Water

20 pages, 6530 KB

Open AccessArticle

Monthly Temperature Prediction in the Han River Basin, South Korea, Using Long Short-Term Memory (LSTM) and Multiple Linear Regression (MLR) Models

by Chul-Gyum Kim, Jeongwoo Lee, Jeong-Eun Lee and Hyeonjun Kim

Water 2026, 18(1), 98; https://doi.org/10.3390/w18010098 - 31 Dec 2025

Abstract

This study compares and evaluates the performance of a statistical model, Multiple Linear Regression (MLR), and a deep learning model, Long Short-Term Memory (LSTM), for predicting monthly mean temperature in the Han River Basin, South Korea. Predictor variables were dynamically selected based on [...] Read more.

This study compares and evaluates the performance of a statistical model, Multiple Linear Regression (MLR), and a deep learning model, Long Short-Term Memory (LSTM), for predicting monthly mean temperature in the Han River Basin, South Korea. Predictor variables were dynamically selected based on lagged correlation analysis between climate indices and temperature over the past 40 years, identifying the top ten variables with the highest correlations for lag times ranging from 1 to 18 months. The MLR model was developed through stepwise regression with cross-validation, while the LSTM model was constructed using an 18-month input sequence to capture temporal dependencies in the data. Model performance was evaluated using percent bias (PBIAS), Nash–Sutcliffe efficiency (NSE), Pearson’s correlation coefficient (r), and tercile-based probability metrics. Both models reproduced the seasonal variability of monthly temperature with high accuracy (NSE > 0.97, r > 0.98). The LSTM model showed slightly higher predictive skill in several periods but also exhibited larger prediction variance, reflecting the sensitivity of nonlinear architectures to variations in predictor–response relationships. In contrast, the MLR model demonstrated more stable predictive behavior with narrower uncertainty bounds, particularly under low signal-to-noise conditions, owing to its structural simplicity. These findings indicate that the two approaches are complementary; the LSTM model better captures nonlinear temporal dynamics, while the MLR model provides interpretability and robustness. Future work will explore advanced hybrid architectures such as CNN–LSTM and Transformer-based models, as well as multi-model ensemble methods, to further enhance the accuracy and reliability of medium-range temperature prediction. Full article

(This article belongs to the Section Hydrology)

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21 pages, 1198 KB

Open AccessArticle

pH-Dependent Reactivity, Radical Pathways, and Nitrosamine Byproduct Formation in Peroxynitrite-Mediated Advanced Oxidation Processes

by Zhe Chen, Dandan Rao, Jian Zhang and Bo Sun

Water 2026, 18(1), 97; https://doi.org/10.3390/w18010097 - 31 Dec 2025

Abstract

Peroxynitrite (ONOOH/ONOO⁻) is increasingly recognized as a key intermediate in advanced oxidation processes (AOPs), yet its role in water treatment remains insufficiently defined. This study provides mechanistic insights into peroxynitrite-mediated AOPs through competition kinetics method, demonstrating that both decomposition and pollutant [...] Read more.

Peroxynitrite (ONOOH/ONOO⁻) is increasingly recognized as a key intermediate in advanced oxidation processes (AOPs), yet its role in water treatment remains insufficiently defined. This study provides mechanistic insights into peroxynitrite-mediated AOPs through competition kinetics method, demonstrating that both decomposition and pollutant degradation are strongly pH-dependent, with ONOOH dominating stability and radical pathways across pH 5.0−9.0, while its decay rate decreases from 1.2 s⁻¹ to 0.0022 s⁻¹. The interplay of HO^• and diverse reactive nitrogen species (RNS, including reactive nitrogen radicals and peroxynitrite) dictates pollutant-specific degradation efficiencies, with RNS showing a unique reliance in degrading bisphenol A—contributing up to 66.7% at pH 8.0. Buffer chemistry further modulates these pathways: bicarbonate accelerates peroxynitrite decay via CO₂ and CO₃^•−-mediated acceleration (resulting in a 361.9% increase at pH 9.0), while borate promotes reactive nitrogen radical formation but suppresses HO^• contributions. Importantly, peroxynitrite was shown to facilitate N-nitrosodimethylamine formation in the presence of dimethylamine, with yields maximized under alkaline conditions and attenuated by bicarbonate. These quantitative findings underscore the critical roles of pH and buffer chemistry in optimizing peroxynitrite-based water treatment while mitigating byproduct risks. Full article

(This article belongs to the Special Issue Novel Advanced Oxidation Technology for Water Treatment)

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16 pages, 731 KB

Open AccessReview

Neglected Genetic Coefficients for Bacterial Diversity as a Supporting Tool for Public Health and Wastewater-Based Epidemiology

by Karol Korzekwa, Oliwia Obuch-Woszczatyńska and Małgorzata Krzyżowska

Water 2026, 18(1), 96; https://doi.org/10.3390/w18010096 - 31 Dec 2025

Abstract

In the review, the collection of population genetics papers from 1973 to 2025 comprises 400 publications, 81 of which were significant and consulted with representatives from water and sewage companies. Reviewed Proteobacteria (mean H_S = 0.42), Firmicutes (mean H_S = 0.43), [...] Read more.

