ABSTRACT. Climate non‑stationarity significantly affects rainfall processes, challenging traditional stormwater design methods. Continuous hydraulic simulations are comprehensive but computationally intensive, while stochastic approaches—analytical‑probabilistic models and Monte Carlo simulations—offer efficient alternatives. These methods enable integration of future climate scenarios into storm modeling and support the design of nature‑based solutions (NBS) such as permeable pavements, detention basins, and green roofs. By discretizing rainfall into independent events, stochastic models capture diverse storm characteristics and long‑term performance. Applied to case studies in Brescia and Messina, these models applied, compared and critically discussed under varying climatic conditions, incorporating non‑stationary rainfall trends.

ABSTRACT. In recent years, sustainable drainage infrastructures have been integrated within conventional stormwater systems to reduce the pressure exerted on the latter during rain events. Swales are effective in reducing peak runoff flows, but their response is strongly affected by the initial soil moisture (ISM) at the start of the event, which is in return influenced by the length of antecedent dry weather period (ADWP). In this work, rain and soil moisture data collected from three swales within a peri-urban area in Luleå were analyzed to investigate the relationship between ADWP and normalized ISM. Despite the variability of event conditions and of data between sensor locations, a first important drop of initial soil moisture was observed for values of ADWP up to 60 h. Furthermore, for a fixed ADWP, the influence of seasonality on normalized ISM was observed.

ABSTRACT. Permeable pavements are essential components of Sustainable urban Drainage Systems (SuDS), delivering multiple advantages and addressing challenges posed by urbanization and climate change. This study evaluated permeable pavements through field tests on pedestrian and vehicular sites. Infiltration rates were measured before and after vacuum cleaning and pressure washing, while sediment analysis was carried out. Results show that pedestrian pavements maintained high performance, while vehicular pavements experienced severe clogging. Pressure washing restored infiltration more effectively, whereas vacuum cleaning is more practical for routine maintenance. Timely interventions are essential to ensure long-term functionality.

ABSTRACT. The growing urbanisation significantly influences the urban hydrological cycle by increasing the impervious surfaces, reducing the surface roughness, and increasing the stormwater runoff. Under these conditions sewer networks may be forced beyond their capacity, causing pressurization phenomena with potential flooding of the urban areas. A possible mitigating solution to this challenge is the implementation of Nature-based Solutions (NbSs). This study investigates the effects achievable from two different NbSs, namely Green Roofs (GRs) and Permeable Pavements (PPs), to improve the hydraulic operation of the drainage network serving the urban catchment of Ganzirri, in Messina (Italy). Preliminary tests based on the EPA SWMM 5.2 employment reveal that GRs and PPs retain the stormwater volumes giving an effective reduction of the maximum flow discharge along the sewer system. The influence of the pluvial return period and the NBSs coverage area on the performance indicators of such measures is also analyzed.

ABSTRACT. This study aims to optimize sensor placement in urban drainage systems (UDS) using predictive models of water levels and flows. The methodology involves assessing system observability through the observability Gramian matrix. The study uses open source software to implement the Saint-Venant equations in a state-space form. A genetic optimization algorithm adjusts sensor placements, maximizing the rank of the observability matrix. The approach is demonstrated on a drainage network in a small Swedish community.

ABSTRACT. Near Reitwein at the River Oder (Germany), riverbank and groyne deterioration for decades over an 800 m reach led to impaired conditions for navigation and icebreaking, while producing ecologically valuable hydromorphological diversity. To restore navigability and simultaneously conserve emergent habitats, several variants of river training structures were tested through numerical and physical modelling. A longitudinal training wall with openings and inlet and outlet sills was selected for construction as it achieved similar flow concentration to groynes in the main channel while maintaining hydraulic and morphological diversity behind the training wall. Post-construction monitoring so far (2019–2025) confirms stable channel morphology, a dynamic equilibrium behind the longitudinal training wall with large temporal and spatial variability, and sustained ecological functionality. The Reitwein project exemplifies how adaptive river training structures can reconcile navigation, sediment dynamics, and habitat preservation in large lowland rivers.

ABSTRACT. Accurate estimation of suspended sediment discharge is essential for river management in large rivers characterized by strong spatial heterogeneity. This study investigates cross-sectional spatial distribution characteristics of suspended sediment based on field measurements conducted at three sites in a large river basin in Korea. Flow velocity was measured using an Acoustic Doppler Current Profiler(ADCP), and suspended sediment concentration profiles were obtained using a Laser In-Situ Scattering and Transmissometry(LISST) instrument. Spatial variability in velocity and sediment concentration was analyzed using descriptive statistics, and suspended sediment discharge was estimated through cross-sectional integration. The results reveal pronounced lateral variability in both velocity and sediment concentration, leading to notable differences in discharge estimates compared with conventional depth-integrated approaches. These findings highlight the importance of considering spatial distribution characteristics in suspended sediment assessments.

ABSTRACT. Accurate flood prediction and risk assessment are essential for effective river management, particularly in dynamic alluvial and regulated river systems where sediment transport significantly influences flood behavior. This study investigates the role of sediment dynamics in shaping flood hydraulics and inundation characteristics through two case studies: the Kor River in southwestern Iran and the Middle Vistula River in Poland. For the Kor River, which is regulated by the Mollasadra and Doroodzan dams, sediment transport and deposition processes were incorporated into the HEC-RAS hydraulic model to simulate flood events along a 5.4 km reach upstream of the Doroodzan Dam. Field data on sediment characteristics and hydrological parameters were collected to inform the model. Results indicate that moveable-bed conditions lead to reduced water surface levels compared with fixed-bed assumptions, with sediment deposition and erosion processes substantially affecting flood inundation patterns. In the Middle Vistula River, downstream of the Dęblin hydrometric station, hydrodynamic simulations were conducted under fixed-bed and moveable-bed conditions for floods with 2-, 5-, and 10-year return periods. The results reveal that bed mobility markedly alters flow behavior, with flow velocity increasing by up to 22%, stream power rising by nearly 500% for the 2-year flood, and the Froude number more than doubling for the 10-year event. Despite minor changes in inundation area, flood intensity (defined as depth × mean flow velocity²) increased by up to 85%, highlighting the critical influence of sediment transport on flood hazard characteristics. These case studies underscore the importance of incorporating sediment dynamics and morphodynamic feedback into flood modeling to enhance prediction accuracy.

ABSTRACT. A multifunctional cross-structure is being developed on the Lower Salzach to stabilize the riverbed while maintaining ecological functions and promote energy production. The structure combines an asymmetrical ramp, a universal opening, and an overflowed hydropower unit, forming the core of the “River Flow Power Plant” concept. A hybrid modeling approach integrates a 1:27 physical model with 3D numerical simulations. The physical model reproduces ramp stability, sediment transport, and morphological development, while the numerical simulations analyze turbine inflow and fish protection performance. Combining both methods compensates for scale and model limitations and increases planning reliability. Initial results indicate improved turbine approach flow conditions and optimized fish protection systems. Initial laboratory tests examined ramp hydraulics and proved their stability. Further tests scheduled for winter 2025/26 will investigate sediment dynamics and approach flow conditions in the area of the turbine intakes. The study demonstrates how hybrid modeling can evolve a conventional ramp structure into an integrated restoration solution aligning hydraulic, ecological, and energy objectives.

ABSTRACT. Flood hazard mapping in Slovenia follows the EU Floods Directive, whereas erosion hazard mapping lacks a standardised methodology and is still primarily based on empirical judgement. Advances in two-dimensional hydraulic and morphodynamic modelling now enable a more comprehensive assessment of sediment dynamics. This study evaluates the potential of a 2D hydraulic sediment transport model to enhance erosion hazard assessment by integrating hydraulic conditions with geological soil composition, land use and sediment transport formulation. The modelling results provide a more precise representation of erosion–deposition patterns on floodplains and support the development of more reliable erosion hazard maps.

ABSTRACT. Groundwater depletion due to overdraft has been a pressing challenge in the Tangshan Plain, a geologically complex coastal region located in northern China. Existing large-scale assessments were unable to adequately distinguish exploitable freshwater at the local scale or capture spatiotemporal variability for management purposes. This study addresses these issues by developing a machine learning-based spatiotemporal modeling framework in the multi-aquifer system setting of Tangshan. A random forest regressor was trained based on the groundwater level time series records of multiple wells, each treated as an indivisible analytical unit, and both static and dynamic features were used as covariates. Cross-validation explained approximately 0.62 of the variances. SHAP analysis revealed that elevation, sand content, and hydrogeology were the leading spatial drivers, while lagged precipitation and irrigation were the dominant temporal controls. The observed-predicted time series comparison at the 13 test wells yielded a correlation coefficient of r = 0.934 and an RMSE = 8.989, with all predictions falling within the 90% prediction confidence interval. Spatial predictions of the groundwater head at the wet and dry seasonal extremes showed a maximum seasonal head change of 8 m, and the mid-term groundwater prediction showed a mild recovery trend with some localized declines. The results demonstrate that the framework can provide continuous, high-resolution tracking of groundwater head in complex coastal aquifers. Such an approach also enhances the local understanding of exploitable freshwater dynamics, discovers potential areas under abstraction stress, and offers a transferable tool for groundwater monitoring and adaptive management.

ABSTRACT. Piano key weirs are types of nonlinear weirs characterized by their advantages for implementation in space-constrained environments, such as spillway structures over dams or head control weirs over horizontal channels. Several researchers investigated the geometric optimization aspects and energy dissipation capabilities of these structures. However, knowledge of their downstream air entrainment characteristics is essential in enhancing design practices and has not been sufficiently addressed. Thus, this experimental study evaluated the basic air-water flow characteristics downstream of an A-type trapezoidal piano key weir under the influence of variable tailwater. These air-water flow properties were measured spatially along the inlet and outlet key centerlines using double-tip conductivity probes. The results revealed that the overall air entrainment and air concentrations were notably affected by the changes in downstream tailwater levels under a constant inflow. Simultaneously, the bubble countrate profiles also depicted significant dependence on the downstream condition. In such cases, an increase in tailwater generally reduces the air concentration and the bubble countrates throughout the downstream region.

