Environmental and Earth Sciences

Abstract: Riverbank filtration (RBF) is a sustainable technology for securing drinking water resources; however, many existing systems operate below their design capacities due to lack of optimization for site-specific hydrogeological conditions. Improving the performance of existing facilities is therefore an important challenge for sustainable groundwater management. This study proposes an operational management framework for improving the performance of a multi-well RBF system using long-term field monitoring data and groundwater modeling. A collector-well system located along the Nakdong River, South Korea, was selected as a case study. A MODFLOW groundwater model was calibrated using observed groundwater levels and single-well pumping tests and applied to evaluate hydraulic interference among wells and alternative pumping scenarios under multi-well operating conditions. The calibrated model reproduced observed pumping rates with errors ranging from 1.34% to 7.25%. Simulation results showed that simultaneous operation of multiple wells reduced abstraction efficiency because of hydraulic interference, whereas appropriate grouping of productive wells mitigated the loss of pumping performance. The recommended operation strategies increased simulated groundwater abstraction by approximately 72% compared with the current operating condition, without structural modifications. Integrating long-term operational monitoring with groundwater modeling provides a practical decision-support approach for improving the operational performance of existing multi-well RBF systems.

Abstract: The pollution of the shallow groundwater with nitrate (NO₃⁻) is considered as one of the problems concerning the water quality of semi-arid agricultural zones of northeastern Algeria. In this study, the physicochemical analysis of 80 groundwater samples was performed in order to characterize the hydrochemistry of the alluvial aquifer of the Garet Tarf plain in the Oum El Bouaghi wilaya, Algeria, and to estimate the degree of NO₃⁻ contamination. Twelve parameters were determined: the major ions HCO₃⁻, SO₄²⁻, Cl⁻, Ca²⁺, Mg²⁺, Na⁺, K⁺, and NO₃⁻; electrical conductivity (EC); pH; total dissolved solids (TDS); and a Water Quality Index (WQI). Nitrate concentrations vary in the range of 0 to 134 mg/L (mean concentration is 32.6 ± 27.7 mg/L); 18.8% of samples exceeded the WHO (2017) standard of 50 mg/L. Based on the results of piper diagrams, four hydrochemical facies were identified, including the dominance of Ca²⁺–SO₄²⁻ (46.3%) and Ca²⁺–HCO₃⁻ (27.5%), probably reflecting the effect of gypsum/anhydrite dissolution and carbonate weathering. The model based on the Random Forests® algorithm was used as an explorative method to determine which co-measured physicochemical parameters are most likely to be correlated with NO₃⁻ variability. The model demonstrated limited out-of-bag (OOB) R² performance of 16.36% (RMSE = 25.21 mg/L; MAD = 19.12 mg/L). One should consider this result with caution taking into account the limited number of data and predictor variables included. Random Forests® analysis revealed HCO₃⁻, Cl⁻, Ca²⁺, and Mg²⁺ as physicochemical parameters most strongly associated with NO₃⁻ variability within the evaluated dataset (OOB R² of the model is 16.36%). HCO₃⁻ is the first predictor in terms of variable importance (normalised value is 100%). It should be noted that this figure reflects the relative importance of HCO₃⁻ normalised to the most influential predictor. It means that HCO₃⁻ explains 100% of the nitrate variability. WQI values (mean is 53.4) indicate that the predominant quality of the water is poor due to geogenic mineralisation and, sometimes, due to nitrate content. These are different aspects of the water quality issue and cannot be mixed.

Abstract: In this research, a falling film reactor with UV light lamps as a photon emission source was designed and constructed for the degradation of the organic pollutant pyridine. Doping of the catalysts, zinc oxide with gold (ZnO/Au), and titanium dioxide with gold (TiO₂/Au) were performed by photodeposition technique. Subsequently, the doped photocatalysts were supported on ceramic clay sheets at 550 °C. The characterization of the photocatalysts was carried out by Scanning Electron Microscopy (SEM) and UV-vis DR spectroscopy. The following operating conditions were used for pyridine degradation: pH (acidic pH =5.5, natural pH =7.2 and basic pH =8.5) and hydraulic residence time (HRT) (0.2 L/min, 0.5 L/min and 1 L/min). Degradation monitoring was performed by UV-vis Spectroscopy, Total Organic Carbon (TOC), and High-Performance Liquid Chromatography (HPLC). A maximum pyridine removal of 97.64% was obtained using the ZnO/Ag photocatalyst, demonstrating the viability of this photocatalytic system for the degradation of organic pollutants such as pyridine.

