River Research and Applications

Journal: River Research and Applications

Abbreviation

River Res. Appl.

Publisher

Wiley

ISSN

1535-1459
1535-1467

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Publications 1 - 10 of 10

Systematic comparison of 1D and 2D hydrodynamic models for the assessment of hydropeaking alterations
Bürgler, Matthias; Vetsch, David F.; Boes, Robert; et al. (2023)
River Research and Applications
Numerical hydrodynamic models enable the simulation of hydraulic conditions under various scenarios and are thus suitable tools for hydropeaking related assessments. However, the choice of the necessary model complexity and the consequences of modelling choices are not trivial and only few guidelines exist. In this study, we systematically evaluate numerical one-dimensional (1D) and two-dimensional (2D) hydrodynamic models with varying spatial resolution regarding their suitability as input for hydropeaking-sensitive, ecologically relevant hydraulic parameters (ERHPs), and their computational efficiency. The considered ERHPs include the vertical dewatering velocity, the wetted area variation between base and peak flow and the bed shear stress as a proxy for macroinvertebrate drift. Furthermore, we quantified the habitat suitability of brown trout for different life stages. The evaluation is conducted for three channel planforms with morphological characteristics representative for regulated Alpine Rivers, ranging from alternating bars to a braiding river morphology. For the prediction of habitat suitability and bed shear stress, a 1D model appears to be always insufficient, and a highly resolved 2D model is suggested. Reducing the spatial resolution of 2D models leads to computational efficiency similar to 1D, while providing more accurate results. Thus, our results suggest, that while a highly resolved 1D model is sufficient for accurate predictions of the dewatering velocity and wetted area in the less complex alternating bar morphology, a 2D model is recommended for more complex wandering or braiding morphologies. This study can serve as guideline for researchers and practitioners in the selection and setup of hydrodynamic models for hydropeaking.
Innovations in hydropeaking research
Vanzo, Davide; Bejarano, María Dolores; Boavida, Isabel; et al. (2023)
River Research and Applications
Patchiness in flow refugia use by macroinvertebrates following an artificial flood pulse
Mathers, Kate L.; Robinson, Christopher T.; Weber, Christine (2022)
River Research and Applications
Flow refugia, locations that maintain substrate stability and low hydraulic stress during periods of high flow, can ensure riverine resilience in the face of increasing hydrological unpredictability. Despite their known importance, they have been overlooked in recent years with work on drought refugia currently seeing greater attention. Moreover, research on the role of flow refugia during artificial flood pulses in regulated rivers, where flood disturbances are no longer part of the hydrograph, is essentially absent. Here, we compared flow refugia for benthic macroinvertebrates among six habitats (main channel, side channel, riffle, margin, lentic including a floodplain pond, and inundated floodplain) within four different sites in response to an artificial flood pulse. We found that the grain-size distribution and macroinvertebrate community composition changed at each site following the flood. Macroinvertebrate assemblages became longitudinally homogeneous, but within-site beta diversity and taxa richness remained temporally stable following the flood pulse, suggesting the presence of flow refugia. In this respect, margin, inundated floodplain and lentic (a floodplain pond) habitats provided important flow refugia locations, particularly for the mobile mayfly Rhithrogena sp. In contrast, low substrate stability in riffle and side channels resulted in limited refugia potential for most taxa. Refuge use was however patchy with high levels of intra-habitat variability being evident for Rhithrogena sp. and the amphipod Gammarus fossarum in margin and side channel habitats. Further work is required to advance our knowledge of flow refugia in rivers with differing flow regimes to enable their integration into management and restoration schemes.
Ecological traits of Saliceae and the species replacing them on the active floodplain
Edwards, Peter (2024)
River Research and Applications
The dominant woody plants of active floodplains in the northern temperate zone are various species of Salix (willows) and Populus (poplars and cottonwoods) in the tribe Saliceae of the family Salicaceae. In this review, I consider the traits that enable these species to thrive in the dynamic floodplain environment and ask why they are now declining in the northern hemisphere, yet spreading rapidly in the southern hemisphere. I reach four main conclusions. First, floodplain Saliceae exhibit traits, notably huge numbers of minute, wind- and water-dispersed seeds and an exceptional capacity for vegetative propagation, that uniquely fit them for life on the active floodplain. Second, there are no functional equivalents to floodplain Salix and Populus in the southern hemisphere, which accounts for their remarkable success in invading riparian ecosystems. Third, the replacement of Saliceae by other species in the northern hemisphere has been caused mainly by changes in flow through dam construction, regulation and abstraction. The species that replace Saliceae vary according to site conditions: fertile sites in humid climates become occupied by various broadleaved trees (e.g., Acer negundo, Fraxinus pennsylvanica, Ailanthus altissima); nitrogen-fixing shrubs dominate in areas where nitrogen is limiting but phosphorus is adequate (Amorpha fruticosa, Robinia pseudoacacia, Elaeagnus angustifolia); sites in more arid regions are occupied by various Tamarix spp. The different ecological groups of woody species are associated with contrasting changes to the floodplain ecosystem.