ABSTRACT. In dam rehabilitation projects, flap gates are employed to discharge floating ice floes and even other debris. However, the plunging jet can seal the air space downstream of the gate, generating negative pressure within the cavity that causes gate vibrations. Using CFD modeling, this study demonstrates the phenomenon and examines the associated aeration requirements

ABSTRACT. Hydropower is an increasingly important renewable energy source. While large powerplants have largely reached their potential, small hydropower installations on flowing waters with low heads still offer significant development opportunities (Quaranta, 2018). This research project aims to enhance the power output of these decentralized energy converters, focusing on the influence of blade geometry, material selection, and surface structure on breastshot to undershot water wheel performance. Optimized blades are developed using lightweight design concepts, stainless steel, and innovative manufacturing processes instead of using wooden blades. The results are relevant for small and medium-sized enterprises in the hydropower sector and support the UN’s Sustainable Development Goal 7: access to affordable, reliable, sustainable, and modern energy for all

ABSTRACT. The global energy consumption has increased markedly over the past decade, intensifying the need for the exploitation of renewable energy sources. Within this context, hydropower remains the backbone of renewable electricity production, contributing more than 50% of global renewable generation and approximately 14% of total electricity supply. However, climate change is profoundly reshaping hydrological regimes, with several European regions experiencing prolonged droughts and increasingly irregular precipitation patterns. As a result, many run-of-river hydropower plants frequently operate far from their design conditions and are often forced to shut down when river discharge drops below the technical minimum of the turbines. Francis turbines, the most widely adopted technology for medium-head hydropower installations, typically exhibit a minimum operational flow of about 40% of the nominal discharge. Below this threshold, severe instabilities arise, including draft-tube vortex breakdown, large pressure oscillations and strong radial forces that can compromise structural integrity and significantly limit operating time (GI. Krivchenko (1986)). In this context, Variable Speed Generation (VSG) has emerged as a promising strategy to extend the operating range of reaction turbines. By decoupling the generator rotational speed from the grid frequency through power electronics, VSG enables turbines to run at reduced rotational speed during partial-load operation, thereby decreasing swirl intensity at the draft-tube inlet and generally smoothing the flow patterns throughout the hydraulic passages (G. Amul (2023), J. Schmid (2022), I.Iliev (2019)). However, the influence of the velocity variation on the turbine performance and behaviour at deep partial loads, particularly regarding the minimum operational discharge, is not sufficiently clear. This work is aimed at covering this knowledge gap by investigating the stability of a medium specific-speed Francis turbine model operating at variable speed under deep partial-load conditions. The Francis turbine model test of the Turbomachinery and Energy Systems Research Group at the University of Padova was selected as the reference case for this study. A combined numerical and experimental campaign was carried out to assess the influence of rotational speed reduction on the hydraulic behaviour of the machine. A high-resolution numerical model of the entire hydraulic system was first developed, including the spiral casing, stay vanes, guide vanes, runner, leakage flow paths and draft tube. A hybrid URANS/SAS–SST turbulence modelling approach was adopted to accurately capture the large-scale unsteadiness and the characteristic vortex structures associated with off-design operation. A series of transient numerical simulations was then performed to compare the flow field at different guide-vane openings and rotational speed values. Numerical results were subsequently validated through an experimental campaign aimed at characterising the flow behaviour at partial and deep-partial loads within the draft-tube diffuser region, where instabilities are typically most pronounced. The results show that reducing the rotational speed plays a key role in stabilising the draft-tube flow, which represents the primary source of instability during deep partial-load operation. At nominal speed, the strong residual swirl at the runner outlet promotes the formation of multiple interacting vortex structures, generating high-amplitude pressure fluctuations. As the rotational speed is gradually reduced, the tangential velocity component decreases accordingly, leading to a marked reduction in pressure oscillations at the draft-tube inlet. Moreover, the reduction in centrifugal effects at lower rotational speeds promotes a more homogeneous discharge distribution along the runner span, further improving the overall hydraulic behaviour. Numerical analyses also revealed favourable incidence conditions on the runner blades: despite the significant mismatch between flow and blade angles at deep partial load, no critical flow separation zones were detected. Overall, these findings demonstrate that VSG not only increases flexibility by widening the standard operating range of a Francis turbine but it can also mitigate the hydraulic instabilities that typically limit Francis turbines during partial-load operation, enabling stable functioning at lower flow rates up to 20% of nominal discharge. The study also highlights the direct relationship between rotational speed and minimum stable discharge, an insight of particular relevance for industrial implementation, since excessive deviation from synchronous speed may affect generator efficiency and increase converter size. The outcomes of this research underscore the significant potential of variable-speed operation to enhance operational flexibility, increase annual energy production and reduce forced shutdowns in hydropower plants increasingly exposed to climate-driven variability in water availability.

References GI. Krivchenko (1986), Hydraulic machines: turbines and pumps (Translated from Russian). 1st ed. Moscow: MIR Publishers; G. Amul, K. Atmaram, P.B. Lal, C. Sailesh, H.N. Prasad (2023), Numerical analysis of francis turbine being operated in variable speed from sediment erosion perspective. J. Phys. Conf. Ser., 2629, 012006.

J. Schmid, S. Alligné, D. Biner, C. Münch-Alligné, N. Hugo, C. Nicolet (2022) Optimization of turbine start-up sequence of a full-size frequency converter variable speed pump-turbine. IOP Conf. Ser. Earth Environ. Sci. 2022, 1079, 12109

I. Iliev, C. Trivedi, O.G. Dahlhaug (2019), Variable‐speed operation of Francis turbines: A review of the perspectives and challenges, Renew. Sustain. Energy Rev. 103 109–121

ABSTRACT. Hydropower plays a crucial role in the global transition toward renewable energy, yet the environmental impact of conventional lubrication systems used in hydropower turbines and bearings remains a concern. Mineral-oil-based lubricants pose risks of leakage and long-term contamination of aquatic ecosystems. This study presents the development and evaluation of a glycerol-based, fossil-free, fully biodegradable, and water-soluble lubrication concept designed for hydropower bearing applications. The proposed lubrication approach utilizes glycerol derived from renewable resources to provide effective lubrication while ensuring minimal environmental impact in case of leakage or discharge into water systems. Laboratory experiments and tribological testing were conducted to evaluate viscosity behavior, friction characteristics, load-carrying capacity, and compatibility with typical hydropower bearing materials. Results indicate that glycerol-based formulations can provide stable lubrication regimes while significantly reducing friction compared to conventional lubricants. The findings demonstrate the feasibility of environmentally benign lubrication systems for hydropower machinery and highlight their potential role in supporting sustainable hydro-environment engineering. The study contributes to the ongoing green transition in hydropower technology by proposing a fossil-free lubrication alternative that aligns energy production with environmental protection.

ABSTRACT. The rapid penetration of intermittent renewable energy sources is increasing the need for flexible and reliable large-scale energy storage solutions (Suberu et al. 2014). Pumped hydro energy storage (PHES) remains the most mature and efficient technology, yet its deployment is strongly constrained by geographical requirements such as large elevation differences and extensive reservoir volumes (Ammar et al. 2021) (Abdellatif et al. 2019). To address these limitations, an industrial innovation has recently introduced the concept of high-density fluids (HDFs) for pumped storage applications. In particular, RheEnergise has developed the proprietary fluid R-19 (RheEnergise), a non-Newtonian suspension with a density about 2.5 times higher than water, specifically engineered to increase the energy density of PHES systems and thereby reduce the required infrastructure size. By increasing the storable energy per unit volume and reducing the required head and flow rate, high-density fluid concepts also open up the possibility of repurposing sites that are currently not economically attractive for conventional PHES, such as disused mines, quarry pits, or reservoirs characterized by low head differences. This greatly broadens the range of potentially suitable locations, especially in regions where topographical constraints limit the deployment of traditional pumped-storage schemes. The fluid will soon be tested in a dedicated 500 kW demonstrator plant currently under construction in the UK, marking the first real-world implementation of a high-density–fluid pumped-storage system. Despite the increasing industrial interest, no studies are currently available in the scientific literature assessing the technical or economic feasibility of high-density fluids for PHES. This work aims to fill this gap by evaluating, for the first time, the techno-economic potential of R-19-based PHES. The analysis considers both the characteristics of the upcoming DEMO plant and an upscaled configuration representative of a real utility-scale installation. The performance and economic indicators of high-density fluid systems are systematically compared to those of equivalent water-based plants, enabling a coherent assessment of the benefits and limitations of the proposed innovation. Results at small scale confirm that R-19 systems benefit from reduced spatial footprint and lower capital costs due to smaller penstocks and reservoirs, consistent with the density-driven scaling principles. However, system efficiency remains penalized by increased viscous losses and by the absence of hydraulic machinery specifically designed for non-Newtonian fluids; the pump in particular shows reduced performance, lowering the overall round-trip efficiency. Consequently, the economic payback time remains long, although comparable with that of the water-based scenarios, primarily due to low operational revenue relative to the fixed infrastructure cost. When the analysis is extended to utility scale, the effect of geometric and hydraulic scaling becomes evident. Distributed hydraulic losses become comparatively less significant, the influence of auxiliary systems decreases, and overall efficiencies improve for all fluids. Capital costs rise substantially, but the increased power output and improved hydraulic performance produce a proportionally larger annual revenue. As a consequence, payback times decrease sensibly. At this scale, the economic gap between water and HDF-based PHES narrows considerably, suggesting that high-density fluids could become competitive, especially in locations where conventional PHES is not feasible due to limited head or insufficient reservoir volume. These findings highlight that the main current barrier for HDF-based PHES is not the fluid itself but rather the absence hydraulic machines specifically optimized for high-density, shear-thinning working fluids. The results confirm the promising potential of HDF-based pumped storage as a compact solution for site-constrained installations and show that economic viability strongly benefits from scale effects. As future full-scale prototypes and DEMO results become available, and as hydraulic machinery is redesigned to match HDF properties, high-density fluids may offer a viable pathway to expand the applicability of PHES in support of renewable-dominated energy systems.

References Abdellatif, D., AbdelHady, R., Ibrahim, A. M., & Abu El-Zahab, E. (2018). Conditions for economic competitiveness of pumped storage hydroelectric power plants in Egypt. Renewables: Wind, Water, and Solar, 5, Article 2. https://doi.org/10.1186/s40807-018-0048-1. Ammar, A., Bajpai, P., & Singh, S (2021) Pumped hydro storage systems: A review. Renewable and Sustainable Energy Reviews. Suberu, M. Y., Mustafa, M. W., & Bashir, N. (2014). Energy storage systems for renewable energy power sector integration and mitigation of intermittency. Renewable and Sustainable Energy Reviews, 35, 499-514. https://doi.org/10.1016/j.rser.2014.04.009 RheEnergise. https://www.rheenergise.com/how-it-works