Abstract: The Moving Bed Biofilm Reactor (MBBR) is commonly used for NH₄⁺-N removal from seawater recirculating aquaculture systems (RAS), while total nitrogen (TN) reduction is increasingly required. Aerobic denitrification offers a potential solution for simultaneous TN and NH₄⁺-N removal, but rapid reactor start-up remains challenging. This study investigated the start-up of aerobic denitrifying MBBRs treating mariculture wastewater. Eight MBBRs were operated at 25 ℃ with four C/N ratios (5.5, 4.5, 3.5, and 0) and two aeration rates (1.0 and 0.4 L/min). Only the CN4.5-0.4 MBBR met the predefined start-up criteria, achieving start-up in 26 days with an NH₄⁺-N removal efficiency of 93.8%. Effluent NH₄⁺-N and NO₂⁻-N remained below 0.5 mg/L without NO₃⁻-N accumulation. External carbon addition was essential, but excessive carbon did not accelerate start-up; CN3.5 MBBRs showed slower and less stable NH₄⁺-N removal, whereas CN5.5 MBBRs showed higher NO₃⁻-N removal but still accumulated NO₂⁻-N. Low aeration increased the average NO₃⁻-N removal efficiency at C/N = 5.5 from 39.0% to 66.2%. Microbial community analysis identified Pseudomonas, Vitellibacter, and Paracoccus as the dominant nitrogen-removing genera, with a combined relative abundance of 41.0% in the CN4.5-0.4 MBBR. Metagenomic sequencing identified genes associated with multiple nitrogen-transformation pathways and supported the potential for aerobic denitrification.

Abstract: Increasing reliance on groundwater, declining water tables and saltwater intrusion have intensified water stress along the coastal regions. This study evaluates the availability of source water for Managed Aquifer Recharge (MAR) in the Tiwi coastal aquifer, Kenya. Runoff, as a key potential source for artificial recharge, was quantified for the Pemba–Shimbo and Kongo/Mwachema watersheds using the Soil Conservation Service Curve Number (SCS-CN) method within a Geographic Information System (GIS) environment. Ten years (2015–2024) of rainfall data from three meteorological stations were spatially distributed using the Thiessen polygon method, while land use and soil characteristics informed curve number estimation under varying antecedent moisture conditions. Results indicate that excess runoff and thus potential recharge water is highly seasonal, occurring mainly during the long and short rainy seasons (March–May and October–December). The Pemba–Shimbo watershed exhibited significantly higher recharge potential, with runoff volumes ranging from 0.1 to 77.7 million cubic meters (MCM), compared to 0.1 to 5.5 MCM in Kongo/Mwachema. On average, approximately 13 MCM and 0.7 MCM of water were available annually for recharge in Pemba–Shimbo and Kongo/Mwachema, respectively. The findings demonstrate substantial, yet underutilized, opportunities for MAR, particularly in larger catchments. Strategic planning, including real-time flow monitoring and integration of weather forecasts, is recommended to optimize recharge interventions and enhance groundwater sustainability under changing climatic conditions.

