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Search Results (1,185)

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15 pages, 3796 KB  
Article
A Synergistic Remote Sensing Inversion Study of Water Depth in Inland Lakes Integrating Chlorophyll-a Concentration and Optical Indices
by Junzhen Meng, Yunfei Wang, Jiajun Ren, Liya Xu and Linnan Fan
Sensors 2026, 26(12), 3780; https://doi.org/10.3390/s26123780 (registering DOI) - 13 Jun 2026
Abstract
Accurate bathymetric information for inland lakes is essential for water resource management, ecological monitoring, and environmental research. However, the accuracy and robustness of remote sensing-based bathymetric retrieval are often constrained by the complex optical properties of inland waters and the limited representation of [...] Read more.
Accurate bathymetric information for inland lakes is essential for water resource management, ecological monitoring, and environmental research. However, the accuracy and robustness of remote sensing-based bathymetric retrieval are often constrained by the complex optical properties of inland waters and the limited representation of conventional inversion features. To address these challenges, this study systematically compared the performance of a multiband logarithmic ratio model and three machine learning models, including Random Forest (RF), XGBoost, and AdaBoost, for inland lake bathymetric retrieval. Furthermore, a synergistic retrieval framework integrating chlorophyll-a concentration (Chla) and a Water Optical Index (WOI) was proposed. The results show that: (1) The overall accuracy of the Random Forest, XGBoost, and AdaBoost models constructed with the integration of chlorophyll-a concentration and WOI (R2=0.93, 0.93, and 0.91; MAE =0.06 m, 0.07 m, and 0.12 m; RMSE =0.14 m, 0.14 m, and 0.16 m) outperforms that of models using only multispectral band information (R2=0.93, 0.91, and 0.82; MAE =0.06 m, 0.07 m, and 0.14 m; RMSE =0.14 m, 0.16 m, and 0.22 m). Moreover, all these machine learning models significantly outperform the traditional numerical model (R2=0.27; MAE =0.29 m; RMSE =0.45 m), with the Random Forest model achieving the best overall performance. This indicates that the proposed method offers higher applicability and retrieval accuracy in complex inland lake environments. (2) The optimal Random Forest model integrating chlorophyll-a concentration and WOI achieved high-precision bathymetric inversion for inland lakes (R2=0.93, MAE =0.06 m, RMSE =0.14 m). Based on the three-dimensional bathymetry derived from this model, the estimated lake storage capacity was 1072.11×104 m3, compared with a measured volume of 1094.27×104 m3, yielding a relative error of 2.03%. This result provides reliable and highly accurate data to support water resource management. Full article
(This article belongs to the Section Remote Sensors)
18 pages, 5224 KB  
Article
Relationships Among Groundwater Depth, Vegetation Dynamics, and Evapotranspiration in an Arid Basin: Identification of Groundwater-Dependent Vegetation Ecosystems and Ecological Reference Thresholds
by Ruoyi Li, Gaoqiang Zhang, Li Li, Yi Guo, Qian Zhang and Zhengkun Zhu
Water 2026, 18(12), 1440; https://doi.org/10.3390/w18121440 - 11 Jun 2026
Viewed by 101
Abstract
In arid and semi-arid regions, groundwater plays an important ecohydrological role in sustaining ecosystem stability under climate-warming-induced surface-water uncertainty. Disentangling precipitation and groundwater recharge effects on vegetation growth remains challenging, limiting robust identification of groundwater-dependent vegetation ecosystems (GDVEs) and quantitative ecological groundwater level [...] Read more.
In arid and semi-arid regions, groundwater plays an important ecohydrological role in sustaining ecosystem stability under climate-warming-induced surface-water uncertainty. Disentangling precipitation and groundwater recharge effects on vegetation growth remains challenging, limiting robust identification of groundwater-dependent vegetation ecosystems (GDVEs) and quantitative ecological groundwater level estimation. Taking the Daihai Basin, a typical inland closed-lake basin, as a case study, we integrated multi-source remote-sensing data (2005–2025) with in situ groundwater monitoring to develop a comprehensive framework for ecohydrological response analysis and management quantification. Using an improved Mann–Kendall test together with spatiotemporal correlation analyses, we analyzed the spatial relationships between vegetation dynamics and groundwater depth. Results show: (1) basin-wide vegetation exhibits a greening trend (Sen’s slope = 0.00014) with spatial heterogeneity; (2) vegetation dependence on groundwater displays a clear threshold behavior, with low-cover areas (fractional vegetation cover, FVC < 0.3) showing relatively strong groundwater dependency (r = 0.698) whereas high-cover areas exhibit a weaker relationship; and (3) approximate ecological groundwater reference thresholds are estimated as 1.0 m (90% assurance) for forest land and 0.6 m for grass land (80% assurance). The proposed GDVE identification scheme provides a scientific reference for adaptive groundwater management and ecological assessment. Full article
(This article belongs to the Section Ecohydrology)
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18 pages, 7575 KB  
Article
Response Patterns of Wetland Vegetation Distribution to Changes in Inundation Processes in the Dongting Lake Wetland
by Jialei Zhang and Congzhu Cheng
Sustainability 2026, 18(12), 5991; https://doi.org/10.3390/su18125991 - 11 Jun 2026
Viewed by 72
Abstract
Natural climate variations and human activities have significantly altered the river–lake hydrological regimes in the middle and lower reaches of the Yangtze River, leading to substantial changes in the inundation patterns of the Dongting Lake wetland, which in turn profoundly affect the spatial [...] Read more.