ABSTRACT. The region of Thessaly located in central Greece (Fig. 1), was highly impacted by severe storms in the recent past (Vasiliades et al. 2022). In September 2023, the region of Thessaly witnessed a catastrophic two-strike hydrological event. Previous researchers highlighted the devastating effects of Storm Daniel unveiling its extreme nature and excessive damage (Leivadiotis et al. 2025), (Diakakis et al. 2025). To start, Storm Daniel saturated the basin with heavy rainfall (Sept 4-7), and only 20 days passed before Storm Elias passed through the area (Sept 26-28). Although a considerable amount of rainfall did not accompany Storm Elias, its floods were much more intense than had been indicated by the rainfall alone. This research examines the concept of the "Wet Sponge" and proposes that an enormous, unrecorded residual amount of remaining ground moisture—the "Invisible Lake"—was sufficient to fill the basin's capacity for absorption to overflow exceptionally when the burst of the second storm occurred. The aim of this research is to establish the amount of antecedent moisture and whether real-time risk was identifiable from satellite sources. Antecedent soil moisture content was estimated by the Antecedent Precipitation Index (API) with a decay constant of k = 0.90, incorporating the low drainage characteristic associated with the saturated plain. Attention focuses on 25th September 2023, the crucial day leading into the outbreak of Storm Elias. A multi-data source validation approach compared the observations from 21 meteorological stations with the API. Three latency levels derived GPM IMERG satellite data included Early Run (Real-Time), Late Run (Post-Processed), and Final Run (Gauge-Adjusted) data. API data from the weather stations were converted into specific storage (tons/km²) and mapped by Inverse Distance Weighting (IDW) to estimate the total basin-wide volume. The spatial aggregation of the ground-station data showed that a massive antecedent moisture volume of 837 million m³ existed in the basin, more than double the storage capacity of the Lake Plastiras Reservoir. As shown in figure 2, the specific storage analysis highlighted the key areas where the moisture was trapped: the mountainous headwaters of Pertouli with 114,200 tons/km² (retaining ~70% of the previous storm's moisture) and the saturated plains of Trikala with 142,800 tons/km², acting as a filled reservoir rather than a drainage basin. Looking at the satellite estimates, the Late Run (Post-Processed) showed the highest reliability in capturing this spatial anomaly, achieving a strong correlation of r=0.60. On the other hand, the Final Run (Gauge-Adjusted) performed poorly for specific storage estimation with a negative bias of -45% (r=0.38), effectively under-estimating the moisture in the critical zones. This indicates that the algorithms applied in standard gauge correction dampened the large signals present in this event. The “Invisible Lake” was thus a physical phenomenon that preconditioned the area for the disaster that was to come; the cataclysmic runoff during Storm Elias was intensified by the pre-existent storage of over 100,000 tons of water per square kilometer within the soil. From the methodological perspective, there is a ‘Correction Trap’: reliability of near-real-time satellite observations (Late Run) was found to improve substantially upon the gauge-corrected research products for events as extreme as those in the analysis.

ABSTRACT. This work develops a numerical model based on the EPANET-DD (dynamic dispersion) model to simulate sodium chloride (NaCl) intrusion through a leak under negative pressure and the subsequent advective–diffusive–dispersive transport of the contaminant in the water network. The model solves the solute transport equation under variable flow conditions using the random walk method, including axial and transverse dispersion processes in the pipelines and coupling the quasi-steady hydraulic simulation with the calculation of mass transport. Based on the study by Fontanazza et al. (2015), contaminant intrusion was simulated by imposing a transient subatmospheric pressure event (e.g., a water hammer) at a leak, causing the impulsive influx of NaCl into the pipeline. The model was calibrated and validated by comparing the simulations with experimental data obtained in the study by Fontanazza et al. (2015), showing an excellent ability to reproduce both the peak concentration and the propagation of the contaminant along the network

ABSTRACT. Addressing water scarcity in extensive Mediterranean agriculture requires accessible precision irrigation tools. We introduce OASIS, a low-cost, open-source IoT sensor network designed to make precision irrigation accessible for extensive Mediterranean agroecosystems facing economic and infrastructural constraints. The system combines distributed soil and weather sensing with FAO-56 ETo modeling and plot-scale water balance for adaptive irrigation scheduling. Deployed in Viñalta (Palencia, Northwestern Spain), the network's weather node provided daily ETo estimates showing strong agreement (R²=0.83) with the regional reference. Continuous soil moisture data allowed for the identification of percolation losses and refinement of irrigation strategies, demonstrating potential water savings up to 39% in an experimental alfalfa (Medicago sativa L., 1753) field without yield impacts. OASIS's modular and open-source design facilitates broader adoption, promoting water-use efficiency and digital inclusion as climate adaptation pathways in agriculture.

ABSTRACT. This study presents a cloud-native machine learning framework for 30m flood depth mapping in the Aqqala basin of northern Iran. Open Earth-observation and geospatial data from Google Earth Engine captured terrain, hydrography, land cover, soils, and hydrologic forcing. Three ensemble-tree models, namely Random Forest, XGBoost, and LightGBM, were trained for return periods of 30, 100, 300, and 1000 years. Gradient-boosted trees achieved the highest accuracy, with XGBoost yielding an R² of 0.95 and an RMSE ≈ of approximately 0.11 m, while the Random Forest was slightly less precise but more robust. SHAP analysis identified Height Above Nearest Drainage, elevation, and distance to river as dominant predictors, confirming strong topographic control on inundation depth. The automated, solver-free workflow eliminates the need for gauge calibration while maintaining hydrologic realism, allowing for rapid and reproducible flood mapping using open data. The results demonstrate the potential of cloud-native ensemble learning for accurate, interpretable, and scalable inundation modelling in low-gradient, data-limited floodplains such as Aqqala.

ABSTRACT. This study proposes a two-step artificial neural network (ANN) framework for oil spill diffusion prediction in the Port of Augusta (Italy) based on tabular, non-temporal data. The proposed approach aims to provide a reliable and computationally efficient alternative to traditional numerical models, which are computationally expensive and therefore unsuitable for real-time or early-warning applications. The port domain was discretized into 105 spatial segments and 90 spill locations, generating 14040 scenarios per segment through systematic variation of eight environmental and spill-related parameters. The framework consists of a binary classification model that predicts oil arrival at each segment, followed by a regression ANN that estimates the oil arrival velocity. The classification model achieved an accuracy of 0.95 on unseen data, while the regression model attained a percentage global RMSE of 6%

ABSTRACT. Ocean currents and winds can transport passive drifters, including human bodies, over large distances, complicating the reconstruction of shipwreck events. In the Mediterranean Sea, irregular migration has led to numerous shipwrecks followed by delayed and spatially dispersed body recoveries. This study makes use of Lagrangian drift modelling to reconstruct shipwreck locations and dates from recovery data, and conversely to predict potential recovery areas from known shipwreck events. Simulations were performed using the OpenDrift framework with the Leeway module, driven by Copernicus Marine Service oceanic and atmospheric data. Backward simulations were applied to a real case involving five bodies recovered in the southern Tyrrhenian Sea in 2024 and a documented shipwreck along the Tunisia-Sardinia route. The results identify coherent spatio-temporal convergence zones, demonstrating the potential of stochastic drift modelling as a practical tool to support forensic investigations and maritime incident reconstructions.

ABSTRACT. The Scheldt estuary is a key waterway that connects to major ports between the Netherlands and Belgium. Its morphodynamic evolution has been studied under tides, waves, and dredging influences, yet the contribution of cohesive sediments and waves remain poorly quantified. This study aims to evaluate how sand-mud interactions shape the large-scale development of the estuary, with an emphasis on intertidal areas. A 3D process-based model will be applied to represent sand-mud effects in erosion and bed roughness. The outcomes will be a hindcast of the Scheldt estuary morphodynamics between 1955 and 2020, and will be expected to highlight the role of cohesive sediment in estuarine morphodynamics, and will identify the dominant natural or anthropogenic drivers.

ABSTRACT. Understanding microplastics transport in the nearshore zone requires an accurate representation of wave-induced circulation and vertical mixing processes. This study presents a methodological framework for reconstructing continuity-consistent quasi-three-dimensional velocity fields from depth-averaged outputs of the Nonlinear Shallow Water (NSW) and Boussinesq equations. A benchmark configuration is first employed to verify the numerical consistency and physical plausibility of the model. The framework is then extended to compare shallow water and Boussinesq formulations over a simplified planar bathymetry, enabling the influence of individual equation terms on tracer evolution to be isolated and physically interpreted. The proposed technique offers a valuable tool for extending the utility of efficient two-dimensional models toward quasi-three-dimensional hydrodynamic analysis.

ABSTRACT. Shore-fixed X-Band Marine Radar (XBR) collected data during a relatively energetic storm at our study site. We analyzed XBR images with Lightweight Image Assimilation Framework (LIMASSI) to retrieve wave characteristics. Comparison with field measurements showed that the LIMASSI reconstructed the sea state satisfactorily. These conditions were provided to a phase-resolving model, inundation analyses were conducted, and the results were compared with empirical methods. Consequently, the empirical methods could not capture the peak runup location and alongshore variability

ABSTRACT. This study improves the numerical modelling of the swash zone by addressing limitations of the hydrostatic pressure assumption in numerical models based on the Non‑Linear Shallow Water Equations (NSWE). It highlights the importance of higher‑order non‑hydrostatic pressure terms associated with vertical accelerations occurring during wave run‑up and rundown. These terms are approximated using a depth‑averaged numerical model coupled with a log‑law‑based Bottom Boundary Layer (BBL) sub-model that analytically reconstructs the vertical structure of the flow. The approach retains the computational efficiency of NSWE models while capturing the essential physics of vertical accelerations. Validation against a laboratory-based experiment and a depth-resolving Reynolds-Averaged Navier-Stokes (RANS)- based Computational Fluid Dynamics (CFD) model shows that the analytically reconstructed vertical velocity is more accurate than that from the CFD model when compared with the measurements. The higher-order pressure terms involving accelerations in the vertical velocity are generally comparable with the ones estimated from the CFD model, especially in the backwash phase.

ABSTRACT. Wave-induced hydrodynamic and sediment-transport processes in nearshore regions are crucial in the design of coastal protection measures. Waves in the coastal zone interact with the seabed, resulting in wave breaking, wave-generated currents, wave boundary layer development and sediment transport in the form bed and suspended loads. These processes have the potential to cause bed morphological changes, such as small-scale bed formations, i.e. ripples, or large-scale ones, i.e. berms and seasonal beach profiles. Occasionally, large-scale bed morphological changes may cause beach erosion and/or threaten the stability of coastal infrastructures. These issues motivate the need for predictive models that explicitly couple hydrodynamics and sediment transport. In this work, such an in-house numerical model was developed and results are presented of flow and suspended sediment transport induced by breaking waves over a constant-slope beach.

ABSTRACT. Before constructing pumped hydropower storage (PHS) plants, it is crucial to evaluate their potential ecological impacts. This study examines how reservoir selection, initial thermal conditions, and pumping operations influence internal flow dynamics. A full-factorial simulation design was applied, systematically varying key parameters over a 24-hour pumping cycle. The results indicate that stratification is an important parameter governing flow behavior, with inflows tending to follow the thermocline under stratified conditions, whereas in unstratified cases they propagate along their density-equivalent layers. Future work should extend this analysis to real reservoirs and longer timescales, incorporating external inflows and meteorological forcing. Overall, this work is an important step towards understanding the subsequent processes of PHS operation such as sediment transport and habitat alterations.