In the review, the collection of population genetics papers from 1973 to 2025 comprises 400 publications, 81 of which were significant and consulted with representatives from water and sewage companies. Reviewed Proteobacteria (mean H_S = 0.42), Firmicutes (mean H_S = 0.43), Actinobacteria (mean H_S = 0.33), and Spirochaetes (mean H_S = 0.54) represent the 60 species under investigation through the lens of “h” coefficients related to gene diversity and expected heterozygosity. The research also included ESKAPE, emerging pathogens, bacterial indicators of wastewater treatment efficiency, environmental sanitary surveillance and public health. The restoration of the expected heterozygosity for haploids “h” was proposed in wastewater-based epidemiology as an innovative tool for public health. The unique “h” coefficient allows for the comparison of genetic variability in various organisms, regardless of their ploidy, using multiple markers and traits. The parameter represents a noble character for both the variability of phenotypes (proteins) and genotypes (nucleic acids). Leveraging the genetic diversity highlighted by the “h” coefficient can support wastewater-based epidemiology, offering the ability to predict the stages and trajectories of disease outbreaks. Full article

(This article belongs to the Special Issue Evaluation of Microbiological Indicators for Water and Wastewater Treatment and Reuse)

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15 pages, 2230 KB

Open AccessReview

A Comparative Trends of Watershed Health and Its Driving Forces

by Ning Mao, Zitong Yin, Tanveer M. Adyel, Jun Hou and Lingzhan Miao

Water 2026, 18(1), 95; https://doi.org/10.3390/w18010095 - 31 Dec 2025

Abstract

In recent decades, rapid socioeconomic development and population growth have led to the degradation of river and lake health worldwide, posing severe challenges to watershed ecological management. The growing intensity of land-use has significantly contributed to the accelerated deterioration of aquatic ecosystems. River [...] Read more.

In recent decades, rapid socioeconomic development and population growth have led to the degradation of river and lake health worldwide, posing severe challenges to watershed ecological management. The growing intensity of land-use has significantly contributed to the accelerated deterioration of aquatic ecosystems. River and lake health assessment has evolved from single-parameter metrics (e.g., water quality) to multidimensional frameworks integrating hydrological, biological, and anthropogenic factors. This research conducted a bibliometric analysis of 1302 publications from 1996 to 2023 in the Web of Science database to identify research trends and hotspots. Results showed that publications exhibited a three-phase growth incubation (1996–2000), expansion (2001–2012), and acceleration (2013–2023), with the U.S., China, and Australia as leading contributors characterized by regionally clustered international collaborations. Research themes have shifted from single water quality parameters to integrated assessments. “Land-use”, “water quality”, and “biotic integrity” have emerged as core hotspots, forming a synergistic assessment framework that combines physicochemical, biological, and socioeconomic factors. The research scale underwent a spatial refinement process from the whole watershed to the buffer zone of rivers and lakes, and land-use effects on aquatic ecosystems vary significantly across spatial scales (entire watershed and riparian zones). Fine-scale studies better capture localized pollution pathways, supporting targeted conservation strategies. This review systematically outlines research status, hotspots, and development directions for river and lake health studies, highlighting the need for integrated watershed management, emphasizing conservation through fine-scale land-use monitoring, and providing scientific support for integrated refined governance of watershed ecology. Full article

(This article belongs to the Special Issue NBS for Watershed Management: From Ecological Health Assessment to Ecosystem Restoration)

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16 pages, 4982 KB

Open AccessArticle

Evaluation of Sediment Deposition Processes in Hydroelectric Plant: Case Study of Espora Reservoir, Brazil

by Assunção Andrade de Barcelos, João Batista Pereira Cabral, Fernanda Luisa Ramalho, Patrícia da Silva Gomes, Hudson Moraes Rocha, Valter Antonio Becegato and Alexandre Tadeu Paulino

Water 2026, 18(1), 94; https://doi.org/10.3390/w18010094 - 31 Dec 2025

Abstract

Studying sedimentary distribution in water reservoirs is essential to understand the depositional processes and develop sustainable environmental management strategies. Characterization of deposited sediments provides information about the sources of particulate matter, transport patterns and predominant deposition mechanisms in different compartments of the reservoir. [...] Read more.

