Search Results (5,475)

The Cretaceous-to-Eocene Julian (JB) and Brkini (BK) flysch basins have recently been studied for their heavy mineral assemblages; however, the rutile component has so far been neglected. To fill this gap, this study explores their detrital rutile trace element contents and U-Pb ages to define their possible provenance(s). In JB, there are very few rutile grains, mainly related to amphibolite–eclogite facies metamorphic units, with about 80% metapelitic grains. Among the few rutile grains from JB, only eight gave robust U-Pb ages. These ages are all Palaeozoic, resembling those of the closure/opening of the Rheic Ocean and the Variscan orogeny. In BK, the number of rutile grains is much higher than in JB, testifying to differences in the supply areas. The rutile grains are mainly in the amphibolite–eclogite facies, but they decrease, moving upward, accompanied by an increase in UHT. The metapelitic rutile component is higher than 74%. When considering the BK rutile grains, there are no Palaeozoic ages at the bottom of the sequence, while they are newly visible upward. In BK, the most abundant rutile grains show Mesozoic ages that can be considered as representatives of the opening/closure of the Vardar Ocean and the ophiolite emplacement in the Dinarides area. Full article

Wave energy in short-fetch, semi-enclosedfigur seas depends on how closely the response of a converter matches locally generated, short-period waves. This study makes that match explicit for the Black Sea, the Sea of Marmara, the Aegean, and the Eastern Mediterranean, the four seas around Türkiye, as four distinct regions within a single study area. Twenty years (May 2006 to March 2026) of three-hourly significant wave height and energy period from the Copernicus Marine global wave reanalysis (0.2°) were combined with GEBCO 2026 bathymetry to map the wave power flux, to screen cells inside a first-order 25–100 m deployment-depth band, and to rank three candidate sites in each region. Specific power matrices were applied to three full-scale reference converters (Pelamis P-750, AquaBuOY and Wave Dragon) and to two shallow-water archetypes, the Oyster surge flap and the Wavestar multi-float machine, standing for contemporary shallow-water design classes, at full scale and under Froude similitude. The best deployable sites of the Black Sea and the Aegean carry mean fluxes of 3.1–3.6 kW m⁻¹, and the Marmara sites define the low-resource end member at 0.2–0.8 kW m⁻¹; mean energy periods at the twelve sites range from 2.7 to 5.4 s. At their original scale the three reference converters reach capacity factors of up to 3.4%, because their specific power matrix response bands fall largely outside the regional sea-state distribution. Scaling changes that. Froude scaling to 0.20–0.25 of the original linear dimensions moves the response into the dominant 4–5 s band and raises the capacity factor to 30–47% at the seven sites where the mean flux exceeds 2.5 kW m⁻¹, at scaled rated powers of about 2–25 kW; the two archetypes reach 7–19% at full scale and 49–59% once scaled at the same sites. Both the preferred scale and the achievable capacity factor are near-uniform along the Black Sea rim, the Aegean archipelago, and the Levantine shore, so the analysis yields a single regional design specification, as follows: a small, short-period converter deployed in modular arrays. Full article

Although drought is recognized as one of the major hydroclimatic hazards affecting the Mediterranean Basin, local-scale assessments to support planning for its agricultural, hydrological, and food security impacts remain limited. This study investigates historical and future drought dynamics in Manisa (Western Türkiye) using a multi-scale framework integrating the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) with CMIP6 climate projections. A comprehensive dataset including ERA5-Land, CHIRPS, TerraClimate, and station observations was evaluated, revealing strong agreement in temperature but higher uncertainty in precipitation. SPI results indicate recurrent short-term droughts with extreme events reaching −2.5 in 2007–2008, alongside intensified long-term hydrological droughts since the early 1990s, while SPEI reveals a stronger temperature-driven drought signal, peaking near −2.0 during 2020–2024 as the most severe cumulative drought period in the past 40 years. Rapid wet–dry transitions have increased since 2000, indicating a more unstable hydroclimatic regime. Future projections (2025–2100) under a high-emission scenario suggest a progressive intensification of thermally driven drought conditions, with SPEI trends declining more steeply than SPI, indicating that evapotranspiration-driven water deficits may increasingly outweigh precipitation deficits as a driver of future drought risk. These findings offer localized, data-driven evidence relevant to climate adaptation and water resource planning in semi-arid Mediterranean agricultural regions. Full article