ABSTRACT. This study evaluates the effectiveness of rainwater harvesting reservoirs as an adaptation measure to enhance drought resilience during the potato growing season in the Temmesjoki River Basin, northern Finland. A daily water balance model (1981–2023) was used to simulate reservoir performance across a range of storage capacities (0–550 m³ per hectare) under variable climate conditions. Even small reservoirs (50–200 m³) substantially reduced irrigation shortfalls, decreasing deficit days by over 90% and deficit volume by up to 95%, while storages of 300–400 m³ nearly eliminated deficits in most years. Storage benefits declined beyond 400 m³, indicating diminishing returns. Spatial variation showed that northern and coastal sub-basins required larger storage due to lower precipitation and higher evaporative demand. Overall, reservoir capacities of 200–400 m³ per hectare provided the most cost-effective improvement in water supply reliability, demonstrating the potential of decentralized reservoir systems to support climate-resilient agriculture in Nordic regions.

ABSTRACT. Sediment deposition is a critical problem in water reservoirs. It decreases storage capacity, hydropower efficiency, and water supply reliability. Dredging is one of the efficient sediment management approaches for solving this problem especially when flushing or bypassing are empirical. Cutter suction dredgers (CSDs) are widely utilized in reservoir dredging. Its rotating cutterhead makes it suitable for disintegrating different bed deposits. Also, its stationary swinging-stepping working method allows for accurate cutting profiles. However, the near-field environment around the cutterhead is not sufficiently understood. It includes different sediment resuspension mechanisms and dynamic interactions. In this study we are covering one of the knowledge gaps related to cutter suction dredging in reservoirs. This study experimentally investigates the dynamic interaction between the rotating cutterhead and the generated turbidity currents and the impact on its dynamic characteristics and sediment transport capacity. The results of this study show that increasing the rotational speed of the cutterhead enhances water entrainment and vertical mixing inside the turbidity current promoting less stratified turbidity currents. On the other hand, increasing the suction discharge decelerates the turbidity current and reduces its thickness. These findings provide process-level insight for designing CSD operations in reservoirs and contribute to sustainable sediment management strategies.

ABSTRACT. Reservoir sedimentation represents a pervasive and increasingly critical issue worldwide, leading to the gradual loss of storage capacity and the degradation of dam functionality (Oehy & Schleiss, 2007). As sediments accumulate within reservoirs, they reduce the available water storage volume, disrupt sediment continuity, and alter downstream river morphology and ecosystems. Given that dams are essential water infrastructure for flood control, irrigation, hydropower generation, and water supply, sedimentation poses a significant threat to their operational efficiency and long-term sustainability (Chamoun et al., 2016). To address these challenges, the implementation of effective sediment management strategies has become imperative. Figure 1 shows a number of these strategies, which aim to mitigate the adverse impacts of sediment deposition through methods that either prevent, route, or remove sediments from the reservoir system (Annandale et al., 2016). With regard to dredging, water injection dredging (WID) has emerged as an innovative and energy-efficient technique for sediment mobilization and redistribution. In WID, low-pressure water jets are directed onto the reservoir bed, inducing sediment resuspension and generating turbidity currents capable of transporting sediments toward the dam outlet. These artificially-induced turbidity currents facilitate sediment routing, a process conceptually aligned with the naturally-occurring turbidity currents traditionally utilized for sediment venting (Chamoun et al., 2018). WID involves several physical processes, starting from the injection of low-pressure water until the final deposition of sediments at the target location. These processes should be well understood in order to apply WID optimally for sediment management. In this paper, the state-of-the-art knowledge on the WID technique is presented with the aim of providing deeper insight into the underlying physics and identifying future research directions. To date, the main application of WID is maintenance dredging in ports and navigation channels. This explains why the vast majority of the state-of-the-art knowledge of WID comes from research related to ports and waterways (e.g., Kirichek et al., 2021). The continual accumulation of fine sediments in harbors and waterways presents a persistent challenge for port authorities, necessitating periodic dredging operations to preserve adequate depths for safe and efficient navigation. WID harnesses natural processes (e.g., gravity, currents and tides) to remobilize and redistribute sediment away from silted areas. In WID, specialized vessels employ a series of nozzles positioned close to the seabed to inject substantial volumes of low-pressure water directly into the sediment bed (Sigwald et al., 2015). This process decreases the bulk density of the seabed material, resuspending it and generating turbidity currents, that propagate horizontally or downslope under the influence of natural hydrodynamic forces such as gravity and ambient river or tidal currents (see Fig. 2). The resulting run-out distance of the turbidity currents primarily depends on the initial flow thickness, sediment concentration, and bed slope.

ABSTRACT. The breaching of embankment dams has led to some of the most catastrophic flooding events the world has ever seen. The 2023 breaching of the Bu Mansour Dam in Libya, for example, resulted in casualties exceeding 10,000, and the destruction of a large portion of the city of Derna. The risk posed by the potential for dam failure is undeniable; however, the consequences of failure for thousands of dams worldwide are unknown. To evaluate failure consequences, an estimate of the breach outflow hydrograph is necessary. Breach outflow hydrographs can be estimated for embankment dams using various methods, such as based on the software framework BASEbreach, which hosts multiple parametric numerical models for simulation of embankment dam failure (Vetsch et al., 2023).

Most parametric numerical models simulate a progressive erosion process that is applicable to homogeneous embankment dams. However, this erosion process is not realistic for zoned embankment dams that contain a cohesive core zone. For zoned embankment dams, which make up a significant percentage of large dams worldwide, numerous failure mechanisms are possible. One such failure mechanism is a two-stage process of cracking due to bending followed by cantilever rotation. This failure process was identified in experiments by Halso et al. (2025). A parametric numerical model has been developed specifically for zoned embankment dams, that assesses dam stability against this two-stage process (Halso et al., 2024).

1. Processes of zoned dam breach failure The new model for zoned embankment dam failure is designed for simulation of breaching due to overtopping. Simulation begins from initial overtopping of a low or weak spot along the dam crest. The overtopping flow causes erosion of the embankment material, resulting in the formation of a breach channel through the dam crest and along the dam downstream face. The breach channel through the crest deepens until reaching the top of the core zone, which acts as a rigid structure that resists further vertical breach growth. Continued erosion causes the breach to widen above the core, and the flow passing down the downstream face causes erosion that can both widen and deepen the breach channel downstream of the core. Eventually, the reduction of embankment material from downstream of the core causes the core to be unsupported against upstream water and sediment pressures. The core is pushed in the downstream direction, and eventually cracks along the center of the breach. The core splits into two separate pieces along the crack. Thes two separate pieces subsequently experience cantilever rotational failure due to the upstream pressures. A large breach forms through the core, and breach discharge increases rapidly. Continued erosion of downstream embankment material reduces stability of the remaining sections of the core, and additional cantilever rotational failures cause the breach to grow, allowing breach discharge to continue increasing in a discontinuous manner. The breach discharge causes the reservoir level to decrease, and eventually the breach discharge reaches a maximum and begins to decrease. The simulation continues until a specified simulation time, or until the breach width reaches the abutments of the dam.

2. Software framework for dam breach outflow estimation In this article, application of the new model for simulating zoned embankment dam failure in the dam breaching software BASEbreach is described. BASEbreach is an open-source freeware developed and maintained at the Laboratory of Hydraulics, Hydrology and Glaciology, ETH Zurich. The parametric numerical models for simulating progressive dam breaching of Macchione (2008) and Peter et al. (2018) are already available in the software. These models are both designed for progressive erosion of homogeneous embankment dams due to overtopping. These models require as inputs information about reservoir shape and volume, embankment size and shape, and embankment erodibility.

The new model of Halso et al. (2024) is designed for erosion of zoned embankment dams. The model simulates the progressive erosion process of the embankment shell material, and the discontinuous erosion process of the core material. To apply this model in BASEbreach, the same inputs as the progressive erosion models are required, as well as additional details about core size, shape, and strength. The software can be applied to any zoned embankment dam that contains a central vertical cohesive core, with simulation times on the scale of just a few seconds. Important dam breach parameters that the software outputs include estimations of the breach discharge hydrograph, sediment discharge hydrograph, and breach width. For dams in which shell erodibility and core strength parameters are uncertain, which is common, the model can be run numerous times with those parameters varied throughout their ranges of probability. This results in a probabilistic representation of results. This software can be applied by dam engineers and operators to perform a probabilistic simulation of zoned dam failure due to overtopping, which can be applied in dam breach studies for risk assessment, hazard mapping, and emergency planning.

Acknowledgements This research was funded by the Swiss National Science Foundation (project #192223).

References Halso, M. C., Evers, F. M., Boes, R. M., & Vetsch, D. F. (2024). A simplified method for simulation of the overtopping failure of zoned earthen dams and dikes. 12th International Symposium on Fluvial Hydraulics, Liverpool, UK. https://doi.org/10.3929/ethz-b-000726714 Halso, M. C., Evers, F. M., Vetsch, D. F., & Boes, R. M. (2025). Breach development and core failure during overtopping of zoned embankment dams [in review]. Journal of Hydraulic Engineering. Macchione, F. (2008). Model for predicting floods due to earthen dam breaching. I: Formulation and evaluation. Journal of Hydraulic Engineering, 134(12), 1688–1696. https://doi.org/10.1061/(ASCE)0733-9429(2008)134:12(1688) Peter, S. J., Siviglia, A., Nagel, J., Marelli, S., Boes, R. M., Vetsch, D., & Sudret, B. (2018). Development of Probabilistic Dam Breach Model Using Bayesian Inference. Water Resources Research, 54(7), 4376–4400. https://doi.org/10.1029/2017WR021176 Vetsch, D. F., Halso, M. C., Seidelmann, L., & Boes, R. M. (2023). Software tool for progressive dam breach outflow estimation. 12th ICOLD European Club Symposium, Interlaken, Switzerland. https://www.taylorfrancis.com/chapters/edit/10.1201/9781003440420-111

ABSTRACT. Pump it up: Zooplankton and Macroinvertebrate Diversity in Pumped-Storage Hydropower Reservoirs

ABSTRACT The change to renewable energy sources depends on intermittent sources like wind and solar energy. However, the intermittency of these sources challenges the stability of the power grid and energy storage systems are gaining relevance (Harby et al., 2013). Pumped-storage hydropower (PSH) is one of the most common energy storage systems and as of today the largest contributor to energy storage worldwide (Hunt et al., 2020). In PSH systems water is pumped from a lower altitude to a higher altitude reservoir and stored for later energy generation via conventional hydropower operations. Moving water against the natural flow direction entails several environmental challenges for the freshwater ecosystems involved. Stratification of temperature and oxygen can be shifted, nutrient levels can change, and species can be introduced to new environments (Bermúdez et al., 2018; Bonalumi et al., 2012; Buikema & Loeffelman, 1978; Cunha et al., 2011). Potential negative effects on biodiversity such as zooplankton and macroinvertebrates may emerge due to the changing physical and chemical properties of the ecosystems. At the same time species may be transported between reservoirs and thereby changing species composition (Kokavec et al., 2017; Potter & Meyer, 1982). Mapping shifts in biodiversity composition can be challenging due to costly and time-consuming sampling and morphological identification, especially when several species-rich taxonomic groups are of interest. Environmental-DNA (eDNA) samples can be a useful tool to overcome these challenges (Bruce et al., 2021).

