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1. Understanding rivers and their social relations: A critical step to advance environmental water management

   https://doi.org/10.1002/wat2.1381  

   Anderson, Elizabeth P. ; Jackson, Sue ; Tharme, Rebecca E. ; Douglas, Michael ; Flotemersch, Joseph E. ; Zwarteveen, Margreet ; Lokgariwar, Chicu ; Montoya, Mariana ; Wali, Alaka ; Tipa, Gail T. ; et al ( September 2019 , WIREs Water)

   River flows connect people, places, and other forms of life, inspiring and sustaining diverse cultural beliefs, values, and ways of life. The concept of environmental flows provides a framework for improving understanding of relationships between river flows and people, and for supporting those that are mutually beneficial. Nevertheless, most approaches to determining environmental flows remain grounded in the biophysical sciences. The newly revised Brisbane Declaration and Global Action Agenda on Environmental Flows (2018) represents a new phase in environmental flow science and an opportunity to better consider the co‐constitution of river flows, ecosystems, and society, and to more explicitly incorporate these relationships into river management. We synthesize understanding of relationships between people and rivers as conceived under the renewed definition of environmental flows. We present case studies from Honduras, India, Canada, New Zealand, and Australia that illustrate multidisciplinary, collaborative efforts where recognizing and meeting diverse flow needs of human populations was central to establishing environmental flow recommendations. We also review a small body of literature to highlight examples of the diversity and interdependencies of human‐flow relationships—such as the linkages between river flow and human well‐being, spiritual needs, cultural identity, and sense of place—that are typically overlooked when environmental flows are assessed and negotiated. Finally, we call for scientists and water managers to recognize the diversity of ways of knowing, relating to, and utilizing rivers, and to place this recognition at the center of future environmental flow assessments.

   This article is categorized under:

   Water and Life > Conservation, Management, and Awareness

   Human Water > Water Governance

   Human Water > Water as Imagined and Represented

    

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2. Riverine macrophytes control seasonal nutrient uptake via both physical and biological pathways

   https://doi.org/10.1111/fwb.13412  

   Riis, Tenna ; Tank, Jennifer L. ; Reisinger, Alexander J. ; Aubenau, Antoine ; Roche, Kevin R. ; Levi, Peter S. ; Baattrup‐Pedersen, Annette ; Alnoee, Anette B. ; Bolster, Diogo ( October 2019 , Freshwater Biology)

   In low‐gradient, macrophyte‐rich rivers, we expect that the significant change in macrophyte biomass among seasons will strongly influence both biological activity and hydraulic conditions resulting in significant effects on nutrient dynamics. Understanding seasonal variation will improve modelling of nutrient transport in river networks, including annual estimations of export, which could optimise decision‐making and management outcomes.

   We explored the relationships among seasonal differences in reach‐scale nutrient uptake, macrophyte abundance, solute transport and transient storage in the River Gudenå (Denmark), a large macrophyte‐rich river. We used the minimal pulse addition technique to measure uptake of ammonium, nitrate, soluble reactive phosphorus, as well as reach‐scale metabolism, and surface transient storage in spring, summer, and autumn.

   We found that riverine uptake changed among seasons and was linked to macrophyte biomass via both biological activity, reflected in reach‐scale metabolism, and through physical processes, as solute transport was influenced by longitudinal dispersion. In this macrophyte‐rich river, seasonal changes in macrophyte biomass affected contact time between the water and biota, which influenced ammonium and soluble reactive phosphorus uptake. Using stoichiometric scaling of reach‐scale metabolism, we found that seasonal variation also influenced the relative contributions of autotrophic and heterotrophic biota in assimilatory uptake.

   In summary, riverine nutrient uptake was not static, highlighting the importance of seasonality, with significant implications for modelling of nutrient export in river networks. Moreover, current management strategies that remove macrophyte biomass (i.e. weed cutting and dredging) will short‐circuit the positive effects of enhanced nutrient uptake resulting from abundant macrophytes in rivers.

    

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3. Classifying flow regimes of the Amazon basin

   https://doi.org/10.1002/aqc.3582  

   Siddiqui, Sharmin F. ; Zapata‐Rios, Xavier ; Torres‐Paguay, Sandra ; Encalada, Andrea C. ; Anderson, Elizabeth P. ; Allaire, Mark ; da Costa Doria, Carolina Rodrigues ; Kaplan, David A. ( April 2021 , Aquatic Conservation: Marine and Freshwater Ecosystems)

   The Amazon River basin contains a vast diversity of lotic habitats and accompanying hydrological regimes. Further understanding the spatial distribution of flow regimes across the Amazon can be useful for recognizing riverine ecohydrological processes and informing river management and conservation, especially in areas with limited or inconsistent streamflow monitoring.

   This study compares four inductive approaches for classifying streamflow regimes across the Amazon using an unprecedented compilation of streamflow records from Bolivia, Brazil, Colombia, Ecuador, and Peru.

   Inductive classification schemes use attributes of streamflow data to categorize river reaches into similar classes, which then may be generalized to understand streamflow behaviour at the basin scale. In this study, classification was accomplished through hierarchical clustering of 67 flow metrics calculated using indicators of hydrologic alteration (IHA) and daily streamflow data from median annual hydrographs (MAHs) for 404 stations (representing >7,000 station‐years) across five Amazonian countries.

