ABSTRACT. Understanding the interaction between hydrodynamics and particle capture is essential for improving gully pot performance in urban drainage systems. This abstract presents the experimental components of a broader PhD project which consists of two complementary parts: (1) hydrodynamic characterization, and (2) solid separation efficiency analysis. In the first part, hydrodynamic analyses in the gully pot revealed two key flow regions: a bubble-dominated region near the surface created by the plunging inlet jet, and a lower region where a rotational vortex occupied the sump. In the second part, the solid separation efficiency of the gully pot was evaluated. Controlled laboratory experiments with sand particles were conducted for flow rates ranging between 0.5 to 4 L s⁻¹. These complementary experimental parts aim to establish benchmark data linking hydraulic parameters with separation efficiency, providing guidance for improved gully-pot design and maintenance strategies under current and future climate conditions.

ABSTRACT. Urban stormwater runoff transports complex contaminant mixtures to receiving waters, where sediments act as long-term sinks. This study combined in vitro bioassays and targeted chemical analyses to assess sediment toxicity along rural–urban gradients in four Swedish streams. Five bioassays targeting receptor-mediated and oxidative-stress responses were applied to sediment extracts, and results were compared with chemical profiles of 82 stormwater-related contaminants. Estrogenic activity was highest at rural or agriculturally influenced sites, whereas AhR and Nrf2 were strongest downstream of urban areas, reflecting urban stormwater inputs. However, bioassay responses often diverged from chemical concentrations, and iceberg modelling showed that known contaminants explained only parts of the observed effects. We demonstrate the importance of effect-based tools for capturing toxicity beyond the analytical scope of conventional chemical monitoring.

ABSTRACT. Water quality in UK rivers is a pressing concern, particularly ensuring compliance by sewage companies with current water quality regulations. The Environment Act 2021 requires sewage companies to perform continuous water quality monitoring of sewage outfalls. These water quality monitors need to be placed where the plume is cross-sectionally well mixed (concentration, c across the channel, = c ̅(1±0.05); Fischer et al., 1979) to prevent the recording of unrepresentative water quality parameters, compromising public trust. This study aimed to determine the distance to well mixed conditions, L_m using a preliminary dye tracing study at Alfreton Brook, Nottingham, UK and assess the reliability of existing predictive methods. The observed L_m was ~ 40 m. An analytical solution Eq (1), failed to estimate this value because it assumes uniform, steady flow in the channel and a point tracer source. The solution also presents difficulties in selecting a single D_y value for the reach, as field estimates from previous studies report D_y varying along a natural channel. The findings highlight the need for prediction methods that account for spatial variability and outfall momentum in a channel to ensure reliable water quality monitoring.

ABSTRACT. Urban stormwater systems are increasingly exposed to clustered rainfall patterns, requiring a deeper understanding of recovery dynamics in biofiltration systems. Although antecedent soil moisture is known to influence infiltration and drainage behaviour, the response of biofilters under consecutive storm events remains insufficiently characterised. This study experimentally investigates the hydrologic performance of raingarden columns under clustered storm conditions, evaluating recovery dynamics across controlled antecedent dry periods and comparing distinct hydraulic conditions (healthy, surface clogged, preferential flow). Results reveal distinct diagnostic moisture signatures and evidence of hydrologic memory, with divergence among conditions increasing as drying duration lengthens.

ABSTRACT. Nature-based solutions are sustainable strategies for urban stormwater management; however, their large-scale implementation remains limited. Thus, this study evaluates the efficiency of a green roof and a green wall panel through experimental results, while assessing the performance of a rain garden using a predictive model.

ABSTRACT. This study investigates the capability of a two-dimensional Smoothed Particle Hydrodynamics (SPH) model to simulate turbulent flow structures in a partially vegetated channel, an approach that has received limited attention in previous research. The model incorporates the Sub-Particle Scale (SPS) eddy-viscosity formulation with a fixed Smagorinsky constant (C_s=0.12). Numerical results were validated against detailed experimental data obtained from large-scale flume tests conducted at the Coastal Engineering Laboratory of the Polytechnic University of Bari, Italy. High-resolution measurements of the instantaneous three-dimensional velocity components were acquired using a Vectrino 3D Acoustic Doppler Velocimeter (ADV). The SPH simulations successfully reproduced the principal spatial flow features, including the velocity field structure, shear layer development, turbulence intensity distribution, and vortical patterns. Nevertheless, the model exhibited some limitations in quantitatively reproducing the observed turbulence levels.

ABSTRACT. The study of the fate of tiny particles in turbulent flows is of primary importance for several applications, among which the biodiversity reconstruction in aquatic systems by detecting eDNA traces in water samples. Here we aim at inspecting the influence of particle size on the breakage rate of small aggregates in turbulent flows through a series of computational fluid dynamics analysis. Results show that the particle diameter is correlated with the breakup frequency of brittle light particles.

ABSTRACT. The aftermath of deep-sea mining may cause a blanketing of the ocean floor by stirred up fine-grained sediments. Hence, the near-bed shear stress is a key control on erosion and resuspension to estimate the long-term damage. Using digital elevation models of two seabed samples collected in the Clarion-Clipperton Zone (CCZ) in 2018, we combine laboratory shear-plate and PIV measurements with computational fluid dynamics (CFD) to (i) validate numerical predictions of bed shear stress over realistic nodule fields (original and blanketed conditions) and (ii) test a first two-phase framework for fine-sand erosion.

ABSTRACT. The growing dependency on renewable energy sources has created an urgent need for flexible and rapid-response storage systems capable of stabilizing power grids. Integrating reversible pump-turbine technology into Run-of-River hydropower plants presents a promising and environmentally sustainable approach to enable pumped storage hydropower functionality without building new dams. This study examines the hydraulic behaviour of river reaches under cyclic pumping schemes using a parameterization tool to generate generic but physically realistic river geometries. Simulations were conducted in Delft3D-FM for a 3 km long river reach with varying slopes (0.1%–0.02%) and cross-sectional shapes, where flow was pumped from downstream to upstream. Result reveals that pumping induces unsteady flow characterized by rapid initial oscillations in water level followed by gradual stabilization toward a steady profile. The rate and intensity of transient damping depend strongly on slope and geometry, influencing operational efficiency. These findings enhance understanding of transient hydraulic responses in Run-of-River Pumped Storage Hydropower, supporting safer and more reliable integration of energy storage into existing river systems.

ABSTRACT. This study investigates how vegetation traits influence wave attenuation in Living Dikes. A 3D CFD model was developed to simulate wave–vegetation–dike interactions and to assess how vegetation branch density affects wave energy dissipation and hydrodynamic loading on the dike.

ABSTRACT. Human activities in the Dutch part of the North Sea, such as offshore wind farms, sand extractions, gas platforms, network cables, and recreation, add an estimated 25 billion euros to the Dutch GDP. However, the increase in planned offshore wind turbine farms and sand extractions could potentially lead to significant changes of hydrographical properties of the North Sea – both close to and further away from the interventions. We aim to create a user-friendly dashboard to quantify and visualise the spatial extent of salinity stratification, temperature stratification and residual currents in different scenarios, with varying amounts of offshore wind turbine farms and sand extractions on the basis of detailed 3D numerical model simulations. The dashboard serves as digital exploratory tool for finding and tuning relevant indicators for hydrographical alteration.

ABSTRACT. Sea level (SL) and river flow (Q) are the primary factors that influence the water surface elevation (WSE) along a river in coastal areas. However, quantifying the combined effects of SL and Q on WSE is not straightforward due to the different behavior of these factors and their complex inter-relationship. Although the joint probability of the simultaneous occurrence on SL and Q can be quantified, there is no guarantee that the resulting WSE has the same probability as the combination. In this study, an alternative methodology was developed to quantify the compound effects of SL and Q on WSE along a river using the output from numerical simulations using long-term input series for SL and Q. Based on such simulations, empirical relationships were developed to directly determine WSE from SL and Q based on statistical analysis. The study was conducted over an 11-km stretch of the Rönner River in southern Sweden. The HEC RAS 1D hydraulic model was used for the numerical simulations. The results showed how the influence of SL decreases upstream, as well as increasing influence of Q. Around 5 km from the coast, SL and Q have nearly equal influence on WSE.

ABSTRACT. Porous biopolymer foams derived from seaweed stipes are investigated as candidate materials for Up-flow Sponge-like porous body (SPB) stormwater storage systems. Spontaneous water uptake was quantified using sensitive mass-gain experiments and analysed using a sharp-front imbibition model based on Darcy’s law. Good agreement between experimental measurements and theoretical predictions is observed at early times. Further work is required to capture water uptake at later stages, when the wetting front becomes increasingly diffuse and the sharp-front assumption is no longer valid.

ABSTRACT. In the spring of 1995, the lower reaches of the Piteå River (Piteålven) experienced an exceptional flood, with reported stages of about 7 m above low-water levels compared to a typical 3-4 m spring rise. The event caused widespread inundation in the communities of Vidsel and Älvsbyn and created near-damage conditions for critical bridge infrastructure. This extended abstract outlines an ongoing reconstruction of the 1995 flood by combining (i) local, community-facing stage observations from the River Online monitoring system and (ii) snow-depth and precipitation observations from the Swedish Meteorological and Hydrological Institute (SMHI). A central hypothesis is that the magnitude and rapid rise of the 1995 flood were strongly conditioned by the pre-flood liquid water content of the seasonal snowpack, which governs both runoff efficiency and the sensitivity to rain-on-snow inputs. We present the data integration workflow, a stage reconstruction approach based on correlation between River Online stage and Sikfors power-plant discharge, and a snowpack representation that emphasizes snow bulk density and resulting snow water equivalent (SWE). The contribution is a transferable, data-driven methodology for attributing extreme spring floods in largely unregulated Nordic rivers, with direct implications for early-warning and flood preparing measures as well as decision support in real-time.

ABSTRACT. Flood hazards in urban areas are increasing due to extensive human alterations, such as land sealing and channelisation, as well as the growing frequency of extreme rainfall events driven by climate change. Traditional flood protection measures often degrade river morphology and aquatic ecosystems. In response, river renaturalisation and restoration have become more important, with the aim of enhancing both ecological status and urban resilience. However, inadequately planned restoration projects combined with altered hydrological regimes can increase the risk of flooding during short, intense storms. Key challenges include insufficient consideration of flash-flood dynamics, degraded and morphologically static channels, and oversimplified treatment of the effects of vegetation. The Flood-Resilient Urban Rivers initiative aims to develop a comprehensive framework for urban river revitalisation. The project focuses on synthesising lessons learned and establishing a virtual centre of excellence to support long-term, interdisciplinary collaboration on sustainable urban river management. The project's outcomes will support the development of comprehensive best practice guidelines for urban river restoration, balancing ecological revitalisation with robust flood resilience, an essential step towards creating sustainable, climate-adapted cities.