1. Methods eDNA samples were collected in 10 reservoirs and 6 natural lakes in the Sira and Kvina watercourses in southern Norway to map zooplankton and macroinvertebrate biodiversity. To assess biodiversity in these lakes and reservoirs, eDNA was collected for up to four 30 minutes boat transects in each lake. While driving along the shoreline in 2-3 knots, water was continuously pumped through a 2.0 µm glass fiber filter to collect eDNA. Additionally, a plankton net was dragged behind the boat to collect zooplankton. Compared to traditional eDNA samples, where water samples are collected at single points along the shoreline, this method will provide a more representative biodiversity estimate for the lakes. Currently, there is no standardized procedure for mapping lake biodiversity using eDNA. Our goal is to develop a standard methodology using the transect approach. Furthermore, physical and chemical parameters such as pH, oxygen, nutrient content, turbidity and heavy metals were measured by collecting water samples. Temperature loggers were placed at several depths to detect changes in temperature stratification related to pumping activity. Reservoirs where PSH is established will be compared to reservoirs used only for production of hydropower and lakes not affected by any hydropower.

2. Pilot study Preliminary findings from a pilot study in the Sira and Kvina watercourses suggest that altitude is an important predictor of biodiversity, where lower altitude reservoirs typically host a higher number of species than higher altitude lakes for both macroinvertebrates and meiofauna (Fig. 1).

Fig 1. Cumulative species richness in the lakes at different elevation levels in southern Norway, based on combined water and sediment samples. The lines show the total observed (solid line) and estimated (dashed line) number of species. Benthic macroinvertebrates include oligochaetes, coleopterans, dipterans, trichopterans, plecopterans, ephemeropterans, and odonates. Meiofauna comprises all other invertebrates except insects, arachnids, and oligochaetes.

Even if higher biodiversity is typically seen as positive, high-altitude lakes are naturally characterized by lower temperatures, higher oxygen levels and lower nutrient and organic matter load, limiting biodiversity. Species thriving in mountainous freshwater environments are adapted to these specific conditions and therefore sensitive to changes in the environment (Loria et al., 2020). PSH will likely transport nutrient-rich water and introduce new organisms into the higher altitude lakes, potentially increasing biodiversity, but it may also affect the locally adapted species negatively (Cunha et al., 2011).

3.Future Work We will assess biodiversity as well as the physical and chemical environments in lakes with (i) no hydropower, (ii) conventional hydropower production and (iii) PSH. This will allow us to investigate potential effects of PSH on biodiversity in high-altitude mountainous lakes in relation to the chemical and physical environment in each reservoir.

References Bermúdez M, Cea L, Puertas J, Rodríguez N, Baztán J (2018) Numerical Modeling of the Impact of a Pumped-Storage Hydroelectric Power Plant on the Reservoirs' Thermal Stratification Structure: a Case Study in NW Spain. Environmental Modeling & Assessment, 23, 71-85 Bonalumi M, Anselmetti FS, Wüest A, Schmid M (2012) Modeling of temperature and turbidity in a natural lake and a reservoir connected by pumped-storage operations, Water Resources Research 48: W08508 Bruce K, Blackman R, Bourlat SJ, Hellström AM, Bakker J, Bista I, Bohmann K, Bouchez A, Brys R, Clark K, Elbrecht V, Fazi S, Fonseca V, Hänfling B, Leese F, Mächler E, Mahon AR, Meissner K, Panksep K, Pawlowski J, Schmidt Yáñez P, Seymour M, Thalinger B, Valentini A, Woodcock P, Traugott M, Vasselon V, Deiner K (2021) A practical guide to DNA-based methods for biodiversity assessment, Advanced Books Buikema AL, Loeffelman PH (1978) Effects of pumped storage operations on rotifer populations: With 6 figures in the text, SIL Proceedings, 1922-2010, 20(3), 1597–1603 Cunha DGF, Grull D, Damato M, Blum JRC, Lutti JEI, Eiger S, Mancuso PCS (2011) Trophic state evolution in a subtropical reservoir over 34 years in response to different management procedures, Water Science and Technology, 64, 2338-2344 Harby A, Sauterleute J, Korpås M, Killingtveit Å, Solvang E, Nielsen T (2013) Pumped Storage Hydropower, In Transition to Renewable Energy Systems, 597-618 Hunt JD, Byers E, Wada Y, Parkinson S, Gernaat DEHJ, Langan S, van Vuuren DP, Riahi K (2020) Global resource potential of seasonal pumped hydropower storage for energy and water storage, Nature Communications 11: 947 Kokavec I, Navara T, Beracko P, Derka T, Handanovičová I, Rúfusová A, Vráblová Z, Lánczos T, Illyov M, Šporka F (2017) Downstream effect of a pumped-storage hydropower plant on river habitat conditions and benthic life – a case study, Biologia 72, 652-670 Loria KA, McKnight D, Ragar DM, Johnson PT (2020) The life aquatic in high relief: shifts in the physical and biological characteristics of alpine lakes along an elevation gradient in the Rocky Mountains, USA. Aquat. Sci. 82: 11 Potter DU, Meyer JL (1982) Zooplankton communities of a new pumped storage reservoir, JAWRA Journal of the American Water Resources Association, 18, 635-642

ABSTRACT. This study analyses long-term hydrological data (1979–2024) to assess the management of a hydrosystem where a conflict between hydropower production and irrigation activity appears. Trend analysis suggests a tendency for lower inflows to the reservoirs during April–June and a slight tendency for higher inflows in January–March, likely related to shifts in the snowmelt period. However, these inflow tendencies alone do not justify the recent significant reduction in water allocated for irrigation, which appears primarily driven by operational management prioritizing energy production. The findings highlight the need for comprehensive multicriteria operational strategies to balance hydropower profitability with water availability for agriculture.

ABSTRACT. Cementitious grout injected into dam foundations to seal rock fractures undergoes long-term degradation driven by hydrogeochemical interactions with groundwater. Although reactive solute transport models are widely used in durability assessments of cementitious materials, the influence of site-specific reservoir water chemistry is often simplified or neglected. In hydropower dams, spatiotemporal variations in reservoir water composition can therefore play a significant role in controlling degradation processes and, consequently, the service life of the structure. This study presents a modelling framework for evaluating the impact of reservoir water composition on the hydrogeochemical degradation of cement grout in typical Swedish dam foundations. The framework combines advective–dispersive transport and groundwater flow, solved using the finite element method, with geochemical reactions simulated in PhreeqcRM through an operator-splitting approach. Changes in cement mineralogy are translated into porosity evolution, which is dynamically coupled to hydraulic conductivity and effective diffusion. Representative reservoir water compositions from Swedish hydropower sites serve to define chemically realistic boundary conditions. The proposed framework enables systematic investigation of how key chemical parameters, including pH, ionic strength, and carbonate concentration, influence the extent of decalcification, secondary phase formation, and the development of spatially heterogeneous porosity and permeability over time. The framework supports the development of more realistic predictive models for dam foundation performance by enabling explicit consideration of site-specific hydrogeochemical conditions.

ABSTRACT. This abstract presents a practice-oriented learning framework designed to address the challenge of operationalizing water infrastructure asset management. Triallled with Swedish utilities, its abductive and collaborative methodology created a 'learning sandbox' that fostered the psychological safety needed to bridge the theory-practice gap. This resulted in the co-development of practical artifacts and the emergence of a professional Community of Practice.

ABSTRACT. Currently, Spain is undergoing an energy transition process where hydraulic storage will play a significant role. As the country expands its use of renewables, there is a critical need to store energy in order to improve the stability and reliability of the grid. The latest revision of the Spanish Integrated National Energy and Climate Plan (PNIEC) aims to construct 22 GW of storage by 2030, and 30 GW by 2050. To achieve these goals, Pumped Storage Hydropower (PSH) emerges as a technology with great potential to balance supply and demand and integrate renewable energy sources, specifically in a country like Spain, which has favorable conditions for its development. When there is an excess energy from a renewable source, the system pumps water uphill to a reservoir. When energy demand is high or renewable energy production is not enough, the stored water generates electricity. Currently, there is an installed capacity of around 6 GW, with PSH facilities strategically distributed across the country. In addition to the PNIEC goals, Spanish legislation has lately paved the way for further PSH developments, addressing barriers related to the administrative process such as concession incompatibilities, or recognizing hydraulic energy storage as a priority within the order of precedence in the use of water. The plan is ambitious: increase the use of already available water storage capacity in the country, prevent waste as other renewable sources are integrated, and extend substantially the installed capacity. A key point for this growth will be the National Hydraulic Energy Storage Program (PNAHE), which focuses on using state-owned reservoirs for new PSH projects. In particular, the National Program PNAHE, will focus on 37 technically relevant locations, with a total storage capacity of around 77 GWh of energy, and a daily capacity of around 8 GW.