Natural climate variations and human activities have significantly altered the river–lake hydrological regimes in the middle and lower reaches of the Yangtze River, leading to substantial changes in the inundation patterns of the Dongting Lake wetland, which in turn profoundly affect the spatial distribution and landscape patterns of wetland vegetation. Determining the response mechanisms and appropriate thresholds of wetland landscape patterns to hydrological rhythm changes is of great importance for maintaining the health of wetland ecosystems and optimizing the ecological operation of water conservancy projects. Based on long-term measured water level data (1992–2023) and multi-temporal Landsat remote sensing images (1997–2022), combined with a digital elevation model (DEM), this study systematically analyzed the spatiotemporal evolution characteristics of the inundation processes in Dongting Lake before and after the operation of the Three Gorges Project (TGP) and their driving mechanisms on the plant landscape patterns of the floodplain wetland. The results show that after the TGP operation, the inundation pattern of Dongting Lake exhibited a drying trend, with a significant decline in annual mean water level (the largest drop of approximately 0.7 m in East Dongting Lake) and a marked reduction in the lake-wide average inundation duration (T) and inundation frequency (F). From 1997 to 2022, the total area of wetland vegetation in Dongting Lake showed a significant expansion trend, and the succession of the landscape pattern experienced a nonlinear process of stability, fragmentation, and recovery. The stepwise regression model revealed that the three elements of the inundation process explained more than 80% of the landscape pattern variation, among which inundation frequency (F) and inundation duration (T) were the core driving factors. Specifically, inundation frequency primarily regulated landscape diversity (SHDI) and contagion (CONTAG) through an environmental filtering effect, while maximum inundation depth (H) mainly maintained the physical connectivity (COHESION) of the landscape. Furthermore, the study quantified the stable hydrological range of the Dongting Lake wetland ecosystem: when the inundation frequency is maintained at 0.40–0.50 and the annual inundation duration is controlled at 4–5 months, the wetland landscape is in an optimal structural state. Once the warning thresholds are breached (e.g., F < 0.35 or T < 90 days), it may trigger the rapid expansion of cultivated poplar forests under combined hydrological and anthropogenic influences, leading to severe habitat fragmentation. These findings deepen the understanding of the response mechanisms of vegetation landscape patterns in large lake wetlands under altered hydrological rhythms. Full article
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28 pages, 28466 KB  
Article
A Global–Local Residual Refinement Framework for Accurate Lake Boundary Delineation in Remote Sensing Imagery
by Shangyuan Yu, Jienan Tu, Zhaocheng Guo and Peng He
Remote Sens. 2026, 18(12), 1919; https://doi.org/10.3390/rs18121919 - 10 Jun 2026
Viewed by 104
Abstract
Accurate lake boundary extraction from optical remote sensing imagery remains challenging in high-altitude regions such as the Tibetan Plateau due to ice cover, snow, shadows, and spectrally similar backgrounds. Although recent deep learning models achieve strong region-overlap performance, they often fail to ensure [...] Read more.