ABSTRACT. The transition to sustainable energy production must be balanced with global biodiversity commitments. In Norway, several watercourses previously protected from hydropower are now being reconsidered, yet public debate often relies on limited knowledge. The Biodiversity–Energy Nexus project aims to improve this knowledge base by developing a toolbox to assess both existing anthropogenic impacts in protected rivers and the potential effects of new hydropower development. Alongside biodiversity hotspot mapping, we are developing a hydromorphological (HyMo) classification system and testing the suitability of various HyMo indicators for use with available remote sensing (RS) data. We established an initial HyMo assessment framework capable of accessing relevant RS sources, delineating data at the reach scale, calculating indicator levels, and producing preliminary HyMo classifications. The framework is tested in a control reach using UAV-based multispectral imagery, LiDAR, and national datasets for ground-truthing. Early results indicate that several HyMo indicators can be derived from RS data at reach scale, but that field measurements are still required to ensure robust indicator estimates. These findings highlight the potential for RS-supported HyMo assessment as part of a broader decision-support tool for evaluating protected watercourses under renewed hydropower interest.

ABSTRACT. This research focuses on developing an image processing framework capable of identifying structural damage in hydraulic systems through advanced deep learning. By implementing the UNET model, a convolutional neural network specialized in pixel-level classification, this study successfully isolated cracked regions within complex image data. The proposed semantic segmentation approach demonstrates high levels of precision and accuracy during feature extraction, suggesting significant potential for monitoring the structural integrity of water-related facilities.

ABSTRACT. This research utilizes a method for detecting building occupation changes near riverside areas using the Bitemporal Image Transformer as the change detection model, with LEVIR-CD database used for training and detection. The model combines CNN based feature extraction with context learning based on transformers, then generates a pixel level change mask by computing and segmenting the refined feature differences between the two times. This change detection method shows to be a usable tool for identifying building changes near riverside areas.

ABSTRACT. This study aims to quantitatively validate the accuracy and repeatability of bathymetric data acquired using a multibeam echo sounder (MBES) mounted on an unmanned surface vehicle (USV), and to evaluate its applicability for monitoring river-crossing structures through comparison with a single-beam echo sounder (SBES). Repeated surveys were conducted over the same section influenced by sluice gate operations at the Chungju regulating dam. GNSS-derived depth measurements were adopted as reference values to assess the vertical accuracy of the MBES. Subsequently, point density and depth discrepancies within the scour zone were comparatively analyzed between SBES and MBES datasets. The MBES exhibited vertical deviations within 1–2 cm relative to the reference values and maintained a consistent maximum depth of approximately 10.8 m across three repeated surveys. The MBES generated approximately 15,470,000 points, compared to 1,034 points acquired by the SBES, representing more than a 15,000-fold increase in spatial density. Within the scour region, a mean depth difference of 1.07 m was identified between the two systems. These results demonstrate that MBES-based USV surveying provides substantially superior spatial resolution and localized scour detection capability compared with SBES, and constitutes a high-reliability measurement technique for safety monitoring of river-crossing infrastructures.

ABSTRACT. Arctic rivers contribute a large part of the global freshwater discharge into the Arctic Ocean although the later comprises of a very small fraction of the global ocean volume (Wang et al., 2025). The present study investigates the terrestrial water balance (WB) of two major Arctic river basins, the Ob and the Lena. The Ob river basin is one of the largest Arctic-draining basins, covering approximately 30,00,000 km², with headwaters in the Altai Mountains and drainage northward into the Kara Sea. The Lena river basin, drains an approximate area of 25,00,000 km² and flows into the Laptev Sea. In the current study, the monthly water balance components – precipitation (Pr), evapotranspiration (ET), change in storage (dS) and runoff (RO) – from multiple satellite, reanalysis and land-surface model products are utilized to examine the basin scale water balance of the aforementioned Arctic basins during the period 2003 to 2020. Gridded Pr data are obtained from Global Precipitation Climatology Centre (GPCC), Global Precipitation Climatology Project (GPCP), Integrated Multi-satellitE Retrievals for GPM (IMERG), Multi-Source Weighted Ensemble Precipitation (MSWEP), Multi-Source Weather (MSWX), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) and TerraClimate. Further, gridded ET data are obtained from fifth-generation ECMWF reanalysis (ERA5), the Famine Early Warning Systems Network (FEWS NET) Land Data Assimilation System (FLDAS), the NASA Global Land Data Assimilation System (GLDAS), the Global Land Evaporation Amsterdam Model (GLEAM), Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA2) and TerraClimate. Four post processed versions of dS products from GRACE: CSR (Center for Space Research), GFZ (GeoforschungsZentrum Potsdam), JPL (Jet Propulsion Laboratory), and JPL-Mascons are used. Additionally, the recently reconstructed GRACE like dataset (BNML TWSA) developed by Mandal et al. (2025) has been used in this study as a fifth dS product and also for filling the data gaps in the GRACE based products. For the RO data, ERA5, FLDAS, MERRA2 and TerraClimate are used in this study. The multiple gridded data products used here are available at different spatial resolutions; the basin average of all the grids falling with the study basins are considered. Figure 1 shows the location of the study basins Lena and Ob along with the median monthly water balance residuals (from eq 1) calculated from the screened ensemble dataset. For each of the water balance components, the outliers from the multi-source data products are removed first by comparing each dataset with the median of the corresponding ensemble. This screening process leads to four Pr, three ET, four dS and three RO datasets, which are used for further analysis. Pr datasets from GPCC, MSWEP, MSWX and TerraClimate are retained for both Ob and Lena basins. Among ET datasets, ERA5 is retained in both the basins whereas TerraClimate is retained in none. All the four GRACE based dS products and RO from FLDAS and TerraClimate are retained in both the basins. For each of the screened dataset combinations, the error closure or residual r is calculated as follows: r=Pr-ET-RO-dS ≠0 (1) The median monthly residual is found to be 11.2 mm for Ob and 9.8 mm for Lena basin. Using the residuals from all combinations of the screened datasets, a First Order Reliability Method (FORM) is employed to assess the reliability of the dataset combinations in closing the water balance (Luo et al., 2021). The best Pr-ET-dS-RO combinations for the Ob and the Lena are found to be GPCC-MERRA2-CSR-MERRA2 (probability of failure 0.09) and GPCC-GLDAS-GFZ-ERA5 (probability of failure 0.22) respectively. Three water balance closure correction (WBCC) methods – Proportionality Redistribution (PR), Multiple Collocation (MCL) and Constant Kalman Filter (CKF) are applied to address the WB non-closure errors from all the combinations of the screened dataset (Abolafia-Rosenzweig et al., 2021). The ‘corrected’ WB components for the ‘best combination’ (as selected by FORM analysis) are plotted (Fig. 2) against the corresponding ‘weighted mean’ (WM) values of the components, the largest weights being assigned to those with the least variability. These WM values of the WB components are considered as proxy for the true observations to assess the relative performance of the correction methods. Figure 2 shows that for Ob, the best correction performance is achieved by PR for the components ET, dS and RO whereas, MCL performs best (correlation coefficient = 0.98) for the component Pr. For Lena, MCL performs best for Pr and ET, whereas PR performs best for dS and RO. However, the correction for RO is far from satisfactory. It may be noted that the gridded RO datasets used in this study have substantial uncertainty as both reanalysis and land surface models are found to underestimate river discharge in Arctic basins compared to gauge observations (Winkelbauer et al., 2022). Even gauge observations suffer from monitoring challenges due to remote locations and unstable gauge-discharge relationships owing to ice jams, which are more pronounced in the Lena. Overall, PR may be noted as the preferred correction method, owing to its wider applicability and computational simplicity. References Abolafia-Rosenzweig, R., Pan, M., Zeng, J. L., & Livneh, B. (2021). Remotely sensed ensembles of the terrestrial water budget over major global river basins: An assessment of three closure techniques. Remote Sensing of Environment, 252, 112191. https://doi.org/10.1016/j.rse.2020.112191 Luo, Z., Shao, Q., Wan, W., Li, H., Chen, X., Zhu, S., & Ding, X. (2021). A new method for assessing satellite-based hydrological data products using water budget closure. Journal of Hydrology, 594, 125927. https://doi.org/10.1016/j.jhydrol.2020.125927 Mandal, N., Das, P., & Chanda, K. (2025). Machine-learning-based reconstruction of long-term global terrestrial water storage anomalies from observed, satellite and land-surface model data. Earth System Science Data, 17(6), 2575–2604. https://doi.org/10.5194/essd-17-2575-2025 Wang, Z., Hui, F. & Cheng, X. (2025). A Machine Learning-Reconstructed Dataset of River Discharge, Temperature, and Heat Flux into the Arctic Ocean. Sci Data 12, 1255. https://doi.org/10.1038/s41597-025-05582-9 Winkelbauer, S., Mayer, M., Seitner, V., Zsoter, E., Zuo, H., and Haimberger, L.(2022). Diagnostic evaluation of river discharge into the Arctic Ocean and its impact on oceanic volume transports, Hydrol. Earth Syst. Sci., 26, 279–304, https://doi.org/10.5194/hess-26-279-2022

ABSTRACT. The Rambla Salada, with an approximate drainage area of 133 km2, is a torrential sub-basin within the Segura River basin and exhibits a high susceptibility to flash-flood events due to the marked irregularity of precipitation and the low permeability of its soils, conditions that are characteristic of semi-arid Mediterranean catchments. Currently, the Segura River Basin Authority (CHS) provides a hydrological study based on the semi-distributed HEC-HMS model. However, the availability of high-resolution LiDAR topographic data and the increasing use of advanced fully distributed hydrological modeling approaches highlight the need to compare modeling frameworks and update the estimation of design flood discharges. This work proposes a comparative analysis between a semi-distributed hydrological model implemented in HEC-HMS and a fully distributed model developed using IBER, employing design storm events corresponding to different return periods. The numerical results of the study are currently under development and will be presented at the conference.

