Water

16 pages, 2038 KB

Open AccessArticle

Surface Soil Moisture Retrieval over Winter Wheat Fields Based on Fused Multispectral and L-Band MiniSAR Data

by Ziyi Luo, Xianyu Zhang, Yonghui Wang, Chengcai Zhang, Mingliang Jiang and Xingxing Zhu

Water 2025, 17(23), 3345; https://doi.org/10.3390/w17233345 (registering DOI) - 22 Nov 2025

Surface soil moisture (SSM) is a critical indicator of crop growth conditions, and its accurate retrieval is essential for agricultural monitoring. Integrating multispectral and microwave remote sensing data can enhance SSM estimation, but discrepancies among platforms often reduce accuracy at local scales. In [...] Read more.

Surface soil moisture (SSM) is a critical indicator of crop growth conditions, and its accurate retrieval is essential for agricultural monitoring. Integrating multispectral and microwave remote sensing data can enhance SSM estimation, but discrepancies among platforms often reduce accuracy at local scales. In this study, we fused Sentinel-2 and UAV multispectral images through resampling to generate fusion data, which were then combined with miniature synthetic aperture radar (MiniSAR) data. A modified water cloud model (WCM) was applied to mitigate vegetation effects on radar backscattering coefficients. Three machine learning algorithms—random forest (RF), extreme gradient boosting (XGBoost), and extreme learning machine (ELM)—were employed to retrieve SSM. Field measurements at two depths (0–10 cm and 0–20 cm) over winter wheat fields in Xunxian, Hebi City, Henan Province, China, were used for validation. Results showed the following: (1) Fused multispectral data improved retrieval accuracy compared with single-satellite data, with the best configuration (fused data + VV + RF) achieving an R² of 0.85 and an RMSE of 1.51% at 0–10 cm. (2) At 0–20 cm, the fused data combined with VV polarization and XGBoost achieved the best performance (R² = 0.67, RMSE = 2.61%). (3) ELM exhibited the largest accuracy improvement after incorporating fused data, with R² increases up to 0.40 and RMSE reductions up to 18.24%. These results demonstrate the strong potential of multi-platform multispectral fusion combined with MiniSAR data for improving field-scale SSM retrieval in winter wheat regions. Full article

(This article belongs to the Section Soil and Water)

► Show Figures

Figure 1

21 pages, 2952 KB

Open AccessReview

A Review of Urban Flood Disaster Chain Research: Causes, Identification, and Assessment

by Xichao Gao, Pengfei Wang, Zhiyong Yang, Weijia Liang, Wangqi Lou and Jinjun Zhou

Water 2025, 17(23), 3344; https://doi.org/10.3390/w17233344 (registering DOI) - 22 Nov 2025

Abstract

Urban flood disasters have become one of the most significant natural hazards under the dual pressures of rapid urbanization and intensified climate change. With the increasing interconnection among urban subsystems, these disasters often evolve into urban flood disaster chains, characterized by cascading failures [...] Read more.

Urban flood disasters have become one of the most significant natural hazards under the dual pressures of rapid urbanization and intensified climate change. With the increasing interconnection among urban subsystems, these disasters often evolve into urban flood disaster chains, characterized by cascading failures across infrastructure, environment, and society. Current research hotspots mainly focus on three key aspects: the formation mechanisms, identification methods, and risk assessment approaches of urban flood disaster chains. In terms of formation mechanisms, most studies qualitatively describe the triggering and transmission processes of cascading events, revealing how interactions among hazard-inducing factors, disaster-formative environments, and disaster receptor generate chain reactions. Identification methods are categorized into four paradigms: qualitative identification based on experiential reasoning, semantic identification driven by data, structural identification through model inference, and behavioral identification using simulation modeling. Risk assessment approaches include historical disaster analysis, indicator-based evaluation models, uncertainty models, numerical simulation models, and intelligent algorithm models that integrate machine learning with physical simulations. The review finds that, due to the scarcity and heterogeneity of disaster chain event data, existing studies lack a unified quantitative framework to represent the mechanisms of urban flood disaster chains, as well as dynamic identification and assessment methods that can adapt to their evolutionary processes. Future research should focus on developing integrated mathematical paradigms, enhancing multisource data fusion and causal reasoning, and constructing hybrid models to support real-time risk assessment for urban flooding disaster chains. Full article

(This article belongs to the Special Issue "Watershed–Urban" Flooding and Waterlogging Disasters)

► Show Figures

Figure 1

18 pages, 3550 KB

Open AccessArticle

Experimental Study on the Variation Pattern of Saline Ice Microstructure with Temperature

by Haokun Li, Miao Yu, Peng Lu and Qingkai Wang

Water 2025, 17(23), 3343; https://doi.org/10.3390/w17233343 - 21 Nov 2025

Abstract

By employing high-resolution imaging and image processing techniques, a quantitative analysis was conducted on the changes in volume fraction and size of microstructures, such as brine inclusions and air bubbles, within natural saline ice at different temperatures. This study revealed the distinct stratified [...] Read more.