Accurate lake boundary extraction from optical remote sensing imagery remains challenging in high-altitude regions such as the Tibetan Plateau due to ice cover, snow, shadows, and spectrally similar backgrounds. Although recent deep learning models achieve strong region-overlap performance, they often fail to ensure stable shoreline localization. To address this issue, we propose a Global–Local Residual Refinement Network (GLR-Net) for boundary-aware lake extraction from remote sensing imagery. The proposed framework first captures large-scale semantic context through a global branch and subsequently performs patch-level residual refinement to improve local shoreline geometry. A global-to-local guidance mechanism is further introduced to incorporate structural priors into local refinement. Experiments on a manually annotated Tibetan Plateau lake dataset demonstrate that the proposed method achieves competitive region-level segmentation performance while improving geometric shoreline accuracy. Compared with representative semantic segmentation baselines, including U-Net, SegFormer-B0, SegFormer-B4, and OCRNet, the proposed method achieves the highest Boundary F1 score of 0.811 under a 3-pixel tolerance and the lowest mean BDE of 13.19 pixels. The results indicate that conventional overlap-based metrics alone are insufficient for evaluating shoreline delineation quality in complex alpine environments. Full article
29 pages, 3734 KB  
Article
Bathymetric Inversion of Tibetan Plateau Lakes Using Hyperspectral Imagery and ICESat-2 Data
by Chang Zhong, Yu Zhao, Mengchun Pan, Qi Zhang, Xinxin Sui, Li Chen, Ning Wang and Fan Bu
Remote Sens. 2026, 18(12), 1886; https://doi.org/10.3390/rs18121886 - 8 Jun 2026
Viewed by 188
Abstract
Lake depth is a fundamental parameter for estimating lake storage, analyzing basin morphology, and understanding the evolution of plateau lakes. Compared with typical shallow lakes, Tibetan Plateau lakes are characterized by high elevation, strong radiation, pronounced inter-lake and inter-annual variability, and in some [...] Read more.
Lake depth is a fundamental parameter for estimating lake storage, analyzing basin morphology, and understanding the evolution of plateau lakes. Compared with typical shallow lakes, Tibetan Plateau lakes are characterized by high elevation, strong radiation, pronounced inter-lake and inter-annual variability, and in some cases considerable basin depth, which limits the accuracy, stability, and generalization ability of existing bathymetric inversion methods based on single-source optical imagery. Meanwhile, although ICESat-2 can provide sparse but high-precision along-track bathymetric constraints, a unified framework suitable for plateau-lake scenarios is still lacking. To address this issue, this study proposes TabKAN, a bathymetric inversion framework for Tibetan Plateau lakes under joint constraints from hyperspectral imagery and ICESat-2 data. TabKAN constructs tabular input features from hyperspectral reflectance, water indices, imaging geometry, and environmental variables; employs TabNet for feature selection and encoding; and introduces a KAN regression head to enhance nonlinear bathymetric mapping. A joint-supervision and bias-correction mechanism is further designed to incorporate ICESat-2 samples, thereby improving model robustness across lakes and acquisition dates. To enhance the temporal coverage of training samples, multi-year sample expansion based on stereo-mapping data is introduced, and a stripe-aware self-supervised learning strategy is developed for hyperspectral image restoration and pretraining. Experiments on five Tibetan Plateau lakes, including Anglaren Co, Caiduo Chaka, Cuoe, Geren Co, and Qixiang Co, show that the proposed method outperforms benchmark methods in both overall accuracy and depth-stratified evaluation, while providing more stable recovery of basin morphology and depth gradients. These results demonstrate that combining hyperspectral information, ICESat-2 laser constraints, and stripe-aware pretraining can effectively improve the accuracy and robustness of bathymetric inversion for Tibetan Plateau lakes and provide a new technical route for storage estimation and change monitoring of cold inland lakes. Full article
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35 pages, 5500 KB  
Review
Glacial Lake Outburst Floods in High Mountain Asia: Historical Evidence, Future Changes, and Risk-Reduction Strategies from a Remote-Sensing Perspective
by Asma Tanveer, Juanle Wang and Faith Ka Shun Chan
Remote Sens. 2026, 18(12), 1883; https://doi.org/10.3390/rs18121883 - 7 Jun 2026
Viewed by 339
Abstract
Glacial lake outburst floods (GLOFs) are a major cryosphere-related hazard in High Mountain Asia (HMA), where glacier mass loss and changing hydroclimatic conditions are reshaping glacial-lake systems and increasing the prevalence of potentially unstable lake–dam configurations. However, current knowledge remains fragmented across HMA. [...] Read more.
