Search Results (60)

Qinghai Lake, the largest endorheic saline lake in China, has undergone a pronounced hydrological regime shift from a multi-decadal decline to a rapid post-2004 recovery, reflecting strong hydroclimatic non-stationarity in the northeastern Tibetan Plateau (TP). This paper supplements the current water level and lake area status of Qinghai Lake to provide basic background for future prediction. Reliable forecasting of such climate sensitive lake systems remains difficult because conventional statistical models often fail to capture non-linear fluctuations, whereas standalone deep learning models may overlook long-term deterministic evolution. To address this challenge, we developed a serial decomposition GeoAI framework that integrates autoregressive integrated moving average (ARIMA), one-dimensional convolutional neural networks (1D-CNNs), and long short-term memory (LSTM) networks for non-stationary water level forecasting. Using annual water level observations from 1960 to 2025, the ARIMA component was first used to extract the low-frequency deterministic trend, after which the CNN-LSTM module reconstructed the nonlinear residual variability. The model was trained on the 1960–2012 period and validated over 2013–2025, which represents the most dynamic expansion stage of Qinghai Lake. The hybrid framework outperformed the benchmark models, achieving a Root Mean Square Error (RMSE) of 0.2033 m, Mean Absolute Error (MAE) of 0.1727 m, and Mean Squared Error (MSE) of 0.0413 m² during validation. The decomposition strategy effectively reduced phase lag and amplitude attenuation, improving both predictive accuracy and process interpretability. Multi-step forecasting for 2026–2056 suggests that Qinghai Lake will continue to rise, reaching approximately 3204.08 m by 2056, although the growth rate is projected to slow as negative hydrological feedback strengthen. By explicitly separating deterministic climate scale signals from nonlinear short-term variability, the proposed framework provides a robust and transferable geoinformation based tool for forecasting water level dynamics and supporting adaptive management in climate sensitive, data scarce lake basins. Full article

To elucidate the solute sources, migration and enrichment mechanisms of water bodies in the endorheic lake region of the Qiangtang Plateau on the Tibetan Plateau and clarify the hydrogeochemical cycling patterns in alpine arid environments, this study focuses on two core scientific objectives: quantitative identification of the multi-source contributions of aquatic solutes, and revelation of the key processes governing the enrichment of strategic elements including lithium (Li) and boron (B). To achieve these goals, we conducted systematic hydrogeological field investigations and collected 28 multi-type water samples, covering springs, rivers, thermal springs, freshwater lakes, salt lake brines, atmospheric precipitation, and glacial meltwater. The physicochemical properties, major ions, and trace elements of all samples were comprehensively analyzed. On this basis, the hydrogeochemical characteristics, evolutionary processes, and solute origins of regional waters were systematically explored. Combined with PHREEQC numerical simulation, principal component analysis (PCA), and Pearson correlation analysis, the dominant controlling factors of water geochemistry were quantified, and a conceptual hydrogeochemical evolution model was established. The results reveal a clear hydrogeochemical evolutionary gradient across the study area: water bodies evolve from low-salinity HCO₃-Ca recharge end-members and transitional HCO₃·SO₄-Ca(Mg) type water to highly mineralized Cl-Na (SO₄·Cl-Na) salt lake brines, accompanied by synchronous enrichment of Li, B, arsenic (As), and other characteristic elements. Solute accumulation in regional waters is governed by the ternary coupling effects of evaporative concentration, rock weathering and leaching, and deep geothermal fluid input, while cation exchange and mineral dissolution–precipitation reactions further modulate ionic composition and ratios. Elements including As, Li, B, and chloride (Cl⁻) exhibit conservative migration behaviors in non-hydrothermal waters, whereas thermal springs possess unique geochemical signatures driven by deep fluid recharge. PCA results indicate that evaporative concentration serves as the primary controlling factor with a contribution rate of 55.39%; rock weathering provides the basic solute load (17.09%); and the coupled processes of deep fluid mixing and carbonate precipitation regulate elemental fractionation (14.21%). These findings systematically clarify the hydrogeochemical evolution laws and multi-source coupling mechanisms of inland lake waters in the Qiangtang Plateau. Furthermore, this study establishes a conceptual framework of “multi-source recharge–water–rock interaction–evaporative concentration”, advances the understanding of alpine hydrological cycling under climate change, and provides a solid scientific foundation for hydrological cycle research and green exploration of strategic mineral resources in endorheic salt lake regions. Full article