By employing high-resolution imaging and image processing techniques, a quantitative analysis was conducted on the changes in volume fraction and size of microstructures, such as brine inclusions and air bubbles, within natural saline ice at different temperatures. This study revealed the distinct stratified distribution characteristics of ice microstructure parameters along the depth direction and elucidated the differential response mechanisms of various ice layers to temperature changes. The results indicate that the sizes of brine inclusions and air bubbles decrease progressively from the surface layer to the bottom layer, with the size distribution of microstructures being most concentrated in the bottom layer. Changes in the size of microstructures in the surface ice layer are primarily dominated by solar radiation, showing strong correlations (brine inclusions: r = 0.96, p < 0.01; air bubbles: r = 0.95, p < 0.02). In contrast, the size changes of microstructures in the middle ice layer show a more significant response to ice temperature, with strong linear relationships between the sizes of brine inclusions/air bubbles and ice temperature (brine inclusions: r = 0.70, p < 0.04; air bubbles: r = 0.69, p < 0.05). The temperature of the bottom ice layer, influenced by the stable lake water temperature, remains relatively constant, and no significant correlation was observed between its microstructure size changes and ice temperature. Derived from field experiments, this study provides quantified, layer-specific mechanisms of how saline ice microstructure responds to temperature. These mechanisms offer crucial observational constraints for refining the parameterizations of ice thermodynamics and albedo feedback in cryosphere and climate system models. Full article

(This article belongs to the Special Issue Advances and Challenges in the Lake, River, and Sea Ice Sciences and Engineering)

► Show Figures

Figure 1

22 pages, 4153 KB

Open AccessArticle

Geo-Hydrological Characteristics that Contributed to the Choice and Configuration of the Ancient Roman Aqueduct Aqua Augusta from Serino Springs

by Libera Esposito, Michele Ginolfi, Guido Leone and Francesco Fiorillo

Water 2025, 17(23), 3342; https://doi.org/10.3390/w17233342 - 21 Nov 2025

Abstract

The Augustan Aqueduct, built between 33 and 12 BC at the command of Augustus and designed by Marcus Vipsanio Agrippa, stands as one of the most remarkable hydraulic engineering feats of the Roman era. The main route of the aqueduct extends over 100 [...] Read more.

The Augustan Aqueduct, built between 33 and 12 BC at the command of Augustus and designed by Marcus Vipsanio Agrippa, stands as one of the most remarkable hydraulic engineering feats of the Roman era. The main route of the aqueduct extends over 100 km, starting from the caput aquae, represented by the Acquaro-Pelosi springs located at the foot of the Terminio karst massif, near the village of Serino (Campania region) and ending at Castellum Aquae, which corresponds to the Piscina Mirabilis in Bacoli, near Neapolis. Hydrogeological and hydrological features have been analyzed to reconstruct the rationale behind the selection of the aqueduct’s water sources: flow rate, ground level, and quality of the karst waters of the Serino springs best met the supply requirements. These characteristics, and others of historical and archaeological nature, suggest that the Augustan Aqueduct had a hydraulic connection with the Sannitico Aqueduct, also fed by Serino springs. The Sannitico Aqueduct fed the town of Benevento towards Nord, and it is believed to have been built in the first century AD. As shown by this study, both aqueduct systems could be part of a unique and great hydraulic system, built in the 1st century BC to supply areas of great residential importance (cities and patrician villas) or military importance (Miseno harbor and Benevento). The several studies available on the Augustan Aqueduct primarily focus on archaeological, architectural, and engineering aspects and less on hydrogeological aspects. In this paper we highlight that the hydrogeological perspective represents a key to understand the rationale behind the selection of the water sources feeding both aqueducts, built probably at the same time, and their interconnection. Full article

(This article belongs to the Special Issue Hydrogeology and Water Management in Ancient Hydraulic Systems)

17 pages, 939 KB

Open AccessArticle

Assessment of Groundwater Vulnerability from Source to Tap Using TIN Approach

by Tamara Marković, Nikolina Novotni-Horčička, Laszlo Palcsu and Igor Karlović

Water 2025, 17(23), 3341; https://doi.org/10.3390/w17233341 - 21 Nov 2025

Abstract

Groundwater and water supply systems are increasingly vulnerable to contamination, yet most assessments consider either hydrogeological or infrastructure risks. This study introduces the Total Integrated Network (TIN) approach, a framework designed to evaluate vulnerability comprehensively from source to tap. Field investigations were conducted [...] Read more.

Groundwater and water supply systems are increasingly vulnerable to contamination, yet most assessments consider either hydrogeological or infrastructure risks. This study introduces the Total Integrated Network (TIN) approach, a framework designed to evaluate vulnerability comprehensively from source to tap. Field investigations were conducted in Varaždin County, Croatia, focusing on the Belski Dol spring, Briška reservoir, and PS Filipići. Hydrochemical analyses, stable isotope of water (δ¹⁸O, δ²H), tritium, noble gases, and radon concentrations were monitored and combined with system-level assessments. Results show that the Belski Dol spring exhibits high stability and low vulnerability, with a TIN index of approximately 25%, supported by long groundwater residence times and consistent water quality. PS Filipići displayed moderate vulnerability (35%), while the Briška reservoir showed the highest index (53%), linked to elevated radon and nitrate concentrations and infrastructure-related risks. These findings indicate that natural hydrogeological protection alone cannot ensure safe drinking water. The TIN approach highlights the importance of integrating aquifer conditions with distribution system performance to identify critical control points and prioritize interventions. This integrated methodology offers a more realistic basis for water safety management, supporting proactive measures to safeguard supply resilience and public health. Full article

