Search Results (894)

Remote sensing inversion of suspended solids (SS) in karst plateau lakes is challenging due to spectral mixing and strong nonlinearity. This study develops an inversion framework using Sentinel-2 MSI imagery and field data from 40 sampling sites at Pingzhai Reservoir. An Extremely Randomized Trees (ERT) model was constructed with 20 spectral features selected via correlation analysis and multicollinearity control. The ERT model demonstrated excellent performance (R² = 0.90, RMSE = 0.95 mg/L, MAE = 0.66 mg/L), outperforming conventional linear models (improved by 57%) and other machine learning algorithms. The near-surface SS concentrations exhibited significant seasonality, peaking in spring and summer (7.3 mg/L) and concentrating in inflow zones. TOC and water temperature were identified as key drivers, while a negative correlation with total nitrogen under alkaline conditions highlighted unique karst nutrient dynamics. This framework provides an accurate, high-spatiotemporal-resolution remote sensing solution for SS monitoring, supporting water-quality management in karst regions. Full article

Mountain glaciers constitute sensitive indicators of climate variability and represent essential freshwater reservoirs for downstream ecosystems and societies. Although glacier change in the Greater Caucasus has been extensively investigated at regional scales, detailed long-term reconstructions of individual glacier systems remain comparatively scarce. In this study, we reconstruct two centuries of evolution of Georgia’s largest Lekhziri Glacier and document the recent formation of its proglacial lake. The Little Ice Age glacier extent (AD ~1820) was reconstructed from moraine complexes, whereas later glacier outlines were derived from historical topographic maps, Landsat, SPOT, PlanetScope, and unmanned aerial vehicle (UAV) data spanning 1890–2025. Glacier terminus elevation was analysed using the Copernicus Digital Elevation Model, whereas long-term climatic variability was evaluated from summer air temperature and winter precipitation records obtained from the local meteorological station. The results demonstrate that Lekhziri Glacier experienced substantial and accelerating retreat during the past two centuries. Glacier area decreased from 46.67 ± 2.53 km² in ~1820 to 28.31 ± 0.62 km² in 2025, representing a net reduction of −18.36 km² (−39.34%) with an average annual decrease of −0.19% yr⁻¹. Area loss accelerated markedly after 2000, reaching −0.66% yr⁻¹ during 2000–2014 and −0.87% yr⁻¹ during 2014–2025. Over the last two centuries, the glacier terminus retreated by approximately −4.78 km, equivalent to an average retreat rate of −32.4 m yr⁻¹, while the terminus elevation migrated upward by nearly 600 m, from ~1718 to ~2317 m a.s.l. The glacier also underwent pronounced structural fragmentation after 2014, fundamentally altering its geometry and flow configuration. Concurrently, a proglacial lake first identified in 2019 with an area of 10,805 m² expanded rapidly to 28,947 m² in 2022 and 38,260 m² in 2025, with its continued existence confirmed by UAV observations in 2026. Meteorological records indicate a persistent increase in summer air temperature since the mid-twentieth century, accompanied by a decline in winter precipitation, consistent with the observed acceleration of glacier recession. This study provides one of the most comprehensive reconstructions of glacier evolution to date for an individual glacier in the Greater Caucasus and contributes new insights into the changing dynamics of glacierized mountain landscapes under continued climate warming. Full article

Lake Baikal is a UNESCO World Heritage Site and the largest freshwater reservoir on the planet. It is located in the center of Eurasia, in an industrially developing region—Eastern Siberia. Although a regulatory and legal framework exists, quantitative estimates of the pathways of pollutant transport from industrial sources to the lake water area remain insufficiently studied, particularly in the context of seasonal dynamics and the influence of developing industrial sectors. In the present work, a quantitative analysis of the direct atmospheric transport of pollutants from three groups of stationary sources (the Irkutsk agglomeration, the Republic of Buryatia, and the oil-and-gas production areas of Irkutsk Oblast) to the lake surface was carried out for the first time using the HYSPLIT model for the period 2005–2025. About 4.7 million forward trajectories were computed at three heights (250, 500, 1000 m AGL) for each group of sources. It was established that conditions favorable for the transport of impurities to the lake occur in more than half of the cases. However, the spatial distribution of the impact on the Baikal air basin is heterogeneous: the Irkutsk agglomeration accounts for 67.5% of the “hits” (the main contribution being to the air basin of the Southern Basin), the Republic of Buryatia 18.8% (to the Central Basin), and the oil-and-gas areas 19.9% (to the Northern Basin). On the basis of a multifactor analysis, a combined Potential Impact (PI) index was developed that makes it possible to rank regional sources by the degree of their impact on the lake ecosystem, taking into account the emission volume, the probability of delivery, the residence time, and the height of trajectory passage. The results form a scientific basis for optimizing the spatial placement of environmental monitoring networks and for preliminary zoning of environmental risk assessment over the Lake Baikal water area. Ultimately, this study contributes to the sustainable management of the Baikal Natural Territory by providing actionable insights for balancing regional industrial growth with the long-term ecological preservation of the planet’s largest freshwater reservoir. Full article