Studying sedimentary distribution in water reservoirs is essential to understand the depositional processes and develop sustainable environmental management strategies. Characterization of deposited sediments provides information about the sources of particulate matter, transport patterns and predominant deposition mechanisms in different compartments of the reservoir. This study aimed to evaluate active deposition processes and to improve the understanding of sedimentation in water reservoirs. In this case, the Espora hydroelectric power plant, located on the Corrente River, southwestern Goiás, Brazil, was employed as a model environment. Sediment cores were collected at 29 points along the reservoir, covering different aquatic compartments. Particle-size analysis of the sediments was performed based on established methodologies using textural classification to identify sedimentary facies. The results indicated the predominance of stream deposits (sandy material) in areas where water flow velocity was higher, and bed deposits, composed predominantly of clays and silts, in regions of lower water flow velocity and greater depth. Full article

(This article belongs to the Special Issue River Channel Hydraulics, Fluvial Dynamics and Re-Opening Floodplains)

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Graphical abstract

18 pages, 1187 KB

Open AccessArticle

Detection of Water Quality COD Based on the Integration of Laser Absorption and Fluorescence Spectroscopy Technology

by Hanyu Zhang, Zhaoshuo Tian, Xiaohua Che, Ying Guo and Zongjie Bi

Water 2026, 18(1), 93; https://doi.org/10.3390/w18010093 - 30 Dec 2025

Abstract

Chemical oxygen demand (COD) serves as a critical indicator for assessing the extent of water pollution caused by organic matter. This study proposes an integrated COD detection methodology that combines laser absorption spectroscopy with laser-induced fluorescence spectroscopy, enabling accurate measurement of COD parameters [...] Read more.

Chemical oxygen demand (COD) serves as a critical indicator for assessing the extent of water pollution caused by organic matter. This study proposes an integrated COD detection methodology that combines laser absorption spectroscopy with laser-induced fluorescence spectroscopy, enabling accurate measurement of COD parameters across a wide concentration range. For high-concentration COD, conventional ultraviolet absorption spectrophotometry based on the Lambert–Beer law is employed. However, since laser absorption spectrophotometry exhibits substantial errors in detecting low-concentration COD, laser-induced fluorescence spectroscopy is adopted for the precise quantification of trace-level COD. By integrating these two laser-based approaches, a spectroscopic COD detection system has been developed that simultaneously records absorbance after the laser passes through the sample and quantifies fluorescence intensity perpendicular to the beam with an image sensor, thereby achieving comprehensive COD analysis. Laboratory validation using COD standard solutions demonstrated relative errors below 11% across the concentration range of 2–220 mg/L. Further application to natural water samples confirmed that the integrated laser absorption–fluorescence spectroscopy approach achieves wide-range COD measurement with high sensitivity, a compact configuration, and rapid response, demonstrating strong potential for real-time online water quality monitoring. Full article

(This article belongs to the Section Water Quality and Contamination)

25 pages, 16923 KB

Open AccessArticle

A Framework for Refined Hydrodynamic Model Based on High Resolution Urban Hydrological Unit

by Pan Wu, Tao Wang, Zhaoli Wang, Haoyu Jin and Xiaohong Chen

Water 2026, 18(1), 92; https://doi.org/10.3390/w18010092 - 30 Dec 2025

Abstract

With the accelerating pace of urbanization, cities are increasingly affected by rainstorm and flood disasters, which pose severe threats to the safety of residents’ lives and property. Existing models are increasingly inadequate in meeting the accuracy requirements for flood simulation in highly urbanized [...] Read more.

With the accelerating pace of urbanization, cities are increasingly affected by rainstorm and flood disasters, which pose severe threats to the safety of residents’ lives and property. Existing models are increasingly inadequate in meeting the accuracy requirements for flood simulation in highly urbanized regions. Thus, it is urgent to develop a new method for flood inundation simulation based on high-resolution urban hydrological units. The novelty of the model lies in the novel structure of the high-resolution Urban Hydrological Units model (HRGM), which replaces coarse sub-catchments with a fine-grained network of urban hydrological units. The primary innovation is the node-based coupling strategy, in which the HRGM provides precise overflow hydrographs at drainage inlets as point sources for LISFLOOD-FP, rather than relying on diffuse runoff inputs from larger areas. In this paper, a high-resolution hydraulic model (HRGM) based on urban hydrological units coupled with a 2D hydrodynamic model (LISFLOOD-FP) was constructed and successfully applied in the Chebeichong watershed. Results show that the model’s simulations align well with observed data, achieving a Nash efficiency coefficient above 0.8 under typical rainfall events. Compared with the SWMM model, the simulation results of HRGM were significantly improved and more consistent with measured results. Taking the rainstorm event on 10 August 2021 as an example, the Nash coefficient increased from 0.7 to 0.85, while the peak flow error decreased markedly from 15.8% to 3.1%. It should be emphasized that urban waterlogging distribution is not continuous but appears as patchy, discontinuous, and fragmented patterns due to the segmentation and blocking effects of roads and buildings in urban areas. The framework presented in this study shows potential for application in other regions requiring flood risk assessment at urban agglomeration scales, offering a valuable reference for advancing flood prediction methodologies and disaster mitigation strategies. Full article

(This article belongs to the Topic Basin Analysis and Modelling)

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23 pages, 4147 KB

Open AccessArticle

Physicochemical Conditions Shaping Phytoplankton Development in Shallow Lakes of Bellsund During the Ablation Season, West Spitsbergen

by Marta Ziółek, Małgorzata Poniewozik, Łukasz Franczak and Magdalena Kończak

Water 2026, 18(1), 91; https://doi.org/10.3390/w18010091 - 30 Dec 2025

Abstract

The small freshwater lakes of Spitsbergen remain poorly studied compared to surrounding marine ecosystems despite their sensitivity to rapid environmental changes. During the short ablation season, these shallow lakes exhibit physicochemical variability influenced by the harsh Arctic climate, local geology, and hydrology. This [...] Read more.

