Initial observations of egg mortality downstream of a hydroelectric facility on the Yellowknife River in the Northwest Territories prompted the investigation of habitat use by adfluvial lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis), and cisco (Coregonus artedi). It was conducted to meet regulatory requirements under the Fisheries Act (1985) for the facility and was focused on results from annual snorkel surveys completed from 2016 to 2019. The design principles of the installed habitat were based on habitat rehabilitation projects for anadromous salmonids in rivers, artificial spawning reefs constructed in lakes for lacustrine populations of lake trout, and lake whitefish and the 2016 study results. The evaluation of the installed habitat was based on results from snorkel surveys that collected data on egg density and survival using 1 m2 plots on both natural and artificially enhanced substrates. Three years of postenhancement monitoring indicated higher egg densities and a greater proportion of live eggs in the artificially enhanced habitat compared to the natural habitat, with more pronounced trends observed for coregonids (lake whitefish and cisco) compared to lake trout. These findings suggest that habitat enhancement has the potential to enhance juvenile recruitment for adfluvial fish. A critical factor in the design was ensuring the substrate composition provided adequate interstitial spaces for egg development and protection. This study represents the first documented attempt at habitat improvement in a regulated sub‐Arctic river in Canada. The results and design principles for the installed habitat offer a valuable framework for new or existing development projects in Northern Canada that require conservation actions to maintain fisheries productivity.
{"title":"Effectiveness of spawning substrate enhancement for adfluvial fish in a regulated sub‐Arctic river","authors":"M. Miller, C. Stevens, M. S. Poesch","doi":"10.1002/rra.4358","DOIUrl":"https://doi.org/10.1002/rra.4358","url":null,"abstract":"Initial observations of egg mortality downstream of a hydroelectric facility on the Yellowknife River in the Northwest Territories prompted the investigation of habitat use by adfluvial lake trout (<jats:italic>Salvelinus namaycush</jats:italic>), lake whitefish (<jats:italic>Coregonus clupeaformis</jats:italic>), and cisco (<jats:italic>Coregonus artedi</jats:italic>). It was conducted to meet regulatory requirements under the Fisheries Act (1985) for the facility and was focused on results from annual snorkel surveys completed from 2016 to 2019. The design principles of the installed habitat were based on habitat rehabilitation projects for anadromous salmonids in rivers, artificial spawning reefs constructed in lakes for lacustrine populations of lake trout, and lake whitefish and the 2016 study results. The evaluation of the installed habitat was based on results from snorkel surveys that collected data on egg density and survival using 1 m<jats:sup>2</jats:sup> plots on both natural and artificially enhanced substrates. Three years of postenhancement monitoring indicated higher egg densities and a greater proportion of live eggs in the artificially enhanced habitat compared to the natural habitat, with more pronounced trends observed for coregonids (lake whitefish and cisco) compared to lake trout. These findings suggest that habitat enhancement has the potential to enhance juvenile recruitment for adfluvial fish. A critical factor in the design was ensuring the substrate composition provided adequate interstitial spaces for egg development and protection. This study represents the first documented attempt at habitat improvement in a regulated sub‐Arctic river in Canada. The results and design principles for the installed habitat offer a valuable framework for new or existing development projects in Northern Canada that require conservation actions to maintain fisheries productivity.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Flood‐related policies for England are reviewed, updating needs in the light of recent flood‐rich decades and in recognition of future climate trends. This review updates one we published in 2021—a significant year for extreme floods in Europe that were part of a continuing trend; governments now require fast‐track adaptation and resilience policies. Currently, the event signals that increasing spatial and temporal variability of impacts are insufficiently incorporated in hazard/risk assessments. We advocate a transformative policy change towards place‐based strategies, based on the fast‐emerging evidence from three sciences: hydroclimatology, hydrology and hydromorphology. It is vital that policy actions recognise factors such as atmospheric rivers, surface water flooding, and the role of eroded and transported sediments in localised hazards and risks. Located vulnerabilities require local strategies. Attribution of extreme events to climate change, and the recognition and specification of genuinely vulnerable sites, need further refinement and extension into public decision making. Risk assessment needs reform, both from science but also for institutions and individuals, with accompanying reform of flood risk management expenditure. Data analysis of rainfall and river flows need more disciplined clarity; standard sets are needed together with their variable spatial/temporal application. We further recognise sediment hazards (and other entrained debris spread in flood flows) as new and important components for the located risk of present and emerging ‘hot spots’.