Abstract: Percentile-based thresholds widely used in flash drought monitoring lack a clear physical basis, as the same percentile may correspond to substantially different soil moisture states under different soil and climatic conditions. This study constucted a framework based on the soil moisture loss rate function L(SM) to identify root-zone loss stages, estimate physically informed thresholds, and compare them with statistical percentile thresholds. Using ERA5-Land reanalysis data from 1950 to 2024, the framework combines non-parametric identification of L(SM) with piecewise linear fitting to characterize root-zone soil moisture loss stages and estimate physically informed thresholds in the Dongjiang River Basin, southeastern China. Two physically informed critical thresholds were identified: SMWT, representing the wet–transitional boundary, and SMTD, representing the transitional–dry boundary. Their relationships with statistical percentile thresholds and reference soil hydraulic parameters were then evaluated through spatial comparison and regression analysis. Results showed that root-zone L(SM) curves were overwhelmingly dominated by a wet–transitional–dry three-stage structure, accounting for 92.5% of all grid cells, while the gravitational drainage stage was absent at the root-zone scale. The basin-mean SMWT and SMTD were 0.36 and 0.27 m³/m⁻³, respectively, with mean bootstrap 95% confidence interval widths of 0.03 and 0.02 m³/m⁻³. The 40th and 20th percentile thresholds were fully nested between SMWT and SMTD, and their correlations with the physically informed thresholds reached 0.98–0.99. However, the statistical threshold window covered only approximately 55.6% of the physically informed transition zone, indicating weaker ability to characterize terminal drought severity than flash drought onset. The proposed framework provides physically informed reference thresholds for flash drought monitoring and supports regional adaptation of percentile-based methods.

Abstract: Efficient simultaneous nitrification, denitrification, and phosphorus removal typically requires either separate tanks with oxic and anoxic conditions or aerobic granular sludge (AGS) with granules larger than 0.2 mm. In this study, we cultivated small granular flocs (50-100 µm) capable of simultaneous heterotrophic nitrification and aerobic denitrification (HN-AD) in a sequencing batch reactor. The bioreactor was seeded with biomass from a municipal wastewater treatment plant and fed acetate-based synthetic wastewater for 114 days. The small granular flocs formed densified activated sludge (DAS), with biomass accumulating to approximately 12 g/L mixed liquor suspended solids. DAS was cultivated under selection pressures commonly used for AGS formation, including anoxic feeding, extended anoxic mixing, elevated hydrodynamic shear, and a gradual reduction in settling time. The sludge volume index (SVI) improved to 30 mL/g, comparable to that of granular sludge, with a moderate SVI₃₀/SVI₅ ratio of 72%. The relative abundance of Paracoccus reached 72.9%, indicating the metabolic capability of these small granular flocs to carry out HN-AD. Overall, these findings show that efficient simultaneous nutrient removal does not strictly depend on large granular structures. Achieving DAS and HN-AD offers a scalable approach to intensify biological nutrient removal while reducing reliance on distinct anoxic zones.

Abstract: We describe a harmonic analysis system for predicting annual peak snow water equivalent (SWE) at SNOTEL monitoring stations operated by the Natural Resources Conservation Service (NRCS) across the western United States. The algorithm, frqsrchX, performs greedy harmonic regression on daily SWE records, identifying persistent periodic climate signals and superimposing volcanic impulse functions to account for episodic radiative forcing from major eruptions. A five-phase characterization pipeline applies distinct band-limited search strategies per site, and a two-winner selection system identifies optimal configurations by both maximum pass rate and a reliability score that balances accuracy with period stability. Validation uses out-of-sample holdout testing over fifteen graded years drawn from holdout cutoffs 2008–2025, graded by an asymmetric scale that penalizes over-prediction more harshly than under-prediction. This version reports the network re-graded under a corrected annual-peak extraction routine. The original routine assigned peaks by calendar year rather than water year, mis-crediting early-season November and December maxima by a full year. Correcting this leaves interior continental results essentially unchanged and reduces maritime results substantially, separating the network into three tiers — interior states within a third of a percentage point (pp) of zero change, maritime-influenced Idaho at −1.29 pp, and the three Pacific states clustered between −4.10 pp and −4.97 pp — a spatial structure that tracks maritime influence and independently confirms the diagnosis. Corrected average pass rates range from 87.3% (Montana, 89 sites) to 44.3% (California, 119 sites, including 86 SNOW SENSOR stations). The three commercially targeted states — Montana (89 sites), Colorado (108 sites), and Wyoming (86 sites) — achieve average pass rates of 87.3%, 86.3%, and 84.1%, with 83–91% of sites meeting the ≥80% operational pass-rate threshold under identical universal parameter search procedures and no state-specific tuning. Idaho (82 sites) remains strong at 81.8%; Washington (69 sites) falls to 76.0% under the correction and is reclassified. Utah (86 sites, 75.2%) and Oregon (78 sites, 65.7%) show mixed and poor performance respectively, and California is non-viable at 44.3%, with no station reaching the operational threshold. Among sites clearing that threshold, 53–93% achieve stable signal detection. Two hundred and six stations qualify for the two- year-ahead product. The 2026 season, the first fully prospective test, produced a near-universal over-prediction across all commercially targeted states. A station-level decomposition for Colorado, recomputed here against consistently constructed full-record baselines, attributes this outcome predominantly to rain-versus- snow partitioning during a warm snow drought — 51% of the total SWE shortfall and 57% of the model's own prediction error — rather than to a precipitation-forecasting failure. We accordingly treat warm-drought years as outside the method's scope and ungraded, while precipitation-driven (dry) snow drought, a deficit the method does forecast, is graded normally.