Glacial lake outburst floods (GLOFs) are a major cryosphere-related hazard in High Mountain Asia (HMA), where glacier mass loss and changing hydroclimatic conditions are reshaping glacial-lake systems and increasing the prevalence of potentially unstable lake–dam configurations. However, current knowledge remains fragmented across HMA. Therefore, this review synthesizes historical evidence, future changes, and risk-reduction strategies of GLOFs across HMA from a remote-sensing perspective. Historical evidence derived from satellite archives, multi-temporal lake inventories, geomorphological analyses, and documented event records indicate that reported GLOFs in HMA are strongly clustered by sub-region and dam type, with moraine-dammed lakes representing the dominant source of documented events, while ice-dammed lakes remain important in several mountain belts. The compiled record also shows that GLOFs have caused severe human, economic, geomorphic, and ecological losses. Future projections based on glacier evolution, glacial-lake expansion, and climate-sensitive hazard assessments indicate continued glacial-lake growth under global warming. However, reliable prediction of future GLOF event timing, magnitude, and frequency remains constrained by uncertainties in glacier evolution, dam stability, and triggering processes. This review further shows that effective GLOF risk reduction in HMA requires integrated systems that combine hazard and risk mapping, early warning, structural interventions, and non-structural measures. It also highlights the need to better link remote sensing with monitoring, assessment, and implementation frameworks, and proposes an integrated management cycle to support practical risk reduction. It concludes that the most urgent research priorities are harmonized multi-temporal lake inventories, targeted field observations, explicit consideration of heatwaves and compound extremes, transparent uncertainty propagation, and stronger operationalization of monitoring and warning systems to support durable climate adaptation and disaster risk reduction across HMA. Full article
(This article belongs to the Special Issue Advances in Remote Sensing for Glacier Preservation)
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19 pages, 7082 KB  
Article
Remote Sensing Study of the Impact of Revegetation on Lake Shrinkage in a Semi-Arid Inland Lake Basin, Inner Mongolia
by Yamei Shao, Nan Wang, Lijun Zhao, Guohui Yao, Yicong Chen, Weilun Li, Hao Wang and Haidong Li
Remote Sens. 2026, 18(11), 1833; https://doi.org/10.3390/rs18111833 - 3 Jun 2026
Viewed by 240
Abstract
Revegetation serves as a critical ecological safeguard, while these interventions have added complexity to the evapotranspiration processes and water balance. Dalinor Lake basin (DLB), located in the southeast of Inner Mongolia Plateau, serves as a vital habitat for migratory birds and plays an [...] Read more.
Revegetation serves as a critical ecological safeguard, while these interventions have added complexity to the evapotranspiration processes and water balance. Dalinor Lake basin (DLB), located in the southeast of Inner Mongolia Plateau, serves as a vital habitat for migratory birds and plays an important role in the ecological security of northern China. To enhance biodiversity, numerous ecological restoration projects have been carried out in this area in recent years. Dalinor Lake, a large inland lake within the basin, has experienced persistent shrinkage. Although existing studies have explored its driving factors, the potential influence of revegetation activities on lake shrinkage remains unclear. In this study, we used remote sensing imagery, combined with supervised classification and visual interpretation methods, to extract changes in the surface areas of lakes within the DLB (i.e., Dalinor Lake and Ganggeng Lake), and analyzed the effects of total terrestrial evapotranspiration (ETt), precipitation (PPT), runoff, soil moisture content, and the vapor pressure deficit on these changes. Results showed that the Dalinor Lake’s area decreased by 18.68% from 2000 to 2020, and was mainly influenced by ETt, with the Normalized Difference Vegetation Index (NDVI) contributing the most to ETt (54.02%). In contrast, Ganggeng Lake expanded by 5.68% and was strongly driven by PPT. Compared with Ganggeng Lake, there have been more revegetation activities around Dalinor Lake, resulting in significant increases in NDVI and ETt, together with widespread declines in soil moisture in its surrounding areas, suggesting that revegetation exerted non-negligible water pressure on Dalinor Lake. These findings can provide valuable information for policymakers to balance large-scale ecological restoration with sustainable water management in semi-arid regions. Full article
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26 pages, 3932 KB  
Article
A Robust Spatiotemporal Fusion Algorithm for Wetland Vegetation Phenology Retrieval in Cloud-Prone Regions
by Tianci Xie, Jinquan Ai, Ni Xie and Man Qiao
Remote Sens. 2026, 18(11), 1832; https://doi.org/10.3390/rs18111832 - 3 Jun 2026
Viewed by 224
Abstract
Vegetation phenology refers to the cyclical growth patterns of vegetation in nature, which are influenced by climatic conditions, human activities, and genetic factors. It plays an irreplaceable role in regulating carbon cycling and energy flow within natural ecosystems. However, the combination of a [...] Read more.