The Xianglaqu River Basin, a major recharge area of the Xiagacuo endorheic lake basin on the Tibetan Plateau, provides an ideal setting for investigating hydrochemical evolution in alpine arid closed basins. In this study, 27 groundwater, spring-water, and surface-water samples collected from June to August 2023 were analyzed using correlation analysis, Piper diagrams, Gibbs diagrams, and ion-ratio methods. The results show that groundwater, spring water, and most surface water are predominantly of the HCO₃⁻–Ca·Mg type, indicating overall hydrochemical consistency across the basin. However, marked spatial differentiation occurs along the flow system: upstream waters are relatively simple and stable, whereas downstream and terminal surface waters show pronounced increases in Na⁺, Cl⁻, SO₄²⁻, and TDS, and some samples exhibit a tendency toward HCO₃⁻–Na facies. These patterns reflect progressive solute accumulation and terminal enrichment in the closed basin. Hydrochemical evolution is controlled mainly by water–rock interaction, with carbonate weathering as the dominant source of major ions, while silicate weathering, minor local saline-mineral dissolution, cation exchange, and evaporation concentration further influence water chemistry. Overall, the basin is characterized by local weathering release, along-path solute accumulation, and terminal evaporative enrichment. Full article

The carbonate massifs of the southern Italian Apennines host extensive karst aquifers, which represent the principal drinking water resources. This study focuses on the Dragone Plain polje, a vast closed karst depression located in the main recharge sector of the Terminio–Tuoro carbonate massif. The polje drains a ~55 km² endorheic catchment and may be flooded during the cold and wet season, forming a temporary lake. We employed continuous hydroclimatic time series (rainfall, groundwater level, spring discharge, and river level) together with sparse Sentinel-2 true color satellite images for the period 2020–2024 to analyze the flooding process in the polje and its hydraulic connection with the saturated zone of the karst aquifer. Results indicate that lake formation depends on the balance among soil moisture, rainfall intensity, and runoff development, which were modeled on a daily scale. Daily recharge was also estimated and compared with groundwater level time series from the deep karst aquifer. The modeling was integrated with cross-correlation analysis of the time series, providing insights into the propagation of precipitation pulses through the hydrogeological system. This case study represents an important example for understanding the relationship between karst polje hydrological functioning and climate in a Mediterranean area. Full article

Lake Balkhash is a large endorheic lake experiencing ongoing hydrological and climatic variability. This study aimed to evaluate the species composition and structure of the forage base across three trophic levels—phytoplankton, zooplankton, and zoobenthos—and to analyze trophic interactions of fish communities, including non-native species, in order to assess the functioning of the food web in the western and eastern basins of the lake. A 2025 assessment revealed a structurally reorganized yet relatively stable ecosystem. Phytoplankton showed an increase in taxonomic richness, while zooplankton and zoobenthos demonstrated compositional restructuring with a greater representation of ecologically tolerant taxa. The presence of certain invertebrate taxa in both Lake Balkhash basins indicates persistent spatial heterogeneity of the ecosystem. Despite moderate ecological resilience, biodiversity has not yet returned to historically recorded peak levels. Trophic analysis of fish communities showed generally moderate niche overlap among benthivorous species with localized differentiation of resource use. Predatory fishes also exhibited moderate overlap: pikeperch (Sander lucioperca) maintained stable dietary patterns with partial overlap with Volga pikeperch (Sander volgensis), whereas snakehead (Channa argus) and asp (Aspius aspius) demonstrated clearer trophic segregation. Non-native species displayed relatively narrow trophic niches (Bi < 0.30), indicating summer feeding specialization. Full article