While low-impact development and retention strategies are widely studied in urban and agricultural contexts, a distinct knowledge gap remains regarding the quantitative evaluation of dispersed, natural microretention structures in small, ungauged, mountainous forested catchments under complex topographic conditions. To address this limitation, this study provides a novel quantitative assessment of how natural bioretention interventions—specifically arcuate deadwood log barriers, cascading reservoir systems, and strategic afforestation—influence runoff reduction and substrate infiltration dynamics. Focusing on the 4.57 km² basin of the Stankowice Stream in southwestern Poland, the research integrates field geodetic and hydrological measurements with Iszkowski’s empirical flow formulas and high-resolution digital elevation modeling (SCALGO platform). Delineation of 10 key subcatchments revealed that surface runoff potential is heavily concentrated within specific flow pathways rather than determined solely by subbasin area. In unit No. 9, deploying an arcuate arrangement of 19 deadwood logs achieved an 11% reduction in surface runoff (retaining 8662.50 m³), whereas coupling these log structures with a downstream cascading two-dam system significantly enhanced retention performance by establishing 79,065.68 m³ of depression storage and driving 264,066.16 m³ of subsurface infiltration. Furthermore, multi-scenario land use modeling demonstrated that transforming land cover to forest reduced surface runoff by over 70% in topographically steep subcatchments (e.g., unit No. 7). These findings demonstrate that effective flood mitigation in headwater catchments requires a systemic, targeted hybrid strategy combining decentralized bioretention with localized storage nodes, offering a transferable framework for sustainable regional water governance. Full article

Aerosols exert significant impacts on Earth’s radiation balance through direct and indirect effects, with the latter representing the largest uncertainty in current climate models. To clarify aerosol–cloud interactions over China, this study synergized MODIS satellite retrievals (2015–2020) with in-situ MA60 aircraft observations across six representative regions. Satellite data provided aerosol optical depth (AOD), cloud optical depth (COD), cloud effective radius (CER), and cloud phase, while aircraft measurements delivered vertical profiles and microphysical properties of aerosols and cloud droplets. Results show that AOD exhibits a “high east, low west” pattern, with hotspots in the North China Plain and Sichuan Basin, and a significant decreasing trend over polluted regions. Cloud phase is spatially heterogeneous, with water clouds dominating the southeast and ice clouds prevailing in the northwest (>85% over the Tibetan Plateau). Water cloud COD shows a southeast-high–northwest-low distribution, with a clear inverse CER-COD correlation. Aircraft data reveal that polluted northern sites have high near-surface aerosol concentrations with small effective diameters (~0.3 μm), while cloud droplet number concentration and size spectra vary markedly across regions. These findings provide a robust observational foundation for improving aerosol–cloud interaction parameterizations in climate models. Full article

Water security is a significant challenge for the Saudi Arabia Kingdom’s development and stability, affecting other economic sectors beyond the water sector. Insufficient water resources are causing economic and social crises; addressing this issue is crucial for the country’s growth and stability. This study aims to manage water resources in central Saudi Arabia (Wadi AS SAHBAA) through a two-level approach. The first level involves extracting rainfall amounts from satellite imagery to predict future rainfall intensity using PERSIANN-CCS-CDR data. The second level focuses on monitoring groundwater recharge using geographic information systems (GIS) and remote sensing techniques. The study further seeks to understand rainstorm behavior influenced by climate variability and applies geomatics techniques for quantitative analysis. The results show that the Wadi AS SAHBAA basin receives an annual precipitation of 116.6 mm/year and mean annual precipitation of 9.7 mm. The year 2019 experienced the highest recorded precipitation, reaching 222.3 mm and mean annual precipitation of 18.5 mm. Between 2013 and 2019, the AS SAHBAA region experienced increased rainfall driven by intense storm events; however, it declined during the period 2020–2022. Moreover, 2021 recorded the lowest annual precipitation of 53.8 mm with mean annual precipitation of (4.5 mm), possibly linked to reduced storm activity due to the COVID-19 pandemic. The study uses several methods to estimate groundwater recharge from rainfall and concludes that the average infiltration during 2013–2022 was varying from 1.59–36.63 mm, representing about between 1.03 and 28.5% of total rainfall. This is reflected in groundwater storage capacity, which ranges from approximately 1.65 to 38.27 million m³ yearly. This study provides a framework for monitoring precipitation and groundwater recharge and offers practical recommendations for regional development and sustainable water management. Full article