(This article belongs to the Section Hydrogeology)

15 pages, 862 KB

Open AccessArticle

Water Resources Asset Accounting in the Yangtze River Economic Belt Based on the Perspective of Water Resources–Ecological–Economic Circular Coupling

by Quan Zheng, Haoran Wang and Xuyang Liu

Water 2025, 17(23), 3340; https://doi.org/10.3390/w17233340 - 21 Nov 2025

Abstract

As a key element in maintaining ecological balance and ensuring human survival and development, the accounting of water resource assets is a fundamental prerequisite for the preparation of natural resource balance sheets. To achieve regional water resource balance and promote high-quality, coordinated socio-economic [...] Read more.

As a key element in maintaining ecological balance and ensuring human survival and development, the accounting of water resource assets is a fundamental prerequisite for the preparation of natural resource balance sheets. To achieve regional water resource balance and promote high-quality, coordinated socio-economic development, this study is grounded in the cyclical evolution of water resource assets and the concept of water–ecology–economy coupling. A classification method, which integrates physical water resources and virtual water resources, is proposed to define the accounting boundaries of water resource assets. Additionally, a multi-dimensional accounting model is developed that integrates the flows of physical and virtual water, allowing for a systematic assessment of the stock and flow characteristics of water resource assets within an area of 2.0523 million square kilometers across 11 provinces and municipalities in the Yangtze River Economic Belt. It is concluded that the top six water resource assets in the Yangtze River Economic Belt are concentrated in the middle and lower reaches of the river, and the proportion of virtual water in the southwestern provinces is less than 26%, among other significant regional differences in water resource assets. The findings aim to clarify the value transformation pathways of composite water resources, enhance the methodological system of water resource accounting, and provide a scientific basis for informed decision-making regarding optimal water resource allocation within the basin. Full article

(This article belongs to the Special Issue Water Resources, Economic Development and Environment Carrying Capacity)

20 pages, 5819 KB

Open AccessArticle

Estimation of Soil Erosion and Enhancing Sediment Retention in the Lam Phra Phloeng Watershed: Insights from RUSLE and InVEST Modelling

by Uma Seeboonruang, Ranadheer Mandadi, Prapas Thammaboribal, Arlene L. Gonzales and Ganni S. V. S. A. Bharadwaz

Water 2025, 17(23), 3339; https://doi.org/10.3390/w17233339 - 21 Nov 2025

Abstract

The increasing rate of land use change, particularly deforestation and agricultural expansion, has intensified soil degradation, leading to reduced sediment retention and accelerated soil erosion. This study aims to analyze soil erosion and sediment retention in the Lam Phra Phloeng (LPP) watershed, Thailand, [...] Read more.

The increasing rate of land use change, particularly deforestation and agricultural expansion, has intensified soil degradation, leading to reduced sediment retention and accelerated soil erosion. This study aims to analyze soil erosion and sediment retention in the Lam Phra Phloeng (LPP) watershed, Thailand, using a coupled modelling approach integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) model from the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) suite. Six land use classes (forest, cropland, rangeland, flooded vegetation, built-up areas, and water bodies) were identified using Sentinel-2 MSI satellite data, with a Random Forest (RF) classification algorithm achieving an overall accuracy of 91.3% (Kappa coefficient = 0.89). The results indicate that forested areas exhibit the highest sediment retention, whereas croplands and rangelands experience the most significant soil loss due to erosion. The RUSLE model estimated an average annual soil loss ranging between 50 and 90 tons/ha/year, with the highest erosion rates observed in agricultural lands with steep slopes and minimal vegetation cover. The InVEST SDR model further corroborates these findings, showing that sediment retention is predominantly concentrated in densely vegetated areas, reinforcing the crucial role of natural forests in preventing soil displacement. This complementary modelling approach identifies priority areas for soil conservation practices. This study is the first study to integrate the RUSLE and InVEST models for the Lam Phra Phloeng watershed, providing a coupled assessment of erosion risk and sediment retention capacity and offering a novel and transferable framework for watershed-scale conservation planning and soil management in tropical monsoonal environments. Full article

(This article belongs to the Section Water Erosion and Sediment Transport)

► Show Figures

Figure 1

19 pages, 9421 KB

Open AccessArticle

Impacts of Land Use Intensity on Ecological Quality Dynamics in the Central Yunnan Plateau Lake Basins, China

by Chenwei Xu, Shuyuan Zheng, Cheng Chen, Shanshan Liu, Jian Dao, Shixian Lu and Jianxiong Wang

Water 2025, 17(23), 3338; https://doi.org/10.3390/w17233338 - 21 Nov 2025

Abstract

Land use intensification profoundly impacts ecological quality, with this dynamic relationship being particularly pronounced in China’s Central Yunnan Plateau Lake Basin (CYP-LBs), an ecologically fragile area of significant socioeconomic value. Despite the critical importance of their interaction, existing research has largely overlooked their [...] Read more.

