This study investigates the air–water interaction dynamics in jet streams, with particular emphasis on the transition from the cavity to the far-field regions. A dual-tip conductivity phase-detection probe was employed to analyze four distinct downstream water levels. Based on the development of the cross-sectional mean air concentration, the jet flow was divided into four distinct regions: the jet length region, impact region, splash region, and far-field region. The results demonstrate varying trends in the evolution of the mean air concentration and maximum bubble frequency. Downstream water levels exerted a significant influence on these parameters in the splash and far-field regions, whereas minimal variation was observed in the impact region. Additionally, notable differences were identified in the probability density function of water droplets between the cavity and downstream regions. Furthermore, downstream water depth was found to have a negligible effect on the proportion of small-sized droplets in both the impact and splash regions.

Characterized by special morphologic, geographic, hydrologic, and societal behaviors, the water resources management of the Mediterranean catchment often shows a higher level of complexity including security issues of water supply, inundation risks, and environment management under the perspective of climate change. To have a comprehensive understanding of the Mediterranean water-cycle system, a deterministic distributed hydrologic modeling approach has been developed and presented in this study based on an application in the Var catchment (2800 km²) located at the French Mediterranean region. A 1D and 2D coupled model of MIKE SHE and MIKE 11 has been set up under a series of hypotheses to represent the whole hydrologic and hydrodynamic processes including rainfall-runoff, snow-melting, channel flow, overland flow, and the water exchange between land surface and unsaturated/saturated zones. The developed model was first calibrated with 4 years daily records from 2008 to 2011, then to be validated and further run within hourly time interval to produce detailed representation of the catchment water-cycle from 2012 to 2014. The deterministic distributed modeling approach presented in this study is able to represent its complicated water-cycle and used for supporting the decision-making process of the water resources management of the catchment.

The impact of climate change on vegetation ecosystems is a prominent focus in global climate change research. The climate change affects vegetation growth and ecosystem stability in the upper reaches of the Yellow River (UYR). However, the spatiotemporal patterns and driving mechanisms of vegetation growth status (VGS) in the region remain poorly understood. Based on the hydrological model PLS, an innovative WEP-CHC model was developed by integrating regional environmental and vegetation growth characteristics. Furthermore, combined with the PLS-SEM model and other methods, this study systematically investigated the spatiotemporal patterns and driving mechanisms of VGS in the UYR. The results indicated that: ① VGS exhibited significant spatiotemporal variation trends within the study area. In the study period of 1970–2020, the GPP onset time was significantly advanced (p < 0.05) while the GPP peak value was significantly increased. Spatial analysis revealed significant spatial complexity in the GPP onset time and peak values across the region. ② Soil freeze-thaw conditions significantly influenced VGS (p < 0.05). The complete thawing time of permafrost was closely coincided with the GPP onset time, with a correlation coefficient exceeding 0.84. After controlling soil freeze-thaw effects using partial correlation analysis, it was found that better initial soil hydrothermal conditions would lead to better VGS; ③ The model constructed with annual hydrothermal conditions (AHC), soil freeze-thaw period (SFTP), vegetation growth season (VGS), initial soil hydrothermal conditions (ISHC), and annual solar radiation conditions (ASRC), demonstrated good explanatory power for vegetation growth. The R² values of PLS-SEM were above 0.76 in all five subregions. However, their effects on VGS varied significantly across subregions. Overall, AHC and SFTP were the dominant factors in all subregions. Furthermore, the impacts of ISHC and VGC were statistically insignificant, whereas the effects of ASRC exhibited high complexity. This study not only provides new insights into the current state of hydrological-ecological coupling in the UYR but also offers a new tool for ecological conservation and sustainable water management in other cold regions and similar watersheds worldwide.