ABSTRACT. A. Climate change adaptation and mitigation

Central Macedonia is the second most populated region in Greece after Attica. Water management is a matter of considerable importance, necessitating a concerted effort to ensure sustainability, as it is greatly affected by climate change. The predominant characteristic of the impact of climate change on water resources in Central Macedonia, Greece, is the substantial alteration in the contribution of water over time. The recent advancements in hydrological modelling and the implementation of novel flood protection initiatives should incorporate a thorough examination of the evolving hydrological patterns, which are distinguished by a sequence of extreme events. The current climatic conditions are that drought periods are followed by periods of heavy rain and flooding. The major impact of the climate crisis in Greece does not manifest in alterations to the quantity of precipitation. Instead, the region is experiencing a succession of drought and flood periods, occurring in rapid sequence. Consequently, not only should traditional hydrological models be updated to align with these new patterns, but also a range of novel practices, projects, and policies should be evaluated and designed to adapt to the emerging climatic conditions. This paper sets out key changes in practices and policies as adaptation measures for the transition of sustainable water management to the new era of the climate crisis. To adapt to the new climatic conditions, consideration should be given to new hydrologic extremes, new hydrologic patterns, and new return periods. In the Central Macedonia region it has been estimated that the return period of existing flood protection projects has been reduced from 50 to 22 years under the new climatic conditions (3rd phase of WFD River Basin Management Plans in Central Macedonia 2024). It is evident that the hydrological peaks associated with the novel flood protection initiatives are projected to escalate by approximately 2.5 times, a necessity that arises in response to the anticipated alterations in climatic conditions and the necessity to accommodate heightened flooding requirements. This essential change in hydrological modelling does not necessarily imply that large-scale flood protection projects should be constructed in the future. It is imperative that the newly proposed flood protection schemes consider the substantial accumulation of water in the upstream mountainous regions. This remark indicates that flood protection initiatives should be initiated in mountainous regions with greater urgency, as opposed to the current practice of restricting these efforts exclusively to the downstream areas of river basins. The conventional methodologies employed in the context of flood protection initiatives have historically centered on the construction of riverbed defenses in downstream locations. However, there is now a compelling imperative to recalibrate these approaches and implement alternative strategies, namely the construction of a series of small dams in upstream mountainous regions. The primary objective of this revised strategy is to impede the rapid movement of substantial volumes of water during brief periods of intense precipitation. It is important to note that this practice has another key effect, namely that it facilitates groundwater recharge. This, in turn, provides a solution to the problem of water scarcity during drought periods. As previously mentioned, it has been demonstrated that periods of elevated temperature and aridity are associated with an increased frequency of forest fires. Forest fires leading to deforestation in mountainous regions severely influence the management of water resources. These compound hazards exacerbate flood damage in downstream areas. Additionally, they intensify water scarcity issues by increasing erosion and reducing groundwater recharge. A pivotal issue for the adoption of measures in the context of the current climate crisis is the necessity of a substantial shift from a fragmented administrative model to a more integrated one within the entire river basin. This suggests that the fragmented and locally oriented administrative model, within which hydraulic projects are designed and constructed by the state, the region, and the municipality, according to the magnitude of the project, should be integrated within the river basin. This is necessary to consider the interconnections of the projects and the dynamics of the water all over the water basin. This implies that the river basin should incorporate the dispersed and locally focused administration model, in which hydraulic projects are planned and built at the state, regional, and municipal levels, depending on the project's size. The various jurisdictions associated with this fragmented and locally oriented model should prioritize the necessity of cooperation on the part of all state, regional, and municipal authorities for the purpose of integrated water management. Such cooperation is to be extended from source to sea. A paradigm shift is needed from water supply to water demand management. The implementation of water-saving policies, incorporating engineering measures, is imperative to revive outdated hydraulic projects and modernize existing irrigation systems. This approach ensures the conservation of water resources. Demand management is imperative to avert the necessity of undertaking substantial and costly hydraulic projects for the collection and storage of water to tackle the frequent periods of drought. The novel initiative is not focused on increasing water deposits; rather, it is oriented towards reducing water demand and consumption. The final point to be addressed is that of so-called "nature-based solutions" to the issue of adapting to the new climatic conditions. Following the implementation of measures to reforest areas affected by forest fires, the construction of small dams from wood or stone has been shown to be an effective method of preventing rapid water fluctuations downstream and recharging groundwater. This approach utilizes the capacity of nature to mitigate the impact of natural disasters. An alternative to the construction of technical barriers along riverbanks is the creation of natural retention areas for the purpose of flood protection. Creating natural retention areas to prevent flooding is an alternative to building technical barriers along riverbanks. These illustrations show how nature-based solutions can help ensure that the shift to the new climate period is both successful and financially feasible.

ABSTRACT. The transition toward a low-carbon European energy system requires the integration of large shares of variable renewable energy sources (RES), particularly wind and solar. However, the inherent intermittency of these technologies introduces significant operational challenges related to system flexibility, balancing, and reliability. This study investigates the potential of expanding hydropower storage capacity—specifically retrofited pumped hydro storage—to enhance renewable integration at the European scale. The objective is to assess the techno-economic impact of additional hydro-storage capacity on system operation, generation mix, and total system costs under CO₂ emission constraints.

ABSTRACT. This study estimates the economic value of improving water quality in Swedish lakes and watercourses to inform policy implementation under the EU Water Framework Directive. Household willingness to pay (WTP) for reductions in acidification, eutrophication, pollutants, and physical impact is elicited using a stated preference choice experiment based on regional and national survey data. The results indicate a positive and significant WTP for all environmental problems, with higher values for pollutants and acidification than for physical impact. Nevertheless, improvements related to physical impact generate substantial societal benefits based on the national sample, with estimated values of approximately SEK 780,000 per kilometre of improved watercourse and SEK 1 million per square kilometre of improved lake area over a six-year period. The findings highlight the importance of incorporating non-market values into cost–benefit analyses and support the use of national-level estimates in water management decisions.

ABSTRACT. Recreational fishing is one of the most widely practiced outdoor activities in Sweden and constitutes an important societal value expected to be affected by the ongoing national revision of hydropower licenses, which aims to balance ecological improvements with the needs of hydropower production. Understanding both the current value of recreational fishing and how this value may change under improved fishing conditions in Swedish rivers is therefore essential for informed decision making about hydropower relicensing. This study combines revealed preference data with contingent behaviour responses obtained through a survey administered to fishing permit holders in three different rivers. The resulting meta-analysis provides a useful tool for estimating economic values from improved fishing under different ecological conditions.

ABSTRACT. This paper investigates how ecological baselines influence stated preferences and willingness-to-pay (WTP) for environmental improvements in regulated river systems. Using a discrete choice experiment (DCE) conducted in Sweden’s hydropower-affected Mo and Gide rivers, we examine the sensitivity of preferences to both the magnitude of ecological change (scope) and the initial ecological conditions from which improvements occur. Respondents faced repeated choice tasks involving river restoration programs characterized by changes in salmon populations, otter presence, and riverine ecological quality, alongside a cost attribute. We estimate a series of random utility models to capture preference heterogeneity and test alternative representations of ecological change, including linear, non-linear, and piecewise formulations. The analysis focuses on whether WTP is consistent with theoretical expectations of scope sensitivity and how baseline ecological conditions affect marginal valuations. We assess whether identical improvements yield different WTP depending on the initial state of the ecosystem, thereby contributing to the literature on reference dependence and embedding effects in environmental valuation. Our findings provide evidence on the importance of baseline specification in DCE design and interpretation, with implications for benefit transfer and policy appraisal in the context of hydropower relicensing under the EU Water Framework Directive. The results highlight that ignoring baseline conditions may bias welfare estimates and lead to misleading conclusions about the value of ecological restorations.

ABSTRACT. University partnerships with the Global South are increasingly important for addressing pressing hydro-environmental and sustainability challenges, as outlined in the UN Sustainable Development Goals (SDGs). These collaborations offer unique opportunities to co-develop innovative solutions for affordable and clean energy (SDG 7), climate action (SDG 13), and sustainable infrastructure (SDG 9), while fostering equitable knowledge exchange and capacity building. However, such partnerships often face barriers including resource disparities, power imbalances, and limited access to advanced tools and technologies. This study explores how collaborative research and education in energy transition can be achieved, e.g., through the adaptation of technical curricula or research adaptation to local contexts, supporting SDG 4 (Quality Education) and SDG 10 (Reduced Inequalities). Case studies highlight successful joint programs and research networks that advance SDG 17 (Partnerships for the Goals). Results implicate the importance of equitable, co-created partnerships that prioritize mutual benefit and local relevance. By enabling inclusive collaboration, universities can play a pivotal role in achieving the SDGs and addressing global energy transition.

ABSTRACT. The presence of antibiotics in wastewater treatment plants and their subsequent release into receiving water bodies poses significant environmental and public health risks, particularly due to their persistence and contribution to antimicrobial resistance. This review synthesizes data from 55 studies across 35 countries to assess the occurrence, removal efficiency, and ecological risks of antibiotics in WWTPs and freshwater systems. Frequently detected antibiotic classes – β-lactams, quinolones, macrolides, and sulfonamides – were often found at concentrations exceeding predicted no-effect concentrations, indicating potential harm to aquatic ecosystems. Removal efficiencies varied widely across treatment technologies, with some wastewater treatment plants exhibiting negative removal rates. Ecological risk assessments revealed that several antibiotics, including amoxicillin, azithromycin, ciprofloxacin, clarithromycin, and sulfamethoxazole, pose high risks due to concentrations significantly above PNEC thresholds. The findings underscore the urgent need for improved monitoring, advanced treatment technologies, and policy interventions to mitigate antibiotic pollution and safeguard environmental and human health.

ABSTRACT. 1. Introduction Decentralised wastewater treatment facilities (on-site and small scale) play a vital role in Finland’s sanitation system, as roughly 15% of the population (approximately 800,000 people) reside in permanent residences that are not connected to centralised sewerage networks (Lapinlampi, 2021, as cited in Laukka et al., 2022). Additionally, as of 2024, Finland had around 495,000 leisure homes, most of which are not connected to municipal sewer networks, resulting in additional pressure on decentralised wastewater systems, particularly during the summer and holiday seasons (Statistics Finland, 2025). Although decentralised units are typically small in scale, they can have a considerable environmental impact. In regards to the release of contaminants with discharging water, research indicates that upgrading 20 malfunctioning wastewater treatment systems (serving 20–99 PE) in the Helsinki and Vantaa regions led to reductions in biological oxygen demand (BOD) and phosphorus (P) loads equivalent to those produced by a 10,000 PE wastewater treatment plant (Luodeslampi et al., 2019, as cited in Laukka et al., 2022). Moreover, one of the past projects at the University of Oulu (ON-SITE, Interreg Nord) revealed low compliance with current regulations for on-site wastewater treatment systems, even though the median age of the units studied was only 3.8 years (Kinnunen et al., 2023). While data on water-linked emissions are lacking, information on GHG emissions from decentralised facilities in Finland is non-existent. Current knowledge of GHG emissions from decentralised sanitation largely comes from a limited number of studies conducted in regions where these systems dominate - typically in developing countries with warm climates (e.g., Cheng et al., 2022). For climate impact assessment, IPCC default emission factors for sanitation are used, but these are widely recognised as having significant limitations (e.g., Ramirez-Melgarejo et al., 2020), which are even more pronounced when assessing sanitation in the Nordic countries, as they do not account for climatic conditions and different types of treatment systems.

2. Methods Seven decentralised wastewater treatment units were selected in the North Ostrobothnia region in Finland. Permission for the sampling campaigns was acquired from the houseowners and water utilities. Five units represent on-site (one household) treatment systems and include two package plants Uponor Clean, one package plant Uponor WehoPuts, and two soil-based infiltration systems. Small-scale (community) decentralised wastewater treatment units were represented by two rotating biological contactors (RBCs), 500 PE and 750 PE. Uponor Clean is a biochemical treatment plant (so-called package plant) intended for continuous household use (Fig. 1A). Both our units consist of 2-cell septic tanks, followed by the process tank, where aeration takes place. Uponor WehoPuts is also a biochemical miniature package plant of a different design (Fig. 1B). It works as a sequencing batch reactor (SBR) without any pre-treatment. Two soil-based infiltration systems represent the most common type of on-site wastewater treatment technology in the region (Fig. 1C). They consist of a septic tank followed by a specifically designed infiltration field with several perforated pipes buried within it. Wastewater percolates through the soil until it reaches groundwater (no specific outflow). Two RBCs represent conventional aerobic biological treatment units, which serve two different small communities (Fig. 1D). GHG emissions were measured from the soil (infiltration fields), septic tanks, vents, and aeration process tanks using a Gasmet GT5000 Terra portable FTIR gas analyser (Fig. 1A). The analyser records data every 20 seconds for the gases of interest (CO2, CH4, N2O). Flux chambers were used for the soil and septic tanks (floating chambers, if the condition of a septic tank allows). For vents and aeration process tanks, the load of GHGs per time interval is calculated based on gas concentrations and flow rate, measured by a hot-wire anemometer. Wherever possible, inflow, outflow and mid-process samples were taken and analysed for COD, P (total and PO4-P), N (total, NH4-N and NO3-N), turbidity, alkalinity, pH, etc. Dissolved CO2 and CH4 were measured for septic tanks, RBCs’ pools and outflow samples. The research is currently in progress, and the extensive monitoring campaign ends in November 2025. All in all, different types of package plants were sampled 17 times, soil-based infiltration systems 13 times, and RBCs 6 times, with 1 more planned. The work with municipalities to obtain data for mapping areas in Finland not connected to the centralised sewage system is ongoing.