Long-term reconstruction of energy fluxes in an alpine river: Effects of flow regulation and restoration
Consoli, Gabriele; Siebers, Andre R.; Bruder, Andreas; et al. (2023)
River Research and Applications
Flow regulation of montane and alpine headwater streams can fundamentally alter food web structure and energy flows through changes in productivity, resource availability, and community assembly. Dam flow-release schemes can be used to mitigate the environmental impacts of flow regulation via environmental flows, which can increase discharge variability and other ecologically important hydrological properties. In particular, managed floods can reintroduce disturbance to the system and stimulate the reactivation of physical habitat dynamics. However, how managed floods might restore ecosystem processes is virtually unknown. In this study, we examined patterns in potential energy fluxes before, during and after a long-term experimental flood program on the river Spöl, a regulated alpine River in southeast Switzerland. We used benthic samples collected during long-term monitoring and stable isotope analysis (δ13C and δ15N) of macroinvertebrates and their potential food sources to reconstruct secondary production, and potential energy fluxes, over a 20-year study period. The experimental floods did not alter the relative importance of basal resources but resulted in a considerable decline in secondary production, which remained low after the discontinuation of the floods. Our data suggest that a lack of recolonization by mosses following the discontinuation of the experimental flood program on the river Spöl may have driven patterns in energy fluxes by limiting macroinvertebrates using mosses for habitat. The effects of environmental flows on energy flows in this system thus depend on flood disturbance and the environmental context following the discontinuation of floods.
Monitoring invasive alien macroinvertebrate species with environmental DNA
Altermatt, Florian; Blackman, Rosetta C.; Brantschen, Jeanine; et al. (2022)
River Research and Applications
Regular monitoring of ecosystems can be used for the early detection of invasive alien species (IAS), and provide information for management and preventing them from becoming established or advancing into new areas. Current methods of monitoring freshwater systems for IAS can be both financially costly and time-consuming, with routine monitoring often carried out at low intensity and at only a small number of sites. In this study, we evaluate how environmental DNA (eDNA) metabarcoding for monitoring freshwater macroinvertebrate IAS compares to traditional kick-net sampling as part of a national (Switzerland) and a catchment monitoring programme. Kick-net sampling was more fruitful for the detection of several well-known target macroinvertebrate IAS. However, eDNA samples proved complementary for the detection of IAS that belong to species often being unnoticed by traditional sampling due to methodological or taxonomic reasons. Specifically, the invasive jellyfish Craspedacusta sowerbii, hardly detectable using classic kick-net sampling, was found to be widespread in both the national and the catchment-scale monitoring with the eDNA method only. Our study shows that IAS detection using eDNA is easily implemented in both national- and catchment-scale monitoring campaigns. However, successful detection of target IAS is still highly dependent on primer choice, species' biology, and availability of adequate markers. Specifically, multiple markers should be considered for detecting IAS from several different taxonomic groups, such as those under the 'freshwater macroinvertebrate' umbrella term. While eDNA is still developing in terms of these fundamental methodological requirements, surveillance for both target and non-target IAS using eDNA is likely to increase efficiency in early detection of IAS in freshwater systems.
Introducing HyPeak: An international network on hydropeaking research, practice, and policy
Alp, Maria; Batalla, Ramon J.; Bejarano, Maria D.; et al. (2023)
River Research and Applications
An increase in the demand for renewable energy is driving hydropower development and its integration with variable renewable energy sources. When hydropower is produced flexibly from hydropower plants, it causes rapid and frequent artificial flow fluctuations in rivers, a phenomenon known as hydropeaking. Hydropeaking and associated hydrological alterations cause multiple impacts on riverine habitats with cascading effects on ecosystem functioning and structure. Given the significance of its ecological and socio-economic implications, mitigation of hydropeaking requires an inter- and transdisciplinary approach. An interdisciplinary network called HyPeak has been conceived to enrich international research initiatives and support hydropower planning and policy. HyPeak has been founded based on exchange and networking activities linking scientists from several countries where hydropeaking has been widespread for decades and numerous studies dedicated to the topic have been carried out. HyPeak aims to integrate members from other countries and continents in which hydropower production plays a relevant role, and grow to be a reference group that provides expert advice on the topic to policy-makers, as well as researchers, stakeholders, and practitioners in the field of hydropeaking.
