Study region The Manas River Basin in northwestern China is a snowmelt-fed, seasonally frozen oasis that depends strongly on mountain snowmelt for irrigation. High evaporative demand, shallow groundwater, drainage heterogeneity, and water-saving irrigation create spatially variable salinity, sodicity, and water-status constraints, making it suitable for examining associations between antecedent cold-season hydroclimatic conditions and late-season soil water–salt management. Study focus We asked whether a management-oriented water–salt constraint index (WSCI) can integrate moisture, salinity, alkalinity, sodicity, carbonate status, and texture to identify dominant constraints; whether snow, snowmelt, and freeze–thaw covariates add predictive information beyond surface, terrain, groundwater, and climate conditions; and whether the resulting maps support irrigation–drainage zoning. We constructed weighted-average (WSCI_WA) and dominant-constraint-sensitive (WSCI_DE) formulations from 1250 topsoil samples and predicted them using multisource covariates under 10-fold spatial block cross-validation. Extreme gradient boosting (XGBoost) best predicted WSCI_DE: coefficient of determination (R²) = 0.761, root mean square error (RMSE) = 0.108, mean absolute error (MAE) = 0.086, and residual prediction deviation (RPD) = 2.05. New hydrological insights for the region Removing snow, snowmelt, and freeze–thaw predictors reduced R² to 0.707 and RPD to 1.85, indicating non-redundant statistical information for 2024 late-season topsoil WSCI prediction. Moderate, high, and very high relative constraints covered 38.7%, 19.6%, and 3.2% of cropland, respectively. Salinity was dominant, while sodicity, carbonate alkalinity, water-status imbalance, and texture created distinct management needs. The framework translates cold-season signals into relative priorities for leaching, drainage, sodicity mitigation, irrigation adjustment, and compound remediation.
Study region The Nalinxili Coalfield, situated in the ecologically fragile and water-stressed Yellow River Basin, experiences intensifying conflicts between underground coal extraction and groundwater-dependent lacustrine ecosystems, particularly Hadatu Naor Lake. Study focus This study develops and applies a dynamically coupled SWAT-MODFLOW-Mine framework to quantify the spatiotemporal evolution of mining-induced surface subsidence, hydraulic fracture zone (HFZ) permeability, and surface water-groundwater interactions, aiming to evaluate hydrological alterations, ecological thresholds, and adaptive management pathways. New hydrological insights Mining operations trigger a mechanistic hydrological reversal wherein Hadatu Naor Lake transitions from a groundwater-receiving system to a terminal discharge sink, driven by the upward propagation of the HFZ (28.71–116.35 m) that establishes a new deep seepage pathway (Q) of 5000–50,000 m³ /year. Concurrently, regional groundwater drawdown reduces lateral lake recharge by 24.6%, while subsidence (2.24–3.92 m) increases lake storage capacity by 4.5 million m³ , fundamentally altering bathymetry, thermal stratification, and littoral habitat connectivity. Despite an overall volumetric loss of < 1%, the system crosses a critical ecological threshold as the hydraulic gradient inversion disrupts natural groundwater-driven flushing mechanisms, amplifying shoreline capillary salinization and reducing drought resilience. These process-based dynamics demonstrate that hydrological pathway integrity, rather than absolute water volume, governs ecological stability in arid mining landscapes, providing a quantitative, threshold-driven basis for lake conservation and adaptive water governance.mine
Study region This study focuses on mainland China, spanning arid, semi-arid, semi-humid, and humid climatic zones. Study focus A Stacking ensemble model integrating CLDAS land data assimilation product, AMSR2 microwave soil moisture, GPM precipitation, and static environmental variables is developed to estimate pentad-scale relative soil moisture (RSM) at a 0.1° (~10 km) resolution. The model uses Cubist, Random Forest, and Bagging as base learners. The contributions of dynamic and static features are quantified via SHAP analysis. New hydrological insights for the region The estimations reveal pronounced spatial variations and systematic bias patterns across China's climatic gradients. In semi-arid regions, the model systematically underestimates moisture (BIAS = −3.35%), whereas humid regions exhibit overestimation (+1.81%). The semi-humid transitional zone shows negligible bias (−0.31%) but the highest random error (RMSE = 18.62%), driven by localized spatial heterogeneity. Furthermore, the spatial distribution of moisture is closely associated with static environmental features, particularly topography and soil texture, through their interactions. Under severe drought (RSM < 30%), the model substantially overestimates soil moisture (BIAS = +17.48%), posing a critical limitation for operational drought warning. These findings provide quantitative insights into the varying dominant controls on soil moisture across diverse climatic gradients.
Study region Dongjiang Delta, China, where rapid urbanization since the 1980s has significantly altered deltaic channel networks and hydrological connectivity. Study focus The topology of channel networks controls drainage efficiency and hydrological connectivity in river deltas. However, existing studies have predominantly focused on main distributaries and overlooked the widespread small channels. As such, we quantitatively examined how urbanization has altered the channel network and hydrological connectivity of the Dongjiang Delta, using a super-resolution technique to reconstruct high-resolution historical channel networks. New hydrological insights for the region Our results reveal a hidden pathway of hydrological degradation, i.e., the selective loss of small channels can substantially reduce the complexity and connectivity of the channel network even when main distributaries remain. Specifically, the loss of small channels caused decreases in the geometric and structural fractal dimensions of the channel network, indicating reduced space-filling capacity and weakened topological connectivity. Furthermore, we found a significant increase in the mean connectivity distance, signifying a reduction in river–floodplain connectivity of the Dongjiang Delta. Spatial analysis confirmed a positive relationship between urban expansion and the loss of river–floodplain connectivity, driven by both local direct effects and regional spillover effects. Our findings show that small channels are more susceptible to urbanization while playing crucial hydrological roles. Therefore, protecting and restoring small channels should be integrated into regional monitoring and coastal flood management.
Study region River warming threatens aquatic ecosystems in temperate Europe. The Tisza is a large regulated lowland river influenced by barrages and a reservoir. The study covered its 571 km Hungarian reach at 11 monitoring stations. Study focus This study assessed changes in water temperature, their seasonal and spatial differences, and projection uncertainty where future discharge and operating conditions are unknown. An equilibrium-temperature model was calibrated using daily observations from 2001 to 2023 and independently validated for 2024–2025. Fourteen climate-model chains were run separately under RCP4.5 and RCP8.5 for 2030–2050, 2051–2080 and 2081–2100. Historical relationships with air temperature and discharge were examined. New hydrological insights for the region The equilibrium temperature concept showed robustness for climate change assessment providing R² = 0.951 and RMSE = 1.821 °C for the validation. By 2081–2100, annual mean water temperature was projected to increase by 1.0–1.3 °C under RCP4.5 and 2.0–3.0 °C under RCP8.5 relative to 2030–2050. Under RCP8.5, station-specific median frequencies of days above 25 °C increased from 28.9 to 56.8–71.0–86.9 days year⁻¹ between these periods. Warming varied across seasons and river sections, while differences among climate-model chains were substantial. The study provides an assessment of future warming and prolonged warm-water conditions to support river management and ecosystem protection. These projections describe the response to atmospheric warming under the calibrated conditions; future changes in discharge and barrage operation remain unquantified.
