Wednesday 2nd of july – from 10:30 to 19:00
Session D3 : River health and pollution
Assessing pressures on an anthropized river: the case of the Sorgue
HÉRITIER Coline, PRED’HOMME Margaux, BROUILLAUD Nathan, SANTOS Raphaël, HONEGGER Anne, CHIU Victoria, PARAN Frédéric, TENTORINI Christel, RHODET Laurent, PUDU Marjolaine
France
Short abstract : Water pollution and scarcity have become a major issue over the last twenty years, posing both a public health problem and a threat to ecosystems (IFPEN | Gestion du cycle de l’eau et changement climatique, 2024). Water is a precious resource linking ecosystems (biotopes and biocenoses) and socio-systems (humans), and it is necessary for everyone in terms of ecosystem functions and services: biological life, food, hydration, agricultural crops, places for relaxation, leisure, cooling zones…). Faced with the challenges of climate change and the need to preserve this resource, it seems important to identify, quantify and monitor the various pressures it is subject to, particularly in rivers, in interaction with their immediate environment. This is the case for the Sorgue river, which will be studied from different angles – hydrology, eco-toxicology, social geography and water law – in order to link them up and identify the key levers that can change its use and encourage its protection, by developing an interdisciplinary problem within the framework of this cluster.
Smart Laboratory on Clean Rivers- An Approach to Small River Rejuvenation in India
SINGH Nikhilesh, GAUR Shishir, OHRI Anurag, JOSHI Dheeraj
India
Short abstract : Climate change and anthropogenic stress have severely affected ecosystems and water bodies and exploited natural resources all over the globe and India is not any exceptions. To counter all these issues associated with the rivers a holistic river rejuvenation plan is needed that tests, innovates and implements sustainable solutions in the river space for sustainable river management. Smart Laboratory for Clean Rivers (SLCR) an Indo-Danish collaboration project, provides a living lab setup that brings all the stakeholders together to engage, learn, co-create and experiment for a clean and sustainable river that lasts for ages. SLCR has opted for a small catchment of the Varuna River for piloting, located in the Middle Ganga Basin in India. Considering the integrated approach of river rejuvenation, SLCR embraces various techniques and upgrades for rejuvenation, likely to maintaining clear perineal flow, thriving biodiversity, connecting community to the river and embrace the symbiotic relation. In its completion, SLCR with provide a restoration manual for small rivers, which will strategize the detailed plan and way of implementation for stakeholders and local administrations to keep our rivers clean and sustainable.
Challenges in managing water quality and ecological status between rural and urban pressures.
PRED’HOMME Margaux, DOPIERALA Romain, FORET Arnaud, RIVIER Clélia
France
Short abstract : Freshwater systems, face significant challenges in peri-urban areas due to competing pressures. This study investigates the Yzeron watershed France, integrating ecological, spatial, and regulatory analyses to assess its water quality and the drivers of change. Using long-term monitoring data, the research examines land-use changes, regulatory impacts, and pollution sources from 1993 to 2024. Despite advancements in water management policies and localized restoration efforts, the ecological status remains poor, hindered by inconsistent data, inadequate monitoring of emerging pollutants, and limited intersectoral coordination. The study emphasizes the need for integrated governance, enhanced monitoring, and innovative policies to address complex water management challenges in peri-urban environments.
Flood vulnerability in relation to land use change in the floodplain of a peri urban river, the case of the Yzeron, France
JOET Océane, GEORGE Clément, ESTIENNE Louis, HÉRITIER Coline, SONAGNON Donald, BABIN Lucas
France
Short abstract : This study quantifies land use changes in the Yzeron floodplain and their impact on flood vulnerability and flood risk management policies from the 19th to the 20th century. The Yzeron catchment, located in the west of Lyon, has undergone significant urban expansion since the mid-20th century. The analysis highlights a direct correlation between urban expansion and the increase in flood damage, underlining that increased vulnerability has probably played a more decisive role than hazard in the increase in flood risk. Furthermore, the evolution of flood risk management policies, from reactive measures to more structured frameworks such as French Flood Risk Prevention Plans and Local Urban Plans (PPRi and PLU), reflects a growing awareness but also persistent challenges in reconciling urban development and risk prevention. Despite the progress made, historical flood data and associated damage, hazard mapping and the need for dynamic hydrological modelling remain key areas for improvement. This research offers an approach never explored before on the Yzeron, questioning the dynamics of land use in the floodplain to explain risk, before hazard, and providing a reflection on how to reconcile urban development and flood risk reduction in the floodplain.