Land use intensification profoundly impacts ecological quality, with this dynamic relationship being particularly pronounced in China’s Central Yunnan Plateau Lake Basin (CYP-LBs), an ecologically fragile area of significant socioeconomic value. Despite the critical importance of their interaction, existing research has largely overlooked their dynamic interplay—especially within plateau lake basins. To address this gap, this study employs the Remote Sensing Ecological Index (RSEI) to assess the ecological quality dynamics of CYP-LBs from 2005 to 2025 and its association with land use intensity (LUI), revealing spatiotemporal patterns of ecological quality evolution and its linkage to land use. Results indicate that CYP-LBs maintained overall moderate ecological quality (average RSEI ~0.50), exhibiting an initial increase followed by decline, peaking at 0.5519 in 2015. The center of gravity for ecological quality shifted eastward in most watersheds, with Moran’s I index consistently above 0.50 indicating significant spatial autocorrelation. The LUI showed an overall upward trend, with high-intensity areas primarily concentrated in lakeshore zones (e.g., eastern Dianchi Lake, Xingyun Lake) and exhibiting regional expansion over time. RSEI and LUI generally showed a negative correlation, but positive correlations emerged in localized areas of eastern and northern Dianchi Lake due to concurrent urbanization and ecological restoration efforts. Among land types, grasslands and forests were identified as the primary drivers influencing ecological quality changes in CYP-LBs. These findings provide crucial scientific basis for integrated conservation, land use optimization, and sustainable development in ecologically fragile plateau lake basins. Full article

(This article belongs to the Special Issue Applications of Remote Sensing and GISs in River Basin Ecosystems)

43 pages, 5776 KB

Open AccessArticle

Environmental Impacts of Post-Closure Mine Flooding: An Integrated Remote Sensing and Geospatial Analysis of the Olkusz-Pomorzany Mine, Poland

by Artur Guzy

Water 2025, 17(23), 3337; https://doi.org/10.3390/w17233337 - 21 Nov 2025

Abstract

Mine closure by flooding initiates hydrogeological changes that affect land stability, soil moisture, and surface ecosystems, further shaped by regional climatic trends that increase pressure on water resources. This study examines the Olkusz–Pomorzany mine (Poland), flooded between 2021 and 2022, focusing on the [...] Read more.

Mine closure by flooding initiates hydrogeological changes that affect land stability, soil moisture, and surface ecosystems, further shaped by regional climatic trends that increase pressure on water resources. This study examines the Olkusz–Pomorzany mine (Poland), flooded between 2021 and 2022, focusing on the links between groundwater rebound, land movement, and environmental transformation after closure. This analysis combines EGMS-based land movement (2018–2023), groundwater levels (2022–2024), meteorological records (1981–2024), and Sentinel-2-derived Normalized Difference Vegetation Index, Normalized Difference Water Index, and Moisture Index time series (2016–2024). Land cover changes were assessed using Sentinel-2 data for 2019–2024. Results show climate-driven subsidence of less than 1 mm/year across the area and a shift to uplift within the mining zone, with maximum groundwater rebound of 103 m in the central depression cone and uplift of up to 3.6 mm/year. Climatic water balance remained negative, with Vertical Water Exchange averaging −11.6 mm/month in 2022–2024. Hydrospectral indices indicate seasonal variability and modest increases in vegetation activity and moisture after flooding. Land cover analysis shows an expansion of surface water and wetlands where historical drainage and rebound overlap. These findings confirm that groundwater recovery is already reshaping surface conditions and highlight the need for integrated monitoring in post-mining areas. Full article

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

24 pages, 4465 KB

Open AccessArticle

A Novel Biomorphodynamic Model to Enhance Bedload Transport Modelling in Emergent and Submerged Rigid Vegetation

by Antonia Dallmeier, Rebekka Kopmann, Roser Casas Mulet, Hannah Schwedhelm, Frederik Folke and Nils Rüther

Water 2025, 17(23), 3336; https://doi.org/10.3390/w17233336 - 21 Nov 2025

Abstract

Riparian and floodplain vegetation play a key role in controlling flow resistance, sediment transport, and channel morphology, shaping the dynamics of riverine ecosystems. Accurately representing these vegetation–flow–sediment interactions in numerical models is essential for predicting system responses and supporting sustainable river management. This [...] Read more.

Riparian and floodplain vegetation play a key role in controlling flow resistance, sediment transport, and channel morphology, shaping the dynamics of riverine ecosystems. Accurately representing these vegetation–flow–sediment interactions in numerical models is essential for predicting system responses and supporting sustainable river management. This study introduces an enhanced biomorphodynamic model in the open-source framework openTELEMAC, which combines multiple vegetation friction approaches with a method for predicting sediment transport in vegetated flows. The modular structure of the framework enables flexible configurations for different vegetation types (rigid or flexible) and flow conditions (emergent or submerged) by selecting suitable vegetation friction approaches, improving usability and extending model applicability. Model performance is evaluated using two laboratory experiments on bedload transport through emergent and submerged rigid vegetation. Simulations reproduce the measured bed and water surface profiles with high accuracy, yielding low goodness-of-fit errors (RMSE ≈ 0.5–1.8 cm, MAE ≈ 0.5–1.6 cm). The results highlight the sensitivity of predictions to vegetational input parameters such as the drag coefficient. Overall, the enhanced biomorphodynamic model advances the representation of vegetation–sediment interactions and provides an adaptable, open-source tool for eco-hydraulic and morphodynamic research. Full article