Vegetation phenology refers to the cyclical growth patterns of vegetation in nature, which are influenced by climatic conditions, human activities, and genetic factors. It plays an irreplaceable role in regulating carbon cycling and energy flow within natural ecosystems. However, the combination of a cloudy and rainy climate with a landscape characterized by the interplay of land and water and fragmented patches has long posed challenges for remote sensing phenological monitoring data, including a scarcity of valid observations, frequent temporal gaps, and spectral distortion in mixed pixels. These issues make it difficult to reliably support the needs of wetland phenological inversion and mapping. To address this issue, this study uses vegetation inversion in the Poyang Lake wetlands as a case study and reconstructs high-spatiotemporal-resolution time-series kNDVI data based on multi-source remote sensing data. Methodologically, we propose an improved and enhanced spatiotemporal adaptive reflectance fusion model, IESTARFM. This model enhances the homogeneity of similar pixel selection through adaptive matching windows and land cover constraints. Additionally, it explicitly incorporates cloud probability and time-lag factors into the weighting structure to systematically downweight unreliable observations, and further employs quadratic term corrections to account for the nonlinear growth response of kNDVI. Using the reconstructed dataset, key phenological information is extracted by combining third-order harmonic analysis with a dynamic thresholding method, thereby enhancing the robust characterization of seasonal trajectories under conditions of missing data and noise. Accuracy evaluation results show that the 10m/8d high-frequency kNDVI dataset reconstructed by IESTARFM achieves at least a 12.61% improvement in fusion accuracy compared to classical methods such as ESTARFM, STARFM, and FSDAF, with a maximum reduction in RMSE of 0.026, and effectively restores details in areas with thin cloud cover. The reconstructed kNDVI series achieved a coefficient of determination R2 = 0.875 and RMSE = 0.066 relative to Sentinel-2 observations, indicating that the reconstructed series closely reproduces the reference imagery in both amplitude and spatial structure. The phenological parameters derived from kNDVI exhibit an RMSE of 4.81 days compared to field observations, demonstrating that the reconstructed time series reliably captures the timing of key phenological events. It should be noted that the proposed approach is designed for post-event time-series reconstruction and is not intended for real-time forecasting. In summary, this study collaboratively enhanced the reliability of high-resolution index time-series reconstruction and phenological identification in cloudy and rainy wetlands through three key aspects: cloud noise suppression, heterogeneous boundary preservation, and nonlinear growth characterization. It provides a generalizable technical foundation for dynamic monitoring of wetland vegetation, ecological restoration assessment, and refined management in regions with frequent cloud and rainfall. Full article
(This article belongs to the Special Issue High-Throughput Phenotyping in Plants Using Remote Sensing)
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22 pages, 12907 KB  
Article
Water Quality Monitoring and Assessment of Inflow Rivers on a Central Island of Lake Taihu Using UAV Remote Sensing and Machine Learning
by Yong Yan, Ying Wang, Cheng Yu and Wei Zhao
Water 2026, 18(11), 1318; https://doi.org/10.3390/w18111318 - 29 May 2026
Viewed by 259
Abstract
Lake Taihu is a vital source of surface water for the Yangtze River Delta region, so effective monitoring of its water quality is essential for protecting the water source. However, most existing studies on unmanned aerial vehicle (UAV)-based water quality remote sensing have [...] Read more.
Lake Taihu is a vital source of surface water for the Yangtze River Delta region, so effective monitoring of its water quality is essential for protecting the water source. However, most existing studies on unmanned aerial vehicle (UAV)-based water quality remote sensing have focused on single large rivers or lakes, primarily employing validation methods involving randomly selected samples. This makes it difficult to assess the generalisability of the models to unfamiliar watercourses. This study focuses on 13 inflow rivers on Xishan Island, a central island in Lake Taihu, which are characterized by short flow paths, independent catchment areas, and varying land use influences. Using a UAV multispectral remote sensing platform, we have designed a water quality monitoring and assessment framework tailored to multi-river systems with small sample sizes. First, various water body indices were developed and analysed for correlation with measured water quality parameters. Then, machine learning algorithms such as Backpropagation (BP) neural networks, Random Forest, XGBoost, Convolutional Neural Networks (CNN) and Support Vector Machines (SVM) were selected to construct retrieval models. For accuracy evaluation, a spatial independent validation strategy was employed whereby one sample was forcibly set aside from each river to constitute the validation set. Using this method, we generated spatial distribution maps of water quality parameters for the inflow rivers and evaluated the influencing factors of spatial variation in water quality by area, taking into account water body functional types and ecological characteristics. The experimental results indicate that under the conditions of spatial independent validation strategy, the SVM model achieved the highest retrieval accuracy for dissolved oxygen (R2 = 0.892, RMSE = 0.414 mg/L and MRE = 0.057), whereas the XGBoost model achieved the highest retrieval accuracy for turbidity (R2 = 0.853, RMSE = 0.632 NTU and MRE = 0.065). The spatial pattern of water quality exhibited a pronounced gradient: dissolved oxygen (DO) concentrations followed the order of aquaculture area rivers > agricultural area rivers > urban area rivers, while turbidity displayed the opposite trend, reflecting that surrounding land use types, phytoplankton density, and human activity intensity are the dominant factors driving the spatial differentiation of river water quality on Xishan Island in spring. The full-chain technical framework of “multi-river synchronous retrieval—spatially independent validation strategy—area mechanistic assessment” proposed in this study provides a replicable evaluation paradigm for rapid water quality monitoring of Lake Taihu islands and similar watersheds, and holds significant implications for the construction of the Lake Taihu Eco-Island and the protection of the water environment. Full article
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23 pages, 7764 KB  
Article
Spatio-Temporal Dynamics of Vegetation and Water Stress in the Trichonida Basin Using Remote Sensing and Climatic Drought Indicators
by Fatima Daide, Eleni Ioanna Koutsovili, Mohammed Mouad Mliyeh, Abderrahim Lahrach, Isavela N. Monioudi and Ourania Tzoraki
Limnol. Rev. 2026, 26(2), 22; https://doi.org/10.3390/limnolrev26020022 - 28 May 2026
Viewed by 220
Abstract
Freshwater lakes in Mediterranean regions are highly sensitive to climatic variability, particularly to droughts intensified by rising temperatures and increasing atmospheric evaporative demand. This study investigates drought variability and ecosystem responses in the Trichonida basin, the largest natural freshwater system in Greece, using [...] Read more.