ABSTRACT. We present a research on the sediment transport and riverbed material analyses along a study reach on the Hernád River, Hungary. We did fieldwork and laboratory analyses, furthermore with physical and numerical modeling for three particular goals: (1) to quantify sediment transport and qualify the riverbed material of the Hernád (2) to assess the river reach from morphological point of view; (3) to contribute to the River Ecosystem Service Indexing of the river in terms of Sediment regulation. In our presentation we show the results of the research and we conclude in terms of the research goals. Our research was carried out in frame of the Hungarian National Laboratory for Water Science and Water Security project (RRF 2.3.1 21 2022 00008).

ABSTRACT. The presence of hydropower plants in river ecosystems has a negative impact on downstream migrating fish species by either partially or completely restricting their movements. Although angled bar racks are increasingly employed to direct fish at water intakes, their effectiveness for potamodromous species during downstream migrations remains inadequately quantified, especially across different structural configurations. This study experimentally examined the behavioural responses of fish to hydraulic conditions using the Oppermann fine screen, both with and without an elliptical guidance wall. The experiments were performed at a 45° screen angle, with a bar spacing of 10 mm, for two potamodromous fish species, the Colchic nase (Chondrostoma colchicum) and the Sakarya bleak (Alburnus escherichii). Results indicated that the guidance wall markedly increased passage success for Alburnus while positively influencing passage trends for Chondrostoma. Total body length was identified as a highly significant predictor of success for Chondrostoma, whereas it was not for Alburnus. Consequently, incorporating fish length into predictive models significantly enhanced their classification accuracy (as indicated by AUC) for Chondrostoma.

ABSTRACT. Hydropower is Switzerland’s main domestic renewable energy source and a key pillar of its plan to decarbonize electricity by 2050. Its flexibility supports the integration of variable renewables, such as wind and solar. However, hydropower operations can harm river ecosystems, especially through hydropeaking (i.e. rapid discharge fluctuations that affect downstream habitats). As a result, Switzerland’s Federal Waters Protection Act (WPA, Art. 39a) obliges operators of hydropower facilities to reduce their impact on downstream flora and fauna. Mitigation measures include operational changes (e.g., turbine scheduling) and structural solutions such as compensation basins (CB), battery energy storage systems (BESS), or the combined use of CB and BESS (hybrid hydropower plants, HHPPs). Despite their high costs, structural options are often the preferred solution. In this study, we analyze potential hydropeaking mitigation solutions for a Swiss HPP. For each solution, we assess the sensitivity to hydropeaking ramping rates (HRR) and implementation costs (CAPEX). The first solution is a purely operational measure in which turbine operation is restricted by HRR. For that solution, a sensitivity analysis (SA) evaluates the sensitivity to the applied HRR The second solution is the implementation of structural measures. For the structural solution, an SA is performed to assess the sensitivity to HRR in combination with the CAPEX price of each structural measure. Results show that stricter HRR limits increase the need for structural solutions. For battery costs below 50∙103 CHF/MWh, measures including BESS are favorable. For CB costs below 300 CHF/m3compensation basins alone are sufficient; with higher costs encouraging hybrid solutions with BESS. In general, HRR is found to be the main driver of the structural technology choice, as well as the size of each structural system and whether a combination of both CB and BESS will be needed.

ABSTRACT. This study examines how ice blocks formed from fractured sheet ice may collect on the crest of labyrinth weirs in cold regions and how such blockages may affect hydraulic performance. Based upon field observations, scale-model tests with varying idealized ice block shapes, sizes, and thicknesses were studied for typical river flow conditions. Results indicate that that ice geometry and flow conditions at the crest (flow depth, local velocity) strongly influence passage behavior. Thicker ice blocks tend to pass only at higher discharges, while thinner and smaller blocks pass more easily. Experimental results include locations of ice block accumulation on the crest and, if blocks passed over the weir, were they likely to be transported downstream or accumulate within the outlet cycles. Furthermore, even partial ice block accumulation on the labyrinth crest noticeably reduced discharge efficiently, highlighting the need to consider ice effects in the design and winter operation of labyrinth weirs.

ABSTRACT. The influence from natural convection on internal flow in a freezing sessile water droplet on a cold surface is in focus. By the implementation of an enthalpy-porosity solidification model and a temperature-dependent water density, a new OpenFOAM solver is developed to simulate the freezing process of water. The results capture the directional change of the internal flow reported by experiments, although the numerical velocities are lower than the measured ones. The findings highlight the role of natural convection for the directional shift of the internal flow and justify further investigations of the effects of additional mechanisms in the freezing process.

ABSTRACT. The assessment of climate change impacts on flood hazard in high-elevation Alpine basins is of growing relevance for the hydrological safety of large dams. Many of these structures were designed under the assumption of stationary hydrological conditions, yet warming temperatures have already altered snowfall–rainfall partitioning and seasonal runoff generation in mountain environments. The analytical framework presented by Evangelista et al. (2025) provides a parsimonious but physically consistent methodology to quantify how increases in air temperature may modify the magnitude of design floods in Alpine environment. Applying this methodology to approximately 200 basins, many of which closed by large dams in the Alps, offers a coherent and scalable approach to evaluate the potential non-stationarity of extreme inflows and to guide future dam-safety assessments.

ABSTRACT. Urban runoff in cold climate regions presents unique treatment challenges such as episodic pollutant loads, freezing conditions, and complex surface-subsurface runoff contributions. This study presents a year-round pilot-scale hybrid system in Oulu, Finland, combining settling tanks and woodchip bioreactors to treat alternately stormwater from an industrial area and snowmelt from a snow dump site.

ABSTRACT. In-situ data collection is essential for monitoring coastal environments, identifying vulnerabilities, managing coastal resources, ensuring coastal protection, and validating numerical models. In addition, such observations are also important in studying the impacts of the climate crisis and its influence on coastal and oceanographic processes. The need for in-situ data is especially important in the Arctic regions, one of the regions most affected by climate change. Improving understanding of fjord hydrodynamics is essential to project and mitigate climate impacts. In this study, in-situ data were collected from strategically selected coastal locations in Isfjorden, Svalbard Archipelago. The experiments were conducted near the key settlements that host most of the Svalbard’s infrastructure, Adventfjorden (near Longyearbyen), Grønfjorden (near Barentsburg) and Billefjorden (near Pyramiden). The dataset, acquired over a one-year period, provides valuable insights into local hydrodynamic variability. This work focuses particularly on high-energy events during the winter season, demonstrating how wave characteristics within Isfjorden are shaped by coastal dynamics.

ABSTRACT. The Sava River, the longest river in Slovenia, plays a vital role in the country’s hydrological and energy systems. The Krško Nuclear Power Plant (NEK) began operation in 1983, using river water for cooling, followed by the commissioning of run-of-river hydropower plants in 1994, 2006, 2009, 2013, and 2017. Thermal impacts of these facilities were evaluated already during the planning phase, with modelling results indicating negligible effects on river temperature. This study builds on more than three decades of temperature observations to verify those predictions under real operating conditions and to assess long-term thermal trends of the Sava River under ongoing climate warming.

ABSTRACT. More intensified events such as extreme precipitation are increasingly occurring in urban areas, leading to waterlogging (surface water accumulation) and pluvial flooding. These events adversely affect urban assets, facilities, and critical infrastructure networks, causing not only financial damages but also disruptions in accessibility and essential services. Climate adaptation is therefore essential to address these hazards. Since climate change is already underway and its impacts cannot be fully prevented, adaptation strategies must be prioritized. Climate adaptation measures vary in scale, functionality, and composition. The composition of these measures can be defined by the degree of integration of natural (green) and engineered (grey) elements. This range forms a hybrid spectrum, where green and grey components are combined and designed for synergistic performance. Hybrid measures provide various benefits such as reducing flood events by enhancing infiltration, increasing storage capacity, and delaying runoff in terms of both volume and timing. Additionally, they contribute to several co-benefits as: urban aesthetics, mitigate heat stress, and promote biodiversity. Considering these measures in urban planning frameworks is crucial for creating multifunctional spaces that address both hydrological, ecological and social challenges. The study focuses exclusively on urban hybrid measures and collects expert interviews to capture practical insights into their design, implementation, and performance. Interviews are aimed to develop a structured classification of urban hybrid measures based on spatial scale, cost, and multifunctional benefits. Experts identified key challenges, including maintenance and governance, and to provided several examples of successful implementations with key lessons learnt for international knowledge exchange. The study concludes with recommendations that link tested design principles and operational practices to scalable strategies for resilient urban water management with key messages related to finance, governance and institutional challenges with practical guidelines for the design, implementation and maintenance ensuring a long-term efficiency of hybrid measures.

ABSTRACT. The appropriate handling of stormwater samples is important to keep sample integrity and obtain representative results, as sample storage conditions may influence the changes in stormwater sample quality. However, the extent to which the storage temperature and time are reported in stormwater quality studies varies widely between studies. This study aimed to review stormwater sample handling with respect to storage temperature and time from sample collection, during transportation to the laboratory and until analysis. The results showed that 53% of the 375 reviewed articles failed to mention sample storage temperature and time from collection until analysis and 47% partially mentioned the storage conditions. Moreover, 74% and 72% of the 375 articles did not mention storage temperature from field to laboratory and from lab until analysis, respectively. The storage time from field to laboratory was not mentioned in 84% of the articles and storage time from laboratory until analysis was not mentioned in 79%. Among the studies that reported storage temperature of stormwater samples, the storage temperature ranged from -80°C to 25°C, while the sample storage time ranged from immediate analysis to 3 months of storage prior to analysis. The storage conditions were different depending on the parameters analyzed.