Siltation in semi-enclosed basins is commonly ascribed to the combined action of horizontal entrainment, tidal filling/emptying, and density flow, yet the interplay among these processes complicates a mechanistic understanding of siltation in artificially modified macrotidal bays. In this study, Dyer’s decomposition method for suspended sediment flux (SSF) and end-member analysis (EMA) were applied, combined with in situ hydrodynamic, suspended sediment concentration (SSC), and surface sediment grain-size measurements. Using Wuyuan Bay (Xiamen, China) as a case study, we examined its sediment dynamics and siltation patterns from a tidal-cycle perspective. Results show that the contribution of density flow is negligible. A recirculating gyre, formed during flood and suppressed during ebb, creates flood–ebb velocity asymmetry and net landward sediment transport, producing a central siltation body (CSB) that accounts for 45% of the total deposition. Near the entrance, Eulerian residual transport (gyre advection) dominates, with a notable contribution from tidal pumping. Further landward, tidal pumping weakens and gyre-induced Eulerian transport prevails. Grain-size analysis and EMA decomposition reveal uniform sedimentary dynamic conditions in this zone, with flood-phase deposition averaging 83% of the total siltation. Full article

The development of arid-oasis agriculture and territorial spatial restructuring strongly influence regional eco-environmental quality. Clarifying production–living–ecological space (PLES) transitions and the nonlinear mechanisms driving eco-environmental quality is important for sustainable agricultural land use and ecological governance. Northern Xinjiang combines economic agglomeration with ecological sensitivity, making it a representative region for examining changes in eco-environmental quality and their underlying drivers. Land-use data for 1990, 2000, 2010, and 2020 were analyzed using land-use transition matrices, the eco-environmental quality index (EEQI), spatial autocorrelation, and hotspot analysis to characterize spatiotemporal changes under PLES transitions. XGBoost–SHAP was applied to identify the dominant factors, nonlinear responses, and interactions. The results showed that: (1) ecological space remained dominant from 1990 to 2020, but its share declined from 91.72% to 87.36%. Production and living spaces increased from 7.78% and 0.50% to 11.72% and 0.92%, respectively. Agricultural production space expanded most markedly, and spatial restructuring was most intense during 2000–2010. (2) EEQI decreased from 0.3100 to 0.2922 and showed an overall fluctuating decline. Significant spatial clustering was observed, with Moran’s I values consistently above 0.81 (p < 0.001). High-value areas were mainly distributed in the Ili River Valley and along the northern slope of the Tianshan Mountains, whereas low-value areas were concentrated in the Junggar Basin interior and the arid areas along its eastern margin. (3) During 2000–2020, LAI and NPP in agricultural production space increased by 45.7% and 48.2%, respectively. These increases indicated overall improvements in canopy condition and productivity. After 2010, NPP growth slowed markedly while LAI remained relatively stable, indicating a stage-specific divergence. (4) XGBoost–SHAP showed good robustness and spatial generalizability, with R² values of 0.868–0.918 and RMSE values of 0.059–0.075. NDVI remained the primary driver, while Elev contributed consistently. The dominant interaction shifted from NDVI ∩ PopDen in 1990 and 2000 to NDVI ∩ Elev in 2010 and NDVI ∩ GDP in 2020. This shift indicated fundamental natural constraints and stronger joint effects of population and economic activities during the later stages. These findings provide a scientific basis for optimizing PLES, regulating arid-oasis agriculture, and safeguarding regional ecological security. Full article