The small freshwater lakes of Spitsbergen remain poorly studied compared to surrounding marine ecosystems despite their sensitivity to rapid environmental changes. During the short ablation season, these shallow lakes exhibit physicochemical variability influenced by the harsh Arctic climate, local geology, and hydrology. This study analyzed six lakes located on marine terraces, moraine areas, and outwash plains in the Bellsund region to assess how physicochemical variability in their waters affects phytoplankton development. The lakes exhibited local and temporal variations in temperature, conductivity, ion composition, and nutrient levels, with generally low nutrient availability limiting biological productivity. Phytoplankton communities were quantitatively and qualitatively poor, dominated by green algae, either flagellates or mixed communities, including cyanobacteria. Green algae clearly dominated in lakes closest to the fjord shoreline, while dinoflagellates and cryptophytes dominated in inland lakes. Phytoplankton abundance and biomass were extremely low in one of the lakes situated on the raised marine terraces within the tundra vegetation zone (3 × 10³ ind L⁻¹ and 0.004 mg L⁻¹, respectively). In contrast, the much larger lake situated within the tundra zone nearer the fjord shoreline had values that were comparable to fertile lakes in the temperate zone (~30 thousand × 10³ ind L⁻¹ and ~28 mg L⁻¹, respectively). It should be noted that Monoraphidium contortum and Rhodomonas minuta dominated some of the lakes almost entirely. Phytoplankton abundance was related to physicochemical conditions: green algae increased with increasing ion concentrations (Cl⁻, Na⁺, K⁺, SO₄²⁻), P_min, Fe, and Mn; flagellates preferred colder waters with higher N_min and low TOC; cyanobacteria occurred in waters with lower COND, TOC, Ca²⁺, Si, Cu, and Zn. Phytoplankton biomass increased in July with increasing water temperature. Bird activity likely facilitated phytoplankton dispersal, increasing taxonomic diversity in frequently visited lakes. Full article

(This article belongs to the Special Issue Contaminants in Aquatic Systems: Biogeochemical Processes, Ecological Impacts)

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Graphical abstract

18 pages, 10160 KB

Open AccessArticle

Hydrogeochemistry of Thermal Water from Lindian Geothermal Field, Songliao Basin, NE China: Implications for Water–Rock Interactions

by Yujuan Su, Fengtian Yang, Xuejun Zhou, Junling Dong, Ling Liu, Yongfa Ma, Minghua Chen and Chaoyu Zhang

Water 2026, 18(1), 90; https://doi.org/10.3390/w18010090 - 30 Dec 2025

Abstract

To explore the hydrogeochemical characteristics and dominant water–rock interaction processes of thermal water in Lindian geothermal field (northern Songliao Basin, NE China), this study analyzed 16 thermal water samples (1900–3000 m depth) and 3 shallow groundwater samples using hydrochemical indices, water isotopes, and [...] Read more.

To explore the hydrogeochemical characteristics and dominant water–rock interaction processes of thermal water in Lindian geothermal field (northern Songliao Basin, NE China), this study analyzed 16 thermal water samples (1900–3000 m depth) and 3 shallow groundwater samples using hydrochemical indices, water isotopes, and statistical methods (Pearson Correlation and Principle Component Analysis). Results show that the thermal water originates from precipitation and exhibits an “oxygen shift” indicating a long-time water–rock interaction under low to medium reservoir temperature. The thermal water is alkaline with a high TDS and dominated by Na⁺, Cl⁻, and HCO₃⁻, and its hydrochemical facies changes from HCO₃·Cl–Na to Cl·HCO₃–Na and Cl–Na along the groundwater flow path. Leaching of halite, silicates, and carbonates is the primary process controlling solute accumulation. The geothermal reservoir is in a relatively closed, strong reducing environment, and thermal water reached water–rock equilibrium with respect to Na-, K-, Ca-, and Mg-alumino silicates. Principle Component Analysis identifies three key controlling factors, including mineral leaching, organic matter degradation, and sulfate reduction/mineral precipitation. This study establishes a hydrogeochemical baseline for the initial exploitation stage, providing a scientific basis for predicting long-term water quality changes and formulating differentiated sustainable development strategies for the Lindian geothermal field. Full article