{"title":"The developing flood rich period: Science evidence and policy evolution for England. Is it time for place‐based socio‐ecological solutions?","authors":"Malcolm Newson, John Lewin","doi":"10.1002/rra.4363","DOIUrl":"https://doi.org/10.1002/rra.4363","url":null,"abstract":"Flood‐related policies for England are reviewed, updating needs in the light of recent flood‐rich decades and in recognition of future climate trends. This review updates one we published in 2021—a significant year for extreme floods in Europe that were part of a continuing trend; governments now require fast‐track adaptation and resilience policies. Currently, the event signals that increasing spatial and temporal variability of impacts are insufficiently incorporated in hazard/risk assessments. We advocate a transformative policy change towards place‐based strategies, based on the fast‐emerging evidence from three sciences: hydroclimatology, hydrology and hydromorphology. It is vital that policy actions recognise factors such as atmospheric rivers, surface water flooding, and the role of eroded and transported sediments in localised hazards and risks. Located vulnerabilities require local strategies. Attribution of extreme events to climate change, and the recognition and specification of genuinely vulnerable sites, need further refinement and extension into public decision making. Risk assessment needs reform, both from science but also for institutions and individuals, with accompanying reform of flood risk management expenditure. Data analysis of rainfall and river flows need more disciplined clarity; standard sets are needed together with their variable spatial/temporal application. We further recognise sediment hazards (and other entrained debris spread in flood flows) as new and important components for the located risk of present and emerging ‘hot spots’.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Logjams, in‐channel accumulations of downed wood, play important roles governing biophysical processes in river ecosystems. In this study conducted in the mountainous inland Pacific Northwest, we leveraged a basin‐scale inventory to carry out a comprehensive analysis of logjam frequency, volume, and their associations with a suite of biophysical landscape characteristics and anthropogenic influences. We complemented this analysis with one that relies on the concept of process domains. We found that logjam frequency increased with drainage area up to ~10–30 km2 and declined thereafter, while the mean jam volume steadily increased downstream up to the area of >300 km2. Combined, these variables yielded a nonlinear downstream pattern of large wood storage in jams, peaking at drainage areas of ~10–100 km2. Logjam characteristics were associated with multiple predictors, used as proxies for biogeomorphic processes relevant for large wood supply and redistribution: bank erosion, landslides, avulsions, wood availability in riparian forest, and wood transport. Additionally, anthropogenic disturbances were inferred to strongly influence logjam‐forming processes in the study basin. A riprapped forest road disrupted a process chain responsible for large wood supply, wherein erosion undercuts slope toe, ultimately triggering landslides. Timber harvest influenced large wood supply by reducing forest biomass. Overall, these findings contribute to improved understanding of logjams: they provide insight into the complex suite of interacting natural and anthropogenic factors which, by regulating large wood inputs and redistribution, generate a basin‐scale pattern in jam frequency and volume. We believe that our study will be useful in informing river management and restoration practices.