Lakes on the Inner Mongolia–Xinjiang Plateau (IMXP) are increasingly vulnerable to eutrophication under climate change and human pressure, yet long-term monitoring remains limited by sparse field sampling. Here, we reconstruct multi-decadal trophic dynamics across the IMXP using Landsat time series and temporally transferable machine-learning models and further quantify the underlying natural and anthropogenic drivers. We compiled monthly in situ water-quality observations (chlorophyll-a, Chl-a; total phosphorus, TP; total nitrogen, TN; Secchi depth, SD; and permanganate index, COD_Mn;) and calculated the trophic level index (TLI). After rigorous quality control and monthly aggregation, we compiled a dataset of 1345 matched lake–month samples spanning 2000–2024, and divided it into a training set (n = 1076; ≤2019) and an independent test set (n = 269; 2020–2024) to evaluate temporal transferability. We utilized Google Earth Engine to generate monthly surface reflectance composites from Landsat 7 ETM+, Landsat 8 OLI, and Landsat 9 OLI-2. Four supervised regression algorithms—ridge regression (RR), support vector regression (SVR), random forest (RF), and eXtreme Gradient Boosting (XGBoost)—were trained to estimate TLI. On the independent test period, XGBoost performed best (R² = 0.780, RMSE = 3.290, MAE = 1.779), followed by RF (R² = 0.770, RMSE = 3.364), SVR (R² = 0.700, RMSE = 3.842), and RR (R² = 0.630, RMSE = 4.267); we then used XGBoost to reconstruct monthly and yearly TLI for 610 perennial grassland lakes from 2000 to 2024. From 2000 to 2024, the annual mean TLI (48–49) across the IMXP exhibited a statistically significant upward trend (slope = 0.0158 TLI yr⁻¹; 95% confidence interval (CI) = 0.0050–0.0267; p = 0.006). Meanwhile, spatial heterogeneity was distinct (TLI: 41.51–59.70). High values concentrated in endorheic and desert–oasis basins (e.g., Eastern Inner Mongolia Plateau, >51), whereas lower values characterized high-altitude regions (e.g., Yarkant River, <45). Overall, trends ranged from −0.49 to 0.51 yr⁻¹, increasing in 54% of lakes (15.6% significantly) and decreasing in 46% (15.4% significantly). Attribution analyses identified NDVI (33.92%) and temperature (21.67%) as dominant drivers (55.59% combined), followed by precipitation (13.99%) and human proxies (30.42% combined: population 10.66%, grazing 10.31%, built-up 9.45%). Across 53 sub-basins, NDVI was the primary driver in 28, followed by temperature (11), population (7), precipitation (3), grazing (3), and built-up land (1); notably, the top two drivers explained 56.6–87.1% of variations. TWFE estimates revealed bidirectional NDVI effects (significant in 31/53): positive associations in 22 basins were linked to nutrient retention, contrasting with negative effects in nine basins associated with agricultural return flows. Temperature effects were significant in 15 basins and predominantly negative (14/15), except for the Qiangtang Plateau. Overall, eutrophication risk across the IMXP lake region reflects the combined influences of climatic conditions, vegetation conditions, and human activities, with their relative contributions varying among basins. Full article

Microplastics (MPs) are widespread worldwide and have become a significant environmental problem due to their durability and the large quantities that enter ecosystems. As the global spread of microplastic pollution continues, the Armenian gull (Larus armenicus) in the Lake Van Basin has emerged as an important bioindicator. This study highlights the widespread impact of human-generated waste on natural habitats by detecting the presence of microplastics in gull feces using a non-invasive, polymer-supported method. Methods: The study was conducted between 10 May 2024 and 26 April 2025. A total of 480 fecal samples were analyzed from four stations with different characteristics and exposed to various anthropogenic effects. Instead of individual-level statistical inference, we performed temporal comparisons descriptively at the composite level. Results: We categorized suspected MPs by type, shape, size, and color, using FTIR to confirm the polymer identity of a representative subset (>300 µm; ~20%) and SEM–EDX to examine particle surfaces. A total of 8197 MP particles were observed in the feces collected from the stations. The most frequently observed MP type, size, shape and color were fiber (32.6%), 100–300 µm (30.8%), spherical (29.2%) and brown (18.4%), respectively. The chemical structures of all examined MPs were polyethylene (PE) (42.6%), polystyrene (PS) (28.38%) and polyethylene terephthalate (PET) (8.5%). SEM-EDX confirmed that the microplastics are polymers by showing their degraded surface and carbon/oxygen ratio. Conclusions: Identifying polymer species in ingested plastics is valuable for future studies, as the results can be used to assess the relationship between microplastics. Full article