Abstract: Water lost from drinking-water distribution systems has already consumed electricity, yet the associated operational greenhouse gas burden is rarely quantified because water balances and organizational emission inventories use different system boundaries. This study links the two within the Greek managerial-adequacy framework using a purposive availability sample of eight utilities and 14 utility-year observations for reference years 2024–2025. We calculate water-supply energy intensity, operational electricity-related carbon intensity per cubic metre of system input (ISO 14064-1 Category 2), and emissions allocated to reported real losses. Because organizational inventories include activities outside water supply—fugitive wastewater emissions reach 94% of the declared total in one island municipality—we classify itemized electricity supply points by activity and grade attribution quality. Energy intensity ranges from 0.538 to 2.434 kWh/m³ and system-input carbon intensity from 0.198 to 0.895 kg CO₂eq/m³. Under proportional average-intensity allocation, reported real losses are assigned 22.0–67.5% of each utility’s water-supply electricity emissions and 2,708 t CO₂eq in the 2025 cross-section. These are accounting allocations from top-down water balances, not direct measurements of leak-specific energy use. A conditional screening analysis shows that, under a one-for-one production response and the illustrative unit-cost assumptions adopted here, leakage-reduction scenarios overlap selected European public-investment carbon-value benchmarks. The results support activity-level electricity reporting and joint consideration of leakage, energy intensity, and system scale when prioritizing mitigation.

Abstract: Water-loss indicators answer different management questions, yet they are often used as interchangeable rankings. This exploratory study examines the 2024 and 2025 IWA water balances of eleven Greek water service providers documented under a harmonised regulatory framework, together with the twelve Infrastructure Leakage Index (ILI) values that seven of those providers declared in their regulatory reference tables or that could be reproduced from their WB-EasyCalc files. In 2025 non-revenue water (NRW) ranged from 26.7% to 71.1% of system input volume (mean 46.2%). For Fournoi Korseon and Trifylia, billed-unmetered consumption represented 36.6 and 31.6 percentage points of system input, respectively; plausible errors in these estimates therefore transfer directly to NRW. Six of the eleven providers declared an identical NRW in both reference years, and for four providers the leakage level declared in the reference table departs from the real losses in their own water balance by 3.8 to 17.5 percentage points. The declared ILI values span 1.25 to 21.40, but average pressure is stated for only four of the seven ILI cases and measured in none, two systems fall below the 2009 minimum-size expression, and one case (Chios, 2023) operates under a four-hour supply regime. Interpretation therefore depends on data completeness, pressure documentation and supply regime rather than on the indicator value alone. The findings support multi-indicator reporting: NRW as both percentage and volume, billing-meter coverage, real losses per connection and per kilometre when pressurised, and ILI as a supplementary metric accompanied by its inputs and uncertainty. The purposive sample and top-down loss estimates preclude national generalisation or inferential ranking claims.