(This article belongs to the Section Water Erosion and Sediment Transport)

► Show Figures

Figure 1

21 pages, 2779 KB

Open AccessArticle

Study on the Adsorption of Tetracycline Hydrochloride in Water by Modified Highland Barley Straw Biochar

by Jiacheng Song, Huijun Xi, Xiaogang Gu and Jian Xiong

Water 2025, 17(23), 3335; https://doi.org/10.3390/w17233335 - 21 Nov 2025

Abstract

Global antibiotic pollution (represented by tetracycline hydrochloride, TCH) threatens water environmental safety, and resource recovery of agricultural waste remains a key challenge for sustainable development. Given that utilizing biochar for adsorption is widely recognized as a circular economy-compliant method, this study aimed to [...] Read more.

Global antibiotic pollution (represented by tetracycline hydrochloride, TCH) threatens water environmental safety, and resource recovery of agricultural waste remains a key challenge for sustainable development. Given that utilizing biochar for adsorption is widely recognized as a circular economy-compliant method, this study aimed to verify its applicability in TCH pollution control while recycling agricultural waste by preparing modified biochar from the Xi Zang highland barley straw via chemical activation (KOH, H₃PO₄, NaHCO₃, and ZnCl₂) and pyrolysis at 750 °C. Among the products, H₃PO₄-modified (P-BC) and ZnCl₂-modified (Zn-BC) biochars performed best: their abundant micro/mesoporous structures and surface functional groups (–OH/–COOH) enabled excellent TCH adsorption, with the mechanism involving synergy of physical adsorption (dominated by pore filling) and chemical adsorption (hydrogen bonding, electrostatic attraction, cation bridging), alongside multi-layer adsorption. Adsorption was pH-dependent—acidic conditions favored it, while Zn-BC restored efficiency at pH = 9 via Zn²⁺ bridging. The two biochars were complementary: Zn-BC had higher adsorption capacity, while P-BC showed better stability and ionic interference resistance. Thus, Zn-BC suits high-concentration, low-ionic-strength TCH wastewater, and P-BC is ideal for complex high-ionic-strength water (e.g., industrial/aquaculture wastewater). This study provides theoretical and technical support for high-value utilization of regional agricultural waste and targeted TCH pollution control. Full article

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

► Show Figures

Figure 1

27 pages, 1813 KB

Open AccessArticle

Designing an Optimal Environmental Policy for Omura Bay, Japan: A Simulation Study on Water Quality Improvements

by Shiima Yamauchi and Takeshi Mizunoya

Water 2025, 17(23), 3334; https://doi.org/10.3390/w17233334 - 21 Nov 2025

Abstract

This study aimed to explore the trade-offs between regional economic activity and environmental policy to explore economic approaches for reducing and managing pollutant discharge while maintaining a balance between socioeconomic activities and the marine environment. A linear programming simulation was conducted to model [...] Read more.

This study aimed to explore the trade-offs between regional economic activity and environmental policy to explore economic approaches for reducing and managing pollutant discharge while maintaining a balance between socioeconomic activities and the marine environment. A linear programming simulation was conducted to model the interactions between socioeconomic activities, pollutant emissions, and reduction policies in the Omura Bay watershed. The model was designed to maximize Gross Regional Product (GRP), using inflow pollutant loads as a constraint. The simulation showed that a 12.7% reduction in 2015 pollutant loads is feasible under total load control. However, this level of reduction would cause a 14% decrease in watershed GRP. Further analysis revealed that reductions beyond 12.4% would significantly lower GRP and increase the cost of mitigation, making a 12.3% reduction the most realistic upper limit. The estimated cost of implementing countermeasures to manage pollutant inflow was JPY 6.7 billion, which would translate to a JPY 37.6 billion reduction in the cost to maintain current conditions and a JPY 26.7 billion reduction in the maximum reduction scenario (12.3%) with minimal economic impact. This analysis highlights the tradeoff between environmental protection and economic performance. A key innovation is the proposal of a “proper nutrient management” scenario, moving beyond uniform reductions to assess region-specific targets that consider ecological needs, such as those of the fishery industry. This approach emphasizes the importance of setting realistic and ecologically balanced reduction targets. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

► Show Figures

Figure 1

16 pages, 7267 KB

Open AccessArticle

Study on the Generation and Output Characteristics of Non-Point Source Pollution in the Process of River Migration

by Min Zhang, Yao Qu, Linyu Xu, Xiaoyan Li, Min He, Wenbin Zhao and Tianhao Liu

Water 2025, 17(23), 3333; https://doi.org/10.3390/w17233333 - 21 Nov 2025

Abstract

After the non-point source pollutants are generated at the source position and migrate to the target water body, they will have different degrees of loss under the action of precipitation, adsorption, or absorption by plants, resulting in differences in pollution output load and [...] Read more.