Closed-basin lakes are highly sensitive to climatic variability, yet for the Lake Van Basin (Türkiye), the dynamic and spatially heterogeneous linkages among atmospheric drivers and lake-level changes (particularly their lag structure and predictive directionality) remain insufficiently quantified in a unified multivariate setting. This study examines how temperature and precipitation jointly influence hydrological behavior in the Lake Van Basin using a multi-station Vector Autoregression (VAR) framework. By integrating long-term observations from multiple meteorological stations, the analysis explicitly captures the spatial heterogeneity that characterizes this complex endorheic system and provides a consistent basis for comparing station-specific dynamics. The results show strong persistence in lake-level dynamics across specifications, with lagged lake-level coefficients of 0.2595 to 0.3685 (p < 0.01), indicating a buffered endorheic response. Temperature exhibits a highly consistent seasonal dependence across stations, reflected by a uniformly negative and significant four-month temperature lag in the temperature equations (−0.34 to −0.42, p < 0.01). Granger-causality tests further indicate robust bidirectional coupling between temperature and precipitation in all station specifications (p < 0.01 and typically p ≤ 0.05), while climate-to-lake-level linkages remain spatially heterogeneous but are statistically supported across both Tatvan-based and Gevas-based specifications (Tatvan-Tatvan: p < 0.01 for both climate variables; Tatvan-Ahlat: temperature p = 0.000; Gevas-Van, Gevas-Ercis, and Gevas-Muradiye: temperature p = 0.000 and precipitation p = 0.013, 0.008, and 0.015, respectively). Distinct station-level patterns further demonstrate that topographical differences modulate the strength and direction of climate–hydrology linkages across the basin. By providing a coherent, causally consistent understanding of these interactions and explicitly incorporating season-specific VAR and Granger-causality evidence, this study offers a transferable methodological framework for analyzing climate-sensitive lake systems and highlights the need to incorporate temperature-driven processes into water-management and climate-adaptation strategies in endorheic basins. Full article

Phytoplankton are key indicators of water quality and low-cost tools for freshwater monitoring, yet their diversity and ecological drivers remain poorly documented in the Tropical Andes. This study provides the first national-scale, multi-ecosystem assessment of net phytoplanktonic communities (including microalgae and cyanobacteria), across Ecuador, integrating physicochemical, multivariate, and geospatial analyses. Eighteen lakes and rivers from three biogeographic regions and a wide altitudinal gradient were surveyed, yielding 129 taxa, 77 identified at species level, the most comprehensive checklist reported to date for Ecuador. Community structure showed a clear lentic–lotic differentiation driven by hydrodynamic contrasts, while the absence of distance–decay patterns indicated high dispersal and environmental filtering pattern rather than spatial structuring. Anthropogenic pressure acted as a secondary gradient: pristine high-Andean lakes were dominated by desmids and diatoms, whereas agricultural and urban basins showed chlorophyte and potentially toxic cyanobacterial assemblages. Palmer’s Index detected organic pollution but underestimated eutrophication in endorheic, geochemically enriched lakes. Land-use effects presented strong basin-scale signals in lakes but weak correlations in rivers due to overriding hydromorphological constraints. These findings establish a robust spatial baseline for freshwater bioassessment in the Andes, demonstrating the value of phytoplankton as effective, low-cost indicators readily applicable to national water-quality assessment programs. Full article