(This article belongs to the Special Issue Groundwater Environment Evolution and Early Risk-Warning)

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27 pages, 6323 KB

Open AccessArticle

Multivariate Analysis and Hydrogeochemical Evolution of Groundwater in a Geologically Controlled Aquifer System: A Case Study in North Central Province, Sri Lanka

by Uthpala Hansani, Sapumal Asiri Witharana, Prasanna Lakshitha Dharmapriya, Pushpakanthi Wijekoon, Zhiguo Wu, Xing Chen, Shameen Jinadasa and Rohan Weerasooriya

Water 2026, 18(1), 89; https://doi.org/10.3390/w18010089 - 30 Dec 2025

Abstract

This study investigates the coupled relationship between groundwater chemistry, lithology, and structural features in the dry zone of Netiyagama, Sri Lanka, within a fractured crystalline basement. Groundwater chemistry fundamentally reflects geological conditions determined by rock-water interactions, we hypothesized that the specific spatial patterns [...] Read more.

This study investigates the coupled relationship between groundwater chemistry, lithology, and structural features in the dry zone of Netiyagama, Sri Lanka, within a fractured crystalline basement. Groundwater chemistry fundamentally reflects geological conditions determined by rock-water interactions, we hypothesized that the specific spatial patterns of groundwater chemistry in heterogeneous fractured systems are distinctly controlled by integrated effects of lithological variations, structurally driven flow pathways, aquifer stratification, and geochemical processes, including cation exchange and mineral-specific weathering. To test this, we integrated hydrogeochemical signatures with mapped hydrogeological data and applied multi-stage multivariate analyses, including Piper diagrams, Hierarchical Cluster Analysis (HCA), and Principal Component Analysis (PCA), and various bivariate plots. Piper diagrams identified five distinct hydrochemical facies, but these did not correlate directly with specific rock types, highlighting the limitations of traditional methods in heterogeneous settings. Employing a multi-stage multivariate analysis, we identified seven clusters (C1–C7) that exhibited unique spatial distributions across different rock types and provided a more refined classification of groundwater chemistries. These clusters align with a three-unit aquifer framework (shallow weathered zone, intermittent fracture zone at ~80–100 m MSL, and deeper persistent fractures) controlled by a regional syncline and lineaments. Further analysis through bivariate diagrams revealed insights into dominant weathering processes, cation-exchange mechanisms, and groundwater residence times across the identified clusters. Recharge-type clusters (C1, C2, C5) reflect plagioclase-dominated weathering and short flow paths; transitional clusters (C3, C7) show mixed sources and increasing exchange; evolved clusters (C4, C6) exhibit higher mineralization and longer residence. Overall, the integrated workflow (facies plots + PCA/HCA + bivariate/process diagrams) constrains aquifer dynamics, recharge pathways, and flow-path evolution without additional drilling, and provides practical guidance for well siting and treatment. Full article

(This article belongs to the Special Issue Advancing Applications in Hydrogeochemical Processes in Groundwater Systems)

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23 pages, 12331 KB

Open AccessArticle

Bedload Transport Velocities in Alpine Gravel-Bed Streams

by Rolf Rindler, Dorian Shire-Peterlechner, Sabrina Schwarz, Helmut Habersack, Markus Moser and Andrea Lammer

Water 2026, 18(1), 88; https://doi.org/10.3390/w18010088 - 30 Dec 2025

Abstract

The present study presents long-term monitoring data on the dynamics of bedload transport processes in alpine gravel-bed river systems in Austria (Urslau, Strobler-Weißenbach) using radio frequency identification (RFID) technology. The detection of embedded RFID tracers was facilitated by the use of stationary antennas. [...] Read more.

The present study presents long-term monitoring data on the dynamics of bedload transport processes in alpine gravel-bed river systems in Austria (Urslau, Strobler-Weißenbach) using radio frequency identification (RFID) technology. The detection of embedded RFID tracers was facilitated by the use of stationary antennas. This methodology enabled the acquisition of high-resolution data on particle transport velocities, transport distances, and sediment dynamics. Monitoring has been in operation permanently over a period of 8 years, including several intense flood events. In total, 1612 RFID-tagged stones were deployed, and the maximum measured particle velocity was 2.47 m s⁻¹. The measurements at the Urslau stream revealed seasonal variability and long-term trends, while targeted short-term measurements at the Strobler-Weißenbach stream provided valuable insights into the dynamics of flood events. The results underscore the significance of environmental factors, including the grain size, river gradient, and hydraulic parameters, in the dynamics of bedload transport in alpine gravel bed streams. Furthermore, the efficiency of stationary antennas was optimised to ensure uninterrupted monitoring. This study underscores the importance of contemporary monitoring technologies in analysing river processes and addressing challenges, including those brought about by climate change. Full article

(This article belongs to the Special Issue Flow Dynamics and Sediment Transport in Rivers and Coasts)

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21 pages, 5372 KB

Open AccessArticle

Hydrological Response of an Enclosed Karst Groundwater System to Drainage Induced by Tunnel Excavation in a Typical Anticline Geo-Structure

by Xiantao Xu, Qian Zhao, Xiangsheng Kong, Lei Zhang, Xiaojie Zhang, Tao Yu, Xiaowei Zhang and Qiang Xia

Water 2026, 18(1), 87; https://doi.org/10.3390/w18010087 - 29 Dec 2025

Abstract

The drainage of groundwater in mountainous tunnel projects always leads to substantial decline of the regional water table, which may induce numerous environmental issues, such as spring depletion, surface subsidence, vegetation degradation, and impacts on local water supplies, especially in the enclosed karst [...] Read more.

