaking on epilithon and invertebrate community trophic structure

Abstract

Hydropower generation induces rapid and frequent fluctuations of hydrodynamic parameters in rivers downstream of hydroelectric impoundments. On the Fontauliere river (Ardeche basin, France , water releases come from the Loire basin and the flow varies from 1.3 to 20m3/s for one reach and from 0.1 to 20m /s for another reach. A reference site upstream was chosen to compare the communities with two downstream impacted sites. These two sites enabled two different base flow situations to be studied simultaneously and also the effect of base flow enhancement at one site. Benthic and epilithic samples were collected at the three sites on three dates. Epilithon development was linked to hydraulic regimes, with a major increase in algal biomass, dominated by filamentous algae, linked to the minimum base flow level and to the duration of periods without peaks. The macroinvertebrate communities of impacted reaches were less diversified and more specialized, with predominance of one or two taxa, whereas communities in upstream reaches were more diverse. The different morphological units specificity was attenuated in hydropeaking situations. In the case of a very low base flow, the lentic units with very low velocities (less than 4cms-') had different fauna. The downstream algal development explained part of the change in benthic community structure in trophic groups (i.e. dominance of scrapers) in the site with the higher base flow. When the base flow was too low, a trophic discordance was observed and excess algal biomass represented a limiting factor. Thus, this study indicated that base flow level and duration had important effects on epilithic development and on invertebrate trophic structure in terms of mean velocities and of number of days without peaks. J supplies from Montpezat power plant 3 reservoirs VEYRIERES DAM Peak Row = 20 mWs Micm-power p l a a g * _ * SITE3 Peak Row = 13 to 20 m3/s Base Row = 0.12 m3/s

Simulation of river water temperatures during various hydro-peaking regimes

“…Hydropeaking is a variant of hydropower production, characterised by introducing rapid and frequent changes in discharge through a hydropower plant. The term 'hydro-peaking' is, however, broad and vaguely defined in the literature, and other terms are also found describing the same phenomenon, such as intermittent hydropower generation (Moog 1993), hydropower peaking (Valentin et al 1995), rapid flow decreases (Bradford 1997), sudden flow variations (Liebig et al 1999), fluctuating flow (Vehanen et al 2000), rapid changes in flow (Saltveit et al 2001), pulse power generation (Scruton et al 2003) and peaking flows (Berland et al 2004). Hydro-peaking has been used to describe both the operational pattern of hydropower plants (e.g.…”

Evaluation of Juvenile Fall Chinook Salmon Stranding on the Hanford Reach of the Columbia River, 1999 Annual Report.

“…Valentin et al (1995) found less diverse and more specialized macroinvertebrate communities in reaches affected by frequent flow fluctuations on the Fontauliere River, France.…”

Effects of hydrological regime on the drift algae in a regulated Mediterranean river (River Verdon, southeastern France)

“…The impact of hydrological regime was mainly studied on periphyton (Biggs and Close, 1989;Acs and Kiss, 1993;Valentin et al, 1995). Nevertheless phytoplankton represents a very sensitive indicator of various environmental changes (Maberly et al, 1994).…”