Impact of aquaculture farming on water quality in the lower Saône
WISSEL Björn, QUIÑONES-RIVERA Zoraida
France
Short abstract : Within the Rhône-Mediterranean Basin, the lower Saône is characterized by some of the poorest water quality due to upstream contaminants that are often associated with industry and agriculture. To assess the additional potential impact of France’s largest inland fisheries (la Dombes) on the lower Saône, water samples were collected bi-weekly (April 2023 to July 2024) upstream (Chalon-sur-Saône and Mâcon) and downstream (Lyon) of the two main tributaries (Veyle and Chalaronne) that are connecting la Dombes to the river. Samples were analyzed for dissolved C, N and P as well as particulate C and N concentrations and stable isotopes. With up to 10-fold higher concentrations, the tributaries were significant sources of dissolved nutrients and organic matter. Yet, due the relatively low discharge of the tributaries no clear effects were identified on downstream water quality. Nevertheless, the impact could be more visible during times of low discharge of the Saône, in combination with artificially high discharge and nutrient concentrations of the tributaries when ponds are drained during the fish harvest in fall and winter. Stable isotope analyses will be employed to quantify the relative impact of aquaculture on water quality in the lower Saône. Ultimately, this project will help to 1) identify environmental controls of current water quality in the lower Saône (e.g., nutrient sources / tributaries, hydrology, temperature) and 2) forecast future impacts based on climate change scenarios (temperature, precipitation, hydrology, land use).
Clean sensors, happy data: Field test of low-tech wiper designs for optical sensors and river applications
F. S. GISI Maria, NAVRATIL Oldrich, CHERQUI Frédéric, JAMES Robert, RUSSELL Kathryn, FLETCHER Tim
France
Short abstract : Biofouling significantly impacts the accuracy and long-term functionality of optical sensors used to monitor natural water bodies. This study investigates the effects of biofouling on the measurement accuracy and precision in six low-cost turbidity sensors over the period of 11 weeks. The sensor output was monitored biweekly using fixed turbidity bentonite solutions (0 and 1000 NTU), while biofouling development was quantified through image analysis and data trends. Results show that biofouling progressively reduces sensor accuracy, with significant effects after prolonged exposure. To address this, an adaptable, open-source and affordable mechanical wiper was developed and tested, offering a practical solution to mitigate biofouling. The wiper’s design is versatile and can be applied to other optical sensors, expanding its utility beyond turbidity monitoring. These findings emphasize the viability of low-cost sensors for short-term use and highlight the importance of integrated mitigation strategies for extended deployments. This research provides valuable insights into enhancing sensor performance in natural water monitoring applications.
Fluocopée® probe deployment in the Seine river (France): towards high-frequency in situ monitoring of aquatic environments using fluorescence spectrometry
RAOULT Antoine, GOFFIN Angélique, RAYMOND Vivien, DESBOURDES Flavien, SHAHVAR Anicée, PAIN-LE-QUERE Camille, YILMAZ Metehan, BOURREAU Johanna, DOMINATI Moreno, KRIMOU Rania, MOUGIN Jérémy, GUERIN-RECHDAOUI Sabrina, ROCHER Vincent, VARRAULT Gilles
France
Short abstract : Over the past two decades, there has been a notable advancement in the development of high-frequency measuring equipment for the monitoring of biophysical and chemical parameters in surface water. The joint development of the Fluocopée® probe by LEESU and SIAAP represents a further contribution to this dynamic. This innovative fluorescence probe is capable of monitoring temporal evolution of 25 fluorophores in situ at high frequency, thereby enabling the characterization of dissolved organic matter (DOM). The extensive range of fluorophores monitored by the Fluocopée® probe facilitates the monitoring of water quality and the investigation of the biogeochemical processes linked to DOM in aquatic environments. Furthermore, its sensitivity is compatible with the levels of OM concentration observed in continental aquatic environments.
Since October 2023, several instances of this probe have been implemented on the Seine and two of its primary tributaries (the Marne and the Oise), distributed across six sites situated upstream and downstream of the Paris conurbation. This provides a valuable opportunity to enhance our comprehension of the biogeochemical dynamics of the Seine and to discern the pressures it is subjected to in relation to the OM. The objective of this presentation is to present the scientific findings derived from the data collected by this network of sensors since the end of 2023. Additionally, it will provide a detailed account of the methodology employed to process these data sets, from the initial acquisition of raw data to its subsequent validation.