The drainage of groundwater in mountainous tunnel projects always leads to substantial decline of the regional water table, which may induce numerous environmental issues, such as spring depletion, surface subsidence, vegetation degradation, and impacts on local water supplies, especially in the enclosed karst aquifers of anticlines in the area, such as the Jura mountain type. A systematic hydrological monitoring was conducted during the excavation of the Wufu Tunnel in Chongqing, China. The monitoring data includes discharge rate and water level collected from tunnels, boreholes, coal mines, springs, and ponds, respectively. Hydrological responses of karst aquifers and surface water bodies to tunnel drainage and precipitation were investigated by statistical analysis, Mann–Kendall test, heat map, and wavelet analysis. Results show that the enclosed karst water system has strong hydraulic connections and good water storage conditions. Tunnel drainage is the dominant factor causing dynamic changes at monitoring points, while the influence of rainfall is relatively limited. Borehole water levels and coal mine drainage have a close correlation with tunnel inflow, while springs are influenced by both rainfall and tunnel drainage. Few pond monitoring points are related to rainfall. Tunnel drainage has transformed the regional groundwater dynamic conditions, causing local groundwater flow direction reversal and reconstructing the groundwater recharge-flow-discharge pattern. Full article

(This article belongs to the Special Issue Geotechnical and Underground Engineering Problems Caused by Water Action)

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6 pages, 165 KB

Open AccessEditorial

Water-Induced Geological Disaster Prevention and Sustainable Water Resource Utilization in Mines

by Helong Gu, Fan Feng and Yuan Zhao

Water 2026, 18(1), 86; https://doi.org/10.3390/w18010086 - 29 Dec 2025

Abstract

The deep areas and surface slopes of mines exhibit complex geological conditions [...] Full article

(This article belongs to the Special Issue Theory and Technology of Water-Induced Geological Disaster Prevention and Water Resource Utilization in Mines)

18 pages, 10385 KB

Open AccessArticle

Coupled SWAT–MODFLOW Model for the Interaction Between Groundwater and Surface Water in an Alpine Inland River Basin

by Zhen Zhao, Xianghui Cao, Guangxiong Qin, Yuejun Zheng, Shuai Song and Wenpeng Li

Water 2026, 18(1), 85; https://doi.org/10.3390/w18010085 - 29 Dec 2025

Abstract

For an alpine inland river basin affected by climate change, the interaction between groundwater (GW) and surface water (SW) within the watershed plays a crucial role in water resource management. To explore the bidirectional dynamic coupling of surface water and groundwater, this work [...] Read more.

For an alpine inland river basin affected by climate change, the interaction between groundwater (GW) and surface water (SW) within the watershed plays a crucial role in water resource management. To explore the bidirectional dynamic coupling of surface water and groundwater, this work adopted the extensively employed SWAT–MODFLOW model. Results indicate that statistical parameters including R² (0.81 for calibration periods and 0.79 for validation), NSE (0.79 for calibration periods and 0.75 for validation), RMSE (0.59~1.25 m), and PBIAS (15.21%) demonstrate the dependability of the SWAT–MODFLOW model in evaluating groundwater–surface water exchange processes within alpine inland river basins. Long-term monitoring data show that groundwater levels exhibited an upward trend, rising from 2895.35 m in 2005 to 2906.75 m in 2022. Notably, since 2018, groundwater levels have entered a period of being consistently above the long-term average. In terms of spatial distribution, the groundwater level patterns in 2005, 2010, and 2015 remained relatively consistent, marked by a west-to-east decreasing gradient. However, by 2020, this spatial distribution pattern shifted, marked by an east-to-west decreasing gradient. Meanwhile, our results reveal a pattern of upstream surface water recharge, bidirectional fluctuation in the middle reaches, and downstream groundwater-dominated recharge during the period of 2000~2023. During the 2000–2009 period, groundwater in sub5 received recharge from surface water, with the exchange rate ranging from −4987.75 to −374.82 m³/d. Conversely, during 2010–2023, groundwater in sub5 discharged into surface water, with the exchange rate ranging from 1136.75 to 56,646.56 m³/d. Moreover, there is seasonal variability in the SW–GW interchange relationship. In spring and summer, surface water primarily replenishes groundwater, whereas in autumn and winter, groundwater primarily replenishes surface water. This study provides a foundational method for assessing groundwater–surface water interactions in alpine inland river basins, which will contribute to the evaluation and management of local water resources. Full article