Freshwater lakes in Mediterranean regions are highly sensitive to climatic variability, particularly to droughts intensified by rising temperatures and increasing atmospheric evaporative demand. This study investigates drought variability and ecosystem responses in the Trichonida basin, the largest natural freshwater system in Greece, using an integrated approach that combines the Standardized Precipitation Evapotranspiration Index (SPEI) at multiple time scales with satellite-derived Normalized Difference Vegetation Index (NDVI), Crop Water Stress Index (CWSI), and lake surface water temperature. SPEI analysis revealed increasingly recurrent and persistent drought conditions in recent years, especially at medium- and long-term scales. NDVI exhibited pronounced seasonal variability and a moderate long-term increase at the basin scale, largely associated with agricultural activity and irrigation practices, while sharp declines were observed during severe drought episodes. CWSI showed strong seasonal patterns characterized by recurrent summer water stress events, but no significant long-term trend. Correlation analysis indicated positive relationships between NDVI and SPEI at medium- to long-term time scales, and significant negative correlations between CWSI and SPEI at short and medium time scales. A strong relationship between NDVI and CWSI further suggests the sensitivity of vegetation greenness to water stress, particularly during summer and autumn. Lake surface water temperature exhibited seasonal warming trends that coincided with periods of increased vegetation water stress. Drought-related water risks arise for calcareous fens dominated by Cladium mariscus in the Lake Trichonida system, a habitat of high conservation value, whose productivity is strongly seasonally controlled and closely linked to thermal dynamics. Overall, the combined multi-indicator analysis provides valuable insights into drought impacts and seasonal ecosystem vulnerability in Mediterranean lake basin environments, highlighting the importance of integrated monitoring frameworks for sustainable freshwater ecosystem management under increasing climatic variability. Full article
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26 pages, 12747 KB  
Article
Evaluation of Baseline Water Quality Conditions and Episodic Biomass Increases in Lake Villarrica Using Hyperspectral and Multispectral Data
by Oscar Cartes, Santiago Yépez, Germán Velásquez, Lien Rodríguez-López, Luc Bourrel, Frédéric Frappart, Aried Lozano, Rodrigo Saavedra-Passache, Carlo Gualtieri and Jordi Cristóbal
Water 2026, 18(10), 1230; https://doi.org/10.3390/w18101230 - 19 May 2026
Viewed by 374
Abstract
Lake Villarrica, located in southern Chile, is a vital freshwater resource whose ecological status requires continuous evaluation. Chlorophyll-a (Chl-a) is a key indicator of phytoplankton biomass and estimating it using satellite sensors enables efficient and large-scale monitoring. This study compared the performance of [...] Read more.