In recent years, human activities have impacted surface water and groundwater and their interactions with natural water bodies. Lake Cuitzeo is one of Mexico’s most important water bodies but has significantly reduced its flooded area in recent years. Previous studies did not explicitly evaluate the combined effects of hydrological variables on lake dynamics, limiting the understanding of how basin-scale processes influence lake-level. The objective of this study is to evaluate the change in spatio-temporal patterns of hydrological variables under climatic and anthropogenic stress in the Lake Cuitzeo endorheic basin. The proposed methodology uses the SWAT model to analyze at the basin scale, land use and land cover changes, and trends in precipitation and their effect on hydrological processes. Consequently, groundwater flow interactions were assessed for the first time for the Cuitzeo Lake Basin using an automatically coupled SWAT-MODFLOW (v3, 2019), despite limited observational data. A statistically significant change in mean precipitation was detected beginning in 2015, with a decrease of 10.22% compared to the 1973–2014 mean. Land use and land cover changes between 1997 and 2013 resulted in a 26.20% increase in surface runoff. In contrast, estimated evapotranspiration decreased by 1.77%, potentially associated with the reduction in forest cover. As a combined effect of decreased precipitation and land use and land cover change, groundwater percolation declined by 6.34%. Overall, the combined effects of climatic variables and anthropogenic activities have altered lake–aquifer interaction. Full article

Identifying the dominant mechanisms of water and soil salinization in arid and semi-arid endorheic basins is fundamental for our understanding of basin-scale water–salt balance and supports water resources management. In many inland basins, mineral dissolution, evaporation, and transpiration govern salinization, but disentangling these processes remains difficult. Using the Barkol Basin in northwestern China as a representative endorheic system, we sampled waters and soils along a transect from the mountain front through alluvial fan springs and rivers to the terminal lake. We integrated δ¹⁸O–δ²H with hydrochemical analyses, employing deuterium excess (d-excess) to partition salinity sources and quantify contributions. The results showed that mineral dissolution predominated, contributing 65.8–81.8% of groundwater salinity in alluvial fan settings and ~99.7% in the terminal lake, whereas direct evapoconcentration was minor (springs and rivers ≤ 4%; lake ≤ 0.2%). Water chemistry types evolved from Ca-HCO₃ in mountainous runoff, to Ca·Na-HCO₃·SO₄ in groundwater and groundwater-fed rivers, and finally to Na-SO₄·Cl in the terminal lake. The soil profiles showed that groundwater flow and vadose-zone water–salt transport control spatial patterns: surface salinity rises from basin margins (<1 mg/g) to the lakeshore and is extremely high near the lake (23.85–244.77 mg/g). In spring discharge belts and downstream wetlands, the sustained evapotranspiration of groundwater-supported soil moisture drives surface salt accumulation, making lakeshores and wetlands into terminal sinks. The d-excess-based method can robustly separate the salinization processes despite its initial isotopic variability. Full article

The legacy of Soviet-era agricultural practices in Central Asia has contributed to severe environmental degradation through residual organochlorine pesticide contamination, dramatic reduction in surface water, and the near-total desiccation of the Aral Sea. Few studies have investigated hazards to human health, despite the region’s elevated burden of disease. This study aimed to characterize environmental hazards in the Republic of Karakalpakstan, one of the most environmentally and economically impacted regions. Environmental assessment included the collection of 140 soil, water, and sediment samples across 79 unique locations. Pesticide results showed organochlorine pesticides over US reference levels in 100% of water samples, with 30% also exceeding in hexavalent chromium. Water salinity is a primary concern: expressed as total dissolved solids, values ranged from 563 to 3852 mg/L. Over half of the 46 soil and sediment samples tested above reference levels for aldrin. Soil and sediment sample salt content reached up to 8.7%. Residual persistent organochlorine pesticides remain a significant health risk in Karakalpakstan, while water availability is decreasing, and water quality parameters, including salinity, dissolved oxygen, pH, dissolved metals, and nitrate levels, are degrading. Such challenges extend beyond the Aral Sea Basin: as salinization and desiccation of endorheic lakes continue on a global scale, similar situations may become commonplace. Research and interventions from this region can serve to support other similarly impacted areas. Full article