In the context of increased international efforts to reduce greenhouse gas emissions through various measures included in climate agreements, regulatory frameworks, and decarbonization strategies, the utilisation of renewable energy resources represents a solution to sustainable global development. Wave energy is a marine renewable resource that has great potential but has not yet been fully exploited. Considering this, the current work examines the Black Sea’s wave climate variability and wave energy dynamics using SWAN model results applied throughout the basin. Attention is given to the long-term assessment of wave conditions and wave power, the characterization of dominant wave patterns, and the identification of possible changes in sea state parameters over an extended period (30 years). Recent wave climate variability and projections of future changes under the RCP4.5 and RCP8.5 climatic scenarios are evaluated. The assessment of the potential effects of climate change on sea state conditions and the spatial distribution of wave energy resources in the Black Sea basin is performed by comparing the historical and future projections, thereby also facilitating the observation of climate change pattern evolution. The results offer a forward-looking assessment of wave energy potential in the Black Sea and its reliability as a sustainable energy resource in relation to climate change. Full article

This study employs panel data from 11 provinces and municipalities along the Yangtze River Economic Belt spanning 2010–2021. It measures green transport efficiency (GTE) using principal component analysis (PCA) and the undesirable Super-SBM model while constructing an economic high-quality development index (HQEDI) through an entropy-weighted CRITIC approach. The study combines coupling coordination degree modeling with spatial autocorrelation analysis (Global Moran’s I, LISA, hotspot/coldspot detection) to empirically investigate their synergistic evolution mechanism. The findings indicate the following: (1) Multidimensional policy combinations exhibit a nonlinear threshold effect on enhancing green transport efficiency, with efficiency significantly rebounding post-2015 as low-carbon policies deepened. (2) High-quality economic development displays a dual-stage ‘convergence-divergence’ pattern, where downstream regions lead in HQEDI but mid- and upstream regions show faster growth in coordination and green dimensions. (3) The coupling coordination degree exhibits pronounced spatial spillover effects, with the global Moran’s I mean reaching 0.485. High-value clusters form in downstream regions, while upstream areas predominantly exhibit low-value clusters, revealing an ‘east-high, west-low’ regional differentiation pattern. (4) The gradient divergence mechanism stems from heterogeneity in infrastructure density, industrial structure, and policy responsiveness elasticity. Accordingly, it is recommended to establish a multi-level governance mechanism to dismantle administrative barriers and to construct a tripartite policy package integrating ‘digital transport, ecological compensation, and industrial radiation’ to advance coordinated basin development. Full article

The development characteristics of primary fractures in coal serve as a prerequisite, influencing reservoir stimulation outcomes. The propagation of experimentally induced tensile cracks in the reservoir is closely related to the coal’s tensile fracture properties and the distribution of natural fractures. The effectiveness of reservoir stimulation directly determines the productivity of coalbed methane (CBM) wells, with clear variations in natural fracture development observed across different macroscopic coal components. Therefore, accurately evaluating the tensile fracture characteristics of different macroscopic coal components and the interaction patterns between experimentally induced and natural fractures is of great importance for deep CBM resources. This study focuses on vitrain, clarain, and durain from the deep #8 coal seam in the Daning-Jixian Block, located in the southern part of the Jinxi Flexural Fold Belt on the eastern margin of the Ordos Basin, which exhibit varying degrees of natural fracture development. Using the Brazilian splitting test and the centrally grooved three-point bending test, the tensile strength and Mode I fracture toughness of different macroscopic coal components were investigated. The study reveals the propagation behavior of pure tensile cracks and the resulting fracture network morphology in coal specimens with developed natural fractures. The presence of natural fractures reduces the tensile strength and fracture toughness of coal while increasing its brittleness. Compared to durain specimens (with average tensile strength of 2.09 MPa and fracture toughness of 0.338 MPa·m⁰·⁵), vitrain (avg. 0.92 MPa, 0.234 MPa·m⁰·⁵) and clarain (avg. 1.40 MPa, 0.185 MPa·m⁰·⁵) exhibit clearly lower tensile strength and fracture toughness, along with more pronounced brittle characteristics. Differences in geomechanical parameters among macroscopic coal components lead to distinct fracture behaviors: high-strength, high-fracture-toughness durain specimens require higher pressure to initiate fractures, which then propagate in a relatively regular manner; in contrast, low-strength, low-fracture-toughness vitrain and clarain fracture more easily, but their fracture paths are clearly influenced by natural fractures, promoting the formation of complex fracture networks. This study quantitatively characterizes the deflection and arrest behavior of experimentally induced tensile cracks interacting with dense natural fractures, providing a mechanistic basis for understanding fracture network complexity in deep coal. Full article