Aiming to control lake eutrophication, proposed methods for convenient and faithworthy lake water quality evaluation are warranted. Optical measurement of dissolved organic matter (DOM) demonstrates great potential for estimating organic matter (OM) composition, and can thus serve as a proxy for conventional chemical oxygen demand (COD_Mn) measurements, which are considered as imprecise and environmentally unfriendly. Hence, we conducted a field campaign across 30 lakes in Wuhan's metropolitan area, collecting 255 samples from varying trophic states to evaluate the predictive capability of COD_Mn using DOM optical measurements combined with parallel factor (PARAFAC) analysis. The DOM optical properties and chemical composition exhibited considerable variability across varying trophic state levels (TSLs). Fluorescence components C1-C3 and C5, fluorescence index (FI), and absorption at 254 nm (α₂₅₄), increased as TSL increased, while the DOM spectral slope (S_R) decreased. COD_Mn was positively and significantly correlated with fluorescence components C1–C3 and C5, freshness index (β/α), autochthonous index (BIX), humification index (HIX), α₂₅₄, the ratio of α₂₅₀ to α₃₆₅ (E2/E3) while being negatively correlated with S_R. Parameters α₂₅₄, C1, C3, C4, FI, β/α, and HIX were identified as key predictors of COD_Mn. The multiple linear regression model successfully predicted COD_Mn (r² = 0.63, p < 0.01, n = 1113) and demonstrated superior performance in mesotrophic lakes. These findings highlight the potential for establishing high-frequency, continuous, and multi-regional COD monitoring programs.

Fish swimming hydrodynamics serves as a critical foundation for aquatic ecological conservation, with recent research extending from 2D to 3D perspectives. This study employs 3D high-fidelity modeling with dynamic mesh technology to investigate how cylindrical obstacles at varying positions affect Carassius auratus locomotion. Analysis of nine configurations reveals bidirectional flow interactions between fish and cylinders, with cylinder wake influence persisting at 1–2 times the total length intervals but diminishing at 3times. Compared with swimming in uniform flow, the mechanical benefit of C. auratus located 2 times the total length directly behind the cylinder is the largest, and its value reaches 4.19 times. Wavelet analysis of 30-cycle mechanical data demonstrates closer intervals enhance benefit magnitude, whereas greater distances accelerate benefit realization. These 3D computational findings corroborate 2D studies while providing new spatial interaction insights, offering theoretical foundations for fish conservation strategies related to hydraulic structures.

Discharge from sewage treatment plants can deteriorate river water quality due to improper management or insufficient levels of treatment. To address these challenges, constructed wetland systems (CWSs) have been widely used as a sustainable and effective solution for wastewater management. This study provides an overview of the conceptual design for a CWS to treat the discharge from the Papan Regional Sewage Treatment Plant (RSTP). The design influent for the CWS was determined, and the proposed sizing was based on simulation results to achieve the targeted concentrations consistent with Water Quality Index (WQI) Class II. The MUSIC-X software was used in this study to simulate pollutant removal performance, hydraulic behavior, and effluent quality under various flow conditions. The model was set up using site-specific inflow parameters, targeted effluent concentrations, and wetland configuration inputs, including surface area, depth, vegetation zones, and retention times. This study introduces an innovative approach by adopting the paddy field concept as the geometrical design of a multi-cell CWS, covering a total surface area of 1,250,000 m² and divided into two sections (Wetland 1 and Wetland 2), with different planting plots separated by a gabion wall. The innovation lies in reimagining abandoned mining ponds as functional wetland zones, while using a paddy field-inspired grid layout to enhance hydraulic control, pollutant removal, and land efficiency. This approach transforms degraded land into an eco-engineered, cost-effective, and scalable wastewater treatment system—a novel model for tropical developing regions.

Lakes are critical sinks for terrigenous microplastics (MPs), yet understanding their ecological risks remains hindered by data uncertainties and the absence of local background values. In this study, an enhanced pollution load index (PLI) model integrating stochastic mathematical methods and species sensitivity distributions (SSD) was developed. The model was applied to assess and predict the ecological risk posed by MPs in the surface water and sediments of Dongting Lake, the second-largest freshwater lake in China. Results revealed average MP abundances of 4889 (range: 1667–9667) items/m³ in surface water and 7058 (range: 3935–10,736) items/kg in sediments within the Dongting Lake District. Small microplastics accounted for 90% of total MP particles, predominantly as polyethylene fragments. SSD-derived predicted no-effect concentrations values were determined as 8620 items/m³ for water and 7022 items/kg for sediments. While surface water exhibited low MP pollution risk and sediments were classified as unpolluted, both compartments showed signs of potential pollution escalation, suggesting non-negligible ecological risks. Through conditional fragmentation modeling, primary MP sources were identified as Yangtze River upstream inputs, atmospheric deposition, and soil erosion. In conclusion, the enhanced PLI model demonstrates effective ecological risk assessment and forecasting capabilities across environmental media, providing strategic insights for lake MP pollution mitigation.