{"title":"Logjams in a mountain stream network: Patterns, biogeomorphic associations, and anthropogenic impacts","authors":"Piotr Cienciala, Andrew D. Nelson, Andrew D. Haas","doi":"10.1002/rra.4340","DOIUrl":"https://doi.org/10.1002/rra.4340","url":null,"abstract":"Logjams, in‐channel accumulations of downed wood, play important roles governing biophysical processes in river ecosystems. In this study conducted in the mountainous inland Pacific Northwest, we leveraged a basin‐scale inventory to carry out a comprehensive analysis of logjam frequency, volume, and their associations with a suite of biophysical landscape characteristics and anthropogenic influences. We complemented this analysis with one that relies on the concept of process domains. We found that logjam frequency increased with drainage area up to ~10–30 km<jats:sup>2</jats:sup> and declined thereafter, while the mean jam volume steadily increased downstream up to the area of >300 km<jats:sup>2</jats:sup>. Combined, these variables yielded a nonlinear downstream pattern of large wood storage in jams, peaking at drainage areas of ~10–100 km<jats:sup>2</jats:sup>. Logjam characteristics were associated with multiple predictors, used as proxies for biogeomorphic processes relevant for large wood supply and redistribution: bank erosion, landslides, avulsions, wood availability in riparian forest, and wood transport. Additionally, anthropogenic disturbances were inferred to strongly influence logjam‐forming processes in the study basin. A riprapped forest road disrupted a process chain responsible for large wood supply, wherein erosion undercuts slope toe, ultimately triggering landslides. Timber harvest influenced large wood supply by reducing forest biomass. Overall, these findings contribute to improved understanding of logjams: they provide insight into the complex suite of interacting natural and anthropogenic factors which, by regulating large wood inputs and redistribution, generate a basin‐scale pattern in jam frequency and volume. We believe that our study will be useful in informing river management and restoration practices.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jan Henning L'Abée‐Lund, Harald Sægrov, Helge Skoglund, Ola Ugedal, Leif Asbjørn Vøllestad
Hydropower (HP) has become the most important renewable energy source worldwide during the last century. However, the impacts on aquatic ecosystems may be considerable. In the Northern Hemisphere, salmonid fishes are often affected by hydropower‐related temperature alterations. As their metabolic processes are entirely dependent on water temperature, they are strongly affected when the HP development reduces the water temperature during summer by extracting water from below the thermocline of upstream reservoirs. We investigated juvenile growth of Atlantic salmon Salmo salar and brown trout S. trutta in six Norwegian rivers where hydropower has considerably reduced the water temperature during summer. We used observed mass of 1+ juveniles sampled upstream and downstream the tailrace of the hydropower plant and compared these with simulated mass of 1+ juveniles based on daily recorded water temperatures and a bioenergetics model. Establishment of reservoirs have led to reduced growth of juveniles of both species on river reaches downstream HP tailraces. The hydropower development significantly altered the temperature regimes with the downstream reaches having lower temperatures than upstream reaches. Both observed and predicted masses of 1+ juveniles of both species were also lower downstream than upstream. Predicted mass were more similar to the observed mass for Atlantic salmon than for brown trout, indicating that the bioenergetics model for brown trout is not optimal.
{"title":"Thermal alterations of hydro power: Modelling the effect on growth of juvenile salmonids","authors":"Jan Henning L'Abée‐Lund, Harald Sægrov, Helge Skoglund, Ola Ugedal, Leif Asbjørn Vøllestad","doi":"10.1002/rra.4364","DOIUrl":"https://doi.org/10.1002/rra.4364","url":null,"abstract":"Hydropower (HP) has become the most important renewable energy source worldwide during the last century. However, the impacts on aquatic ecosystems may be considerable. In the Northern Hemisphere, salmonid fishes are often affected by hydropower‐related temperature alterations. As their metabolic processes are entirely dependent on water temperature, they are strongly affected when the HP development reduces the water temperature during summer by extracting water from below the thermocline of upstream reservoirs. We investigated juvenile growth of Atlantic salmon <jats:italic>Salmo salar</jats:italic> and brown trout <jats:italic>S. trutta</jats:italic> in six Norwegian rivers where hydropower has considerably reduced the water temperature during summer. We used observed mass of 1+ juveniles sampled upstream and downstream the tailrace of the hydropower plant and compared these with simulated mass of 1+ juveniles based on daily recorded water temperatures and a bioenergetics model. Establishment of reservoirs have led to reduced growth of juveniles of both species on river reaches downstream HP tailraces. The hydropower development significantly altered the temperature regimes with the downstream reaches having lower temperatures than upstream reaches. Both observed and predicted masses of 1+ juveniles of both species were also lower downstream than upstream. Predicted mass were more similar to the observed mass for Atlantic salmon than for brown trout, indicating that the bioenergetics model for brown trout is not optimal.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Katarina Pavlek, Mateo Gašparović, Ronald E. Poeppl