The Guanting Gorge section of the Yongding River features complex terrain and densely distributed hydraulic projects. Under extreme rainstorm conditions, flood disasters are highly likely to occur, triggering secondary disasters such as landslides, barrier lakes, and dam breaks, resulting in prominent chain disaster risks and difficult prevention and control. To accurately evaluate the potential flood disaster chain risks in this region, 12 representative evaluation indicators were selected to establish a flood disaster chain risk evaluation system. The analytic hierarchy process (AHP) and entropy weight method (EW) were adopted to calculate subjective and objective indicator weights, respectively. Game theory was applied to achieve the optimal weight fusion and determine the final indicator weights. On this basis, a variable fuzzy model was constructed to identify flood disaster chain risks, and the Receiver Operating Characteristic-Area Under the Curve (ROC-AUC) was used to verify the accuracy and reliability of the model. The results show that cumulative precipitation, terrain slope, and annual maximum precipitation are the core driving factors inducing regional flood disaster chains, with corresponding weights of 0.2058, 0.1293, and 0.0980, respectively. High- and extremely high-risk areas are mainly concentrated in the western and southern river valleys, among which the Zhaitang–Luopoling river reach and the river section from Luopoling Reservoir to Sanjiadian Hub present the most prominent risks. The spatial distribution of risk zones is highly consistent with the actual disaster sites of the July 2023 Haihe River extreme rainstorm event, and the model achieves an AUC value of 0.901, indicating high accuracy and reliable simulation results. This study accurately identifies the core inducing factors and high-risk sections of flood disaster chains in the Guanting Gorge section of the Yongding River, which can provide scientific references and technical support for regional flood disaster chain prevention and control, hydraulic project operation and management, and disaster prevention and mitigation planning. Full article

This study presents a data-driven methodology to develop and close the continuous water balance of a cascaded hydrological system consisting of two upstream regulating reservoirs and a downstream lake. The analysis is based on monthly hydrometeorological and hydrographic data for the period 1998–2024. A baseline water balance model using raw measured data was first implemented, followed by two bias correction approaches based on multiple linear regression coefficient estimation. The first approach applies uniform coefficients across all months, while the second accounts for seasonal variability by estimating coefficients only for the December–May period, when systematic errors are most pronounced. Model performance was evaluated using calibration (1998–2017) and validation (2018–2024) periods, with Nash–Sutcliffe efficiency (NSE) and residual diagnostics used as evaluation metrics. The baseline model showed substantial cumulative deviations due to systematic errors (NSE: −0.28 and −5.13 for the two reservoirs and −18.70 for the lake), confirming the need for bias correction. Both correction approaches significantly improved model performance, with NSE values up to 0.89 for reservoirs and 0.83–0.86 for the lake during calibration. In validation, the seasonally adjusted model performed more stably in simulating water levels for Lake Velence (NSE = 0.72) than the uniform coefficient model (NSE = 0.60), particularly under extreme hydrological conditions. Residual analysis further indicated improved independence and homoscedasticity when seasonal structure was considered. The results demonstrate that water balance closure in the system is affected by distributed errors across multiple components rather than a single dominant source. The proposed methodology provides a practical, scalable framework for reconstructing consistent water balance time series in data-limited, regulated systems and supports the development of water management scenarios. Full article