Fig. 1. Sampling campaign on Uponor Clean package plant (a); Uponor WehoPuts package plant (b); soil-based system (c); RBC (d).

3. Results Preliminary results (partial analysis of gathered data) indicated that CH4 emissions were observed across most systems, including infiltration fields. N2O emissions were mostly low, except Uponor WehoPuts on-site treatment system. Significant variability in the results was also observed, which was influenced by weather conditions, inflow changes and the owners’ management practices. For example, the maximum values of N2O emissions from the Uponor WehoPuts system during aeration were around 20 ppm on 04.09.25, while the maximum values on 02.09.25 were around 1200 ppm. Another example would be that during 10 minutes of accumulation in the first cell of the septic tank in Uponor Clean system, the concentration of CH4 reached 22.6 ppm on 09.06.25, but on 04.08.25, after 10 minutes, it was already 283 ppm. CH4 emissions from the vents aerating infiltration fields in soil-based systems on some sampling occasions were approaching 4,000 ppm concentration levels. The GHG emissions from RBCs’ vents (24-hour sampling campaigns) displayed some seasonal variation but were relatively stable. The full result will be presented at the conference.

Acknowledgements This research is funded by Maa- ja vesitekniikan tuki ry (MVTT) project “Climate Impact of Sanitation in Finland (CIS-Fin)”, a joint initiative between Aalto University (focusing on centralised sanitation) and the University of Oulu (focusing on decentralised sanitation).

References Cheng, S., Long, J., & Evans, B. (2022). Non-negligible greenhouse gas emissions from non-sewered sanitation systems: A meta-analysis. Environmental Research, 212, 113468. https://doi.org/10.1016/j.envres.2022.113468 Kinnunen, J., Rossi, P. M., Herrmann, I., Ronkanen, A. K., & Heiderscheidt, E. (2023). Factors affecting effluent quality in on-site wastewater treatment systems in the cold climates of Finland and Sweden. Journal of Cleaner Production, 404, 136756. https://doi.org/10.1016/j.jclepro.2023.136756 Laukka, V., Kallio, J., Herrmann, I., Malila, R., Nilivaara, R., & Heiderscheidt, E. (2022). Governance of on-site sanitation in Finland, Sweden and Norway (Reports of the Finnish Environment Institute, 8/2022). Finnish Environment Institute (SYKE). https://helda.helsinki.fi/items/b1c850e3-49f7-47b1-8d79-e5f40e8d767d Ramírez-Melgarejo, M. G., Reyes-Figueroa, A. D., Gassó-Domingo, S., & Güereca Hernández, L. P. (2020). Analysis of empirical methods for the quantification of N₂O emissions in wastewater treatment plants: Comparison of emission results obtained from the IPCC Tier 1 methodology and the methodologies that integrate operational data. Science of the Total Environment, 747, 141288. https://doi.org/10.1016/j.scitotenv.2020.141288 Statistics Finland. (2025). Number of free-time residences by region, 1970–2024 [Data set]. PxWeb. https://pxdata.stat.fi/PxWeb/pxweb/en/StatFin/StatFin__rakke/statfin_rakke_pxt_116j.px

ABSTRACT. This study assesses the performance of five decentralized wastewater treatment plants (WWTPs) operating under subarctic climatic conditions in northern Sweden. The investigated systems, located in the municipality of Luleå encompass a range of technologies, from conventional mechanical, biological and chemical treatment processes to a nature-based system. Six sampling campaigns are being conducted between autumn 2025 and winter 2026 to assess key physicochemical, microbiological and micropollutant parameters, including metals, pharmaceutical and personal care products (PPCPs), antibiotics and per- and polyfluoroalkyl substances (PFAS). Preliminary results indicate substantial variability in treatment efficiency among the systems, with the constructed wetland and large-scale WWTP achieving the highest removal of total suspended solids (up to 97%). The expected outcomes will enable a comparative understanding of the retention and removal performance of emerging contaminants across different treatment configurations. These findings provide valuable insights into the operation of decentralised wastewater treatment technologies in cold climates and support the development of sustainable sanitation strategies for small communities worldwide.

ABSTRACT. Wastewater treatment plants and climate change are interconnected, as climate change creates extreme weather that can overwhelm wastewater treatment plants, while wastewater treatment plants also contribute to climate change through greenhouse gas emissions. This connection is evident in the new EU Urban Wastewater Treatment Directive that mandates stricter treatment standards and requires upgrades to existing infrastructure to mitigate and adapt to climate change. In this work the methodology, indicative challenges and the first preliminary results of a project dealing with the mitigation and adaptation of the Psyttalia wastewater treatment plant in Greece to climate change, according to the EU Directive and following the structured approaches of the EC technical guidelines on climate-proofing infrastructure, are briefly presented.

ABSTRACT. Decentralized wastewater treatment is essential for remote locations lacking reliable sanitation infrastructure. This study assessed the performance of the long-term Engineered Ecosystem of CEADS/UERJ, located in Ilha Grande (Brazil), with a focus on phosphorus removal mechanisms in constructed wetlands (CWs). Monitoring occurred between September 2024 and April 2025, including measurements of phosphate, chemical oxygen demand (COD), dissolved oxygen (DO), oxidation–reduction potential (ORP), and macrophyte biomass. Average COD removal reached 78% in the primary–secondary treatment units, and final effluent COD values were below 8% of influent levels. Phosphate concentrations averaged 27.5 mg/L (influent), 24.7 mg/L (post-secondary treatment), and 9.0 mg/L at the CW outlet, yielding overall phosphorus removal efficiencies of 25–91%, with peak performance during spring. Mass balance analysis indicated limited direct contributions from substrate adsorption, or microbial biomass, suggesting substrate saturation after more than 16 years of operation. Unquantified processes, including microalgal assimilation and inorganic retention and macrophyte uptake, represented the dominant removal pathways. Seasonal macrophyte development appeared to enhance oxygenation and ORP, supporting higher removal rates during periods of greater biological activity. The findings provide relevant insights into the hydraulic and biogeochemical behavior of long-term CWs in decentralized wastewater systems, contributing to optimized design and operation in isolated communities.

ABSTRACT. This study evaluates the potential of apatite-rich mine tailings from northern Sweden in Malmberget and Kiruna to serve as an efficient and environmentally safe reactive medium for phosphorus (P) removal from pre-treated domestic wastewater. A comprehensive batch experimental study is conducted to quantify phosphorus sorption capacity and kinetics, while leaching tests evaluate the release of trace metals and radionuclides. The findings will provide the first systematic assessment of Swedish apatite tailings for P removal and will inform future use of mining by-products as sorbents in decentralised wastewater treatment applications.

ABSTRACT. Micropollutants need to be monitored in greywater treatment to ensure safe discharge and reuse. However, not all micropollutants can feasibly be monitored. In this study, micropollutants detected in greywater using non-target analysis were prioritized using multicriteria analysis (MCA). Bioaccumulation potential, persistency, and toxicity of the compounds were modelled using Quantitative Structure-Activity Relationship (QSAR) models. A shortlist of twenty micropollutants was developed using this ranking strategy. The relative distribution of micropollutant groups in the shortlist closely reflects that of the full dataset, with most compounds in both lists being fragrances and personal care products.

ABSTRACT. One of the bottlenecks for the development of source-separating wastewater systems is the uncertainty among stakeholders about end-users’ acceptance of new sanitation systems, such as vacuum toilets due to the limited information about it. This study explores public perceptions and investigates whether individuals, as end users, are willing to pay for vacuum toilets through discrete choice experiment. Two workshops and one pilot study were held to test the understandability of the questionnaire. Preliminary results identify a willingness to use vacuum toilets with a preference for those that generate less noise.

ABSTRACT. For detailed studies on hydraulics, a precise and versatile instrumentation suitable for both hydraulic laboratory research and field measurements is required. Therefore, ADVP (Acoustic Doppler Velocity Profiler) techniques provide valuable answers but uncertainties require an in-depth investigation and quantification. In this study, one of the sources of uncertainties is investigated: the hydraulic perturbation due to the transducer holder.

ABSTRACT. Low-cost, open-source SmartRocks sensors were deployed in the Partnach catchment (Bavarian Alps, Germany) to monitor temperature, pressure, conductivity, and turbidity. Pressure data, corrected for atmospheric variations, allowed continuous flow depth measurements, while temperature and conductivity showed good agreement with high-end reference sensors. Turbidity measurements were less reliable due to light and algal influences. Deployments using solid anchors demonstrated high stability, and improvements to sensor housing enhanced robustness under alpine conditions. These results highlight the potential of distributed low-cost sensors to complement conventional hydrological monitoring in mountain catchments.

ABSTRACT. This study proposes the application of LiDAR technology as a non-intrusive method to characterize the free surface in rectangular free jets. The system will allow capturing the abrupt transition from a non-aerated flow to a two-phase flow (aerated and fragmented) that occurs at the jet break-up length. A LiDAR SICK LMS4000 sensor will be used, operating at a sampling rate of 600 Hz and with an angular resolution of 0.0833°, to measure the mean profile and the fluctuations of the free surface. The results are expected to assess the feasibility of using LiDAR to accurately identify the jet break-up length as the point where the flow reaches sufficient signal reflectivity. The remote, high spatial and temporal resolution measurements provided by system may represent an effective alternative for the study of aerated free-falling jets.

ABSTRACT. Piano key weirs are nonlinear structures with higher discharge efficiency compared to linear weirs. They offer advantages for climate adaptation, particularly in open channels and dams for flood protection and flow control applications. Understanding the flow and velocity fields near piano key weirs is essential for effective hydraulic planning. This experimental study aimed to investigate the velocity fields in the inlet and outlet keys of a piano key weir under various discharge conditions using particle image velocimetry (PIV). The PIV results were validated against analytical estimates through randomized sampling and showed good agreement. Smooth approaching flow conditions were found for lower discharges, with higher velocities observed in the outlet key compared with the inlet key (ranging from 0.1 ms−1 to 1.2 ms−1). Higher discharges led to turbulent flow characteristics with air entrainment along the crest.