Bridging the knowledge transfer gap on aquatic pollutants
FOURNIER Maïté, BERGE Manon, STROSSER Pierre
France
Short abstract : The TransNet project aims to optimize the transfer towards policymakers and practitioners of knowledge produced by 18 research teams of the Aquatic Pollutants Call. A mapping of stakeholders was first conducted to identify key organizations and understand their roles. Then, a series of interviews and collaborative workshops helped identify their specific knowledge needs regarding emerging pollutants, antimicrobial resistance, and aquatic pathogens. TransNet subsequently evaluated the results of the 18 projects to assess their relevance to the close the knowledge gap and to highlight remaining gaps that should be addressed in future work. Innovative tools were developed, including podcasts, an educational game, a technologies factsheet, and an interactive tool called TransNet Viewer to explore the results. The main steps of the project involved analyzing needs, identifying knowledge gaps, and designing tools tailored to improve knowledge transfer.
This project highlights the importance of a structured approach to make research more impactful by bridging the gap between researchers and end-users of knowledge.
Session D4 : Connectivity and habitat – 1
Variability of temperature variations induced by hydropeaking and associated ecological impacts: bibliographical review and typology of potential alterations according to development schemes
GOURAUD Véronique, BARILLIER Agnès, BARAN Philippe
France
Short abstract : The rapid flow variations induced downstream of hydropower plants by the release of turbined water can be associated with temperature variations. Given the multiplicity of plant configurations and the diversity of structure characteristics, these temperature variations linked to hydropeaking are potentially highly variable from one site to another. The aim of our work was therefore firstly to review the state of the art of thermal alterations linked to hydropeaking and their impact on biological communities. Secondly, using our knowledge of the characteristics of the French hydropower fleet and representative case studies, we sought to define the different types of alteration possible, depending on the characteristics of the facilities. For most facilities, warming in winter and cooling in summer are generally observed, with widely varying amplitudes.. The most likely impacts on organisms are those linked to temperature gradients and the frequency of events. Changes in temperature regimes induced by hydropeaking are highly dependent on site configuration. Nevertheless, whatever the type of configuration, the temperature deviations induced are not systematic and concern a limited number of hydropeaking events. These results highlight the need to acquire knowledge about the effects of high temperature gradients on the physiology and behavior of individuals, and their indirect impacts at population or community level.
Hydropeaking and oviposition habitat availability of mayfly in a large river: towards new evaluation of aquatic organism vulnerability to dewatering
JAULIN Emmanuel, CAPRA Hervé, PELLA Hervé, RODIER Julien, ALP Maria
France
Short abstract : Hydropeaking strongly changes the hydraulic conditions of the river, leading to a (sub)-daily variation of flow velocity and water level. The response of stream insects to these variations has been mainly evaluated for the larval stage and less for the adult and egg life stages. For taxa with high selective oviposition behaviour, such as mayflies of the genus Baetis, these artificial variations may induce a recruitment failure and bottleneck on the population size by a short supply of oviposition habitat and egg mortality by dewatering them. This study aims to determine, over a 38 km sector of the lower Ain river, 1) the quantity of oviposition habitat available for these mayflies versus the discharge and 2) the quantity of favourable habitat dewatered during a sudden drop in discharge. The available habitat was quantified using hydraulic simulations of a two-dimensional model calibrated and validated over an entire sector (1.9 million meshes). The potential oviposition habitat represented up to 6.6 % of the wetted area at 30 m3.s-1 before gradually decreasing to less than 1 % after 165 m3.s-1. The two most frequent decreases of discharge due to hydropeaking observed in the lower Ain river (2012-2022) could cause the dewatering of more than 85 % of the oviposition habitat available at peak flow. These results raise the question of the relevance of assessing the quantity of oviposition habitat useful to the mayfly population in a regulated river to determine its sensitivity to hydropeaking, and in particular to dewatering.
Which sediment management scenario for the Geneva Rhône and the Upper Rhône in France?
PINET Laurent, DIOUF Seydina, LECOMTE Estelle, AESCHLIMANN Candy, DE LA RIVIÈRE Caroline
Switzerland
Short abstract : The Arve River transports approximately 700,000 m³ of suspended sediments (SS) annually, with a significant portion accumulating in the Verbois reservoir, where the average annual infilling is estimated at 360,000 m³. Additionally, at Génissiat, the volume of sediments accumulated outside flushing periods ranges from 50,000 to 150,000 m³ per year. Excessive sedimentation in the Verbois reservoir could lead to raised water levels, increasing the risk of flooding in certain districts of Geneva. Similarly, at Génissiat, significant sediment deposits near the upstream face and flood discharge structures could jeopardize the stability of the dam. Since 1945, sediment transfer downstream of Geneva’s hydroelectric plants has been managed through complete or partial flushing operations, organized every three to four years by the Services Industriels de Genève (SIG), operators of the Verbois dam. These operations, coordinated with the Société des Forces Motrices de Chancy-Pougny (SFMCP) and the Compagnie Nationale du Rhône (CNR), have evolved to mitigate ecological impacts. The last three campaigns (2016, 2021, and 2025), conducted under a ten-year authorization (2016–2026), successfully reduced environmental impacts by adjusting SS levels, representing a significant improvement compared to the complete flushing operations carried out until 2012. A new management approach must be proposed for the next decade (post 2026).