This study employs object‐based image analysis to investigate land cover dynamics and channel changes in the managed corridor of the Orljava River following anthropogenic vegetation removal and a flood event. By classifying RGB and near‐infrared (NIR) images from the decade 2011–2021, five land cover classes within the river corridor were mapped: water, bare soil, sparse vegetation, dense vegetation, and shadows. A digital surface model generated from the images was used to differentiate between bare river channel units (river sediments) and bare soil in the floodplain, as well as to identify high vegetation, while agricultural land was classified manually. The study identified two main phases of river corridor changes, driven by a significant flood event in 2014. In the period 2011–2014, which includes the flood event, a substantial increase in the areas covered by water and river sediments was observed. The most notable decrease was in the bare soil class (90%), which primarily covered riverbanks and adjacent areas in 2011 after vegetation removal. In addition, the formation of large in‐channel bars due to sediment accumulation and significant channel migration was recorded. In the second phase (2014–2021), lower discharges facilitated gradual channel recovery, characterized by channel narrowing and an increase in dense and high vegetation. This study demonstrates the high reliability of object‐based classification in mapping river corridor units using optical photogrammetric data. Furthermore, it highlights the deficiencies in inadequate river management practices that led to considerable bank erosion and a loss of agricultural land.
{"title":"Assessing natural and human‐induced river corridor changes using object‐based image analysis (Orljava River, Croatia)","authors":"Katarina Pavlek, Mateo Gašparović, Ronald E. Poeppl","doi":"10.1002/rra.4369","DOIUrl":"https://doi.org/10.1002/rra.4369","url":null,"abstract":"This study employs object‐based image analysis to investigate land cover dynamics and channel changes in the managed corridor of the Orljava River following anthropogenic vegetation removal and a flood event. By classifying RGB and near‐infrared (NIR) images from the decade 2011–2021, five land cover classes within the river corridor were mapped: water, bare soil, sparse vegetation, dense vegetation, and shadows. A digital surface model generated from the images was used to differentiate between bare river channel units (river sediments) and bare soil in the floodplain, as well as to identify high vegetation, while agricultural land was classified manually. The study identified two main phases of river corridor changes, driven by a significant flood event in 2014. In the period 2011–2014, which includes the flood event, a substantial increase in the areas covered by water and river sediments was observed. The most notable decrease was in the bare soil class (90%), which primarily covered riverbanks and adjacent areas in 2011 after vegetation removal. In addition, the formation of large in‐channel bars due to sediment accumulation and significant channel migration was recorded. In the second phase (2014–2021), lower discharges facilitated gradual channel recovery, characterized by channel narrowing and an increase in dense and high vegetation. This study demonstrates the high reliability of object‐based classification in mapping river corridor units using optical photogrammetric data. Furthermore, it highlights the deficiencies in inadequate river management practices that led to considerable bank erosion and a loss of agricultural land.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Muskrat (Ondatra zibethicus) predation on unionid mussels has been documented since the late 1800s. More recent studies have examined size‐specific predation and potential effects of predation on mussel populations. This study was part of a larger endeavor that examined the effects of dam removal in the Salmon and Little Salmon rivers in northern New York. Muskrat middens were searched for from 2005 through 2012 and all mussel shells were identified, measured, and evaluated for evidence of muskrat predation. Ten species of consumed mussels were collected from 37 middens. Three species of living mussels that were in low abundance were not found in middens. Distribution of middens was uneven in both rivers and few middens were used in more than 1 year. Muskrats did not consume mussels <37 mm shell length in the Salmon River (SR) and <28 mm in the Little Salmon River (LSR). Shell length distribution of living mussels was similar to that of mussels in middens. Shell length of living SR mussels (based on mean ranks) were significantly longer than living mussels in the LSR as were consumed mussels. Size‐selection may be indicated for Elliptio complanata and Lampsilis radiata but relative abundance might also be a factor. Dry empty shell weight and thickness were not significantly correlated to percent predation marks. The muskrat population in these rivers could be small as few middens were used in more than 1 year and there was no evidence of muskrat trapping. If so, muskrat predation would have a limited effect on the unionid population.