   Classification was performed using both flow magnitude‐inclusive and flow magnitude‐independent datasets. For flow magnitude‐independent methods, optimal solutions included six or seven primary hydrological classes for IHA and MAH datasets; for approaches that retained magnitude, variance was sufficiently large to prevent convergence to a specific number of classes.

   Across methods, class membership was strongly associated with the timing, frequency, and rate of change of flow, and spatially coherent clusters were associated with seasonal, elevational, and stream‐order gradients. These results highlight the diversity of flow regimes across the Amazon and provide a framework for studying relationships between hydrological regimes and ecological responses in the context of changing climate, land use, and human‐induced hydrological alteration.

   The methodology applied provides a data‐driven approach for classifying flow regimes based on observed data. When coupled with ecological knowledge and expertise, these classifications can be used to develop ecohydrologically informed and management‐relevant conservation practices.

    

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4. Can environmental flows moderate riparian invasions? The influence of seedling morphology and density on scour losses in experimental floods

   https://doi.org/10.1111/fwb.13235  

   Kui, Li ; Stella, John C. ; Diehl, Rebecca M. ; Wilcox, Andrew C. ; Lightbody, Anne ; Sklar, Leonard S. ( December 2018 , Freshwater Biology)

   Environmental flow releases are an effective tool to meet multiple management objectives, including maintaining river conveyance, restoring naturally functioning riparian plant communities, and controlling invasive species. In this context, predicting plant mortality during floods remains a key area of uncertainty for both river managers and ecologists, particularly with respect to how flood hydraulics and sediment dynamics interact with the plants’ own traits to influence their vulnerability to scour and burial.

   To understand these processes better, we conducted flume experiments to quantify different plant species’ vulnerability to flooding across a range of plant sizes, patch densities, and sediment condition (equilibrium transport versus sediment deficit), using sand‐bed rivers in the U.S. southwest as our reference system. We ran 10 experimental floods in a 0.6 m wide flume using live seedlings of cottonwood and tamarisk, which have contrasting morphologies.

   Sediment supply, plant morphology, and patch composition all had significant impacts on plant vulnerability during floods. Floods under sediment deficit conditions, which typically occur downstream of dams, resulted in bed degradation and a 35% greater risk of plant loss compared to equilibrium sediment conditions. Plants in sparse patches dislodged five times more frequently than in dense patches. Tamarisk plants and patches had greater frontal area, larger basal diameter, longer roots, and lower crown position compared to cottonwood across all seedling heights. These traits were associated with a 75% reduction in tamarisk seedlings’ vulnerability to scour compared to cottonwood.

   Synthesis and applications. Tamarisk's greater survivability helps to explain its vigorous establishment and persistence on regulated rivers where flood magnitudes have been reduced. Furthermore, its documented influence on hydraulics, sediment deposition, and scour patterns in flumes is amplified at larger scales in strongly altered river channels where it has broadly invaded. Efforts to remove riparian vegetation using flow releases to maintain open floodways and/or control the spread of non‐native species will need to consider the target plants’ size, density, and species‐specific traits, in addition to the balance of sediment transport capacity and supply in the river system.

    

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5. MetaIPM: Placing integral projection models into a metapopulation framework

   https://doi.org/10.1111/2041-210X.14156  

   Erickson, Richard A. ; Peirce, James P. ; Sandland, Greg J. ; Thompson, Hannah M. ; Coulter, Alison A. ; Glover, David C. ( June 2023 , Methods in Ecology and Evolution)

   Metapopulation models include spatial population dynamics such as dispersion and migration between subpopulations. Integral projection models (IPMs) can include demographic rates as a function of size. Traditionally, metapopulation models do not included detailed populaiton models such as IPMs. In some situations, both local population dynamics (e.g. size‐based survival) and spatial dynamics are important.

   We present a Python package,MetaIPM, which places IPMs into a metapopulation framework, and allow users to readily construct and apply these models that combine local population dynamics within a metapopulation framework.

   MetaIPMincludes an IPM for each subpopulation that is connected to other subpopulations via a metapopulation movement model. These movements can include dispersion, migration or other patterns. The IPM can include for size‐specific demographic rates (e.g. survival, recruitment) as well as management actions, such as length‐based harvest (e.g. gear specific capture sizes, varying slot limits across political boundaries). The model also allows for changes in metapopulation connectivity between locations, such as a fish passage ladders to enhance movement or deterrents to reduce movement. Thus, resource managers can useMetaIPMto compare different management actions such as the harvest gear type (which can be length‐specific) and harvest locations.

   We demonstrate howMetaIPMmay be applied to inform managers seeking to limit the spread of an invasive species in a system with important metapopulation dynamics. Specifically, we compared removal lengths (all length fish versus longer fish only) for an invasive fish population in a fragmented, inland river system.MetaIPMallowed users to compare the importance of harvesting source populations away from the invasion front, as well as species at the invasion front. The model would also allow for future comparisons of different deterrent placement locations in the system.

   Moving beyond our example system, we describe howMetaIPMcan be applied to other species, systems and management approaches. TheMetaIPMpackages includes Jupyter Notebooks documenting the package as well as a second set of JupyterNotebooks showing the application of the package to our example system.

    

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