(This article belongs to the Section Hydrology)

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16 pages, 3744 KB

Open AccessArticle

Evaluating Environmental Effects of Zero-Discharge Events in a Regulated River in Northern Sweden Using Hydraulic Modelling

by M. Lovisa Sjöstedt, J. Gunnar I. Hellström, Anders G. Andersson and Jani Ahonen

Water 2026, 18(1), 84; https://doi.org/10.3390/w18010084 - 29 Dec 2025

Abstract

Increasing periods of zero-discharge and large fluctuations in discharge are expected in future hydropower operations due to changes in the electricity system, including greater reliance on solar and wind power, as well as increased variability in precipitation driven by climate change. In this [...] Read more.

Increasing periods of zero-discharge and large fluctuations in discharge are expected in future hydropower operations due to changes in the electricity system, including greater reliance on solar and wind power, as well as increased variability in precipitation driven by climate change. In this study, several types of zero-flow periods were analyzed in a regulated northern river in Sweden. The results highlight different mitigation measures that may be suitable for reducing ecological impacts associated with hydropeaking. The study also evaluates potential improvements that could be achieved by implementing a mean annual low flow instead of zero flow. Overall, the findings demonstrate the value of conducting detailed river-specific analyses to identify effective ecological restoration measures in regulated river systems. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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21 pages, 15026 KB

Open AccessArticle

Wind–Wave and Swell Separation and Typhoon Wave Responses on the Dafeng Shelf (Northern Jiangsu)

by Zhenzhou Yuan, Jingren Zhou, Wufeng Cheng, Hongfei Li and Yuyang Shao

Water 2026, 18(1), 83; https://doi.org/10.3390/w18010083 - 29 Dec 2025

Abstract

This study analyzes wave data from Typhoons Hinnamnor and Muifa in 2022, improves the traditional one-dimensional wind–wave and swell separation method (PM method), and proposes a wind–wave and swell separation strategy suitable for the Dafeng sea area during typhoon events. Combining this with [...] Read more.

This study analyzes wave data from Typhoons Hinnamnor and Muifa in 2022, improves the traditional one-dimensional wind–wave and swell separation method (PM method), and proposes a wind–wave and swell separation strategy suitable for the Dafeng sea area during typhoon events. Combining this with the WH enables high-precision separation of wind–wave and swell. A numerical model of MIKE21 SW waves was established based on the superposition of the Holland typhoon wind field and the ERA5 background wind field. Furthermore, the study conducts controlled variable experiments through numerical simulations to systematically quantify the differential effects of the maximum wind speed radius (RMW), translation speed, and track geometry. The mathematical model in this study couples MIKE 21 SW and MIKE 21 FM, importing hydrodynamic conditions through FM as key variables into the SW model. This enables real-time data exchange during the computational process, thereby yielding results that better align with physical reality. The results from factorial sensitivity experiments demonstrate that the significant wave height and average period of offshore waves, far from the typhoons, significantly increase with the expansion of the maximum wind speed radius, with wave heights at offshore points reaching a maximum of 7.5 m. Specifically, when the RMW increased by 50%, the wave height increased by 2.5 m. The wave characteristics of landing typhoons are more influenced by terrain effects and the location of typhoon landfall. Additionally, changes in typhoon translation speed lead to a first increase and then a decrease in significant wave height. The typhoon’s path significantly affects the propagation direction and energy distribution of waves. In the Dafeng area, distant typhoons often generate long-period swells, which continuously exert high loads on actual engineering foundations. These findings inform early warning systems and the design of shelf-aware port and coastal infrastructure in northern Jiangsu and similar regions. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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15 pages, 3521 KB

Open AccessArticle

Magnetic Biochar from Almond Shell@ZIF-8 Composite for the Adsorption of Fluoroquinolones from Water

by Diego Barzallo, Carlos Medina, Zayda Herrera and Paul Palmay

Water 2026, 18(1), 82; https://doi.org/10.3390/w18010082 - 29 Dec 2025

Abstract

This study aimed to synthesize a magnetic biochar@ZIF-8 composite derived from almond shell biomass for the adsorption of fluoroquinolones (FQs) from aqueous media. The biochar was prepared under different pyrolysis conditions using a central composite design (CCD) based on temperature and residence time, [...] Read more.