ABSTRACT. Abstract

1. Introduction European cities are actively seeking integrated strategies to mitigate the urban pollution of water bodies while simultanously promoting and enhancing urban biodiversity. Implementing Sustainable Urban Drainage Systems (SUDS) presents a promising approach to achieve these dual objectives synergistically. Among the different SUDS, green roofs are one element, from which many prototypes have recently been constructed. A critical challenge, however, lies in the transition from individual installations to city-wide planning, requiring robust methodologies to assess their aggregate catchment-scale effects on the urban drainage system. This upscaling presents several interconnected challenges, spanning from the technical difficulties of developing integrated hydrological-hydraulic models (Sañudo et al. 2022) that accurately represent distributed SUDS, to methodological questions regarding the selection of representative rain events (Pampaloni et al. 2024), and practical constraints in quantifying the available roof surface area for potential implementation (Montealegre et al. 2022). In this paper a comprehensive and reproducible methodology for a city-scale hydraulic assessment of green roof implementation plans is suggested. 2. Methodology The methodology is built upon a green roof unit model, adapted from the Storm Water Management Model (SWMM) and the literature, which is particularly suitable for apartment-style buildings. To ensure reproducibility and leverage open data, the methodology is applied to the well-documented case study of Bellinge, Denmark, despite the fact that its building stock primarily consists of single-family homes with sloped roofs, which are less ideal for the selected green roof model. This deliberate choice highlights the methodological focus and transferability of the approach. A green roof unit model suitable for apartment-style buildings have been selected and modelled parting from the green roof SWMM model and the literature (Rossman et al. 2016). The model used is more suitable for cities with apartments, such as Cartagena (Vigueras-Rodriguez et al. 2024). In this work, the methodology has been applied to the well-documented case study of Bellinge, Denmark. Despite the fact that its building stock primarily consists of single-family homes with sloped roofs, which are less ideal for the selected green roof model, and therefore, the simulations will not be realistic as most of the buildings in Bellinge are houses whose roof slope are non suitable to the green roof considered, the availability of the Bellinge urban drainage open data set (Pedersen et al. 2021), allows it to be reproducible. In this way, a Zenodo link will be provided with all scripts developed and used.

The core of the methodology involves a multi-stage process: 1 Automated extraction of building geometries from OpenStreetMap (OpenStreetMap, 2025) through OSMnx library (Boeing, 2025) and their spatial association with hydrological subcatchments. 2. Selection of rainfall events using the Three Points Approach (Sørup et al. 2025). 3. Execution of multiple scenarios in which the penetration ratio of green roofs with regard to the available roof surface (Montealegre et al. 2022) is systematically varied and the three selected events are simulated through pySWMM (McDonnell et al. 2020, Erispaha A et al. 2025), enabling a sensitivity analysis of their impact. 4. Comparative performance assessment based on key hydraulic metrics, including reduction in hydrograph peak flow, total flooding volume, and volume of combined sewer overflows. 3. Conclusions A methodology to assess the hydraulic city-scale effects of a green roof city plan is described. Such methodology is provided and its used is shown using as a benchmark Bellinge, due to availability of a open data set of its drainage system. Results, even though they are not realistic for this town due to the characteristics of their average houses roods, are presented as an example of how it can be applied to different cities. In conclusion, this study provides a workflow for the city-scale hydraulic assessment of green roof plans. The application to Bellinge serves primarily as a benchmark to demonstrate the methodology's practical implementation and reproducibility, facilitated by open data. While the quantitative results for Bellinge are interpreted as a proof-of-concept rather than a direct planning recommendation, they successfully illustrate the workflow's utility and its potential for transferability to other urban contexts where these green roof models are more directly applicable. The study underscores the importance of such assessment tools for evidence-based urban water management planning.

ABSTRACT. This paper presents the development of an integrated guideline for public space design in Het Hogeland municipality, combining climate adaptation, cultural heritage, and social well-being. The approach applies the “Analyse – Ambition – Action” framework and four ambition levels: maintain, optimize, strengthen, and transform. Design principles are structured around the “value compass, balancing the value categories of spatial quality, wellbeing and health, mobility, economy, climate, and environment. Profiles, as representative examples of spatial typologies such as streets, squares, parks, roads and harbors, include phased strategies (Now, Soon, Later) to ensure adaptive implementation. The findings highlight the importance of systemic integration and participatory processes to achieve resilient and inclusive public spaces. The innovative methodology for urban planning can be upscaled for international knowledge exchange on urban planning and governance with focus on climate adaptation in response to increasing climate risks and extreme weather events (IPCC, 2023).

ABSTRACT. This study examines the future rainfall regime of Trnava, Slovakia, using downscaled CMIP6 projections validated against local observations. The IPSL-CM6A-LR model and SSP2-4.5 scenario best captured recent conditions, reflecting a moderate-intensifying climate trajectory. Annual precipitation remains largely stable, with a slight wetting trend (~ +3% by 2049). The analysis of extreme precipitation indices (R95p, Rx1day, R20mm) indicates a shift towards more frequent heavy rainfall events and longer wet spells, which will stress the city’s stormwater infrastructure. While annual rainfall totals remain relatively stable, short-duration, high-intensity rainfall events are expected to increase. This study provides a robust, observation-based framework to support adaptive urban drainage design and water management in western Slovakia.

ABSTRACT. Particularly during extreme events, precise knowledge of the discharges in flowing waters is of great and decisive interest. However, Conventional measurement methods reach their limits precisely then, as they often rely on a sensor that is not contactless. Image-based flow measurement systems offer a flexible non-intrusive alternative with real time measurement. Unlike conventional measurement methods, the ratio of measurement signal to measurement noise is optimal for extreme events. The presented approach provides the users with digitised data, proof images and flood alarm on time. In the present paper, two extreme flood events are presented, which occurred under completely different conditions. A camera-based discharge system (DischargeKeeper) is permanently installed in northern Spain on the northern slopes of the Pyrenees. In November 2021, an event with a 500-year return period was recorded there. Most of the conventional measuring systems installed at this station were destroyed during the flood event but the camera-based system remained intact because it could be mounted on the side of the cross-section far enough away from the flood water. Figure 1 shows three different flow conditions with discharge values from 100m3/s to 980 m3/s within the year 2021. While the left image shows a sudden water level increase occurred at night, the image in the middle shows a relatively moderate flood event with about 200 m3/s discharge. The image on the far right shows the maximum condition with about 975 m3/s discharge at the flood peak. The second case study is about an event in a wadi in the United Arab Emirates (UAE). Wadis are completely dry during most of the time. However, flash floods must then be expected during the very rare but equally heavy rainfall. In April 2021, a DischargeKeeper system was installed in Wadi Naqab in the northern UAE. The wadi is about 100m wide and was completely dry for two years. In January 2022, a first such event was recorded. Within 15 minutes, the flow increased from 0 m3/s to 78 m3/s (see Figure 2). The specific requirements and challenges in such extreme flood situations are presented in this paper.

ABSTRACT. Urban underground systems are particularly vulnerable to intense rainfall events, especially access stairs, which often serve as the main entry points for surface runoff while simultaneously acting as primary evacuation routes for users. This study assesses pluvial flood hazards affecting underground access stairs in Barcelona Metropolitan Area’s metro network using the inputs provided by a detailed 1D/2D coupled model developed in the framework of the EU ICARIA project. The methodology integrates previously defined human stability criteria, based on hydraulic parameters such as water depth (H) and flow velocity (V), with high-resolution hydrodynamic simulations and rainfall scenarios representing current conditions across the Barcelona metropolitan area. The results reveal a clear increasing trend in the number of access stairs exposed to flood hazards as rainfall intensity rises.

ABSTRACT. Flash floods in urban basins are characterized by short response times, strong rainfall intensities, and high uncertainty propagation in hydrological–hydraulic models. This paper presents the results of the INFLOOD project, showcasing the AI-based early warning system developed for the Ribeira das Vinhas basin (Cascais, Portugal). The system integrates real-time multi-sensor monitoring (including precipitation, water levels, wind and temperature), soft-coupled HEC-HMS and HEC-RAS modelling, and machine learning-based forecasting models. By combining dependable hybrid physics-based and AI data modelling, the flood prediction framework enables scenario-based analysis for flash-flood-prone urban basins.

ABSTRACT. A comparative analysis of catastrophic European floods (2007–2025) identifies core vulnerabilities that shape climate-resilient governance. This study focuses on high-impact riverine and flash floods, using standardized descriptors of hazard, exposure, vulnerability and governance to reveal five recurring drivers of impact amplification: short-duration, high-intensity rainfall linked to persistent synoptic blocks; rapid urban expansion and inadequate drainage; fragilities in critical infrastructure; gaps in the usability of early-warning systems; and regional disparities in vulnerability and recovery. These findings highlight the need for climate‑proofed design standards, impact‑based warning systems, improved basin‑scale coordination and risk‑aware spatial planning across Europe.

ABSTRACT. A 3D numerical model is developed and applied to simulate morphological evolution near coastal protection structures. The 3D flow module is based on Openfoam® and provides to morphodynamic module all the required information (i,e, near-bed wave velocity, breaking wave induced current velocity, turbulence fields in the surf and swash zones, …) for the estimation of sediment transport and bed morphology evolution. The model is applied to predict hydrodynamic field and morphological changes behind detached breakwaters.

ABSTRACT. This work examines the suitability of the Lee phase-change model which is an important digital tool for predicting condensation of steam on falling water droplets, with the objective of assessing its performance, identifying key sensitivities, and defining strategies for model tuning. The project further investigates alternative formulations for interfacial mass-transfer modelling that may improve robustness and physical fidelity beyond the empirical Lee approach. The study uses representative droplet–steam conditions drawn from literature to evaluate model response, focusing on condensed mass, temperature evolution, and heat-transfer behavior. Preliminary findings show that the Lee model provides a stable first-order estimate of condensation rates but remains sensitive to mesh resolution, timestep, and the empirical condensation coefficient. This motivates the exploration of alternative mass-transfer models and hybrid formulations. Infrared Photothermal Imaging (IPI) is identified as an option for validation, which will provide detailed temperature fields for benchmarking simulations. This extended abstract outlines the methodological framework and developments for the different phases of the project.

ABSTRACT. Air entrainment and oxygen transfer are increasingly important in various engineering and industrial fields, particularly in wastewater treatment. The plunging jet system is a common air entrainment mechanism, in which a high-speed water jet impinges on a receiving water tank and entrains air bubbles. The efficiency of air entrainment and oxygen transfer depends on several parameters, including jet impact velocity, nozzle configuration, jet angle, and fluid properties such as viscosity and surface tension. As these fluid characteristics change, bubble behaviour and oxygen transfer efficiency are affected. This study employs Ansys FLUENT to model bubble behaviour and air entrainment under different viscosity levels, with validation against data obtained from an in-house plunging jet experimental system. Improved modelling capability in this area can enhance engineering design optimisation, leading to more energy-efficient systems.