Abstract: The Upper Cretaceous and Jurassic karst aquifers of Sierra de Segura (southern Spain) constitute a major groundwater resource within the “Sierras de Cazorla, Segura y Las Villas,” the largest Natural Park of Spain and the second largest in Europe. Both car-bonate aquifer systems are separated by the low-permeability Utrillas Formation (UT), composed mainly of sands, sandstones, and clay-rich sediments, and its hydrogeologi-cal role remains poorly understood. To investigate the hydraulic relationship between the aquifers and assess the existence of groundwater transfer through the Utrillas Formation, major ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻, and HCO₃⁻) and stable wa-ter isotopes (δ¹⁸O and δ²H) were analyzed in 465 groundwater samples from 20 springs between May 2020 and October 2023. Hydrochemical results revealed a progressive evolution from the Upper Cretaceous aquifers, characterized by lower electrical con-ductivity and temperature values (520 µS/cm and 12.2 °C), to the Jurassic aquifer, where these parameters increased to 611 µS/cm and 14.9 °C. Higher concentrations of Mg²⁺, Na⁺, K⁺, Cl⁻, and SO₄²⁻ in the Jurassic system indicate a greater degree of hydro-chemical evolution, consistent with enhanced water–rock interaction and more pro-longed groundwater circulation. Principal Component Analysis identified mineraliza-tion as the dominant control on groundwater variability (48.5% of the total variance) and revealed a hydrochemical gradient from relatively homogeneous Upper Creta-ceous groundwater toward more mineralized Jurassic groundwater, while several Ju-rassic springs overlapped with the Upper Cretaceous group. The convergence of hy-drochemical, isotopic, multivariate, and temporal evidence is consistent with hydrau-lic connectivity between the two aquifer systems. Collectively, these observations support the conceptual “Shower Effect” model, whereby groundwater is inferred to be transferred from the hydraulically elevated Upper Cretaceous aquifers to the under-lying Jurassic aquifer through the low-permeability Utrillas Formation.

Abstract: Areal precipitation series inherit their network’s composition: no record separates a station discontinuity from a regional shift; changing which gauges report moves the mean with none changing. The screen is two-layer, implementable on any network: a four-test relative-homogeneity battery on each gauge’s neighbour-ratio series, then propagation of those verdicts through realized rather than static Thiessen weights. Of Greece’s 187 weight-carrying gauges, 168 were testable and 19 were not; 96 classified useful, 30 doubtful and 42 suspect; relative and absolute verdicts agreed for only 87 of 168 (κ = 0.17). A drop-only screen cannot change a retained slope, so the suspect gauges are deleted, the weights renormalized over the survivors and every areal series rebuilt: of 16 field-significant increases, 14 survive, 2 lose field significance and 3 new detections appear on two distinct series. Individual catchment verdicts are fragile; the field verdict is not: it holds under nulls recalibrated for persistence, skewness and calendar gaps, and under every removal rule but the most aggressive, which leaves 10. That invariance is to detectable, non-shared inhomogeneity only. Deletion itself amplifies, 7 of 71 catchments rising to 16 of 66. Homogeneity screening alone is insufficient: the one field-significant decrease passes it yet is composition-dominated.

Abstract: Emotion analysis, primarily employed in social media text analysis, holds significant potential for unveiling patterns within large-scale scientific corpora. To explore this, I analyzed a corpus comprising 7.36 million sentences sourced from leading hydrological journals, including Water Resources Research and Journal of Hydrology, spanning years from 2010 to 2025. Utilizing emotion analysis coupled with unsupervised clustering, this analysis aimed to automatically track the prevailing progresses and limitations within the hydrological community across years. For instance, a progression in hydrological modeling from simple to hybrid models, a shift from single to integrated observation systems, and the increasing application of machine learning techniques were observed. The data extracted from the negative emotion, however, suggests a more worrying reality. Despite technological advancements, concerns regarding extreme hydrological event predictions, water resource monitoring, and simulation accuracy persist. Ultimately, while hydrological technology has advanced, the water crisis continues to worsen. Addressing this crisis necessitates breaking the negative feedback loop between human activities and water resources. Emotion analysis in hydrology allows us to examine the complex water-human relationship from a historical and broad perspective. It also serves to identify the tangible contribution the field has made toward restoring this relationship and informs prospective future efforts.