{"title":"Muskrat (Ondatra zibethicus) predation on unionid mussels in the Salmon and Little Salmon rivers in northern New York","authors":"John E. Cooper","doi":"10.1002/rra.4368","DOIUrl":"https://doi.org/10.1002/rra.4368","url":null,"abstract":"Muskrat (<jats:italic>Ondatra zibethicus</jats:italic>) predation on unionid mussels has been documented since the late 1800s. More recent studies have examined size‐specific predation and potential effects of predation on mussel populations. This study was part of a larger endeavor that examined the effects of dam removal in the Salmon and Little Salmon rivers in northern New York. Muskrat middens were searched for from 2005 through 2012 and all mussel shells were identified, measured, and evaluated for evidence of muskrat predation. Ten species of consumed mussels were collected from 37 middens. Three species of living mussels that were in low abundance were not found in middens. Distribution of middens was uneven in both rivers and few middens were used in more than 1 year. Muskrats did not consume mussels <37 mm shell length in the Salmon River (SR) and <28 mm in the Little Salmon River (LSR). Shell length distribution of living mussels was similar to that of mussels in middens. Shell length of living SR mussels (based on mean ranks) were significantly longer than living mussels in the LSR as were consumed mussels. Size‐selection may be indicated for <jats:italic>Elliptio complanata</jats:italic> and <jats:italic>Lampsilis radiata</jats:italic> but relative abundance might also be a factor. Dry empty shell weight and thickness were not significantly correlated to percent predation marks. The muskrat population in these rivers could be small as few middens were used in more than 1 year and there was no evidence of muskrat trapping. If so, muskrat predation would have a limited effect on the unionid population.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large‐scale modification of river ecosystems for navigation, power generation, flood control, and irrigation has largely homogenized benthic habitats and altered fish assemblages. Although riverine habitat rehabilitation and enhancement techniques are well‐studied for wadable streams and small rivers, relatively little is known about the potential utility of artificial fish habitat installation in large rivers impacted by hydropeaking. Lightweight artificial fish habitat structures composed of wood or plastic have demonstrated effects on fish populations in static environments; however, these structures are not able to withstand the high discharge and dynamic flows of a large river system. The Colorado River below the Davis Dam is a representative ecosystem impacted by hydropeaking, where water release can range from 2000 to 23,000 ft3/s (56.6–651.3 m3/s) in a single day. In coordination with multiple state and federal government agencies, we deployed a series of concrete river reef structures, mimicking small‐scale artificial reefs, to increase habitat complexity and provide in‐river patches of relief from high‐flow events. Benthic habitat cover measurements were paired with visual surveys of river reef structures 6 months and 2.5 years post‐deployment. Generalized linear models indicated that cobbles increased structure visibility above the riverbed, displayed less erosion, and allowed for greater potential fish use, whereas sand and gravel (i.e., loose bedload materials) decreased visibility and caused structures to sink into the riverbed over time, limiting fish use. Our case study provides instructional information on the construction of artificial river reef structures and recommendations for deployment, and highlights their potential to increase benthic habitat heterogeneity, with conservation and sport fish implications.
