The effects of hydropeaking on riverine plants: a review

Abstract

Hydropeaking refers to frequent, rapid and short-term fluctuations in water flow and water levels downstream and upstream of hydropower stations. Such fluctuations are becoming increasingly common worldwide and are known to have far-reaching effects on riverine vegetation. Novel hydrology caused by hydropeaking has no natural correspondence in freshwater systems, and hence few species have adaptations to all its aspects. Here, we review the literature on hydropeaking effects on riverine plants and define the state of the information on this human alteration of riverine ecosystems. We focus on riparian plants, but also draw on information from aquatic plant species, which exhibit a wide variety of adaptations to inundation and associated processes. Riparian plants face both physiological and physical constraints because of the shifts between submergence and drainage, and erosion of substrates. At the population level, hydropeaking may favour dispersal within, but not between, reservoirs, but may hamper germination, establishment, growth and reproduction. At the community level, strong filtering towards easily dispersed, flexible, flood-tolerant and amphibious plants is expected, although few species share these traits. Hence, most riparian plant species are expected to disappear or be pushed towards the upper boundaries of the regulated river margin. Future research should examine more closely global variation in hydropeaking effects, including other taxonomic groups of species and the diversity of hydropeaking regimes. There is also a need for studies focusing on identifying the boundaries within which hydropeaking could operate without impairing plant life.

The abundance and distribution of guilds of riparian woody plants change in response to land use and flow regulation

“…Structural measures and dam operational rules to mitigate hydropeaking effects have been studied before, but “estimating and predicting their ecological benefit remains challenging” (Bruder et al., ). Examples of hydropeaking mitigation include operational improvement of peak discharges, such as diversion of peak flows to retention basins or downstream lakes, morphological restoration of riverbanks to avoid scouring effects and frequent variation between low‐ and high‐flow events (Bejarano, Jansson & Nilsson, ). Realistic restoration measures should account for technical and economic as well as socio‐economic constraints of dams that may hamper flow manipulation.…”

Fish assemblage responses to flow seasonality and predictability in a tropical flood pulse system

“…Indeed, hydropeaking is widely known to alter hydraulic parameters such as water levels, velocity, and bed shear stress that fragments habitats altering fish assemblage composition and diversity due to, among other factors, stranding and downstream displacement, and reduced spawning and rearing success of fish (Hunter 1992, McLaughlin et al 2006, Habit et al 2007, Poff et al 2007, Clarke et al 2008, Meile et al 2010, Young et al 2011, Kennedy et al 2016, Bejarano et al 2017, Tonolla et al 2017. First, fish stranding was reported in SS (Baird and Meach 2005).…”

Smaller future floods imply less habitat for riparian plants along a boreal river

“…, Bejarano et al. ). Riparian vegetation, being the plant community associated with recurrent flooding and high groundwater tables in riparian areas, has been altered by hydrologic changes resulting from flow regulation for hydropower (Nilsson et al.…”

“…Many studies document strong dependence of riparian plants to variation in river flood regimes, and altered flows typically lead to large changes in the frequency and abundance of riparian plant species (Hill et al 1998, Jansson et al 2000, Auble et al 2005, Bejarano et al 2018. Riparian vegetation, being the plant community associated with recurrent flooding and high groundwater tables in riparian areas, has been altered by hydrologic changes resulting from flow regulation for hydropower (Nilsson et al 1991, Jansson et al 2000, Bejarano et al 2018, channelization (Helfield et al 2007, Rambaud et al 2009) and dykes disconnecting floodplains from rivers (Leyer 2005). Field experiments have proven useful to quantify how riparian vegetation responds to changes in flow (Quistberg and Stringham 2010).…”