Abstract: Determining the recharge sources of adjacent old-working water outlets and their hydraulic connections is essential for zoned pollution control in closed coal mines. This study examined two outlets, S1 and S2, 174 m apart in the Chunjingwa closed coal mine area, Shanxi Province, China. Discharge dynamics, hydrochemistry, hydrogen–oxygen stable isotopes, and a goaf pumping test were combined. S2 showed 9.7 times the discharge variation of S1 and responded more rapidly to rainfall. Most contamination indicators had higher median exceedance levels at S2; isotopically, S1 overlapped with goaf boreholes ZK2 and ZK3, whereas S2 was heavier. During pumping, S1 discharge fell by about 91% and partially recovered, whereas S2 remained stable. The evidence identifies two distinct recharge–discharge systems on opposite sides of F2 and indicates limited cross-fault hydraulic communication at the tested scale and duration. F2 is interpreted as a structural divide, not a uniformly impermeable fault. S1 is regulated mainly by goaf-water storage to the south, whereas S2 is dominated by shallow-catchment, rapid-infiltration recharge to the north. The framework provides a practical alternative to artificial tracer tests for outlet-scale source identification and zoned remediation.

Abstract: Reverse osmosis (RO) desalination is an energy-intensive process, with centrifugal pumps and their electric drives constituting a significant portion of total system power consumption. Accurate estimation of this energy demand during the design phase is critical for optimizing plant efficiency and operational costs. Existing models often overlook or simplify the contribution of electric drive losses, leading to less precise power consumption projections. This study presents a comprehensive Simulink-based model designed to estimate the total power consumption and efficiency of a centrifugal pump system within an RO desalination plant. The model integrates several key components, including an electric drive loss estimation module, a centrifugal pump, a pipeline network, a pressure regulation valve, a fluid reservoir, and the RO system, within a unified simulation environment. A defining feature of this work is the explicit inclusion of electric drive losses, which enables a more holistic and accurate calculation of overall system efficiency and power demand compared to models focused solely on hydraulic power. By simulating system performance, the model demonstrates its utility as a predictive tool. This allows us to optimize pump selection and control strategies at the early design stage, potentially leading to more energy-efficient and cost-effective RO desalination systems.

Abstract: The water unavailability crisis in South Africa significantly contributes to socio-economic challenges affecting some of its underdeveloped former homeland areas. Limpopo province, which is predominantly rural, is nuanced by these challenges. The province is characterised by limited surface and groundwater resources, unevenly distributed, already overallocated and overused with limited scope for further development. At the same time, the province desperately needs high impact development to improve the socio-economic conditions of its communities. Water is the key resource required for those development initiatives to materialize. This study evaluates the water resources yield across the Limpopo District Municipalities. The mapping of the province’s water yield patterns across the five districts provides an insight into the extent of its water challenges and the cascading effects of this on developmental potentials of the province. The Pitman and Water Resources Yield Models were employed to achieve this. The total historical firm yield was estimated at 160.20, 39.84, 72.24, 125.79 and 120.96 Mm³/a for Vhembe, Capricorn, Waterberg, Mopani and Sekhukhune districts respectively. This study provides an insight into approaches that could be deployed by the districts to determine local water resources availability to support planned developmental projects while ensuring sustainable provision of water services to their communities.

Abstract: In summer 2026, record-low Danube water levels twice forced the Paks Nuclear Power Plant to curtail output, prompting public debate about upstream dam operations, drought, and national water security. A companion technical study [1] shows that part of the 2026 record reflects a four-decade, quantifiable shift in the river’s own stage–discharge relationship at Paks: a channel-scale change that was, in principle, statistically detectable for decades before it became an operational constraint. This Perspective argues that the episode is one instance of a recurring pattern in Hungarian water management: risks legible in existing data well in advance surface as institutional surprises, because surface water, groundwater, and the sectors depending on them are governed separately despite being physically one system. The pattern is illustrated with two further cases: on the one hand, the well-documented decline of shallow groundwater across the Hungarian Great Plain since the late 1970s; on the other, the stationary statistics behind the 2014 design-basis low- water criterion of Paks II (the separate expansion project still under construction at the same site), now strained by the 2026 record with no evidence of reassessment. The physical basis for treating Danube surface water and adjacent groundwater as one connected resource is also set out. It is further reported that a dedicated water-balance analysis found no evidence that upstream water management retained water during the drought (if anything the reverse), corroborated by an independent regional water-storage and precipitation record. We close by identifying what an integrated planning instrument would require, and what is currently missing, without prescribing a specific policy response.