Shallow lakes are vulnerable to multiple anthropogenic stressors. However, the spatial responses of benthic ecosystems to these composite disturbances and the underlying mechanisms driving them remain poorly understood. Nansi Lake is a strategic water-regulating reservoir of the Eastern Route of the South-to-North Water Transfers. It has long been subjected to multiple human activities, and its aquatic ecological environment exhibits pronounced spatial heterogeneity. A systematic assessment is thus needed to evaluate the spatial distribution patterns of surface-sediment diatom communities and their trophic response characteristics. This study integrates the Trophic Diatom Index (TDI) with multivariate statistical approaches. It analyzes the spatial distribution and driving factors of surface-sediment diatom assemblages based on diatom and water quality data from 62 sampling sites. The results reveal three distinct community zones across the lake. The first is a high-disturbance zone dominated by hydraulic regulation and mining activities. In this zone, Stephanodiscus parvus Stoermer & Håkansson is the absolute dominant species, indicating a clear eutrophic status. The second is a hydrochemically stable zone dominated by Achnanthidium minutissimum (Kützing) Czarnecki, exhibiting relatively high community integrity. The third is a vast central open-water zone characterized by the dominance of Pseudostaurosira brevistriata (Grunow) Williams & Round, representing a mesotrophic transitional state. Partial redundancy analysis (pRDA) shows that multiple explanatory variables jointly explain 28.91% of the community variation. The independent explanatory powers of anthropogenic variables (9.12%) and environmental factors (7.94%) are both higher than that of pure spatial dispersal processes (0.35%). Redundancy Analysis (RDA) indicates that different types of human activities—such as reservoir regulation, coal mining, and estuarine inflows—may influence the spatial distribution patterns of surface-sediment diatoms. They do so by jointly driving variations in lake trophic status and the ionic environment, particularly Mg²⁺ and SO₄²⁻. This study provides a scientific basis for the water resource management of shallow lakes subject to anthropogenic impacts. Full article

Wild waterfowl constitute the primary natural reservoir of influenza A viruses, and wetlands at the convergence of major migratory flyways serve as critical hubs for viral genetic exchange. Baikal Siberia, situated at the intersection of the East African–West Asian, Central Asian, and East Asian–Australasian flyways, represents a unique yet understudied region in this context. Here we report the results of long-term virological surveillance of wild birds in the Lake Baikal basin conducted between 2018 and 2024. A total of 1036 cloacal swab samples from 28 bird species were screened, yielding 42 influenza A virus isolates belonging to 12 HA/NA subtype combinations: H1N1, H3N1, H3N2, H3N5, H3N6, H3N8, H4N6, H6N1, H6N2, H6N3, H6N8, and H12N5. Among the detected subtypes, H6 viruses—identified with four distinct neuraminidase combinations (N1, N2, N3, N8)—are of particular public health relevance owing to their documented capacity for dual-receptor binding and potential for zoonotic transmission to mammals, including humans. Full-genome sequencing followed by cluster analysis of internal gene segments identified 16 distinct segment constellations, indicating extensive reassortment. BLAST searches against the GISAID database revealed closest genetic relatives in Mongolia, South Korea, Japan, China, and Western Siberia, with more distant links to Bangladesh, Europe, and a possible intercontinental connection via the Pacific flyway. Maximum-likelihood phylogenetic analysis of the HA and NA segments confirmed that all isolates belong to the Eurasian genetic lineage, yet they are distributed across multiple clades rather than forming a single monophyletic group, reflecting the role of Buryatia as a mixing zone for genetically diverse viral populations. These findings substantially expand the understanding of influenza A virus ecology in the Lake Baikal basin and underscore the importance of continued surveillance at this key migratory crossroads in Northern Asia. Full article