ABSTRACT. The application of CFD analyses for assessing the capacity of spillways has become a widely accepted alternative to physical modelling, particularly when a broad range of operational and extreme flood flow conditions must be evaluated. A comprehensive CFD analysis of the entire integrated hydraulic system of the lower reservoir of the “Dlouhé Stráně” pumped-storage power plant was performed, including the emergency spillway equipped with a radial gate, the bottom outlets, the chute, the stilling chamber, and the tailrace tunnel. The numerical simulations were carried out using the Volume of Fluid (VOF) free-surface approach in combination with the SST turbulence model. This contribution focused on the hydraulic behaviour of the spillway over a wide range of reservoir water levels and radial gate positions, including extreme flood conditions involving overflow over the upper edge of the gate. The primary outcome of the analysis is a three-dimensional “flow rating surface” as a function of reservoir water level and gate position. Interesting findings include strange behaviour in several operational areas, especially in the interaction between the free water surface and the lower part of the gate, which disrupts the velocity and pressure fields, resulting in a reduction in discharge capacity relative to the expected trend. Further results include the reaction forces acting on the radial gate bearings as functions of gate position and reservoir water level, providing essential input for appropriate bearing and actuator design. The newly obtained characteristics from CFD analysis in the extreme flow range were compared with the original characteristics at the time of the original design. Differences were identified, and probable causes were discussed.

ABSTRACT. Sediment solvers using an Eulerian approach have been made in the OpenFOAM CFD library. The latest developments include algorithms computing bed elevation changes based on an adaptive grid for the bed and the free water surface. The vertical movement of the bed is based on the pick-up rate of the particles given by a sediment transport formula. The free surface movement is based on the computed pressure field. The model has been tested for local scour around a vertical circular cylinder and the results compared with an empirical formula. The results are presented together with the free surface algorithms showing the water elevation around the cylinder.

ABSTRACT. The Overtopping BReakwater for Energy Conversion (OBREC) is an innovative type of Wave Energy Converter (WEC) that integrates renewable energy generation within the structure of conventional rubble-mound breakwaters. In an OBREC system, incident waves are guided up a sloping ramp, allowing water to overtop into a reservoir positioned above mean sea level. The stored water is then released through low-head turbines to generate electricity, with energy production directly linked to the hydraulic head created by the overtopped flow. Traditionally, the discharged water from the OBREC flows toward the rear side of the structure, into a sheltered area of the sea that remains unaffected by incoming waves or sea level fluctuations. However, the present study numerically investigates a modified configuration in which the overtopped water is discharged seaward, exposing the system to dynamic wave pressures and potential sea level variations. This new setup aims to assess how wave-induced pressures and hydrodynamic feedback from the open sea may influence the overtopping behaviour and overall energy conversion efficiency of the OBREC.

ABSTRACT. Droplet impact on solid surfaces is a ubiquitous phenomenon central to numerous natural and engineering processes. Depending on the impact conditions, these impacts can result in diverse outcomes such as spreading, receding, jetting, rebounding, and splashing. The dynamics of these events are greatly influenced by the wettability and morphology of the solid surface. While droplets impacting horizontally placed homogeneous superhydrophobic surfaces typically exhibit a vertical rebound, the introduction of non-uniform wettability fundamentally disrupts this symmetry. On such patterned surfaces, asymmetric forces acting along the three-phase contact line can redirect the droplet's vertical kinetic energy into lateral motion during rebound. Consequently, there is growing interest in engineering surface wettability patterns to passively control post-impact droplet trajectories. Achieving precise, directional transport of bouncing droplets holds significant promise for advanced applications in self-cleaning materials, anti-icing coatings, antifouling systems, and water harvesting technologies. In this study, we investigate the lateral dynamics of water droplets impacting a surface with hybrid hydrophobic-hydrophilic patterning.

ABSTRACT. Reservoir sedimentation reduces water storage capacity and hydropower efficiency, emphasizing the need for accurate modeling of sediment dynamics. This study develops a two-dimensional model to simulate suspended sediment transport along a reservoir. The case study is the Carrapatelo Reservoir in Portugal, a long run-of-river reservoir approximately 40 km long. Field measurements of Suspended Sediment Concentration (SSC) were conducted along the reservoir's longitudinal profile to provide sediment input data and support model validation. These spatially distributed SSC measurements are essential for capturing longitudinal sediment dynamics and calibrating numerical models in elongated reservoirs. Sensitivity analyses were performed using the Van Rijn, Toffaleti, and Meyer-Peter & Müller sediment transport functions under identical conditions. Results indicate that the Toffaleti formulation provides the best agreement with observed SSC patterns, while the other functions tend to underestimate SSC downstream. The results demonstrate that longitudinal SSC data enhance model calibration and transport function selection in long-run-of-river reservoirs, supporting transferable sediment modeling and morphological predictions.

ABSTRACT. Hydropower plays a central role in the decarbonization of the energy sector, offering dispatchable, low-emission electricity. In 2024, renewables accounted for 92,5% of new global capacity additions, with hydropower contributing 14,3% of total electricity generation and over 4500 TWh annually. However, in recent years, hydropower plants have started to increasingly face a critical challenge: managing sediments transported by the water flowing through the plant. Over time, sediment accumulation reduces available reservoir storage, causes machinery damage due to surface erosion, and may lead to longer operational shutdowns. Inadequate sediment management can also have significant environmental consequences, such as accelerated coastal erosion and disruption of natural habitats, potentially reducing the environmental sustainability of the hydropower sector. Current strategies for sediment removal primarily include dredging and flushing. While effective, these techniques present operational, economic, and environmental limitations, motivating the development of alternative approaches. One promising method is continuous de-sedimentation, which employs specialized equipment to prevent sediment deposition in the reservoir and maintain sediments in suspension downstream. This technique can significantly reduce the need for periodic dredging and flushing, improving plant availability and profitability. However, routing sediments along the same path followed by water to the turbines introduces new possible problems, mainly linked to the erosion and wear caused by suspended sediments on hydroelectric components, especially on turbines walls, and to the risk of sediment deposit in the supply channels from the reservoir to the powerhouse. To obtain valuable preliminary insights into the effects of sediment-laden flows on the fluid dynamics and structural integrity of hydropower plants components, Computational Fluid Dynamics (CFD) tools have played an increasingly important role over the past decades, providing detailed information to better understand and address these complex phenomena. However, achieving accurate results with CFD simulations of sediment-laden flows is challenging: numerical calibration, proper initialization and convergence require significant expertise and computational effort. The complexity increases further in three-phase simulations involving air, water, and sediments, where multiphase interactions strongly affect flow patterns and deposition behavior. Regarding multiphase flow analyses involving air, water, and sediments, several numerical studies were published in recent years, focusing on the investigation of erosion inside Pelton turbines (Qin et al., 2024; Wang et al., 2025). Other works have examined sediment transport in reservoirs (Fadaee et al., 2020; Hillebrand et al., 2016; Souza et al., 2010; Zahabi et al., 2018) or desilting basins (Lakzian et al., 2020). However, there is still a significant lack of numerical investigations addressing sediment-laden flows in open channels of hydropower plants, which are critical for predicting excessive deposition before water reaches the turbines. To date, only one study has explored this aspect using a complex Eulerian–Lagrangian four-way coupling (CFD–DEM) approach to reproduce sediment dynamics from a tributary duct (Nie et al., 2024). Even though this approach allows to closely represent the physical behavior of sediments, it demands very high computational resources and is currently feasible only for scenarios involving low sediment concentrations and absence of packing phenomena. Moreover, in commercial software like Ansys CFX, numerical simulations with two continuous fluids (air and water) and a solid phase are not possible. A possible alternative is represented by the Eulerian–Eulerian approach, enabling simulations with three-phase even with Ansys CFX. This approach allows to simulate high sediment concentrations at a significantly lower computational cost but requires careful tuning of multiple sub-models, and the lack of erosion models suitable for these applications in the current literature. This work presents the first Eulerian–Eulerian analysis of sediment transport in a real siphon channel operating under continuous de-sedimentation conditions. The study aims to assess sediment transport behavior and to determine the potential occurrence of deposition phenomena within the channel, thereby contributing new insights to the understanding and optimization of sediment management strategies in hydropower systems. Numerical analyses were performed under the hydropower plant’s nominal operating conditions (Q_V=7.2 m^3/s) considering a sediment concentration of 0.5 g/L. The simulations were carried out using Ansys CFX with a Eulerian–Eulerian approach, accounting for different particle sizes. Results show that, across all tested configurations, sediment transport remains heterogeneous yet continuous from the inlet to the outlet of the studied channel. These findings provide valuable insights for optimizing sediment management strategies in traditional hydropower plants implementing continuous de-sedimentation techniques.

ABSTRACT. The German Lower Rhine is a heavily engineered waterway where dredging, scour protection, and recurrent sediment nourishments have shaped riverbed conditions for decades. To assess how these interventions have influenced riverbed morphology, a comprehensive sediment sampling campaign was conducted in 2020 and compared with historical datasets. The present-day riverbed is dominated by coarse and medium gravel, with marked lateral heterogeneity and only subtle longitudinal trends. A pronounced coarsening is evident over the past decades, stabilizing after 2012, which suggests a managed dynamic equilibrium. These changes align spatially with sediment nourishments, scour protections, and active transport corridors. The results demonstrate that sediment samples provide a powerful diagnostic tool for identifying management signals in the riverbed and for interpreting natural morphodynamic processes. While granulometry alone cannot fully characterize system behavior, the multi-decadal perspective gained from sediment sampling is essential for evaluating the effectiveness of sediment management strategies in trained gravel-bed rivers.

ABSTRACT. The river confluence is a critical point of the river system where sediment from the tributary interacts with the hydraulics and morphology of the main river. Given that the two rivers differ in hydrological regimes, their interaction at the confluence produces complex morphodynamic responses, often resulting in deposition pattern that restricts river services, such as navigation. The aim of this research was to interpret the sedimentation pattern at the Drava River confluence into Danube using apparent bedload velocity as a measure of bedload sediment transport. The analysis was conducted for five field ADCP campaigns, targeted for low flows. The results show that Drava River transports bedload sediment in equilibrium when Danube is low, achieving sediment continuity. During high flows, Danube creates backwater effect, restricting bedload transport and inducing sedimentation.

ABSTRACT. The Mediano Dam is a gravity dam located in the north of Spain and built in 1959. The height over the riverbed is 74 m and the reservoir capacity is 436,35 hm3. The design flow of the spillway is 2.250 m3/s. The spillway goes from the dam´s crest to a height of 40 m over the riverbed, where a ski jump throws the flow to the stilling basin. Currently the stilling basin has been naturally built by the different flood events occurred. The object of the present study is to analyze the future evolution of the stilling basin and to decide if a man-built rockfill one is needed.

