Nervous habitat patches: The effect of hydropeaking on habitat dynamics

Abstract

Alteration in the river flow regime due to intermittent hydropower production (i.e., hydropeaking) leads to biodiversity loss and ecosystem degradation worldwide.Due to the increasing shear of volatile green energy (i.e., wind and solar), hydropeaking frequency is deemed to increase in the coming decades. However, our mechanistic understanding of how the frequency of repeated hydropeaking (i.e., series of multiple events) affects ecological processes is still limited. Here, we reflect on the impacts of altered flow frequency and relative duration on the persistency of aquatic habitats. We focus on the habitats at patch-scale, being this the scale representing what organisms perceive when interacting with their environment. With a showcase we explore a temporally explicit approach to quantify altered habitat dynamics at patch-scale due to hydropeaking. We then review how changes in habitat dynamics and persistency may affect ecological processes. Our findings suggest that (i) a timeseries approach allows to account for the inherent multi-event nature of hydropeaking; (ii) hydropeaking can increase the dynamics of single habitat patches by at least one order of magnitude if compared to unregulated rivers; (iii) altered habitat dynamics at the patch scale can affect the survival of more sessile species and life cycle stages (e.g., invertebrates) or the energy budget of mobile species and life cycle stages (e.g., adult fish). However, the ecological significance and potential environmental thresholds of patch-scale dynamics and persistency are still poorly investigated and need further attention. Moreover, methods for the aggregation of habitat dynamics and persistency from the patch to the reach-scale are not available yet.

Innovations in hydropeaking research

“…Judes et al (2023) offers new insights regarding how not only current but also past hydraulics affect biotic communities in hydropeaking rivers. Bätz et al (2023) underlines the importance of considering both temporal and spatial habitat shifts in the assessment of hydropeaking alterations. Abernethy et al (2023) illustrates how hydropower dams can act as dispersal barrier for some aquatic insect species.…”

“…The predominant scale of investigations is the reach scale, with investigation and study sites spanning from meters to kilometers. At the smaller scale, that is, at microhabitat and patch‐scale, there are studies on macroinvertebrate (Judes et al, 2023), fish spawning (Pander et al, 2023), early life stages (Auer et al, 2023), habitat dynamics and usage (Bartoñ et al, 2023; Bätz et al, 2023; Boavida et al, 2023). At the larger end of the reach scale, modelling approaches are mostly presented (e.g., Jelovica et al, 2023).…”

“…Judes et al (2023) andBätz et al (2023) analysed both fish and macroinvertebrate habitat distributions, the former focusing onF I G U R E 1 Cumulated number of peerreviewed scientific articles related to hydropeaking, as well as the count of different (unique) scientific journals hosting the articles. Source: Web of Science (WoS) database; search query: "hydropeaking OR hydro-peaking" in "Topic".…”

“…With a focus on the novelties on fundamental knowledge, we highlight the following contributions: while most studies focus on downstream impacts,Pander et al (2023) is among the first to investigate the ecological effects of hydropeaking upstream of the storing reservoir Judes et al (2023). offers new insights regarding how not only current but also past hydraulics affect biotic communities in hydropeaking rivers Bätz et al (2023). underlines the importance of considering both temporal and spatial habitat shifts in the assessment of hydropeaking alterations Abernethy et al (2023).…”

Insectivorous bat foraging tracks the availability of aquatic flies (Diptera)

“…Aquatic invertebrate assemblages of the Colorado River in Grand Canyon are simplified and dominated by generalist aquatic insect taxa, particularly aquatic flies in the family Chironomidae, and non‐insects (e.g., crustaceans, snails, mussels, worms), which lack a terrestrial life stage and are therefore largely unavailable to terrestrial wildlife. Unstable food webs and reduced biodiversity are prevalent in regulated rivers (Power et al 1996, Abernethy et al 2021), especially below dams with hydropeaking practices (Bätz et al 2022) such as Glen Canyon Dam.…”