After the non-point source pollutants are generated at the source position and migrate to the target water body, they will have different degrees of loss under the action of precipitation, adsorption, or absorption by plants, resulting in differences in pollution output load and generation amount. Taking the Xin’an River Basin as an example, this study analyzes the spatial distribution characteristics of non-point source pollution generation and output in the process of river migration and explores the influence of river migration on non-point source pollution based on the soil and water assessment tool (SWAT) model and mathematical statistical methods. The results showed that the spatial distribution intensity of total nitrogen and total phosphorus in different sub-basins of Xin’an River Basin is between 3.88 and 29.16 kg/ha and 0.11–1.18 kg/ha, respectively. The high intensity areas of non-point source pollution generation and output are mainly concentrated in the hydrologically sensitive areas in the southern part of the basin and the erosion-sensitive area in the southeastern part of the basin, and the critical source areas of non-point source pollution are a result of comprehensive effects of crop fertilizer input, soil nitrogen, and phosphorus storage as well as hydrology and soil erosion. There are differences in the spatial distribution of non-point source pollution generation and output in the process of river migration. Some sub-basins have significant changes in their generation and output, and the sub-basin output coefficients of total nitrogen and total phosphorus are between 0.856 and 1.014 and 0.998–1.061, respectively. The change intensity of pollutants after river migration is affected by the combined effects of migration time, runoff intensity, material adsorption, and desorption, etc. The research findings will provide scientific support for zonal management and targeted measures of non-point source pollution in the Xin’an River Basin. Full article

(This article belongs to the Special Issue Monitoring and Modelling of Contaminants in Water Environment)

► Show Figures

Figure 1

19 pages, 2364 KB

Open AccessReview

Microbially Induced Calcium Carbonate Precipitation (MICP): Bibliometric Analysis, Research Hotspot Evolution, and Mechanistic Insights (2005–2024)

by Rui Xiao, Guoping Jiang, Wenbo Chai, Zhengyu Jin, Runbao Du, Mumtaz Khan, Zhenghua Liu, Huaqun Yin and Lechang Xu

Water 2025, 17(23), 3332; https://doi.org/10.3390/w17233332 - 21 Nov 2025

Abstract

Microbially induced calcium carbonate precipitation (MICP) is recognized as a promising, environmentally sustainable technology with diverse applications in environmental engineering. A bibliometric analysis of 5373 publications indexed in Web of Science from 2005 to 2024 was conducted using CiteSpace and VOSviewer to identify [...] Read more.

Microbially induced calcium carbonate precipitation (MICP) is recognized as a promising, environmentally sustainable technology with diverse applications in environmental engineering. A bibliometric analysis of 5373 publications indexed in Web of Science from 2005 to 2024 was conducted using CiteSpace and VOSviewer to identify research trends and hotspots in biomineralization and calcium carbonate (CaCO₃) studies. The results showed exponential growth in publications, increasing from 96 in 2004 to 397 in 2024 and spanning 91 interdisciplinary research areas. China, United States of America, and Germany were identified as the leading contributors. Research evolution was categorized into five distinct phases, progressing from initial crystal formation investigations to the current emphasis on underlying microbial mechanisms. Trend analysis revealed four emerging research hotspots: interfaces (0.22), crystal morphology (0.18), amorphous calcium carbonate (0.05), and bacteria (0.02). Mechanisms of MICP across bacteria, fungi, and algae were examined, revealing diverse metabolic pathways, including urea hydrolysis, denitrification, and photosynthesis. These findings suggest a paradigm shift in research toward microbial diversity and the role of extracellular polymeric substances. This shift provides valuable insights for developing sustainable biotechnological applications in environmental remediation. Full article

(This article belongs to the Special Issue Sediment Pollution: Methods, Processes and Remediation Technologies)

► Show Figures

Graphical abstract

26 pages, 4341 KB

Open AccessArticle

Coordinated Development of Water–Energy–Food–Ecosystem Nexus in the Yellow River Basin: A Comprehensive Assessment Based on Multi-Method Integration

by Jingwei Yao, Kiril Manevski, Finn Plauborg, Yangbo Sun, Lingling Wang, Wenmin Zhang and Julio Berbel

Water 2025, 17(22), 3331; https://doi.org/10.3390/w17223331 - 20 Nov 2025

Abstract

The Yellow River Basin serves as a critical ecological barrier and economic corridor in China, playing a pivotal role in national ecological security and sustainable development. This study develops a comprehensive evaluation framework grounded in the Water–Energy–Food–Ecosystem (WEFE) nexus, employing 25 indicators across [...] Read more.

The Yellow River Basin serves as a critical ecological barrier and economic corridor in China, playing a pivotal role in national ecological security and sustainable development. This study develops a comprehensive evaluation framework grounded in the Water–Energy–Food–Ecosystem (WEFE) nexus, employing 25 indicators across nine provinces and autonomous regions over the period 2000–2023. Utilizing a multi-method approach—including the entropy weight method, coupling coordination degree model, center of gravity migration analysis, principal component analysis, and obstacle factor diagnosis—the research investigates the coordinated development and dynamic interactions among the WEFE subsystems. Key findings include: (1) the calculated weights of the water, energy, food, and ecological subsystems were 0.3126, 0.1957, 0.1692, and 0.3225, respectively, indicating that ecological and water subsystems exert the greatest influence; (2) distinct growth patterns among subsystems, with the energy subsystem exhibiting the fastest growth rate (212%) and the water subsystem the slowest (4%); (3) a steady improvement in the overall coordination degree of the WEFE system, rising from 0.417 in 2000 to 0.583 in 2023—a 39.8% increase—with Henan (0.739) and Inner Mongolia (0.715) achieving the highest coordination levels in 2023, while Qinghai (0.434) and Ningxia (0.417) remained near imbalance thresholds; (4) complex spatial dynamics reflected by cumulative center of gravity migration distances of 678.2 km (water), 204.9 km (energy), 143.3 km (food), and 310.9 km (ecology) over the study period; and (5) identification of per capita water resources as the principal limiting factor to coordinated WEFE development, with an obstacle degree of 0.1205 in 2023, underscoring persistent water scarcity challenges. This integrated framework advances WEFE nexus analysis and provides robust, evidence-based insights to inform regional policy and resource management strategies. Full article