Anthropogenically induced land use/land cover (LULC) transformations and accelerating climatic variabilities have emerged as pivotal forces reshaping the hydrological equilibrium of fluvial systems, particularly in ecologically sensitive basins. This study systematically interrogates the compounded ramifications of LULC dynamics and projected climate change on the hydrological response of the Upper Jemma Watershed an integral sub-catchment of the Upper Blue Nile River system. Employing the advanced QSWAT+ hydrological modeling framework within a GIS interface, the analysis integrates bias-corrected climatic projections under RCP 4.5 and RCP 8.5 scenarios alongside multi-temporal remote sensing-derived land cover datasets. The findings unveil an unequivocal intensification of surface runoff and streamflow due to expansive agricultural encroachment, juxtaposed with a discernible decline in evapotranspiration and soil water retention. Climatic perturbations, notably temperature elevation and precipitation attenuation, further exacerbate these trends, with pronounced seasonality in hydrological fluxes. Importantly, synergistic interactions between land cover transformation and climatic anomalies manifest in nonlinear hydrological alterations, amplifying peak flows and diminishing baseflows. This underscores the riverine system's heightened vulnerability and the necessity for integrated watershed management strategies that account for multifactorial hydrological stressors. The study provides a robust empirical and modeling basis to inform adaptive water governance within transboundary river basins susceptible to environmental transitions.

The operation of cascade reservoirs in a watershed profoundly exerts river water-sediment dynamics and topography evolution, and the terminal reservoir is the focus area for river and waterway management. This paper reveals the process and underlying factors of topography evolution and water level adjustment in the lower Hanjiang River under the action of cascade reservoirs. This study focused on the 263 km river channel downstream of the Xinglong Hydropower Conservancy Project on the Hanjiang River. Using measured flow, sediment, and topography data from 1977 to 2023, we analyzed the changing characteristics of riverbed scouring and deposition intensity, thalweg, and cross-sections. Additionally, we evaluated the response relationship between riverbed scouring and deposition intensity and factors such as sediment transport, runoff, and human activities. From 1977 to 2023, the low-water channel in the Xinglong–Estuary reaches showed a scouring and cutting tendency, and the riverbed slop initially decreased and then increased. The main cause of the riverbed scouring along the Xinglong–Estuary reaches was the reduced sediment load in the watershed, with waterway engineering having a slightly larger influence than runoff in the Xinglong–Xiantao reaches; by contrast, runoff exerted a more significant effect than both waterway engineering and the Yangtze River water level decline in the Xiantao–Estuary reaches. During the autumn flood season from 1983 to 2023, the water level differences between the Hanjiang and Yangtze Rivers at the same flow rate showed an increasing trend, leading to an increase in water surface slope, which intensified scouring forces and riverbed scouring. This study improves our understanding of the impacts of dam construction on river topographical evolution, water level changes, and deep-water waterway resources.

The majority of water utilities, particularly public service providers such as Gidole town, are struggling to deliver a sufficient and consistent supply of water in Ethiopia's developing towns. The primary objective of this study was to assess the hydraulic performance of water supply distribution system in Gidole Town, Ethiopia, a representative case of the challenges facing public water utilities in developing towns. The WaterGEMS v8i hydraulic model was utilized to simulate and evaluate the distribution network's performance. The system was configured as a looped network and analyzed against standard permitted pressure and velocity values in the distribution system. The model was effectively calibrated (coefficient of determination (R²) = 0.969) using measured and observed pressure data. The model simulation run was conducted at peak and low hourly demand with 1.9 and 0.25 hourly factors, respectively. The estimated water demand of the town is 1284.3 m³/day (48.4 liters per capita per day), and it would be increased to 3099.77 m³/day (66.03 l/c/d) by the 2037 design period. The system experiences significant non-revenue water losses (75,434.11 m³/year), accounting for 29.9% of total water production; as a result, the present water supply coverage of the town is only 33.6%. Hydraulic simulations under peak and low demand scenarios revealed nodes with pressures outside the normal range, indicating system-wide inefficiencies. These findings highlight a combined issue of large physical losses and insufficient capacity of the water supply in the town, which is typical of many municipal systems in developing regions. The study concludes that strategic infrastructure rehabilitation, with an emphasis on pressure management and leak reduction, is not only a town necessity but a fundamental requirement for improving water security and financial sustainability for utilities in Ethiopia and similar contexts. The findings and methodology have been forwarded to town's water supply project and institutional development departments for immediate future implementation and provide a replicable framework for evidence-based investment and planning in other struggling municipalities in similar situations.