Against the backdrop of climate change and compounded by human activities, increasing water scarcity has triggered a series of drought disasters, which have already severely impacted both ecological environments and socioeconomic production. The SWAT model, recognized for its strong portability and superior spatial heterogeneity, has gained widespread acceptance in fields such as hydrology and environmental science, and is extensively applied in hydrological simulation studies across large-scale river basins. Hydrological models of the study area can be constructed in the SWAT model to simulate changes in hydrological variables by conducting spatial discretization, parameter specification, and boundary condition definition. Standardized drought index can effectively reflect the spatiotemporal variations in drought disasters, holding significant importance for clarifying and predicting drought characteristics. This study took the Luanhe River Basin as the research area, constructed a watershed hydrological model based on SWAT, and projected changes in the basin’s hydrological processes for the period 2030–2060. Based on the model’s projected data, we calculated drought indices and extracted drought events for the basin. The results indicate the following: (1) During the simulation period, only 30% of the years in the Luanhe River basin had annual runoff above the long-term average, with a range of 228.18 mm. The range of mean annual runoff across sub-basins was 173.32 mm. Drought and uneven water resource allocation over both spatial and temporal scales coexisted, and this issue is expected to intensify under future climate warming and drying. (2) The mid-reaches of the Luanhe River are more prone to drought compared to the upper reaches for its higher water demand. However, due to a stronger capacity for ecological restoration, droughts there are mostly of low intensity in the mid-reaches. In contrast, the upper reaches experience more periods classified as severe or extreme drought, and the drought events encountered are generally more intense than those in the mid-reaches. (3) The method proposed in this study can screen extreme drought events based on outliers in the characteristic values of drought events. Taking the simulation from this study as an illustration, anomalies in drought event characteristic values suggest a potential basin-scale, prolonged extreme drought event in the Luanhe River Basin from June 2038 to July 2042. Proactive drought prevention policies should be formulated for this period. The findings of this study provide guiding significance and practical value for drought assessment, risk management, and policy application in the Luanhe River Basin. This study methodologically combines hydrological model predictions with drought event responses, providing a novel method for predicting basin-scale drought conditions and issuing early warnings for extreme drought events. Full article

This study investigates the impacts of human activities and climate variability on hydrologic alterations in the Mobile River and Perdido River Basins of Alabama. The research uses a machine learning approach, specifically cubist models, to quantify and predict changes in flow duration curves (FDCs) under both historical (1980–2009) and future climate scenarios. Future climate projections include the Representative Concentration Pathways (RCP 4.5 and RCP 8.5) and the Shared Socioeconomic Pathways (SSP2 4.5 and SSP5 8.5), evaluated for two future periods: 1980–2069 and 1980–2099. The models incorporate a wide range of covariates, including basin geomorphology, aquifer characteristics, land cover, water storage, environmental factors, solar radiation, census data, and water use data. Under the baseline period (1980–2009), most level 12 hydrologic unit codes (HUC12s) in both basins showed alterations, with substantial differences observed between pre- and post-alteration FDCs. The model performance varied, with a Nash–Sutcliffe Efficiency between 0.91 and 0.95 for testing and between 0.98 and 0.99 for training during the baseline period. Future projections under the RCP 4.5 and RCP 8.5 scenarios generally differed significantly from baseline conditions across all flow regimes (p < 0.05). In contrast, SSP2 4.5 showed comparatively limited statistical significance, while SSP5 8.5 exhibited significant departures from baseline conditions across all flow regimes, reflecting the greater influence of high-emissions climate forcing on projected hydrologic alterations. Overall, the RCP scenarios projected more widespread statistically significant changes than the corresponding SSP scenarios at the same forcing level, particularly when comparing RCP4.5 with SSP2-4.5, while both RCP8.5 and SSP5-8.5 consistently indicated greater hydrologic alterations than their moderate-emissions counterparts. These findings highlight the importance of considering different flow regimes when assessing the impacts of climate variability on streamflow. This study contributes to the understanding of hydrologic alterations in the Mobile River and Perdido River Basins, providing insights for water resource management and ecological conservation efforts in the region. Full article