This study investigates the spatial distribution of the hydromagnesite (HM) mineral in Akgöl, a closed basin located in the arid southwestern region of Türkiye, through the integration of geochemical analyses and remote sensing techniques. A total of 70 sediment samples were analyzed using X-ray Fluorescence (XRF), X-ray Diffraction (XRD), and spectroradiometry to determine their mineralogical composition. The resulting data were integrated with ASTER satellite imagery, and mineral distribution maps were generated across 13,293 pixels using multiple linear regression and Kriging interpolation techniques within the ArcGIS environment. The findings indicate that hydromagnesite is predominantly concentrated in the central part of the lake, where it represents the dominant mineral phase in contrast to lower concentrations observed along the periphery. The endorheic nature of Akgöl is comparable to other saline lakes with similar geological and climatic settings, such as Salda and Acıgöl, supporting the applicability of this methodological approach to mineral exploration in other arid and semi-arid environments. The study contributes not only to the regional assessment of mineral potential but also to the advancement of remote sensing and GIS-based analytical methods in geoscientific research. Full article

Fluvio-lacustrine systems are highly dynamic continental environments, often developing in tectonically controlled, endorheic basins where sedimentation reflects the interplay of fluvial processes, lake-level fluctuations, climate, and subsidence. The main aim of this paper is to reconstruct the depositional architecture and paleogeographic evolution of the Ludwikowice Formation (Intra-Sudetic Basin, NE Bohemian Massif), which preserves a high-resolution record of a late Carboniferous (late Gzhelian) fluvio-lacustrine system. The formation developed as a fining-upward megacyclothem documenting the transition from proximal alluvial and fluvial fan deposits to distal, organic-rich lacustrine facies referred to as the Lower Anthracosia Shale (LAS). This study integrates lithological data from 92 archival boreholes with high-resolution sedimentological, geochemical, petrological, palynological, and magnetic susceptibility analyses from two fully cored reference sections (Ścinawka Średnia PIG-1 and Rybnica Leśna PIG-1) and selected exposures. Nine facies associations (FA1–FA9) have been identified within the formation, including fluvial, sandy to muddy floodplain, aeolian, playa lake margin/coastal mudflat, nearshore, delta plain, subaqueous delta front and subaqueous fan, prodelta, and open lake. The succession shows progressive thickening into narrow, NW–SE-trending depocenters associated with possible strike-slip faulting. Geochemical and isotopic data indicate alternating hydrologically open and closed lake conditions, while magnetic susceptibility reflects climatically driven variations in detrital influx and microbial activity. Organic petrography and palynofacies analyses reveal redox-controlled maceral associations. The Ludwikowice Formation constitutes a detailed archive of Late Paleozoic environmental change and provides new insights into sedimentation and organic matter preservation in intramontane endorheic basins. Our results highlight the response of fluvio-lacustrine systems to climatic and tectonic factors and provide a framework for interpreting analogous successions throughout the stratigraphic record. Full article

High-altitude lakes are sensitive indicators of climate change, reflecting the hydrological impacts of global warming in alpine regions. This study investigates the long-term dynamics of the water level and surface area of Lake Karakul on the eastern Pamir Plateau from 1991 to 2020 using integrated satellite altimetry data from ERS-1/2, ICESat, and CryoSat-2. A multi-source fusion approach was applied to generate a continuous time series, overcoming the temporal limitations of individual missions. The results show a significant upward trend in both water level and area, with an average lake level rise of 8 cm per year and a surface area increase of approximately 13.2 km² per decade. The two variables exhibit a strong positive correlation (r = 0.84), and the Mann–Kendall test confirms the significance of the trends at the 95% confidence level. The satellite-derived water levels show high reliability, with an RMSE of 0.15 m when compared to reference data. These changes are primarily attributed to increased glacial meltwater inflow, driven by regional warming and accelerated glacier retreat, with glacier area shrinking by over 10% from 1978 to 2001 in the eastern Pamir. This study highlights the value of integrating multi-sensor satellite data for monitoring inland waters and provides critical insights into the climatic drivers of hydrological change in high-altitude endorheic basins. Full article