Effects of Simulated Rapid Water Level Fluctuations (Hydropeaking) on Survival of Sensitive Benthic Species

Abstract

Sudden changes in water releases below hydropower facilities (hydropeaking) can dramatically affect benthic organisms. Aquatic gastropods are an ideal organism for studying such effects because they inhabit littoral areas that are frequently dewatered during hydropeaking and have a low dispersal ability making them highly susceptible. We explored mortality rates of Taylorconcha serpenticola, the threatened Bliss Rapids snail, in four laboratory experiments that simulated hydropeaking during varying seasons and varying hydropower operation scenarios. Experiments were conducted in a light and temperature controlled Conviron® and were designed to simulate conditions on the Middle Snake River, Idaho, USA, in reaches that are subjected to hydropeaking. Experiments examined the effects of three air temperatures (winter = −7°C, spring = 17°C and summer = 37°C), three durations of exposure to air (2, 4 and 6 h), three dewatering rates (instantaneous, 0.3 and 0.15 m h−1), two substrate textures (smooth and vesicular) and consecutive daily exposures (1 to 15 days). With 2 h exposures >80% of gastropods survived under both the summer and winter condition, but with 6 h exposure only 60% survived under winter conditions and almost none survived under summer conditions. Survivorship of gastropods was always high under spring conditions (>90%) even when exposed for 6 h d−1for up to 15 days. When subjected to consecutive daily exposures, survivorship was lowest under winter conditions. Neither rate of dewatering nor substrate texture affected survivorship. Our data suggest that hydropower operations that include rapid stage fluctuations under extreme temperatures can cause high mortality of sensitive benthic species especially when exposure time is prolonged. Future water management policy decisions will need to consider these factors to manage for protection of aquatic species of conservation concern. Copyright © 2013 John Wiley & Sons, Ltd.

Pulsed Flow Wave Attenuation on a Regulated Montane River

“…Long-term changes in morphology and substrate composition can result from the pulsed flow regime and dam operations (Moog, 1993;Grant et al, 2003;Harby and Noack, 2013) as well as a number of detrimental effects on downstream biota (Cushman, 1985). Numerous studies, mainly in Europe and the US, have found combinations of reduced diversity, biomass, and richness of benthic species and changes in community trophic structure resulting from hydropeaking operations (Bain, 2007), with impacts falling heavily on sensitive species (Richards et al, 2014). Increased macroinvertebrate drift from both temperature and discharge changes may cause substantial losses to benthic populations (Bruno et al, 2010;Cereghino and Lavandier, 1998).…”

Effects of hydropeaking on benthic invertebrate community composition in two central Norwegian rivers

“…Hydropeaking causes a fraction of the riverbed to be dewatered, commonly referred to as the ramping zone. For benthic invertebrates and fish, one of the most commonly studied effects of hydropeaking is stranding mortality and predation risk in the ramping zone during low flow periods (Cereghino, Cugny, & Lavandier, 2002;Richards, Gates, & Kerans, 2014;Saltveit, Halleraker, Arnekleiv, & Harby, 2001;Schmutz et al, 2015). Furthermore, hydropeaking is unpredictable, because water level fluctuations exceed those occurring naturally and erosion and sedimentation may affect the river channel morphology, resulting in a more homogeneous habitat (see Armitage, 1984;Casas-Mulet, Alfredsen, Hamududu, & Timalsina, 2015;Fuller et al, 2011;Moog, 1993;Poff et al, 1997).…”

Hydrologic Variability Influences Local Probability of Pallid Sturgeon Occurrence in a Missouri River Tributary

“…Changes to a river's natural flow regime alter the established patterns of natural hydrologic variation and disturbance and create novel conditions to which native fishes may be poorly adapted (Poff et al ., ; Malmqvist and Rundle, ). Extreme daily variations, such as hydropeaking events produced by power generation, have no natural equivalent, and many aquatic populations experience high mortality rates because of stress from washout or from being stranded during periods of low flow (Nagrodski et al ., ; Richards et al ., ). Similarly, streams with low variability in flow have very different fish assemblages than streams with high variability (Meador and Carlisle, ).…”