In conventional hydraulic fracturing of low-permeability sandstone reservoirs, polymer-gel leak-off creates low-permeability filter cakes that impair productivity. This study proposes a prepad acid fracturing technique using a fluoroboric acid (HBF₄) pre-flush to dissolve gel residues and mineral fines. A fully coupled mathematical model integrates HBF₄ hydrolysis kinetics, multi-mineral surface reactions, porosity-permeability evolution via the Panda–Lake model, and dynamic leak-off coefficient feedback. Simulations show HBF₄ decreases monotonically along the fracture while HF peaks at 40–60 m from wellbore. Acid concentration in the leak-off zone decays exponentially, defining a gel-dissolution zone within 0.5 m of the fracture wall. Acid dissolution increases near-wall porosity to 12–15% and permeability to 2.5–3.5 mD (3- to 4-fold). The leak-off coefficient varies dynamically: high in the acid-dominated zone (1.5–2.2 × 10⁻³ m/√min) favoring gel dissolution, and low in the gel-dominated zone (≈0.8 × 10⁻³ m/√min) promoting fracture extension. Compared with conventional polymer gel fracturing, the proposed method achieves a 15.9% higher stimulation ratio and 22.5% higher productivity after 100 days, despite slightly shorter fractures. The core advantage is restoring leak-off zone permeability from 0.45 mD to 0.85 mD and increasing gel filter cake permeability from 8 × 10⁻⁴ mD to 0.1 mD, with an average relative error of 8.2% against experimental data. These findings provide theoretical guidance for optimizing prepad acid fracturing in gel-damaged low-permeability sandstones. Full article

Currently, the “Planning–Dissemination–Empowerment” approach has become a widely adopted practice paradigm for scientific journals to serve industrial scientific and technological innovation. Nevertheless, how to achieve the effective transformation from knowledge production to scientific and technological innovation remains a core issue urgently to be addressed in the academic publishing sector. Taking Yangtze River as the research sample, this paper constructs and conducts an in-depth analysis of a systematic practical path of “Planning–Dissemination–Empowerment” targeting the improvement of research achievement transformation efficiency. Under this path, the planning segment accurately identifies core issues aligned with national strategies and frontline engineering demands through demand anchoring, ensuring the pertinence and application value of academic content; the dissemination segment relies on a diversified digital matrix to realize precise delivery and efficient diffusion of research findings, accelerating the transmission of academic outputs; the empowerment segment intervenes from three dimensions of talent cultivation, decision support, and technology implementation, promoting the conversion of academic achievements into practical innovation capabilities. Practice demonstrates that this path has not only produced more than 1500 high-impact papers but also directly facilitated multiple scientific and technological innovations. Talent empowerment has fostered a cohort of young scientific and technological backbones; decision empowerment has directly underpinned national emergency decision-making via 3 policy advisory reports adopted by central authorities; technology empowerment has driven breakthroughs in key technologies such as barrier lake emergency disposal, with relevant achievements winning the First Prize of Hubei Provincial Science and Technology Progress Award. In addition, the optimal reservoir operation technology was applied in the 2024 basin-wide flood control, reducing flooded arable land by 170,000 hectares and preventing the evacuation of tens of thousands of residents, thus achieving the integration of academic influence and tangible social benefits. Rather than a mere restatement of industry consensus, the path proposed in this paper reveals the underlying mechanism through which scientific journals are deeply embedded in the innovation chain and catalyze the shift from “consensus” to “practical outcomes” via systematic design. Combined with discussions of multi-industry cases, this path provides an operable theoretical framework and practical paradigm for scientific journals to play more substantial and verifiable roles in the national innovation system. Full article

Urban water security in many cities in the Global South is increasingly challenged by ageing infrastructure and the presence of persistent chemical contaminants. This study investigated the Harare metropolitan water continuum between 2020 and 2024 using a longitudinal, systems-oriented observational framework encompassing wastewater discharge, surface water reservoirs, drinking water treatment, and municipal distribution networks. A three-stage approach was employed, comprising qualitative screening for selected pharmaceuticals at the Lake Chivero water–sediment interface in 2020, spatial assessment of physicochemical stability across the treatment and distribution system in 2021, and targeted qualitative evaluation of pharmaceutical and agrochemical occurrence in wastewater-impacted matrices in 2024. Sulfamethoxazole and trimethoprim were qualitatively identified using high-performance liquid chromatography (HPLC), while atrazine was confirmed by gas chromatography–mass spectrometry (GC–MS). These analyses indicated the continued presence of pharmaceutical and agrochemical residues within wastewater-impacted aquatic compartments associated with the Harare water supply. Physicochemical monitoring revealed elevated ammonia concentrations and reduced free residual chlorine across sections of the distribution network. These conditions coincided with detectable heterotrophic bacterial regrowth at distal consumer endpoints. Phenotypic antimicrobial susceptibility testing of bacterial isolates recovered at the source interface showed limited inhibition responses to sulfamethoxazole and trimethoprim under the experimental conditions used. While the observational nature of this study precludes causal inference, the co-occurrence of chemical residues, physicochemical instability, and bacterial isolates exhibiting reduced inhibition responses highlights conditions of potential relevance for antimicrobial resistance risk within wastewater-influenced urban water systems. These findings underscore the importance of integrated water management strategies addressing wastewater control, source water protection, and distribution system integrity within a One Health context. Full article