{"title":"Utility of artificial river reef structures to enhance fish habitat below a hydropeaking dam","authors":"Michael C. Cavallaro, David A. Schumann","doi":"10.1002/rra.4365","DOIUrl":"https://doi.org/10.1002/rra.4365","url":null,"abstract":"Large‐scale modification of river ecosystems for navigation, power generation, flood control, and irrigation has largely homogenized benthic habitats and altered fish assemblages. Although riverine habitat rehabilitation and enhancement techniques are well‐studied for wadable streams and small rivers, relatively little is known about the potential utility of artificial fish habitat installation in large rivers impacted by hydropeaking. Lightweight artificial fish habitat structures composed of wood or plastic have demonstrated effects on fish populations in static environments; however, these structures are not able to withstand the high discharge and dynamic flows of a large river system. The Colorado River below the Davis Dam is a representative ecosystem impacted by hydropeaking, where water release can range from 2000 to 23,000 ft<jats:sup>3</jats:sup>/s (56.6–651.3 m<jats:sup>3</jats:sup>/s) in a single day. In coordination with multiple state and federal government agencies, we deployed a series of concrete river reef structures, mimicking small‐scale artificial reefs, to increase habitat complexity and provide in‐river patches of relief from high‐flow events. Benthic habitat cover measurements were paired with visual surveys of river reef structures 6 months and 2.5 years post‐deployment. Generalized linear models indicated that cobbles increased structure visibility above the riverbed, displayed less erosion, and allowed for greater potential fish use, whereas sand and gravel (i.e., loose bedload materials) decreased visibility and caused structures to sink into the riverbed over time, limiting fish use. Our case study provides instructional information on the construction of artificial river reef structures and recommendations for deployment, and highlights their potential to increase benthic habitat heterogeneity, with conservation and sport fish implications.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Martin Šindler, Maroš Kubala, Dušan Senko, Martin Mišík, Gábor Guti, Ladislav Pekárik, Bořek Drozd
Sturgeons are a group of iconic rheophilic fish whose populations worldwide are currently undergoing significant declines. The study investigates the impact of climate change and anthropogenic activities, particularly the Gabčíkovo barrage system, on the survival and distribution of the sterlet, the last surviving sturgeon species in the Middle and Upper Danube River, specifically in the river part rkm 1708–1920 divided into three river sections: PT1 (Danube river part 1: rkm 1708–Gabčíkovo impoundment), PT2 (Danube river part 2: rkm 1854–1920), and PT3 (Old Danube part 3: rkm 1850–1810). Between years 1996 and 2020, water temperatures in the Danube River (PT1, PT2) rose by over 1°C on average, with the Old Danube (PT3) experiencing an alarming average increase of 3.5°C (df = 2, F = 145.03, p = <2.2e‐16). Consequently, suitable sterlet habitat (depth ≥4 m) in the Old Danube (PT3) now covers only 11% of its total area compared with 67% in PT1 and 75% in PT2 (flow rate = 1924.27 m3 s−1) due to altered flow regimes, water levels, and siltation. Sterlets are increasingly caught in an artificial channel below to the Gabčíkovo Hydroelectric Power Plant (80%–90% of annual total catch), suggesting a shift in their distribution patterns. Conversely, there has been a notable decline in sterlet populations in other river sections, including a decrease in a section with moderate ecological status according to Water Frame Directive criteria. In light of these findings, the study proposes several mitigation measures to improve the status of the sterlet population in the area.
{"title":"Implications of climate‐change‐induced stressors and water management for sterlet populations in the Middle and Upper River Danube","authors":"Martin Šindler, Maroš Kubala, Dušan Senko, Martin Mišík, Gábor Guti, Ladislav Pekárik, Bořek Drozd","doi":"10.1002/rra.4361","DOIUrl":"https://doi.org/10.1002/rra.4361","url":null,"abstract":"Sturgeons are a group of iconic rheophilic fish whose populations worldwide are currently undergoing significant declines. The study investigates the impact of climate change and anthropogenic activities, particularly the Gabčíkovo barrage system, on the survival and distribution of the sterlet, the last surviving sturgeon species in the Middle and Upper Danube River, specifically in the river part rkm 1708–1920 divided into three river sections: PT1 (Danube river part 1: rkm 1708–Gabčíkovo impoundment), PT2 (Danube river part 2: rkm 1854–1920), and PT3 (Old Danube part 3: rkm 1850–1810). Between years 1996 and 2020, water temperatures in the Danube River (PT1, PT2) rose by over 1°C on average, with the Old Danube (PT3) experiencing an alarming average increase of 3.5°C (df = 2, <jats:italic>F</jats:italic> = 145.03, <jats:italic>p</jats:italic> = <2.2e‐16). Consequently, suitable sterlet habitat (depth ≥4 m) in the Old Danube (PT3) now covers only 11% of its total area compared with 67% in PT1 and 75% in PT2 (flow rate = 1924.27 m<jats:sup>3</jats:sup> s<jats:sup>−1</jats:sup>) due to altered flow regimes, water levels, and siltation. Sterlets are increasingly caught in an artificial channel below to the Gabčíkovo Hydroelectric Power Plant (80%–90% of annual total catch), suggesting a shift in their distribution patterns. Conversely, there has been a notable decline in sterlet populations in other river sections, including a decrease in a section with moderate ecological status according to Water Frame Directive criteria. In light of these findings, the study proposes several mitigation measures to improve the status of the sterlet population in the area.