(This article belongs to the Special Issue Sustainable Water Management in Agricultural Irrigation)

► Show Figures

Figure 1

17 pages, 2493 KB

Open AccessArticle

Occurrence of Microplastics in Inland and Island Wastewater Treatment Plants and the Role of Suspended Solids as Monitoring Indicators

by Suthida Theepharaksapan, Paranee Sriromreun, Pradabduang Kiattisaksiri, Athit Phetrak, Chalintorn Molee and Suda Ittisupornrat

Water 2025, 17(22), 3330; https://doi.org/10.3390/w17223330 - 20 Nov 2025

Abstract

Microplastics (MPs) are increasingly recognized as emerging contaminants in aquatic environments; however, their occurrence and fate in tropical wastewater treatment systems remain poorly understood. This study provides the first inland–island comparison of MP removal in wastewater treatment plants (WWTPs) across Thailand’s Eastern Economic [...] Read more.

Microplastics (MPs) are increasingly recognized as emerging contaminants in aquatic environments; however, their occurrence and fate in tropical wastewater treatment systems remain poorly understood. This study provides the first inland–island comparison of MP removal in wastewater treatment plants (WWTPs) across Thailand’s Eastern Economic Corridor. Influent and effluent samples were collected from six WWTPs, encompassing five treatment types: oxidation ditch, aerated lagoon, stabilization pond, aerated tank, and sand filtration combined with reverse osmosis. Polymeric composition and size distribution were examined in parallel with conventional water quality indicators. Across all sites, polyethylene and polypropylene dominated influent MPs, together accounting for 57–92% of total abundance. Inland plants received heterogeneous municipal wastewater, including domestic inputs and agricultural runoff. In contrast, island facilities consistently showed PE-enriched influents (45–60%) in site F, reflecting tourism-driven reliance on single-use plastics and personal care products. In addition, several minor polymers were identified, including poly (vinyl stearate) (up to 26%), polyamide, and ethylene–butyl acrylate, highlighting overlooked pathways of MP entry into WWTPs. Fine MPs (100–300 μm) comprised over two-thirds of influent particles, with stabilization ponds reaching 16,000 MP m⁻³. Removal efficiency ranged from 86.0% to 98.5%. Spearman’s correlation and multiple linear regression analyses revealed strong positive relationships between MPs and both total suspended solids (TSS) and turbidity. Suspended solids parameters emerged as the most reliable predictor of MP abundance (adjusted R² = 0.91, p = 0.001). This finding highlights TSS coupled with turbidity as a practical, cost-effective indicator for monitoring MPs in tropical WWTPs. To achieve greater accuracy, a larger dataset should be built and further analyzed. Full article

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

► Show Figures

Figure 1

17 pages, 298 KB

Open AccessArticle

From Quality to Purpose: Rethinking Groundwater Microbiological Standards for Emergency Urban Water Use

by Pedro Teixeira, Sílvia Costa, João Brandão and Elisabete Valério

Water 2025, 17(22), 3329; https://doi.org/10.3390/w17223329 - 20 Nov 2025

Abstract

Climate change and increasing water scarcity are driving the need for resilient and fit-for-purpose urban water management. This study presents a case from Lisbon, Portugal, where twenty-one groundwater sources were evaluated as potential alternative supplies for emergency drinking and non-potable uses. Between 2018 [...] Read more.

Climate change and increasing water scarcity are driving the need for resilient and fit-for-purpose urban water management. This study presents a case from Lisbon, Portugal, where twenty-one groundwater sources were evaluated as potential alternative supplies for emergency drinking and non-potable uses. Between 2018 and 2022, 127 samples were analyzed for microbiological (Escherichia coli, enterococci, fecal coliforms, heterotrophic plate count, Pseudomonas aeruginosa and Legionella pneumophila, physicochemical and fungal parameters (filamentous and yeast), alongside with microbial source tracking (MST) to determine contamination origins. Most sites showed exceedances of fecal indicators and heterotrophic bacteria, making water unsuitable for direct consumption without treatment, while fungi were ubiquitous and often above proposed guidance levels, highlighting a major regulatory gap. MST results indicated that human-derived contamination was rare and highly localized. Physicochemical parameters generally met legal thresholds, although occasional nitrate or salinity elevations reflected agricultural or coastal influences. Several sources were considered suitable for irrigation (EF, CC, AB, VF, and BS) whilst a subset met the criteria for potable supply with minimal treatment for risk management (CG, MM, CC, QC, EB, GR, PO, and MS). The findings of this study demonstrate that systematic, multiparametric assessment supports adaptive water allocation and emergency planning, aligning with EU regulations and advancing Sustainable Development Goal 6. The study argues for reconsideration of current microbiological standards, to improve public health protection in urban water reuse and emergency supply strategies. Full article