Abstract: In summer 2026, record-low Danube water levels at Paks, Hungary, twice curtailed the Paks Nuclear Power Plant. Using 46 years of daily discharge and water-level records (1981–2026), we test whether the stage–discharge relationship shifted independently of discharge. The published discharge series proves to be a periodically revised rating-curve product, not an independent measurement – confirmed by a 2022 bulk reprocessing and the operator’s own statement that discharge derives from water level – so we reconstruct roughly 11–12 rating epochs, not thousands of daily observations. Water level at a fixed reference discharge (1300 m3/s) has declined 16–17 cm per decade (95% CI −19 to −14), confirmed at a shallower rate (−8.6 to −14.0 cm/decade) in the least circular subset of years. Three comparison stations show a spatially coherent pattern: a stabilized step at the 1992 upstream diversion, a plateaued unrelated historical decline further upstream in Austria, and two stations – including Paks – still declining. The 1980s-vintage rating curve would place the 2026 low-water stage roughly 65 cm higher at the same discharge. We find no evidence that upstream water management retained water during the 2026 drought. Hungary’s current river-basin management plan treats the plant’s thermal discharge as a pressure on the river but, on our review, never the reverse relationship demonstrated here.

Abstract: Marinas support a range of recreational and commercial activities, but their enclosed hydrodynamics, and associated operations can generate diverse and rapidly changing environmental pressures. Conventional monitoring may miss short-lived events, previously unrecognized contaminants and the combined biological effects of multiple stressors. Valvometry, the measurement of bivalve shell behaviour, is an emerging biomonitoring technology that can provide continuous, integrated evidence of environmental variability and stress. This study developed and demonstrated the BioSentinel Health Index, a biologically informed framework combining bivalve-behaviour with assessments of data quality and management and response capability. Minute-scale valve-gape data from the mussel Mytilus galloprovincialis at Mandurah Ocean Marina, Western Australia, were used to derive ecosystem-health metrics. Mussels were classified as open for 87.9% of valid observations and exhibited broadly consistent rhythmic structure (spectral consistency score = 75.9%). Coordinated valve-closure events served as operational alarm indicators linked to a documented investigation and response pathway. At least three active mussels provided valid observations for 86.2% of the period. The single-station deployment only received partial spatial-coverage credit because it did not account for potential environmental variation across the marina. Under the proposed framework, Mandurah Ocean Marina received a preliminary score of 85.2%, placing it within the highest overall rating category.

Abstract: Launched in 2014, China’s Sponge City (SC) initiative represents one of the world’s most ambitious efforts to integrate nature‑based solutions into urban stormwater management for a variety of benefits. Although widely adopted as a dominant planning model across Chinese cities, SC’s long-term effectiveness and viability remain debated. Moreover, the scope and potential impact of SC initiatives have multidisciplinary implications. To address these gaps, this study adopts a novel conceptual framework and further elaborates its theoretical foundation for evaluating SC viability across six dimensions: Environment, Economy, Governance, Civic Engagement, Urban Form, and Human Wellbeing. The framework extends traditional sustainability models by expanding social and spatial considerations, which are critical factors in the urban context and often underexamined in SC research. The vast scope of SC scholarship makes it challenging to assess the viability of the national initiative in China. Thus, we conducted a systematic review of reviews and an assessment of thematic relevance across the six dimensions of the framework. Findings reveal a heavy focus on the Environmental dimension, while other important dimensions receive substantially less attention. This imbalance suggests that current scholarship may offer a partial understanding of SC viability, underscoring the need for more integrated, interdisciplinary, and evidence-based research.