This study aimed to synthesize a magnetic biochar@ZIF-8 composite derived from almond shell biomass for the adsorption of fluoroquinolones (FQs) from aqueous media. The biochar was prepared under different pyrolysis conditions using a central composite design (CCD) based on temperature and residence time, with biochar yield (%) and ofloxacin adsorption capacity selected as the response variables. Subsequently, the composite was obtained by combining KOH-activated biochar with ZIF-8 and magnetic particles, producing a hierarchically porous material with enhanced surface area and functional groups favorable for adsorption. The physicochemical and morphological properties of the composite were characterized by SEM–EDS, FTIR, BET, TGA, and XRD analyses, confirming the successful incorporation of ZIF-8 and magnetic phases onto the biochar surface. The adsorption performance was systematically evaluated by studying the effects of pH and contact time. The kinetic data fitted well to the pseudo-second-order model, suggesting that chemisorption predominates through π–π stacking, hydrogen bonding, and coordination interactions between FQ molecules and the active sites of the composite. Furthermore, the material exhibited high reusability, maintaining over 84% of its adsorption capacity after four cycles, with efficient magnetic recovery without the need for filtration or centrifugation. Overall, the magnetic biochar@ZIF-8 composite demonstrates a sustainable, cost-effective, and magnetically separable adsorbent for water remediation, transforming almond shell waste into a high-value material within the framework of circular economy principles. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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18 pages, 4149 KB

Open AccessArticle

Suppression of Sulfur-Induced Corrosion in Sewer Pipe Using Conductive Carbon and Magnetite Iron Linings

by Miki Watanabe, Gede Adi Wiguna Sudiartha, Shingo Nakamura, Shuntaro Matsunaga, Nishi Kaito and Tsuyoshi Imai

Water 2026, 18(1), 81; https://doi.org/10.3390/w18010081 - 28 Dec 2025

Abstract

Sewer corrosion driven by sulfur metabolism threatens infrastructure durability. Current study examined the effect of conductive lining materials on microbial communities and sulfide control under simulated sewer conditions. Three lab-scale reactors (3.5 L total volume, 2.1 L working volume) were prepared with amorphous [...] Read more.

Sewer corrosion driven by sulfur metabolism threatens infrastructure durability. Current study examined the effect of conductive lining materials on microbial communities and sulfide control under simulated sewer conditions. Three lab-scale reactors (3.5 L total volume, 2.1 L working volume) were prepared with amorphous carbon (SAN-EARTH) and magnetite-black (MTB) linings, while a Portland cement reactor with no coating served as the control. Each reactor was operated for 120 days at room temperature and fed with artificial wastewater. The working volume consisted of 1.4 L of synthetic wastewater mixed with 0.7 L of sewage sludge used as the inoculum source. Sulfate, sulfide, hydrogen sulfide, nitrogen species, pH, and organic carbon were monitored, and microbial dynamics were analyzed via 16S rRNA sequencing and functional annotation. SAN-EARTH and MTB reactors completely suppressed sulfide and hydrogen sulfide, while Portland cement showed the highest accumulation. Both conductive linings maintained alkaline conditions (pH 9.0–10.5), favoring sulfide oxidation. Microbial analysis revealed enrichment of sulfur-oxidizing bacteria (Thiobacillus sp.) and electroactive taxa (Geobacter sp.), alongside syntrophic interactions involving Aminobacterium and Jeotgalibaca. These findings indicate that conductive lining materials reshape microbial communities and sulfur metabolism, offering a promising strategy to mitigate sulfide-driven sewer corrosion. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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22 pages, 2990 KB

Open AccessArticle

A New Semi-Empirical Model to Predict Vehicle Instability in Urban Flooding

by Omayma Amellah

Water 2026, 18(1), 80; https://doi.org/10.3390/w18010080 - 28 Dec 2025

Abstract

Urban floods frequently destabilize most objects they encounter, including vehicles, which potentially worsens flood impacts, leading to significant casualties and material losses. Improving the prediction of vehicle instability under flood conditions is therefore essential for effective risk assessment and emergency management. This work [...] Read more.

Urban floods frequently destabilize most objects they encounter, including vehicles, which potentially worsens flood impacts, leading to significant casualties and material losses. Improving the prediction of vehicle instability under flood conditions is therefore essential for effective risk assessment and emergency management. This work introduces a new physics-based, hazard assessment model for vehicle instability in urban floodwaters. The core of the model is the construction of a comprehensive parameter that integrates the main hydraulic mechanisms responsible for vehicle destabilization within a single and integrative formulation. An extensive set of experimental data covering multiple vehicle types was used and integrated into the modelling framework. Through calibration, model parameters were determined for three representative vehicle categories, allowing the derivation of distinct critical stability curves as functions of flow depth and velocity. Vehicle stability is evaluated using a physics-based force balance approach that explicitly accounts for the interaction between flood hydrodynamics and vehicle physical characteristics, enhancing model adaptability across different vehicle types and flood scenarios. The proposed model is validated through comparison with existing experimental data and stability criteria, including widely used guidelines. The results show good agreement while demonstrating improved accuracy in predicting critical stability thresholds for modern vehicles. Overall, the model provides a generalizable parameter for flood hazard assessment, with direct applications in urban flood risk mapping and decision support for emergency management. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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