To carry out the study, a physical model with a 1:70 scale was built in the CEDEX hydraulic laboratory. In the physical model are represented part of the reservoir as feeding structure, the whole spillway with the sky jump and a long section of the riverbed. In the area of the stilling basin the riverbed is represented with movable gravel in order to represent the real situation, and with fixed concrete in the rest of the model.

Two test campaigns have been carried out. The first one studies the scour produced and its evolution. Three scenarios have been tested with different granulometries of the riverbed. Two scenarios have a homogeneous granulometry of 1 m and 2 m, representing an artificial rockfill basin. The third scenario has a heterogeneous granulometry of 1 m (40%), 2 m (40%) and 5 m (20%), representing the natural riverbed. For each of the scenarios several flows have been tested: 500 m3/s, 1.000 m3/s, 1.500 m3/s, 2.250 m3/s and 3.500 m3/s.

In each test the water has flown for 5 minutes unit the bar after the scour is stabilized. Then, the model is emptied and the bar is removed. This process has been repeated until no new bar is formed and the scour is stabilized. The scours have been studied and compared with photo-restitution.

The second test campaign incorporates a pressure sensor box (Figure 1. Right) at the height of the rock base under the riverbed to measure the pressure produced by the flow jet and compare the results with the geotechnical information. The box is compounded by 12 piezoresistive pressure sensors with a range from 0 to 0,5 bars programmed with a LabView code. The results have been analyzed statistically to characterize the maximal and the average pressures. Several flows have been tested: 500 m3/s, 1.000 m3/s, 1.500 m3/s, 2.250 m3/s and 3.500 m3/s. In these tests no scour is produced.

Comparing the results of the pressure sensor box with the geotechnical study, it is expected that the current situation of the stilling basin implies no risks. Because of that, only minor works will be suggested to improve the behavior of the natural stilling basin.

ABSTRACT. With the increasing dependance on renewable and infrequent energy sources, such as wind and solar energy, the need for long-term storage solutions such as Pump Storage Hydropower (PSH) is crucial in stabilizing energy supply all-year round. Sediment dynamics is a crucial factor in the lifetime assessment of powerplant operation and efficiency; sediment scouring, and deposition are significant processes that might be triggered by hydropower operations. These negatively impact the powerplant in many aspects: e.g., channels section change, reservoir siltation, hydraulic machinery erosion. Numerical models are the most common tool in judging hydropower operation and the resulting effect on intake and outlet structures in terms of hydrodynamics and sediment transport parameters. This study aims to investigate the resulting effects of PSH operation at inflow/outflow typical structures in terms of erosion and deposition. This generates a submerged jet characterized by mean flow strong momentum and high turbulent energy content. The pipe outflowing jet exerts shear stress at the channels loose bed, resulting in scouring. In addition, shear layer develops between inflowing jet and steady water in the basin which might promote the advection and diffusion of eroded sediment eventually settling further downstream. The model was developed on FLOW3D, utilizing both Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) turbulence models. A packed sediment layer has been applied to the domain, consisting of sand and gravel. Preliminary results show that RANS produces a robust prediction of mean velocity fields where the higher values are concentrated along the jet axis. LES yields more variable water velocities and sediment suspension and erosion fields; this is important when investigating shear layer dominated conditions such as local scouring/deposition and re-suspension. Further modifications to the model are planned, such as adding unsteady and oscillating inflow and refining sediment gradation to better represent possible prototype cases.

ABSTRACT. Air conditioning is an intensive energy service essential for health and wellbeing, especially in the context of global warming, and varying strategies have been explored to improve energy efficiency in this sector. Indirect evaporative cooling (IEC) can reduce electricity consumption in indoor air conditioning systems (Srivastava et al., 2024). IEC systems use water latent heat of water evaporation to decrease air temperature without increasing specific humidity of the supply air. However, since water evaporation counts as water consumption, IEC systems require a large amount of water on site. To operate effectively, IEC systems also require hot and dry climates, which are also the regions where water stress conditions are more likely to occur. In these cases, water availability can limit the applicability of IEC systems, and water consumption by air conditioning systems may further exacerbate environmental stress. Traditional systems (TS), on the other hand, consume high amounts of electricity and energy production itself requires water (Santesi et al., 2025), consumed off-site, mainly for cooling power plants, bioenergy production, extraction, and fuel processing. The perspective that highlights the link between water and energy is known as Water-Energy Nexus. The aim of this study is thus to assess whether the use of IEC can lead to a water saving with respect to traditional technologies, using the Water-Energy Nexus and including the virtual water embedded in the energy production. Commercially available devices are considered to perform the analysis.

ABSTRACT. The multiplicity of hydrometeorological characteristics that influence the time evolution of a drought situation may justify why events of that type are becoming more frequent, long lasting and complex. As a result, the development of combined drought indicators that blend several physical indicators into a single indicator is becoming more important. In Portugal, drought monitoring still relies mainly on single hydrometeorological indices, thus existing an opportunity to develop a combined drought indicator. In this regard, this study proposes the development of a Combined Prolonged Drought Indicator (CPDI) for the Portuguese part of the Portuguese-Spanish Guadiana River basin, a region of the Iberian Peninsula regions most affected by prolonged droughts. Having on its basis the Spanish Prolonged Drought Indicator methodology, the proposed indicator considers variables representing the different drought types, as well as the intensity and duration of the events. The CPDI aim is to achieve a comprehensive and harmonized instrument able to improve the Portuguese national drought assessment, under the frame of the Water Framework Directive and European Drought Guidelines, as also to ensure a more coordinated transboundary drought management with Spain

ABSTRACT. Understanding the spatiotemporal evolution of agricultural water deficits is essential for evaluating the sustainability of crop production in Finland amid climate change. This study quantifies historical and projected water deficit volumes and deficit days using a daily water balance model applied across Finnish croplands. The model integrates high-resolution observational data from the Finnish Meteorological Institute (FMI, 1981–2014) with CMIP6 ensemble projections under SSP2-4.5 and SSP5-8.5 scenarios (2015–2100). Strong agreement between FMI observations and CMIP6 historical simulations (r ≈ 0.73 for deficit volume; r ≈ 0.74 for deficit days) validates the model’s ability to capture spatial and temporal patterns. Historically, deficit volumes are highest in southern and western agricultural zones, with deficit days averaging 40–55 annually. Future projections reveal divergent trajectories. Under SSP2-4.5, national deficit volumes increased moderately from 2026 onward, with ratio changes relative to the historical baseline (1981–2014) reaching 1.15–1.3 in southern regions and 1.35–1.45 in eastern northern Finland by late-century periods, before slightly decreasing to 1.1–1.35 by 2086–2100. Under SSP5-8.5, ratios escalate more rapidly, from 0.95–1.35 in early periods (2026–2055) to 1.3–1.6 by 2056–2070, and 1.5–1.9 by 2086–2100, with northern and eastern areas showing the largest proportional increases. Deficit days rise from 48 to 50 under SSP2-4.5 (fluctuating between 50–55 during 2030–2089) and to 61 under SSP5-8.5, with southwestern regions exhibiting the most significant changes. These trends indicate intensifying water stress, particularly post-2050, posing risks to potato cultivation and other crops. Adaptation strategies, including enhanced irrigation efficiency, drought-tolerant varieties, and northward cultivation shifts, are recommended to maintain productivity.

ABSTRACT. Aridification is among the most severe impacts of climate change, with the Middle East being particularly vulnerable due to its already arid climate. The aridity index (AI), defined as the ratio of precipitation (P) to potential evapotranspiration (PET), is a key indicator of aridity. In this study, temporal and spatial variations in the AI across the Middle East were analysed. The aridity index was computed at a spatial resolution of 0.1° using the ERA5-Land reanalysis dataset. Aridity index maps were generated for three distinct periods between 1950 and 2024, allowing for a detailed assessment of long-term trends. Based on the aridity index, land classification was conducted in accordance with the UNEP criteria. In addition to spatial analyses, country-level statistical summaries were provided. These findings highlight the increasing severity of aridification across the region and offer valuable insights for policymakers concerned with climate resilience and agricultural planning.

ABSTRACT. This study examines offensive and defensive water use from ancient civilizations to modern conflicts through historical records, archaeological evidence, and engineering documentation. We identify recurring hydraulic warfare tactics including siege inundation, water supply denial, poisoning, defensive moats, and infrastructure targeting. While technology has evolved, fundamental strategic principles remain consistent across millennia. Five major categories emerge: deliberate flooding, water supply control, defensive hydraulic barriers, dam warfare, and modern water security challenges. Understanding these patterns may provide insights for contemporary water resource management, infrastructure protection, and conflict prevention or resolve amid increasing water scarcity and climate change.

ABSTRACT. The drainage or dewatering system for the bridges deck could also be as important for harvesting of rainfall runoff, as safety and conservative component of the whole bridge construction. The first task for a water system at a bridge is an immediate capturing and transport of collected rainfall water at the bridge deck since accumulation or ponding could be extremely dangerous accounting for slippery, or while freezing temperatures including snow and wind. Bridges, either steel or concrete, always are a complex, in regard to structure, transportation and protection of structure system, for water are designed, constructed and maintained upon a series of components designed with considerations for various compromises. In addition, certain structural and construction characteristics, aesthetic requirements, but also management efficiency of surface runoff are of concern. In modern times, an advanced treatment system for more or less polluted runoff, which incorporates alarm monitoring functionality, is typically included. Pipelines should be installed and securely anchored parallel to the edges of the structure, utilizing either steel or concrete materials, and oriented in vertical, horizontal, or lateral configurations. It is important to note that portions of the bridge structure experience movement due to temperature fluctuations and load conditions, affecting deflections, in the both vertical and horizontal planes. This movement can influence the slope of storm sewers over time, subsequently impacting flow capacity and contributing to significant temporary sedimentation in specific sections of the sewer system.

ABSTRACT. The transition toward climate neutrality is accelerating the adoption of Variable Renewable Energies (VRE) such as wind and solar. While these sources reduce greenhouse gas emissions, their variability increases the need for flexibility in the power grid. Hydropower Plants (HPPs), particularly pumped storage facilities, are the primary providers of clean and reliable grid flexibility. However, more flexible operation introduces frequent start-stop cycles that significantly affect component fatigue and reduce machine lifetime. This study quantifies the impact of such operational patterns on five HPPs, representing Francis, Pelton, and multistage pump types. By mapping operational data onto experimentally derived fatigue damage maps, the results show that start-stop cycles increase damage by approximately 10–16x for Francis Pump-Turbines (PTs), 2x for Pelton turbines, and up to 1,000x for multistage pumps. These findings emphasize the need for optimized maintenance strategies and further research on mitigating transient operation damage in flexible hydropower systems.