Effects of sediment management of the Chambon dam on the movement behaviour of brown trout (Salmo trutta) in the Romanche River (Isère, F).
POLBLANC Antoine, CATTANÉO Franck, BERTIER Christine, CAPRA Hervé
Switzerland
Short abstract : To maintain the efficiency of the production chain at the St-Guillerme plant (Romanche) while ensuring the safety of the facilities, the quantity of fine sediment stored in the reservoirs has been managed. Over the period 2019-2022, several flushing operations (short-term events with potentially high turbidity) per year and one dragging operation (long-term event with moderate turbidity) have been carried out. During three-year, radiotelemetry was used to monitor the mobility of 97 adult brown trout (Salmo trutta) downstream of the dam in order to assess the consequences of sediment management events and natural hydrological events. Two radiotelemetry protocols were used. A “complete” protocol (positioning every two weeks) and an “hourly” protocol (positioning a few selected individuals hourly over the course of a day) allowed to link the individual movement observed with the Suspended Sediment Concentrations (SSC) and hydrology. Preliminary analyses suggest moderate trout mobility on this river. Suspended sediments, whether anthropogenic or natural in origin, appear to have little impact on trout mobility, whatever the radio positioning time step. However, natural hydrological factors, particularly floods, seem to have a greater effect on mobility.
Hydropeaking effects on habitat dynamics at patch-scale: implications for aquatic invertebrates
BÄTZ Nico, FRIESE Nathalie, WEBER Christine
Switzerland
Short abstract : Hydropeaking, characterized by abrupt and sub-daily flow fluctuations, disrupts river ecosystems by causing rapid shifts in habitat conditions. Aquatic invertebrates are particularly sensitive to such changes in habitat dynamics. Here we focus on disturbance occurring at the scale of individual habitat patches. We first review five key impacts of hydropeaking disturbance affecting invertebrate habitats at the patch scale (size <1m): i) increases in hydraulic forces; ii) reduction in persistent wetting; iii) alteration of the sediment dynamics; iv) reduction of the organic matter retention; and v) increase in temperature fluctuations. To demonstrate that impacts of hydropeaking vary at the patch scale, we tested with a portable flume how increases in hydraulic forces affect patch-specific invertebrate drift. We demonstrate that habitats with slow current experience higher invertebrate drift rates compared to habitats with fast current. Finally, we evaluate the potential of small-scale structural-morphological measures, such as boulder clusters, deadwood accumulations, and lateral shelters, to mitigate hydropeaking impacts. Our findings underscore the critical role of patch-scale processes in modulating hydropeaking impacts on invertebrate communities. They also underscore the need for a patch-scale management approach that allows for a more spatially explicit consideration of the habitat characteristics and their associated dynamics.
Removing small dams: and now, what do I do with the sediment?
ROVIRA Albert, BARDINA Mònica, GARCIA Evelyn, BUENDIA Cristina, MUNNÉ Antoni
Spain
Short abstract : Four case studies are presented here to illustrate different sediment management approaches carried out in the Catalan basin district, NE Spain, during the demolition of small dams. The Bojons dam was dismantled in a single phase. Prior to its demolition and as a preventive measure, 15% of the total volume of sand accumulated into the reservoir was removed. Even so, a massive mobilization of material occurred with a temporary impact on a 600-m river reach. At the Ritort dam, between 60% and 70% of the sediment retained was mechanically extracted during the overthrow works. After the demolition, it was determined that this preventive measure was unnecessary, as the river ecosystem downstream remained unaffected. The demolition of the Sant Salvador small dam is being carried out in two phases, each involving partial sand removal through mechanical methods. The sediment extracted during the first phase was relocated to different sections of the river channel where it is expected to be mobilised during floods. The Sentmenat dam is fully filled. Given its magnitude, the response of both the sedimentary package and the riverbed to different demolition scenarios has been modelled to select the best alternative.