Lake Villarrica, located in southern Chile, is a vital freshwater resource whose ecological status requires continuous evaluation. Chlorophyll-a (Chl-a) is a key indicator of phytoplankton biomass and estimating it using satellite sensors enables efficient and large-scale monitoring. This study compared the performance of different empirical models based on reflectance data obtained from atmospherically corrected satellite images using ACOLITE software (Generic Version 20231023.0), calibrated with in situ measurements of Chl-a collected during the spring and summer seasons between 2014 and 2024. For each sensor, the best combination of spectral bands was selected, and retrieval models were generated using a bootstrapping procedure with 1000 iterations to obtain robust regression coefficients; the final models were defined using the median of these coefficients. The top-performing model for Landsat-8 and 9 was based on a blue-red band combination (R2 = 0.79, RMSE = 2.1 µg·L−1, MAE = 1.2 µg·L−1, n = 74). In contrast, the optimal model for Sentinel-2A utilized green and blue bands, yielding higher precision (R2 = 0.75, RMSE = 0.8 µg·L−1, MAE = 0.72 µg·L−1, n = 112). In general, the results obtained through remote sensing reveal a gradual increase in Chl-a levels over the last decade, reflected in recurrent summer biomass increases primarily along the shoreline near the urban area of Pucón and in the vicinity of the Pucón River inflow into Lake Villarrica. These results support the development of an operational satellite-based monitoring framework for inland lake water quality assessment. Full article
(This article belongs to the Section Water Quality and Contamination)
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27 pages, 5563 KB  
Article
Spatiotemporal Dynamics of Wetland Landscape Pattern and Its Driving Mechanisms in the Poyang Lake Region (2000–2020)
by Xiaoyan Duan, Yiwei Jin, Hong Xu and Minghui He
Sustainability 2026, 18(10), 5084; https://doi.org/10.3390/su18105084 - 18 May 2026
Viewed by 272
Abstract
Poyang Lake represents China’s largest freshwater wetland. The wetland landscape has undergone substantial changes driven by climate change and intensive human activities. Nevertheless, long-term classified analyses of wetland evolution and quantitative assessments of its driving factors remain scarce in the region. Based on [...] Read more.
Poyang Lake represents China’s largest freshwater wetland. The wetland landscape has undergone substantial changes driven by climate change and intensive human activities. Nevertheless, long-term classified analyses of wetland evolution and quantitative assessments of its driving factors remain scarce in the region. Based on 21 Landsat images from 2000 to 2020, this study systematically examined the spatiotemporal dynamics of the wetland landscape. Analyses incorporated land-use dynamic degree, landscape metrics, transfer matrices, and standard deviational ellipses, with key driving forces identified via Pearson correlation and structural equation modeling. Results indicate a 3029.63 km2 reduction in wetland area, exhibiting contrasting trends between natural and artificial wetlands. The wetland centroid shifted 7.4 km southwestward. Connectivity of lake increased and fragmentation declined, whereas paddy field fragmentation intensified. Wetland evolution was predominantly driven by socioeconomic factors, whereas climate primarily influenced natural wetlands. The study elucidates the coupled effects of anthropogenic and natural factors, offering insights into wetland restoration and ecological security in the middle and lower Yangtze River. The findings suggest prioritizing natural wetland connectivity, controlling wetland-to-non-wetland conversion, and incorporating long-term remote-sensing monitoring into regional wetland restoration planning. Full article
(This article belongs to the Section Environmental Sustainability and Applications)
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21 pages, 2407 KB  
Review
GRACE Downscaling and Machine Learning Models for Groundwater Prediction: A Systematic Review
by Mohammed S. Al Nadabi, Mohammed El-Diasty, Talal Etri and Mohammad Reza Nikoo
Hydrology 2026, 13(5), 135; https://doi.org/10.3390/hydrology13050135 - 14 May 2026
Viewed by 609
Abstract
Gravity Recovery and Climate Experiment (GRACE) satellites primarily monitor changes in land water storage, including groundwater, soil moisture, lake and river surface water, and canopy and snow water. However, its coarse spatial resolution of 0.25 degrees limits its ability to observe smaller basins. [...] Read more.
Gravity Recovery and Climate Experiment (GRACE) satellites primarily monitor changes in land water storage, including groundwater, soil moisture, lake and river surface water, and canopy and snow water. However, its coarse spatial resolution of 0.25 degrees limits its ability to observe smaller basins. To assess aquifer depletion and evaluate a long-term water resource management framework, GRACE data are crucial. It remains rare for GRACE-focused studies to be conducted in great depth. A comprehensive review of 80 articles published between 2011 and 2025 was conducted using the Scopus and Web of Science databases. These articles focused on downscaling GRACE data using machine learning (ML) methods. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines were used in this review. This study highlights the attributes of ML models, the input variables used, the evaluation metrics, and the output resolution. Based on the analysis of the articles, random forest (RF) methods were used in the majority of the papers. Gradient boosting (GB), artificial neural networks (ANN), support vector machines (SVM), support vector regression (SVR), and long short-term memory (LSTM) were the most widely used ML methods. As input variables, rainfall (Pr), soil moisture (SM), and runoff (Qs) are essential. In 2011, there were very few journal articles; since 2021, the number has increased. The number of published studies from China was the highest (24), followed by the USA (12) and Iran (9). A total of 38 journals published reviewed articles. In terms of articles, Remote Sensing generates 19%, Journal of Hydrology has 10%, and Journal of Hydrology: Regional Studies has 8%. The paper also discusses limitations, challenges, recommendations, and potential future directions for improving the accuracy of the GWS change prediction model. Full article
(This article belongs to the Section Hydrological and Hydrodynamic Processes and Modelling)
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22 pages, 7436 KB  
Article
SA-CNN Model Reveals Opposite Seasonal Trends and Drivers of Water Quality in Dongting Lake Using Multi-Source Remote Sensing
by Yingman Guo, Kaijun Yang, Ruyi Feng and Li Cao
Remote Sens. 2026, 18(10), 1565; https://doi.org/10.3390/rs18101565 - 14 May 2026
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Abstract
The Dongting Lake Basin is a critical ecological zone in the middle reaches of the Yangtze River, playing a pivotal role in safeguarding regional ecological security and supporting socio-economic development. To investigate the spatiotemporal patterns and underlying drivers of water quality in Dongting [...] Read more.