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The willow fascine soil bioengineering technique is commonly used worldwide in river restoration projects to stabilize riverbanks, thanks to high theoretical shear stress resistance and adaptable configuration. Fascines are composed of bundles of living branches fixed between stakes. When positioned in meanders at bank toe, they are subjected to strong hydraulic constraints. Here, we present the field back‐analysis of 470 willow fascines alongside experiments in a small‐scale model (scale 1:25). We describe the dynamics of failure in various situations. The field analysis revealed that 78% of fascines present no signs of bank instability. No fascines were pulled out, and they rarely showed signs of destruction once vegetation had established. Flume experiments confirmed that the main mechanical process of failure is erosion at fascine toe and extremities (9% and 3% of occurrence in the field, respectively). The dynamics of failure occur through: (i) erosion at the fascine toe, removing materials under the bundle; (ii) bank sediments, sliding underneath the fascine; (iii) scouring, leaving stakes exposed to falling into the river. Based on these observations, the fascine toe should be protected sufficiently deeply against undermining to keep sediments in place while vegetation is established. Bank slopes should be reduced as far as possible to decrease scouring. Finally, the mean shear stress values used as reference when designing bioengineering techniques do not capture the local and continuous scouring processes leading to failure. Thus, bend curvature, degradation, grain sizes, and level of fascine implementation should be considered when adapting design.
{"title":"Riverbank fascines mostly fail due to scouring: Consistent evidence from field and flume observations","authors":"Solange Leblois, Guillaume Piton, Alain Recking, Delphine Jaymond, Alexis Buffet, André Evette","doi":"10.1002/rra.4356","DOIUrl":"https://doi.org/10.1002/rra.4356","url":null,"abstract":"The willow fascine soil bioengineering technique is commonly used worldwide in river restoration projects to stabilize riverbanks, thanks to high theoretical shear stress resistance and adaptable configuration. Fascines are composed of bundles of living branches fixed between stakes. When positioned in meanders at bank toe, they are subjected to strong hydraulic constraints. Here, we present the field back‐analysis of 470 willow fascines alongside experiments in a small‐scale model (scale 1:25). We describe the dynamics of failure in various situations. The field analysis revealed that 78% of fascines present no signs of bank instability. No fascines were pulled out, and they rarely showed signs of destruction once vegetation had established. Flume experiments confirmed that the main mechanical process of failure is erosion at fascine toe and extremities (9% and 3% of occurrence in the field, respectively). The dynamics of failure occur through: (i) erosion at the fascine toe, removing materials under the bundle; (ii) bank sediments, sliding underneath the fascine; (iii) scouring, leaving stakes exposed to falling into the river. Based on these observations, the fascine toe should be protected sufficiently deeply against undermining to keep sediments in place while vegetation is established. Bank slopes should be reduced as far as possible to decrease scouring. Finally, the mean shear stress values used as reference when designing bioengineering techniques do not capture the local and continuous scouring processes leading to failure. Thus, bend curvature, degradation, grain sizes, and level of fascine implementation should be considered when adapting design.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Emily C. Palmquist, B. Deemer, Anya N. Metcalfe, Theodore A. Kennedy, Lucas S. Bair, H. Fairley, P. Grams, J. Sankey, C. Yackulic
River flow patterns are primary drivers of lotic ecosystems, and hundreds of metrics have been developed to quantify flow attributes. Although existing metrics have been a powerful tool in designing environmental flows, they are often developed with specific resources in mind and are rarely directly comparable with each other (i.e., units are often different). Here, we focus on natural flows as the resource of interest and develop z‐score metrics that measure the naturalness of regulated flows, incorporating natural means and interannual variation. These “eZ metrics” summarize whole year, subdaily, and functional flow patterns as standard deviations from natural such that their values are directly comparable. We illustrate their utility with a case study from the Colorado River downstream of Glen Canyon Dam in Arizona, USA. We calculated metrics for 1964–2022, spanning >5 decades of changing water policy, hydropower generation, and flow experimentation. We evaluate four options for estimating natural baseline flows. Across metrics, we found that subdaily stage variation deviated the most from baseline. Flows to satisfy regional water policy and power demands altered metrics more than designer flows (which target specific resource outcomes), and years with low water releases were closest to natural. Most of the designer flows have not made flow patterns more natural, due to incorrect seasonal timing, small magnitude, or short duration. By explicitly considering interannual variability and quantifying how regulated flows differ from natural using standard deviations, these metrics can inform management when the goal is to restore a natural flow regime.
