Tuesday 2nd of july – 8:30
08:30
Macrophytes can improve the ecological assessment of rivers in a multi-pressure context: a new diagnostic tool.
AUTHORS
LEBOUCHER Thibault, BACON Jérémy, CHAUVIN Christian, BILLOIR Elise, PIERRE Maud, FULCRAND Augustine, BOURILLON Bastien, USSEGLIO-POLATERA Philippe
France
Short Abstract: Despite the initial objectives of good ecological status set by the WFD for 2015, 60% of water bodies still fail to achieve this status. One of the main reasons for this is the difficulty of accurately identifying the actual causes of degradation of water bodies, especially in a context of multi-pressures. Recently developed diagnostic tools aim at disentangling the effects of these co-occurring anthropogenic pressures on rivers. They are based on the analysis of combinations of taxa and adaptations selected within communities, under the constraint of different categories of pressure impacting water quality and/or habitat integrity. Macrophytes, considered to be good indicators of the ecological status of rivers, can be used to develop this type of tool. On the basis of 518 metrics exploring biological traits, ecological preferences and the taxonomic and functional structure of macrophyte assemblages, 20 high-performance models were developed to assess the specific risks of significant degradation of rivers. The results of the models were explored at various spatial and temporal scales to better identify the causes of the degradation of river reaches. An original grid for interpreting the results, based on several performance metrics, should enable managers to better determine the restoration actions to be undertaken to improve the ecological status of rivers.
08:50
Historical and future patterns of streamflow intermittence in Europe
AUTHORS
ABBASI Mahdi, MESSAGER Mathis Loïc, DÖLL Petra
France
Short Abstract: Even in wet climates, small streams can seasonally dry up. In drier regions, large rivers may lack flow for extended periods. Climate change is expected to exacerbate these drying patterns, making streamflow intermittence—a critical factor for ecosystems and water supply—more widespread. However, its temporal and spatial dynamics remain poorly understood. Here, we combined a global hydrological model, streamflow observations from 3706 gauging stations, and machine learning to estimate historical and future patterns of streamflow intermittence in Europe across over 1.5 million river segments. For 1981–2019, we found that 17% of segments experienced at least one day without flow. Future projections, based on five climate models and two scenarios (RCP2.6 and RCP8.5), indicate an increase in non-perennial months under both scenarios, with 4.9% of all reach-months expected to experience no-flow days by the 2080s under RCP8.5, up from 3.6% in 1985–2014. While areas with reduced precipitation are most affected, even regions with increased rainfall may see shifts from perennial to non-perennial reaches (2.7% under RCP8.5). Mitigating greenhouse gas emissions under RCP2.6 could largely limit these effects, though seasonal increases in intermittence, particularly in late summer, may persist. This study provides a groundbreaking understanding of streamflow intermittence dynamics at a continental scale, offering critical insights for managing freshwater ecosystems under changing climate conditions.
09:10
Rivers flow through cities : how are river landscapes changing on a global scale ?
AUTHORS
BOURGEAU Fanny, BELLETTI Barbara, VAUDOR Lise, DUNESME Samuel, PIÉGAY Hervé
France
On a global scale, in a context of generalized urbanization, most rivers now flow through urban areas (Paul et Meyer, 2008), placing considerable pressure on river systems and, ultimately, significantly altering the landscapes of corridors and floodplains. How are riverscapes changing near major cities? Although the phenomenon of urbanization has undergone profound changes worldwide since the 20th century, its overall impact on river systems is not well known. Through the prism of the global scale, this study aims to (i) describe, (ii) quantify and (iii) compare these changes. We seek to test the hypothesis that characteristics specific to urban and river systems control landscape change. Using an existing database showing changes in water surface area, this study analyzes the role of urbanization in modifying the river patterns in the vicinity of 300 urban areas worldwide.
09:30
Large-scale automation of hydromorphological metrics from LiDAR data
AUTHORS
RÉTAT Alexandre, THOMMERET Nathalie, GOB Frédéric, LESPEZ Laurent, BAILLY Jean-Stéphane, KREUTZENBERGER Karl, DEPRET Thomas
France
Short Abstract: The collection of hydromorphological data, mainly including bed geometry, characterization of riparian vegetation and sediment size, is a key factor in understanding the hydromorphological functioning of watercourses and meeting public policy objectives in terms of monitoring and restoring watercourse quality. In particular, these data can be used to diagnose the deterioration of a watercourse or to assess the consequences of an ecological restoration action. The challenge of this work is based on a double observation and an opportunity: on the one hand, a growing need for hydromorphological characterization data on French rivers and the logistical impossibility of applying field methods on very large scales, and on the other hand, the availability of high-definition data covering the whole of France. The aim of this work is to develop automated methods for measuring and characterizing hydromorphology using LiDAR data throughout France, in order to complete a vast database currently made up of field measurements (Carhyce). These methods and new data will also enable us to envisage a change in the scale of analysis: from station to the entire hydrographic line.
09:50
Building and nurturing overlapping communities of practice with the Riverscapes Consortium
AUTHORS
WHEATON Joseph, PIEGAY Herve, BELLETTI Barbara
United-states
Short Abstract: The Riverscapes Consortium (https://riverscapes.net) was formed as a collaboration between researchers, practitioners and policymakers who came together around the shared vision of “healthy riverscapes for all”. The premise behind the Riverscapes Consortium was that the challenges people face in threats to their riverscapes and adopting the nature-based solutions to building more resilient and healthy riverscape transcend the diversity of riverscapes that dissect the planet and the myriad of cultures, political boundaries, and physiographic settings. Yet, many people feel they are facing these challenges alone, or have to reinvent or struggle to find viable solutions without the insights and perspectives of others experiencing similar challenges elsewhere. Through a series of innovations, specification of standards of practice, adoption of data sharing standards, distillation of science, and improving communication – we have started to build an international consortium of people who come together to freely share, contribute, exchange knowledge, experience and connect to larger communities they may not have the benefit or ease of connecting with. In this presentation, we provide an overview of the applications, the community platform and a peak at the impacts starting to emerge in the self-formed communities that are engaging. Our aim in this presentation is to inform, invite and empower all that are interested to join and shape and grow the Riverscapes Consortium in ways that serve them and others, while amplifying the pace and efficacy of efforts to promote and sustain riverscape health.