The Dongting Lake Basin is a critical ecological zone in the middle reaches of the Yangtze River, playing a pivotal role in safeguarding regional ecological security and supporting socio-economic development. To investigate the spatiotemporal patterns and underlying drivers of water quality in Dongting Lake, this study developed a Spectral-Attention CNN (SA-CNN) inversion model integrated with the Efficient Channel Attention (ECA) mechanism, utilizing multi-source remote sensing data and convolutional neural networks. Results indicate that the proposed SA-CNN model significantly outperforms traditional machine learning approaches in predicting key water quality parameters, including total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH3–N), and turbidity. Notably, the model achieved its highest predictive accuracy for TP, with an R2 value of 0.94. By incorporating spectral weight prior knowledge, the model was successfully transferred and trained on Landsat imagery. The validated model was subsequently applied to reconstruct and analyze the spatiotemporal trends from 2015 to 2025, revealing that water quality in Dongting Lake exhibits a fluctuating decline during winter months, while summer periods show an increasing trend in turbidity and TP concentrations. Further analysis suggests that water quality parameters are positively correlated with temperature and negatively correlated with precipitation, with anthropogenic activities also exerting a considerable influence. Full article
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Article
An Event-Based Remote-Sensing Framework for Quantifying Operational Post-Bloom Recovery and Its Environmental Controls in Lake Taihu and Lake Dianchi
by Jian Li, Jinjin Bai, Tao Xie and Zhengshan Song
Remote Sens. 2026, 18(10), 1535; https://doi.org/10.3390/rs18101535 - 12 May 2026
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Abstract
Most remote-sensing studies of cyanobacterial blooms have focused on bloom onset, peak intensity, and spatial extent, while the post-bloom recovery stage has received far less attention. Yet this stage is directly relevant to water-quality recovery and to the timing of management response. In [...] Read more.
Most remote-sensing studies of cyanobacterial blooms have focused on bloom onset, peak intensity, and spatial extent, while the post-bloom recovery stage has received far less attention. Yet this stage is directly relevant to water-quality recovery and to the timing of management response. In this study, we developed an event-based remote-sensing framework to quantify post-bloom recovery using satellite-derived chlorophyll-a as the core indicator, and applied it to Lake Taihu and Lake Dianchi over the period 2000–2022. FAI-derived bloom-area time series were used to identify bloom days and event termination, while satellite-derived chlorophyll-a was used to determine the post-bloom recovery date relative to an event-specific background threshold. Recovery duration was defined as the period from bloom termination to the first return of chlorophyll-a below an event-specific background threshold. Based on this framework, we quantified recovery duration, event frequency, representative recovery trajectories, and recovery-rate metrics, and then examined their controls using statistical comparison, nonlinear modeling, grouped contribution analysis, and path-based validation. The two lakes showed distinct recovery regimes. Lake Taihu had 82 recovery events, with a mean recovery duration of 8.82 days and a median of 6 days, whereas Lake Dianchi had 28 events, with a mean duration of 25.32 days and a median of 22 days. Events lasting more than 20 days accounted for 9.76% of cases in Taihu but 57.14% in Dianchi. By the recovery date, normalized chlorophyll-a and bloom area had decreased to 44.5% and 12.1% of their peak values in Taihu, compared with 20.4% and 4.9% in Dianchi, respectively. Driver analysis indicated that recovery duration was influenced mainly by phase-specific meteorological forcing and lake background, rather than by bloom magnitude alone. Trigger-stage meteorology, lake identity, and transition-stage meteorology contributed 31.53%, 27.58%, and 19.40% of the grouped explanatory signal, together accounting for about 78.5%. These results show that post-bloom recovery can be quantified as an event-scale remote-sensing metric and compared across lakes. The framework extends remote sensing from bloom detection to recovery assessment and provides a basis for lake-specific post-bloom monitoring and management. Full article
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