河流流动模式是地段生态系统的主要驱动力，目前已开发出数百种指标来量化流量属性。尽管现有指标已成为设计环境流量的有力工具，但这些指标往往是针对特定资源而制定的，很少具有直接可比性（即单位往往不同）。在此，我们将自然流量作为关注的资源，并结合自然平均值和年际变化，制定了衡量调节流量自然度的 z 值指标。这些 "eZ 指标 "将全年、次日和功能性流量模式概括为与自然流量的标准偏差，从而使它们的值具有直接可比性。我们以美国亚利桑那州格伦峡谷大坝下游的科罗拉多河为例，说明了这些指标的实用性。我们计算了 1964-2022 年的指标，跨越了水政策、水力发电和流量试验变化的 50 多年。我们评估了估算自然基线流量的四种方案。在所有指标中，我们发现次日阶段变化与基线偏差最大。满足地区水政策和电力需求的流量比设计流量（针对特定的资源结果）对指标的改变更大，放水量小的年份最接近自然流量。大多数设计流量并没有使水流模式更加自然，原因是季节性时机不正确、水量小或持续时间短。通过明确考虑年际变化并使用标准偏差量化调节流量与自然流量的差异，这些指标可为以恢复自然流量体系为目标的管理提供参考。
{"title":"eZ flow metrics: Using z‐scores to estimate deviations from natural flow in the Colorado River below Glen Canyon Dam","authors":"Emily C. Palmquist, B. Deemer, Anya N. Metcalfe, Theodore A. Kennedy, Lucas S. Bair, H. Fairley, P. Grams, J. Sankey, C. Yackulic","doi":"10.1002/rra.4360","DOIUrl":"https://doi.org/10.1002/rra.4360","url":null,"abstract":"River flow patterns are primary drivers of lotic ecosystems, and hundreds of metrics have been developed to quantify flow attributes. Although existing metrics have been a powerful tool in designing environmental flows, they are often developed with specific resources in mind and are rarely directly comparable with each other (i.e., units are often different). Here, we focus on natural flows as the resource of interest and develop z‐score metrics that measure the naturalness of regulated flows, incorporating natural means and interannual variation. These “eZ metrics” summarize whole year, subdaily, and functional flow patterns as standard deviations from natural such that their values are directly comparable. We illustrate their utility with a case study from the Colorado River downstream of Glen Canyon Dam in Arizona, USA. We calculated metrics for 1964–2022, spanning >5 decades of changing water policy, hydropower generation, and flow experimentation. We evaluate four options for estimating natural baseline flows. Across metrics, we found that subdaily stage variation deviated the most from baseline. Flows to satisfy regional water policy and power demands altered metrics more than designer flows (which target specific resource outcomes), and years with low water releases were closest to natural. Most of the designer flows have not made flow patterns more natural, due to incorrect seasonal timing, small magnitude, or short duration. By explicitly considering interannual variability and quantifying how regulated flows differ from natural using standard deviations, these metrics can inform management when the goal is to restore a natural flow regime.","PeriodicalId":21513,"journal":{"name":"River Research and Applications","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141926289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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