Ecological and biogeomorphological modelling of brown trout (Salmo trutta L.): Hints for improvements
Padoan, Francesca; Calvani, Giulio; De Cesare, Giovanni; et al. (2024)
River Research and Applications
The loss of biodiversity in freshwater environments is becoming an increasing problem globally. As a result, many tools have been developed and improved to reduce this decline. However, there is still a need for the identification and evaluation of precise restoration measures to improve habitats and preserve sentinel freshwater species, such as brown trout. This paper provides an up-to-date viewpoint about the life history, habitat characteristics, suitability conditions, and metapopulation dynamic modelling of brown trout, aiming to identify and discuss gaps and propose possible improvements based on collating and reinterpreting literature data. Results suggest that habitat suitability curves for environmental and hydraulic variables possess some degree of universality, for spawning habitat, fry, juvenile and adult trout. Further, an improved method to estimate the amount of suitable area by including the role of stream obstacles (i.e., macro-roughness with characteristic size in the order of the mean water depth) is proposed and discussed. This approach can be integrated into advanced metapopulation models and will allow experts to evaluate the best measures towards restoring and preserving freshwater riverine environments.
Equilibrium morphology and scour evolution at blunt nosed chevrons
Roy, Deep; Pagliara, Simone (2022)
River Research and Applications
Blunt nosed chevrons are low-head river restoration structures commonly used in large rivers to enhance the navigation and aquatic habitat. These structures usually create scour regions in their vicinity, which provides habitat for various aquatic organisms. Furthermore, the scour pools represent suitable locations for fish nursery. In some cases, the noses of islands are protected by constructing chevrons which reduce the intensity of erosive action. Only a few studies deal with the analysis of the scour phenomena due to chevrons. Therefore, this paper aims at investigating the scour evolution and characteristics at equilibrium due to chevrons inserted in both straight and curved channels. The most influential parameters governing the scour mechanisms (e.g., densimetric Froude number) were identified via dimensional analysis. Experimental evidence allowed us to distinguish and classify different scour morphology types for chevrons in curved channels: Types A(b), B-b and C-b were identified, corresponding to Types A, B and C in straight channels. Moreover, useful empirical relationships are provided to estimate the maximum scour hole depth and length, and the dune height with sufficient accuracy (R-2 ranging from 0.63 to 0.86). Finally, the equations are validated with the data from previous studies, showing a good predicting capacity.
Integrating two-dimensional water temperature simulations into a fish habitat model to improve hydro- and thermopeaking impact assessment
Antonetti, Manuel; Hoppler, Luca; Tonolla, Diego; et al. (2023)
River Research and Applications
Storage hydropower plants, which are an important component of energy production in Switzerland, can lead to hydro- and thermopeaking, affecting river habitats and organisms. In this study, we developed an approach for integrating water temperature simulations into a habitat model to assess the impact of both hydro- and thermopeaking on the availability of suitable fish habitats. We focused on the habitat requirements of juvenile brown trout (Salmo trutta) in a semi-natural braided floodplain along the Moesa River (Southern Switzerland) in early summer. First, we defined different scenarios (with and without hydropeaking) based on the local hydrological and meteorological conditions. Second, we used a two-dimensional depth-averaged hydro- and thermodynamic model to simulate the spatial distributions of water depth, flow velocity, and water temperature. Third, we applied generalized preference curves for juvenile brown trout to identify hydraulically suitable habitats, and developed a new index to assess the availability of thermally suitable habitats. Finally, we quantified the extent to which hydraulically and thermally suitable habitats overlap in space and time. During both base and peak flow phases, most of the hydraulically and thermally suitable habitats are located in the side channels. High flow conditions combined with strong cold-thermopeaking lead to a higher thermal heterogeneity. However, disconnected habitats originate in the dewatering zone, increasing the risk of stranding as well as thermal stress. By helping to better understand the effects of thermopeaking on the availability of fish habitats, our approach could contribute to the design and evaluation of ecological restoration in hydropeaking rivers.

Publications 1 - 10 of 10

Journal: River Research and Applications

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