ABSTRACT. The hydropower sector continues to represent a key component of the European energy scenario. In 2024, it accounted for 680 TWh of electricity generation, supported by an installed capacity of 263 GW, with 207 GW originating from conventional hydropower plants and 56 GW provided by pumped storage facilities. During 2024, the overall hydropower capacity increased by approximately 544 MW, including 184 MW derived from the commissioning of new pumped storage installations (International Hydropower Association, 2025). In addition to wind and solar power, hydropower also plays a crucial role in the ongoing transition toward sustainable energy generation. In particular, pumped hydro storage plants enable hydropower to store surplus electricity produced by other renewable sources, such as solar and wind, and release it during periods of peak demand. This capability not only mitigates the variability inherent to renewable energy generation but also enhances the stability and reliability of the power grid. On the other hand, climate change is expected to increase the frequency and intensity of extreme events, including glaciers melting, heavy rains and droughts, across Europe in the coming decades (Gøtske et al., 2021). A comprehensive literature review also confirmed that climate change is increasingly compromising hydropower performance. Altered precipitation regimes, reduced snowpack, and glacier retreat, especially in Alpine regions, are reshaping runoff dynamics and inflow patterns. These changes lead to sedimentation, seasonal variability, and reduced generation potential, with run-of-river plants particularly exposed to low-flow conditions. In Italy, projections indicate a 10 – 12% decline in output by mid-century. This situation forces the European hydropower sector to develop and adopt new management strategies capable of addressing significant changes in water availability, which directly influence the amount of energy that can be produced over the course of the year (Bongio et al., 2016, Durattore et al., 2020). However, these management strategies have to deal with old power plants whose characteristics cannot be suitable for providing the required flexibility in energy production. To assess the potential contribution of hydropower to Europe’s energy transition, recent studies investigated the current fleet of hydropower plants. Countries, such as Norway, also built a database of operational hydropower plants providing general information about macro-level parameters such as installed capacity and reservoir storage. This makes them particularly suitable for exploring possible general upgrades and efficiency improvements in existing conventional hydropower plants (Quaranta et al., 2021) and pumped hydro storage facilities (Quaranta et al., 2024), along with their associated costs. However, detailed statistical information on turbine typology, net head, and flow rate are generally not included in these databases or analyses. These information are needed to analyse the capacity of the hydropower fleet to adapt to the flexibility needs and/or the need of refurbishment across Countries and over time. To further contribute to the understanding of the current status of the European hydropower fleet, the present study performed a statistical analysis based on data from the Joint Research Centre (JRC) hydropower database (European Commission, 2019) and on data collected from several additional sources. These data were organized and post-processed to define a hydropower plant database providing not only macro-level parameters but also detailed information on the installed turbines. The analysis focuses particularly on plant characteristics, such as plant age and number of installations across Europe, and seeks to identify general design strategies and patterns adopted by engineers over the past decades. As a first step, statistics on total installed capacity, total energy production, number of operational hydropower plants, and average year of commissioning were collected and compared for several European countries with the highest hydropower production, including Norway, Turkey, Italy, Germany, and France. The analysis confirmed that the European fleet is characterized by an average plant age exceeding 50 years with several old facilities. Subsequently, hydropower plants were further analyzed at Country level, focusing on more detailed and technical information such as flow rate, head, and turbine type and numbers. This information was obtained and/or estimated from available data in the database, to analyze the actual flexibility of the hydropower fleet. Proper KPIs will be defined to statistically quantify this flexibility per Country. The results of this analysis were compared with water availability scenarios deriving from literature. The comparison enabled the possibility of highlighting the capacity of the existing fleet to face the changes in water availability. Moreover, it provided information about the need of refurbishment for the existing fleet so as to guarantee a proper support of the clean energy transition.

ABSTRACT. With the increasing penetration of volatile renewable energy sources such as photovoltaic (PV) and wind power, hydropower plants are assuming a progressively more important role as flexible and reliable providers of electrical energy. Unlike solar and wind generation, which are inherently dependent on weather conditions and daily cycles, hydropower offers distinct advantages in terms of dispatchability, energy storage capability, and operational flexibility. These attributes make hydropower particularly well suited for mitigating power fluctuations and maintaining grid stability. Due to their high controllability and rapid dynamic response, hydropower units are widely used to complement variable renewable energy sources. Consequently, they are increasingly required to deliver ancillary services, including primary frequency control and voltage regulation. This evolving operational role has resulted in significant changes in load spectra, characterized by more frequent start–stop cycles and prolonged operation under off-design conditions. While such flexibility is essential for secure power system operation, it also imposes increased mechanical and electrical stresses on hydropower plant components. Recurrent transients, load variations, and off-design operating regimes contribute to accelerated wear and fatigue of turbines and generators. As a result, there is a growing need for improved understanding of the long-term effects of these operating conditions, as well as for the development of advanced methods for condition monitoring, maintenance optimization, and lifetime assessment of hydropower electromechanical equipment. This abstract briefly describes a big data approach for real-time management of hydropower units containing three major parts: power plant damage characteristics, data handling and visual data analysis.

ABSTRACT. Artificial intelligence (AI) and machine learning (ML) are gaining increasing significance and applications in the field of hydropower. Modern predictive maintenance methods utilizing AI and ML hold strong potential to enhance the operational efficiency of hydropower plants, and consequently, the overall efficiency of the power system. This paper discusses the processing and application of predictive systems implemented at the Štěchovice II Pumped Storage Hydropower Plant, located on the Vltava River in the Czech Republic. The plant operates a reversible Francis turbine with an installed capacity of 45 MW. Since March 2023, data have been continuously collected from two sources: sensors deployed by the Brno University of Technology (BUT) and sensors belonging to the plant operator, ČEZ a.s., the leading company owning and operating power plants in the Czech Republic. The ČEZ a.s. sensors provide conventional vibration diagnostics, measuring absolute bearing vibrations and relative shaft vibrations. The measurement complies with ISO 20816-5. The high-speed sensors deployed by BUT include pressure and acceleration sensors installed in the turbine draft tube, as well as two microphones - one positioned near the draft tube and another on the turbine cover. The acquired data are processed using neural network models, specifically unsupervised learning algorithms. The first approach employs data preprocessing through Mel-spectrograms, which facilitate the extraction of characteristic patterns subsequently used to train an autoencoder. The second approach applies graph neural networks (GNNs), which are capable of interpreting the relationships among the sensors themselves, thus providing more relevant and informative diagnostic outcomes. The primary objective of such a system is early fault detection to prevent unplanned outages of the power plant, or conversely, to extend the intervals between scheduled shutdowns and inspections when they are not required. The benefits of predictive maintenance can thus be observed on multiple levels. Implementing such a system can reduce costs, as unplanned outages are often expensive for various reasons. Conversely, if the system determines that an inspection is unnecessary, costs associated with an idle turbine can also be saved. Moreover, by preventing equipment failures, environmental risks - such as leakage of undesirable technical fluids into the water - can be mitigated. The significance of the system also extends to energy security, as reliable hydropower operation enables a stable, cost-effective, and flexible management of the power system.

ABSTRACT. As hydropower adapts to changing power systems, shaped by the energy transition and the rapid integration of volatile renewable energy (VRE), hydropower flexibility is emerging as an important and stabilizing force. This paper examines how hydropower operators' management of increased flexibility, through communication, engagement, and local impact strategies, influences the degree and nature of social acceptance. Framing flexibility operations as a trigger, engagement as a management response, and social acceptance as the outcome, this research attempts to investigate the interplay between technical characteristics and public perception. The study employs a comparative case study approach, drawing on operator-led cases across different European countries, each embedded in unique policy, geographic, and social contexts. Semi-structured interviews with hydropower operators are used to assess perceptions of flexibility demands, communication practices, and experiences with stakeholder engagement. A structured framework of flexibility, social acceptance and organizational factors guides both the data collection and the proceeding thematic analysis. The findings of this ongoing work aim to contribute to both academic understanding and practical guidance on how to align socially responsive management within the energy transition.

ABSTRACT. 1. Introduction

Hydropower reservoirs are increasingly recognised as dynamic sources of methane (CH₄) and carbon dioxide (CO₂), with emissions driven by biological productivity, thermal stratification, hydrological variability, and operational cycles that put at risk hydropower’s clean credentials. Spatial heterogeneity, strong seasonality, and short-lived emission spikes, such as turnover events, rapid inflows, or drawdowns, make accurate quantification challenging. Traditional field-based methods provide high-precision data but are logistically demanding, limited in spatial coverage, and challenging to harmonise across regions, including remote and cold-climate systems. As demand for clean energy and transparent, scalable climate reporting grows, there is an urgent need for observation-driven approaches that enable consistent monitoring of hydropower reservoirs at fine temporal and spatial resolutions. Satellite Earth Observation (EO) has emerged as a transformative tool for characterising the environmental conditions that underpin GHG production and release. Rather than attempting to measure methane directly, EO enables the retrieval of biophysical and thermal proxies that describe trophic status, carbon inputs, thermal structure, sediment-water interactions, and hydrological behaviour. These proxies provide the environmental context required to model CH₄ and CO₂ dynamics with greater robustness and scalability.

We propose a structured framework for organising EO-derived indicators relevant to reservoir GHG processes, grouped into two complementary categories:

2. Remote Sensing Indicators Relevant to Reservoir GHG Dynamics

We propose a structured framework for organising EO-derived indicators relevant to reservoir GHG processes, grouped into two complementary categories:

2.1. Surface-reflectance indicators that directly influence optical properties, including chlorophyll-a and phycocyanin (primary productivity), coloured dissolved organic matter (carbon inputs), and turbidity or suspended sediments (light availability and particle dynamics). These parameters, derived from sensors such as Sentinel-2, Sentinel-3 OLCI, and Landsat 8/9, inform conditions conducive to microbial respiration and methanogenesis.

2.2. Physically derived indicators obtained through thermal infrared, radar altimetry, and multispectral shoreline mapping. These include surface temperature (for stratification strength and mixing potential), water-level fluctuations and drawdown patterns (drivers of littoral sediment exposure), surface vegetation and floating organic matter (often linked to ebullition hotspots), and atmospheric variables from EO–reanalysis products that regulate air–water gas exchange.

