Long-term trajectory of the macroinvertebrate community in the downstream channel of a hydropower dam after the operation of a sediment bypass tunnel

Kobayashi, Sohei; Otsubo, Yusuke; Sumi, Tetsuya; Takemon, Yasuhiro

doi:10.1016/j.ecolind.2023.109988

Cited by 6 publications

(5 citation statements)

References 56 publications

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“…Auel et al (2017) compared the microhabitats and benthic invertebrates between the upstream and downstream sections of four dams with contemporary (0 and 3 years) and aged (17 and 93 years) SBTs constructed in Japan and Switzerland. Similarly, Kobayashi et al (2023) observed benthic invertebrates in the downstream sections of a Japanese dam 17 years after the operation of the SBT in 1998. Both studies revealed an improvement in substrate environments and an increase in the similarity of species composition in the downstream sections compared to that of the upstream sections following SBT operations.…”

Section: Introductionmentioning

confidence: 76%

“…The upstream sections of dams are commonly considered the reference for restoration projects undertaken in downstream dam areas (e.g. Kobayashi et al 2023). However, as exemplified by the Koshibu River case, disparities often exist between upstream and downstream environments.…”

Section: Methodsmentioning

confidence: 99%

“…Sediment bypass connects the upstream and downstream sections of a dammed river through a tunnel that transports sediments in synchrony with natural high‐flow events (Sumi et al 2004). Although sediment bypassing has advantages over other forms of river management because it mimics not only natural flow but also sediment regimes, a limited number of sediment bypass tunnels (SBTs) have been constructed, and there is little empirical evidence for ecological improvements (see short‐term responses in Martín et al 2017: long‐term response of benthos in Auel et al 2017; Kobayashi et al 2023). Martín et al (2017) assessed SBT operation for 2 years in a Swiss river and reported a reduction in periphyton levels and macroinvertebrate density/richness after large sediment bypassing and a few changes in physicochemical environments, suggesting that sediment bypassing acted as a pulse disturbance for downstream ecosystems.…”

Section: Introductionmentioning

confidence: 99%

“…Both studies revealed an improvement in substrate environments and an increase in the similarity of species composition in the downstream sections compared to that of the upstream sections following SBT operations. However, Kobayashi et al (2023) reported substantial improvements in species composition during the early stage (2–3 years) of SBT, with only minor changes observed between subsequent stages (15–17 years). They proposed that in addition to sediment bypassing, other restoration actions are necessary to maintain potential habitat heterogeneity and biodiversity in the long term.…”

Section: Introductionmentioning

confidence: 99%

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Effects of repeated sediment bypassing on stream ecosystems in a Japanese mountainous river

Sueyoshi,

Miyagawa,

Onoda

et al. 2023

Restoration Ecology

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Sediment bypassing connects the upstream and downstream regions of dam impoundments through tunnels and is expected to partly restore natural processes (flood pulse and sediment regime) in dam‐altered river ecosystems. However, few reports examined the effects of restoration on stream biota. We examined the effectiveness of repeated sediment bypassing (12 times) over a period of 5 years in a Japanese dammed river using a before‐after‐reference‐impact design. We compared the abiotic parameters (water quality and substrate environment), biotic assemblages (algae, macroinvertebrates, and fish), and similarities between the dam downstream and undammed reference reaches. The reference sites exhibited high temporal variability in abiotic environments and species composition over the 5‐year period. Most abiotic and biotic parameters downstream of the dam improved and approached those of the changing reference states. However, these indices returned to pretrial conditions after the last trial. Biotic similarities between the downstream and reference reaches gradually increased throughout successive sediment‐bypassing trials for macroinvertebrates and algae; however, these similarities diminished after the last trial. Conversely, the abundance‐based composition of fish assemblages in the restored reach consistently diverged from that of the reference conditions throughout the study period. Our results show that the success and failure of restoration by sediment bypassing may be affected by the amount of bedload in the flushing flows and other regional processes such as migratory connectivity. Sediment bypassing can partially re‐establish natural processes and is a useful tool for improving sediment‐associated environments and biota.