Rainfall–runoff modeling is a key challenge in hydrological research. Despite the extensive application of long short-term memory (LSTM) networks in rainfall–runoff modeling, our understanding of the influence of different hyperparameter configurations on various hydrograph components, as well as the linkages between hydrological concepts and LSTM architectures, remains elusive. Here, we integrated Multi-Objective Particle Swarm Optimization (MOPSO) with LSTM hyperparameter optimization by targeting the root mean square error of the overall hydrograph (RMSE_all), high-flow (RMSE_high) and low-flow (RMSE_low) dynamics, and water volume deviation (Dv). The MOPSO-LSTM framework was applied to the upstream catchments of the Miyun Reservoir in Beijing, China. At a lead time of 1d, the optimal solution achieved an NSE of 0.920 in the Chaohe River Basin, with a minimum RMSE_all of 0.848 m³/s, RMSE_high of 2.081 m³/s, RMSE_low of 0.382 m³/s, and Dv of 0.002%. However, as the lead time increased to 3 and 7 days, the maximum NSE declined to 0.747 and 0.560, respectively, with process-related metrics deteriorating more substantially than water balance-related metrics. The Baihe River Basin performed better, with maximum NSE and KGE values of 0.949 and 0.970 at a lead time of 1d. Clear trade-offs among different evaluation objectives were further identified, particularly the competitive relationship between RMSE_high and RMSE_low, as well as the coupling between RMSE_low and Dv. SHAP (Shapley additive explanation) and partial dependence plots (PDPs) were used to quantify and interpret the effects of hyperparameters on model performance, and the results showed that learning rate, number of units, and lookback window served as the most influential hyperparameters. Moreover, optimization preferences resulted in distinct hyperparameter configurations, where Dv-oriented solutions favored smaller learning rates, longer lookback windows, and larger batch sizes than RMSE-oriented solutions. Compared with the Chaohe River Basin, the larger Baihe River Basin favored LSTM configurations with longer lookback windows, more hidden units, higher learning rates, and lower dropout rates, which was associated with the hydrological memory of the catchment. Overall, this study provides a novel multi-objective LSTM optimization framework, improving the understanding of LSTM hyperparameters and offering practical guidance for hydrological prediction and water resource management. Full article

The Pangjiahe Au deposit is the largest gold deposit in the Fengxian district of the West Qinling Orogen (WQO), Central China. However, the timing of gold mineralisation and its relationship to the regional metallogenic evolution of the WQO remain poorly constrained. In this study, detailed geological investigations, TIMA mineralogical analysis, in situ Rb–Sr dating of hydrothermal sericite, and in situ Fe–S isotope analyses of auriferous pyrite were conducted to constrain the timing of mineralisation, the evolution of ore-forming components, and the regional metallogenic significance of the Pangjiahe Au deposit. Hydrothermal sericite intimately associated with gold mineralisation yields an in situ Rb–Sr isochron age of 207.6 ± 3.1 Ma, providing the first direct age constraint on gold mineralisation at Pangjiahe. This age is consistent with those reported for the nearby Huayagou Au deposit and several other major gold deposits in the West Qinling Orogen, supporting a regionally extensive Late Triassic gold mineralisation event. The Pangjiahe Au deposit shares closer geological, geochronological, and isotopic affinities with the Huayagou Au deposit and the major Au deposits of the Middle Qinling in Gansu than with the traditionally correlated Au deposits of the North Qinling. These results provide new constraints on the regional metallogenic relationship between the Fengtai Basin and the Middle Qinling metallogenic system, contributing to a better understanding of Late Triassic gold mineralisation in the West Qinling Orogen. Full article