Evaluation of the efficiency and use of a unique fishway in Belgium
GELDER Justine, OVIDIO Michaël
Belgium
Short abstract : The installation of fishways is the most common method to restore connectivity and it is essential to assess the performance and effectiveness of these devices. We evaluated the passage efficiency and the use of a fishway installed in 2021 downstream of the Coo waterfall in Belgium. We double-marked 38 individuals (RFID tag and radio transmitter) belonging to three species upstream and released them downstream of the waterfall. A total of 5 antennae were placed around the site, enabling automatic detections. The results show a low attractiveness of the fishway (overall attraction rate < 25%) with a total efficiency of 7.9% (adjusted efficiency 50-60%). However, capture cage monitoring carried out over three consecutive years showed that the fishway was used by a wide variety of species, with 2.328 individuals captured from 19 different species, for a total of 33.7 kg of biomass. The dominant species in terms of biomass and abundance were rheophilic species. The results also showed continuous use of the fishway throughout the year for some species and at specific times for others. The combination of the study of the use and the efficiency of the fishway makes it possible to highlight the ecological added value of opening up a migratory axis, as well as highlighting any weaknesses in terms of the use of the fishway.
Linking Flow Intensity and River Morphology with Refugia Availability
HISCHIER Chantal Mariette, BÄTZ Nico, WEBER Christine
Switzerland
Short abstract : Rivers host an enormous biodiversity and are among the most threatened ecosystems in the world. Many rivers have been channelised, leading to reduced biodiversity and habitat heterogeneity. Refugia are persistent or temporary habitats that mitigate disturbance effects on organisms. Despite their important function for river ecosystem resilience, refugia have been poorly investigated and often neglected in practical management. By comparing near-natural, channelised and restored reaches of eleven rivers in Northern Switzerland, this study investigates how flow intensity and river morphology influence habitat heterogeneity and refugia availability for riverine organisms. The gained observational data will be combined with hydraulic modelling to simulate different flow intensities. The results will provide evidence-based guidance for identification, maintenance and restoration of refugia, which will become even more relevant in the face of climate change.
Session D5 : Groundwater and interaction with surface water
Quantification of Baseflow Enhancement due to Managed Aquifer Recharge
KUMAR Ranveer, GAUR Shishir, OHRI Anurag
India
Short abstract : The design criteria for managed aquifer recharge structures often lack adequate parameterization of baseflow enhancements due to the absence of a quantification method. The river aquifer exchanges in the complex groundwater systems have been determined using a coupled surface water and groundwater model. The response of the baseflow enhancements due to the periodic injection of water from an area has been analyzed to determine the baseflow enhancement using a novel Index named Baseflow Restoration Index (BFRI). The BFRI represents the percentage of streamflow enhancement with unit injection of water. The volume of baseflow enhancement has been determined by injection return ratio (IRR), which represents the total stream flow enhancement due to unit water injection. The relationship between BFRI and IRR has been established. The sensitivity of the BFRI and IRR to the aquifer parameters (Transmissivity and Specific Storage) has been presented. The framework has been implemented in the Varuna River Basin in India. The results show that a large part of the Varuna River Basin has low values of BFRI, rendering them less suitable for stream restoration projects.
How does optimizing water-environment-energy nexus affect river-aquifer exchanges in an alpine river basin ?
MISHRA SHREYANSH, BAJPAI Mayank, GAUR Shishir, OHRI Anurag, KACEM Mariem
India
Short abstract : The interaction between rivers and aquifers, known as river-aquifer (R-A) exchanges, is vital for sustaining both surface and groundwater systems. These exchanges regulate streamflow, recharge aquifers, and influence water quality, yet are increasingly pressured by rising water demands and climate change. This study investigates the impacts of Water-Energy-Environment (WEE) nexus optimization on R-A exchanges in the lower Ain River Basin, France. A simulation-optimization framework integrates MODFLOW for groundwater flow and MT3DMS for nitrate transport modeling. Using multi-objective particle swarm optimization (MOPSO), objectives of maximizing groundwater extraction, minimizing nitrate concentrations, and reducing energy demand are analyzed alongside R-A exchange parameters. Trade-offs among objectives were visualized through Pareto fronts, and stakeholder preferences informed decision-making via weighted TOPSIS. Results reveal critical interdependencies, such as inverse relationships between water withdrawal and natural upwelling, and heightened nitrate risks in downwelling zones. This work provides actionable insights into managing alpine river basins sustainably, balancing human needs and ecological preservation while addressing WEE nexus challenges.