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Section: Introductionmentioning

confidence: 76%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of repeated sediment bypassing on stream ecosystems in a Japanese mountainous river

Sueyoshi,

Miyagawa,

Onoda

et al. 2023

Restoration Ecology

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“…For instance, Fukuda et al (2012) noted that Japan's Asahi Dam's downstream riffle-pool morphology and grain-size distribution (GSD) were recovered after more than 15 years of SBT operations, yet highlighting the uncertainties of long-term effects of SBTs. Similarly, Kobayashi et al (2018) showcased the potential of SBTs in mirroring upstream ecomorphology downstream based on in-field results. The current understanding of SBT impacts largely stems from monitoring post-SBT operations, but these are temporally and spatially constrained.…”

mentioning

confidence: 90%

Modeling the morphological response of gravel–bed rivers subject to repeated sediment bypass tunnel operations

Facchini,

Vetsch,

Boes

et al. 2024

Front. Earth Sci.

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Introduction: Sediment bypass tunnels (SBTs) are operated during floods to re-establish sediment continuity past dams with the ultimate goal of decreasing accumulation in reservoirs. Depending on the location of the intake structure and operational conditions, SBTs may release either bed load-laden or bed load-free flows in the form of sudden floods (pulses). When evaluating the impacts of SBTs, the traditional approach has been to monitor channel changes in the years following project completion. However, by the time these impacts become evident, mitigation is challenging.Methods: This research adopts a forward-thinking methodology, emphasizing the prediction of potential impacts during the project’s early planning stages. We use a one-dimensional morphodynamic model to forecast the potential morphological response of a gravel-bed river with an idealized geometry to a series of SBT operations characteristic of projects in the Swiss Alps.Results: The morphological response of the downstream reach over the medium to long term is influenced by the alternating pattern of bed load-laden and bed load-free flow releases. This pattern is instrumental in forming a transition region near the SBT outlet hydrograph boundary layer (HBL).Discussion: Within the (HBL), fluctuations in bed elevation and slope are localized, while variations in grain-size distribution persist throughout the downstream region.

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Hydroelectric Dams Affect Hyporheic Copepod Diversity

Di Cicco,

Galmarini,

Cerasoli

et al. 2024

River Research & Apps

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This study investigates the ecological impact of a small hydroelectric power plant (SHPP) on the hyporheic zone of the venacquaro stream (VEN), a low‐order groundwater‐fed stream in Central Italy. The hyporheic zone, a critical ecological interface where groundwater and surface water interact, plays a pivotal role in nutrient cycling, pollutant retention, and supporting aquatic biodiversity. However, hydrological alterations from activities such as damming pose significant threats to this zone. The research employs a three‐pronged approach to assess the effect of a SHPP on hyporheic copepod communities. Copepods were selected as the focal group due to their dominance in this habitat. Initially, a generalized estimating equation (GEE) model was used to evaluate changes in copepod diversity, specifically alpha and beta diversity. The study then examines environmental shifts caused by the SHPP using permutational analysis of variance (PERMANOVA) and principal component analysis (PCA). Lastly, a multivariate species distribution model (mSDM) explores correlations between environmental variables and copepod abundances. Results reveal significant alterations in copepod assemblage structure and environmental variables downstream of the SHPP. The GEE model indicates a notable shift in beta diversity, primarily driven by disruptions in hyporheic connectivity rather than environmental changes alone. This disruption favours stygobitic species downstream, suggesting the influence of groundwater upwelling. Environmental analysis shows several differences between upstream and downstream sites, with changes in parameters such as pH, temperature, and dissolved organic carbon. The study highlights the need for effective management strategies to mitigate sediment accumulation and maintain habitat quality in SHPP‐affected streams. Techniques like sediment bypass tunnels (SBTs) are recommended to preserve both economic and ecological values. This research contributes to the still limited understanding of SHPP impacts on hyporheic ecosystems, emphasizing the importance of considering these effects in hydropower development and riverine ecosystem conservation.

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Long-term trajectory of the macroinvertebrate community in the downstream channel of a hydropower dam after the operation of a sediment bypass tunnel

Cited by 6 publications

References 56 publications

Effects of repeated sediment bypassing on stream ecosystems in a Japanese mountainous river

Effects of repeated sediment bypassing on stream ecosystems in a Japanese mountainous river

Modeling the morphological response of gravel–bed rivers subject to repeated sediment bypass tunnel operations

Hydroelectric Dams Affect Hyporheic Copepod Diversity

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