ABSTRACT. Extensive flood events in rivers have led to mobilization of large boulders that previously have remained stable over longer periods of time, and that under normal flow conditions are considered “immobile”. The increased frequency in large-scale flood events expected in the future, emphasizes the importance of predicting boulder displacement. Most research on sediment transport focuses on smaller particles, typically represented by a characteristic diameter, leaving the behavior of larger boulders under high-flow conditions less understood. An ongoing PhD project at NTNU investigates the incipient motion of boulders under varying flow conditions, providing a foundation for this study. Building on this work, the present study addresses a research gap by examining how boulder shape and edge-smoothness influence boulder mobilization, which is essential for improving predictions of large-particle transport and associated hazards in rivers. Understanding when and how boulders begin to move is important for hydropower operations, as mobilized boulders can pose risks to infrastructure, alter flow patters if settling near intakes or outlets, obstruct water conveyance, and ultimately reduce power production efficiency.

ABSTRACT. Accurate determination of water content in porous materials is essential in many hydro-environmental and industrial systems, where moisture levels influence mechanical stability, energy consumption, and process performance. Conventional laboratory-based measurements are often slow and provide limited real-time feedback, restricting effective monitoring and control. This study presents an optical real-time method for determining moisture content based on dual-wavelength infrared reflectance using lasers at 1310 nm and 1940 nm. The approach exploits the strong absorption peak of water at 1940 nm while using the 1310 nm signal as a reference, enabling robust quantification through the ratio of reflected intensities. The method is demonstrated on iron ore concentrates in a pelletizing process, where moisture control is critical. Tests performed on materials from the Malmberget and Kiruna plants show that the intensity ratio compensates for variations in surface roughness and exhibits a clear linear correlation with the gravimetrically determined moisture content. The results confirm that the dual-wavelength approach provides a stable and reproducible signal suitable for continuous monitoring of water content in granular porous materials

ABSTRACT. Physical scaled models remain an essential tool in design and verification of hydropower structures. Particularly for structures such as spillways and flood bypass tunnels with complex hydraulics. Advances in fabrication technologies now provide several potential alternatives to traditional model construction methods. Techniques such as 3D printing, CNC machining of complex cross-sections, and thermoforming or mechanical shaping of acrylic materials may allow more realistic representations of tunnel geometry. However, these methods differ in terms of production time, cost, achievable precision, and practical suitability for hydraulic laboratory experiments.

ABSTRACT. The techniques of Particle Image Velocimetry (PIV) and Particle Tracking (PT) have played a central role in the development of experimental fluid mechanics throughout the past four decades. These techniques provide instantaneous velocity fields in two and three dimensions at a resolution limited only by the hardware used. However, PIV/PT are indirect methods that deduce velocities from a sequence of intensity images, a strategy that makes the resulting velocity estimate algorithm dependent and prone to bandwidth capacity. In this presentation we investigate the possibility to perform experimental flow field analysis utilizing neuromorphic techniques. In particular, an event camera has been introduced in an existing PIV set-up. It is concluded that the technique has three main advantages over the use of traditional cameras. (1) The technique registers an event only when the intensity change in a specific pixel is large enough, which reduces the amount of data by orders of magnitude. (2) The space-time resolution is potentially higher because of the single-pixel response, and (3) the technique is inherently suitable to follow streamlines quantitatively. Despite these inherent advantages, the technique is still somewhat immature and has several drawbacks that all fall back on the hardware of the cameras. (i) the noise-level is high, which results in a significant number of false positives that needs to be handled posteriori, (ii) the resolution of the detector is about an order of magnitude lower than a modern digital CMOS detector and (iii) the pixel size is about three times as large as for a normal camera that together with the lower resolution can cause problems for specific applications. The presentation will introduce neuromorphic techniques and our experiences of using an event camera for flow field measurements.

ABSTRACT. Artificial reefs have gained popularity as a nature-based solution (NbS) for coastal protection services over the past few decades, serving to mitigate wave energy and improve ecological functions. This study aims to investigate the correlation between the porosity of submerged reefs and their ability for wave attenuation, with particular focus on the wave transmission coefficient and the reduction of wave energy. In this context, a comprehensive suite of physical model was performed to investigate the effect of reef porosity on wave attenuation, energy dissipation, and overall hydraulic performances for coastal protection structures. Experiments with PVC-made porous reefs, having porosity levels from 0.1 to 0.5 under various wave conditions, revealed a notable variation in wave heights and energy. This indicates a strong correlation between porosity and wave energy attenuation, highlighting the effectiveness of reefs in dissipating wave energy.

ABSTRACT. Coastal resilience increasingly relies on interventions that modify nearshore mixing to improve water quality, control pollutant dispersion and manage sediment and particulate transport. In this work we present an HPC-enabled 3D free-surface modelling framework, based on OpenFOAM, which resolves the interaction between surface waves and a turbulent jet representative of a coastal outfall. The model captures the full velocity field, free-surface elevation and turbulence structure, allowing the decomposition of the flow into mean, phase-averaged and turbulent components. This provides detailed insight into how waves modulate jet trajectory, vertical and horizontal mixing, and the distribution of turbulent kinetic energy in the water column. The framework is conceived as a numerical tool to support eco-engineered interventions aimed at manipulating nearshore dynamics: enhancing dilution and reducing peak concentrations, steering fine-sediment pathways, and potentially guiding the hydrochorous dispersal of seeds and propagules in the vicinity of coastal habitats. By exploiting HPC resources, the same configuration could be run also for multiple wave climates, and intervention layouts, enabling systematic comparison of alternative designs. The results illustrate how high-resolution, HPC-based CFD models can complement laboratory experiments and field observations for sustainable coastal management.

ABSTRACT. Sea‑level rise and more frequent/intense storms are increasing coastal flooding and erosion by elevating water levels and amplifying wave action. Engineers increasingly adopt low-carbon soft solutions like sand nourishment, complemented by a rising trend in Nature-Based Solutions (NBS) such as oyster reefs. NBS offer an alternative to traditional defenses because they can attenuate waves, adapt morphodynamically and enhance biodiversity. Yet, the design of NBS under varying metocean forcing remains poorly constrained. This work, undertaken within the BRICONS project for Kilkieran and Bertraghboy Bays, develops a long‑term offshore wave characterization to link changing offshore conditions to the required vertical growth of future oyster reef installations. Hourly wave reanalysis data from 1950 to 2025 were validated with multiple nearshore wave buoys at different locations and periods. Annual and monthly statistics for average and maximum values are analyzed, and linear trends are normalized to express changes per year. Results show increasing trends in wave heights with a stronger signal (4 times) in extremes than in means. The analysis demonstrates how such trends can be translated into target NBS vertical growth rates so that their wave‑dissipating function is not lost over time, which is governed by relative crest submergence and incident wave heights. The study also highlights the need for long‑term nearshore data to complement offshore characterization in addition to site specific larval transport modelling to identify reef locations with sufficient larval supply so that biological accretion can meet the target vertical growth rates over time.

ABSTRACT. The present study examines long-term changes in ocean-atmosphere variables, including Mean Sea Level Pressure (MSLP), Sea Surface Temperature (SST), and Sea Level Anomaly (SLA), over Ireland and its adjacent marine areas from 1993 to 2024. ECMWF ERA5 for SST and MSLP, and satellite-derived SLA data were utilised to analyse the spatiotemporal trends. Results show a distinct warming trend in the mean SST reaching 14.6°C. MSLP exhibits a slight north-south gradient, ranging from 1008.7 hPa to 1015.7 hPa, while SLA varies from 3.3 cm to 6.4 cm, displaying a consistent increasing trend. These results indicate Ireland is influenced heavily by global warming, with increases in SST contributing to a rise in sea level, while decreases in MSLP. The acceleration of SLA in recent years indicates climate change is having a greater effect on regional ocean-atmosphere dynamics, and has implications for offshore renewable energy potential and resilience of coastal infrastructure. In addition, a machine-learning (ML) predictive model is considered for modelling SLAs as a function of SST and MSLP variability.

ABSTRACT. Recently, seagrass canopies have been increasingly prioritised as a Nature-based Solution (NbS) for coastal resilience because of their dual benefits of ecological enhancement and wave energy dissipation. Numerous studies have evaluated seagrass-induced wave attenuation over the past few decades, but most focus on idealised, continuous canopies, thereby neglecting the spatial heterogeneity that characterises natural ecosystems. To bridge this gap, this study conducted a series of laboratory wave-flume experiments using scaled artificial seagrass mimics of Zostera marina under irregular wave conditions. This study quantified the hydrodynamic impact of two key parameters: canopy fragmentation (reduction in biomass) and longitudinal gap spacing between two independent seagrass canopies. It was found that canopy fragmentation can significantly compromise wave attenuation, particularly under low submergence-ratio conditions. A fragmentation level of only 12.5% resulted in an average 78% reduction in attenuation. Longitudinal spacing demonstrated a non-linear relationship with wave attenuation. While large gaps were expected to reduce performance by 9.4%-29.3%, smaller gaps resulted in a net increase in attenuation of 4.5%-5.6%. This counterintuitive enhancement can be attributed to the dominance of edge-induced turbulence over flow recovery within the gaps. The findings from this study contribute to the optimisation of the spatial design of seagrass restoration projects and, in turn, to the development of a sustainable coastal protection strategy.

ABSTRACT. Traditional sea defences, including seawalls and breakwaters, are facing escalating pressure from climate change and sea-level rise and are becoming ecologically and economically unsustainable. Hybrid coastal defences that combine natural features with engineered structures offer a promising alternative, but their hydrodynamic performance remains poorly understood. In particular, placing artificial reefs near seagrass canopies may both support seagrass growth and improve wave attenuation. This study investigates the combined wave-attenuation effects of artificial reefs and seagrass through laboratory experiments under irregular wave conditions, using seagrass mimics that closely mimic natural vegetation. Results show that the presence of seagrass reduces wave transmission by an additional 8.6% compared with reefs alone. An equivalent height enhancement index is introduced to translate this benefit into engineering terms, indicating that seagrass can provide wave attenuation equivalent to increasing reef height by up to 39%. The findings of this study provide a practical design tool for coastal engineers developing sustainable hybrid coastal defence systems.

ABSTRACT. Coastal regions are increasingly vulnerable to wave-induced hazards due to sea-level rise and intensified storm activity. Submerged artificial reef balls represent a nature-based solution capable of attenuating wave energy while supporting marine habitats. This study experimentally investigates the effect of longitudinal reef ball spacing on wave energy dissipation using long wave flume. Four spacing configurations (0.0–0.6 m) were tested under two water depths and both swell and storm wave conditions. Wave transmission coefficients were derived from surface elevation measurements upstream and downstream of the reef array. Results indicate that increasing spacing significantly enhances wave attenuation, with the 0.6 m configuration reducing wave transmission to 0.71 under swell and 0.62 under storm conditions, corresponding to up to 71% attenuation at shallower depths. These findings identify reef ball spacing as a key hydrodynamic design parameter for effective, nature-based coastal protection.