Long-term monitoring of surface-water dynamics in hyper-arid reservoir systems requires consistent remote-sensing methods that can distinguish open water from bright desert surfaces, shallow water, wet sand, and mixed shoreline pixels. This study evaluates Landsat-derived spectral water indices for delineating surface water in Lake Nasser and the adjacent Tushka Lakes, generates a multi-decadal record of surface-water extent using Google Earth Engine, and places the resulting surface-water patterns in the context of available hydrogeological observations. Landsat TM and OLI surface reflectance imagery was used to compare seven commonly applied water indices (NDWI, EWI, NDX, WRI, AWEI_nsh, TCW, and NWI) based on mapped water area, relative area differences, and classification accuracy metrics derived from 1000 stratified reference samples. Among the tested indices, NDWI provided stable water–land separation (overall accuracy ≈ 93.6%; κ ≈ 0.898) and was selected for long-term mapping. The NDWI-based workflow was implemented in Google Earth Engine to generate quarterly composites of surface-water extent for the period 1987–2026. The resulting time series reveals stable, persistent surface water in the central and southern sectors of Lake Nasser, in contrast to pronounced seasonal and interannual variability in the shallow, intermittently connected Tushka basins. Total mapped water area increased from 2631 km² in 1987 to 8923 km² in early 2026, with Lake Nasser ranging from 2411 to 6060.7 km² and the Tushka Lakes expanding from no mapped water before 1998 to more than 3300 km² during 2025. To assess possible surface–subsurface interaction, daily lake-stage records (1965–2014) and monthly groundwater levels from 44 observation wells were used to estimate potential seepage losses from Lake Nasser to the Nubian Sandstone Aquifer System using Darcy’s law. Annual seepage estimates ranged from 15.58 × 10⁶ to 36.68 × 10⁶ m³/year, suggesting spatial variability in potential lake–aquifer seepage along the western lake margin. The combined remote-sensing and hydrogeologic results provide complementary, non-causal evidence for interpreting where surface-water persistence and estimated seepage may co-occur. Because spatial correlation analysis, calibrated ground-water modeling, full water-budget analysis, and independent field validation were not performed, the inferred seepage–surface-water relation should be regarded as a cautious hypothesis rather than proof of causality. Full article

Enterococci are environmentally persistent bacteria that are relevant to both water quality and the spread of antimicrobial resistance. This study aimed to phenotypically and genotypically characterize Enterococcus spp. isolated from freshwater (lakes and rivers) in north–central Poland, with a focus on antimicrobial susceptibility, virulence genes, and biofilm-forming capacity. Surface water samples were collected during the vegetation seasons of 2022 and 2023. Enterococci were isolated by culture-based methods and confirmed by MALDI-TOF MS. Antimicrobial susceptibility testing (AST) was performed using the disk diffusion method, virulence-associated genes were detected by multiplex PCR, and biofilm formation was evaluated using a crystal violet assay. In total, 96 Enterococcus spp. isolates representing 12 species were identified from 328 freshwater samples, with E. faecalis (24.0%) and E. hirae (21.9%) being the most frequently isolated. Thirty-one isolates (32.3%) were resistant to at least one antibiotic, and two isolates were classified as multidrug-resistant. The most prevalent virulence genes were gelE, srtA, and hyl. The ace gene was detected exclusively in E. faecalis. Most isolates were non-biofilm producers, while biofilm formation was confirmed in 8 strains (6 weak and 2 moderate producers), with no strong biofilm-forming strains detected. These findings suggest that freshwater ecosystems may constitute important reservoirs of antimicrobial-resistant and virulence-associated Enterococcus spp., underscoring the importance of continuous surveillance within the One Health framework. Full article