(This article belongs to the Special Issue Urban Water Pollution Control: Theory and Technology, 2nd Edition)

17 pages, 3574 KB

Open AccessArticle

Rooftop-Scale Runoff Reduction Performance of Smart Blue-Green Roofs and Their Potential Role in Urban Flood Mitigation

by Sung Min Cha, Jaerock Park, Kyung Soo Han, Jong Dae Kim, Jung Min Lee, Soonchul Kwon and Jaemoon Kim

Water 2025, 17(22), 3328; https://doi.org/10.3390/w17223328 - 20 Nov 2025

Abstract

Urban areas face increasing flood risks due to climate change, intensified rainfall events, and high impervious surface coverage. Blue-Green Roofs (BGR) have emerged as a nature-based solution to retain stormwater, while Smart BGR systems integrate active control functions to enhance performance under varying [...] Read more.

Urban areas face increasing flood risks due to climate change, intensified rainfall events, and high impervious surface coverage. Blue-Green Roofs (BGR) have emerged as a nature-based solution to retain stormwater, while Smart BGR systems integrate active control functions to enhance performance under varying rainfall conditions. This study evaluated the rooftop-scale runoff reduction efficiency of conventional roofs, BGR, and Smart BGR using 31 monitored rainfall events in 2024, while eight years of historical rainfall data (2017–2024) were used only to characterize long-term rainfall patterns in the study area. A multiple-linear regression analysis was performed for exploratory trend identification between rainfall characteristics and runoff reduction; variables unrelated to short-term storm responses such as evapotranspiration or initial storage were beyond the study scope. Results showed that the annual runoff per unit area was 1.115 m³/m² for conventional roofs, 0.547 m³/m² for BGR, and 0.128 m³/m² for Smart BGR, corresponding to reduction rates of 50.98% and 88.53% for BGR and Smart BGR, respectively. In higher rainfall classes, Smart BGR maintained significantly higher performance: for Class 3 (average 53.00 mm), BGR reduced runoff by 54.89% while Smart BGR achieved 86.71%; for Class 4 (average 121.21 mm), the rates were 54.68% and 90.00%, respectively. These findings indicate that Smart BGR’s storage optimization and controlled discharge enable superior effectiveness during intense and prolonged events. The study highlights Smart BGR’s potential as an advanced stormwater management technology, offering clear advantages over both conventional roofs and passive BGR designs. Limitations include the need for testing under more extreme rainfall scenarios, optimization of operational strategies, and economic feasibility assessments. Nevertheless, Smart BGR represents a promising approach for enhancing urban flood resilience in the context of climate change. Full article

(This article belongs to the Special Issue Application of Hydrological Modelling to Water Resources Management)

► Show Figures

Figure 1

28 pages, 1279 KB

Open AccessArticle

Freshwater Phenanthrene Removal by Three Emergent Wetland Plants

by Madeline J. Stanley, Aidan Guttormson, Lisa E. Peters, Thor Halldorson, Gregg Tomy, José Luis Rodríguez Gil, Blake Cooney, Richard Grosshans, David B. Levin and Vince P. Palace

Water 2025, 17(22), 3327; https://doi.org/10.3390/w17223327 - 20 Nov 2025

Abstract

The use of floating wetlands has been receiving increased attention as a minimally invasive method for oil spill remediation, but the species of vegetation incorporated in floating wetlands may influence the success of oil degradation. Therefore, a freshwater microcosm experiment was conducted at [...] Read more.

The use of floating wetlands has been receiving increased attention as a minimally invasive method for oil spill remediation, but the species of vegetation incorporated in floating wetlands may influence the success of oil degradation. Therefore, a freshwater microcosm experiment was conducted at the IISD Experimental Lakes Area, Canada to assess the potential of common wetland plants Typha sp., Carex utriculata, and C. lasiocarpa, to remove phenanthrene, a polycyclic aromatic hydrocarbon ubiquitously found at oil spill sites. Triplicate microcosms containing 3L of lake water were established with either Typha sp., Carex utriculata, or C. lasiocarpa and then treated with nominal concentration of 1 mg/L phenanthrene and monitored over 21 days. Two types of reference microcosms were also included: one set with the same plant allocations but not treated with phenanthrene and another with water only and no plants or phenanthrene. Phenanthrene declined by over 89.30% in all microcosms that received the compound, but the decline was more rapid in microcosms that included Typha sp. and C. lasiocarpa, than those with C. utriculate or no plants. Declining phenanthrene concentrations in microcosms without plants may have resulted from biofilm stimulation. Specific conductivity and pH were influenced by plant type but not phenanthrene, while dissolved oxygen was influenced by both. There was no influence of phenanthrene on plant growth rates or root biofilm bioactivity, measured by adenosine triphosphate or oxygen consumption. Results indicate there may be plant-specific factors influencing remediation success which should be explored in future research. Full article

(This article belongs to the Special Issue Constructed Wetland Systems for Wastewater Treatment and Water Remediation)

Journal Description

Water

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Further Information

Guidelines

MDPI Initiatives

Follow MDPI