3. Integration of Remote Sensing Into GHG Modelling Frameworks

When integrated with mechanistic models, empirical methods, or machine learning approaches, these EO time series improve the modelling of GHG dynamics by capturing nonlinear interactions among productivity, carbon supply, hydrology, and thermal structure. They also enable the detection of key events—such as rapid mixing, episodic inflows, or operational drawdowns—that strongly influence CH₄ and CO₂ release but are often missed in sparse field campaigns.

4. Applications for Sustainability, Monitoring, and Policy

For hydropower sustainability, EO offers several advantages: • scalable and repeatable monitoring across reservoirs and climatic regions; • enhanced accuracy and reduced uncertainty in modelling frameworks; • early detection of high-emission conditions; • consistent environmental indicators supporting certification and sustainability reporting; • improved understanding of how operational practices shape emission patterns.

5. Challenges and Future Opportunities

While remote sensing capabilities are rapidly advancing, major challenges remain: • Cloud cover and optical limitations affecting retrieval accuracy in tropical or turbid systems. • Spatial resolution constraints, particularly for smaller reservoirs. • Data gaps in in-situ GHG flux measurements required for calibration and validation. • Limited current ability to detect methane emissions directly from most reservoirs. However, the outlook is promising. Upcoming missions—such as Surface Biology and Geology (SBG), CHIME, and high-resolution methane imaging satellites—will offer unprecedented opportunities to quantify and model reservoir GHG processes. Advances in hyperspectral imaging, thermal radiometry, and machine learning will further expand the capability of remote sensing to address long-standing uncertainties.

6. Conclusions

Remote sensing does not replace field measurements but complements and amplifies them, bridging gaps between local observations and the spatially complex nature of reservoirs. As satellite technology advances and multi-sensor fusion becomes more sophisticated, EO will play a central role in transparent, efficient, and scalable GHG assessment, supporting hydropower planning, environmental compliance, and climate-aligned decision-making.

Acknowledgements

This article is based on work conducted within the framework and activities of the Working Group 3 of the COST Action Pen@Hydropower (CA21104), supported by COST (European Cooperation in Science and Technology) and acknowledges the activities organised under this initiative.

References

Bullen KE, Bolt BA (1985) An Introduction to the Theory of Seismology, Cambridge, 400 pp. (in the case of a book) Mrokowska MM, Rowiński PM, Kalinowska MB (2015) A methodological approach of estimating resistance to flow under unsteady flow conditions, Hydrology and Earth System Sciences, 19, 4041-4053 (in the case of a journal article)

Blix K, Pálffy KR. Tóth, V and Eltoft, T (2018). Remote sensing of water quality parameters over Lake Balaton by using Sentinel-3 OLCI. Water, 10(10), p.1428.

Dyba K, Ermida S, Ptak M, Piekarczyk J and Sojka M.(2022). Evaluation of methods for estimating lake surface water temperature using Landsat 8. Remote Sensing, 14(15), p.3839.

Ogashawara I, Kiel C, Jechow A, Kohnert K, Ruhtz T, Grossart HP, Hölker F, Nejstgaard JC, Berger SA and Wollrab S. (2021). The use of Sentinel-2 for chlorophyll-a spatial dynamics assessment: A comparative study on different lakes in northern Germany. Remote Sensing, 13(8), p.1542.

Park E, Merino EW, Lewis QO, Lindsey E and Yang X (2020). A pathway to the automated global assessment of water level in reservoirs with synthetic aperture radar (SAR). Remote Sensing, 12(8), p.1353.

Pham-Duc B and Frappart F (2022), July. Monitoring variation of reservoir water volume using SAR sentinel-1 observations and jason-3 Radar Altimetry Data. In IGARSS 2022-2022 IEEE International Geoscience and Remote Sensing Symposium (pp. 7988-7991). IEEE.

Reinart A and Reinhold M (2008). Mapping surface temperature in large lakes with MODIS data. Remote Sensing of Environment, 112(2), pp.603-611.

Soomets T, Uudeberg K, Jakovels D, Brauns A, Zagars M. and Kutser T (2020). Validation and comparison of water quality products in baltic lakes using sentinel-2 msi and sentinel-3 OLCI data. Sensors, 20(3), p.742.

Vanhellemont Q (2020). Automated water surface temperature retrieval from Landsat 8/TIRS. Remote Sensing of Environment, 237, p.111518.

Zhao D, Huang J, Li Z, Yu G and Shen H (2024). Dynamic monitoring and analysis of chlorophyll-a concentrations in global lakes using Sentinel-2 images in Google Earth Engine. Science of The Total Environment, 912, p.169152.

ABSTRACT. This research summarizes field procedures and practical challenges in using acoustic methods to detect defects in sewer pipes. Measurements were conducted on pipes of different materials and diameters using a speaker and microphone setup. Key challenges that can be faced in the field include environmental noise, setup placement limitations, weather effects, signal distortion, and signal attenuation. The measurement protocol involved microphone calibration, repeated measurements, and recordings from both pipe ends to ensure accuracy. The results highlighted how different field conditions affected acoustic responses and explained considerable steps for collecting reliable data in operational sewer networks.

ABSTRACT. This survey paper explores the development and impact of the GeoFlow platform in managing Non-Revenue Water (NRW) within urban water utilities. The paper discusses the system's design, its application for real-time leak detection, and automated reporting. The platform is evaluated using a combination of surveys and operational data to assess its effectiveness in reducing NRW levels and improving water resource management. Results show the platform’s significant contribution to optimizing operational efficiency, offering a scalable, cost-effective solution for water utilities globally.

ABSTRACT. This study demonstrates a quantitative assessment of in-channel aquatic vegetation (filamentous algae and other macrophytes) in a small agricultural watercourse using Object-Based Image Analysis (OBIA) applied to low-altitude Red, Green, Blue (RGB) drone imagery. The approach is evaluated through a direct comparison of two strongly contrasting scenarios observed on consecutive days: a channel reach with dense algal and macrophyte coverage, and the same reach after mechanical removal of the algae on the following day, which represents a unique aspect of this study. The results confirm the OBIA detection accuracy and consistency across highly divergent vegetation conditions. The resulting high-resolution vegetation maps of coverage and spatial distribution may provide critical input for studies on vegetation-induced flow resistance, hydrodynamic alterations, longitudinal dispersion, and transport and mixing processes. By delivering high-resolution quantitative data on in-channel aquatic vegetation dynamics, this work provides crucial input for future research aimed at developing and implementing evidence-based, environmentally friendly channel maintenance strategies in lowland agricultural streams.

ABSTRACT. Laser-Induced Fluorescence (LIF) experiments were performed in a random array of non-uniform, circular cylinders, with the aim of studying the physical drivers of mixing within rigid, emergent vegetation. Two-dimensional concentration maps, C(t,y), were obtained from the LIF data, and used to estimate streamwise, Dx, and transverse, Dy, dispersion coefficients over a comprehensive range of stem Reynolds numbers (50<Red<1200, where Red=Ud/v; U: mean velocity, d : mean cylinder diameter, v: kinematic viscosity). Normalizing the dispersion coefficients confirms that Dy* (=Dy/Ud) is independent of Red for most of the flows tested, except for Red≈100, which is around the expected onset of vortex shedding (Gerrard, 1978). Normalized streamwise dispersion, Dx*, shows a consistently decreasing trend for Red<500, with a subsequent plateau for Red>500, suggesting a change in the underlying mixing processes. To understand the hydrodynamics underpinning the different mixing regimes identified, dispersion results were complemented with previous hydrodynamic data from Particle Image Velocimetry (PIV) tests performed in the same configuration, for a subset of flow rates, 100<Red<900 (Corredor-Garcia et al., 2025). Additional measurements of drag coefficients, Cd, are used to confirm previous parameterisations of dispersion, i.e. Dxi*=f(Cd). Considering the tracer cloud to be independent of initial conditions, ‘Fickian dispersion’ becomes valid at the reach scale. Based on this, a mass-momentum flux relationship can be assumed, such that momentum fluxes can be considering analogous to mass fluxes and used to estimate the different components of each dispersion coefficient. Results show that this framework works well for Red>500; but for slowest flows the components related to boundary layer trapping are missing from the analysis. This study helps shed light on the physical processes driving mixing for different flow regimes, results will help practitioners develop and validate hydrodynamic-based models for mixing in emergent vegetation.

ABSTRACT. Floodplain vegetation strongly influences river hydraulics by modifying flow resistance, sediment transport, and habitat structure. However, predicting drag forces from patchy canopies remains challenging due to variations in spatial scale, canopy density, configuration, and flow submergence. This study examined how patch configuration, density, and relative submergence affect vegetation-induced drag across plant, patch, and reach scales. Flume experiments using nature-like woody vegetation arranged into compact and elongated patches at two densities were conducted under emergent and submerged flow conditions. Drag forces were measured directly with a custom drag plate system. Results show a nonlinear increase in drag with spatial scale, with reach-scale canopies producing the greatest drag. Vegetation caused higher drag under emergent conditions, while increased submergence reduced overall drag and minimized configuration-related differences. These findings emphasize the need to incorporate scale, density, configuration, and submergence in ecohydraulic modeling and nature-based flood management.

ABSTRACT. Vegetation significantly affects solute transport and mixing within open-channel flows. However, most studies simplify vegetation into uniform cylinder arrays, overlooking the hydrodynamic complexity introduced by realistic plant forms. This study quantifies the influence of plant branches on longitudinal dispersion and flow resistance through controlled laboratory experiments. Tracer studies were conducted in a 12.5 m long, 0.30 m wide flume using artificial emergent vegetation with varying branch densities and a cylinder control. Longitudinal dispersion coefficients (Dx) and Manning’s roughness (n) were derived from tracer curve fitting and hydraulic measurements, respectively. Results show that Dx increases linearly with mean velocity and is significantly higher in branched vegetation than in the single-stem and cylinder configurations, while n decreases with velocity but remains larger in denser setups. These findings highlight the strong coupling between vegetation morphology, resistance, and mixing, supporting improved representation of vegetation effects in one-dimensional water quality models.

ABSTRACT. A tracer experiment was conducted in the Warszawicki Channel, a small lowland stream in the Mazovian Voivodeship. The experiment took place during an algal bloom. Two tracer injections were carried out on two consecutive days in May 2025 – before and after removing algae from a 50 m long reach. The experiment enabled a direct comparison of transport dynamics with and without the presence of algae. The results confirmed that filamentous green algae had no substantial effect on longitudinal dispersion.