The High Agri Valley (HAV, Southern Italy) comprises the largest onshore oil field in Europe and has both significant geothermal extraction potential and one of the highest seismic hazards in Italy, as demonstrated by the 1857 Mw 7.0 Basilicata earthquake. However, seismic imaging and geological mapping have so far produced insufficient evidence regarding the location of fluid reservoirs and human-induced migration pathways within the HAV’s tectonic structures. Here, a 3D scattering and absorption tomography, proxy for heterogeneities and fluid content, respectively, detects hydrocarbons and potential geothermal resources within the Apulian Platform. Seismic scattering differentiates the low-scattering Irpinia tectonic mélange, which deepens in the center of the valley, from the fractured high-scattering carbonates of the Apulian Platform. Seismic absorption identifies regions of fluid reinjection, as demonstrated by the Costa Molina 2 case study, and reveals the preferred pathways for fluids that induce seismicity due to seasonal variations in the water level of the Pertusillo artificial lake. The integration of scattering and absorption imaging with direct well information, geochemical and hydrological models, could provide a powerful tool for both seismic hazard assessment and the exploration of sustainable energy resources. Full article

Introduction: Longlines are traditional fishing gear and are widely used in marine systems for both quantitative and qualitative sampling of large predators like tuna, swordfish, sailfish, marlin or sharks. This highly selective method has been applied for the sampling of European catfish (Silurus glanis), the largest freshwater fish in Europe. This apex predator is a highly valuable fish species in its native localities of Central and Eastern Europe (commercial fishing, anglers’ trophy fishing, biomanipulation purposes) but a dangerous alien invasive species in South and Western Europe. Objective: The efficiency and selectivity of longlines for European catfish sampling were compared with more traditional fishing methods like gillnets and electrofishing. Methodology: European catfish were sampled in native areas (Římov, Žlutice, Vrchlice, Hubenov, Lipno, Želivka reservoirs; Czech Republic) and areas of invasion (Lakes Campagna, Avigliana Grande, Maggiore; Italy; Belver, Meimoa, Cedillo reservoirs; Portugal; Iznajar, Mequinenza reservoirs; Spain) following the protocols of best catfish (Silurus glanis) capture methodologies in small and large lakes and reservoirs established for the current needs of the European Commission within the LIFE PREDATOR project. Results: The longline efficiency expressed as the proportion of individual hooks catching catfish (live baits exposed overnight) was from low to medium (5–25%; Czech reservoirs, Italian lakes, Meimoa reservoir) to very high (up to over 50%; Portuguese and Spanish reservoirs). In many water bodies, specifically in areas of invasion, catfish represented 100% of the longline catch (Campagna, Maggiore, Cedillo, Iznajar, Mequinenza). In the rest of the water bodies, the by-catch ranged from 2 to 20% with the highest values occurring in its native localities (due to the presence of large individuals of Northern pike, Esox lucius, another predatory fish in these systems). In areas of invasion, the inconsiderable by-catch was composed of other non-native predatory fish species like pikeperch (Sander lucioperca), European perch (Perca fluviatilis) or channel catfish (Ictalurus punctatus). Both the efficiency and selectivity of longlines were higher compared to gillnets and electrofishing, and longlines also caught larger catfish individuals. Conclusions: Longlines represent an efficient and extremely selective method for European catfish sampling, reduction and even eradication, especially in areas of invasion. Their usage, however, requires specific equipment, skills and also baits. Full article

Reservoir construction and agricultural irrigation have substantially altered the natural hydrological regimes of many Mediterranean watersheds. This study aims to reconstruct the natural flow conditions of the Egirdir Lake Basin (Türkiye) and quantify the impacts of irrigation and reservoir operations on water inflows to Egirdir Lake using the Soil and Water Assessment Tool (SWAT). The SWAT model consisted of 14 subbasins and 274 hydrologic response units (HRUs) and initially calibrated and validated using naturalized flow data provided by the State Hydraulic Works (DSI) for the period from 1990 to 2014. The same model structure and parameters were then applied to simulate a regulated condition representing the combined effects of irrigation and reservoir operation. Results showed a considerable reduction in annual streamflows under the regulated condition. This study demonstrated the significant impact of irrigation water use and reservoir operation on the hydrological dynamics of semi-arid basins. Full article