Jul 2026· Journal of Contaminant Hydrology· Vol 283, pp.
105053
· 0 citations· 52 references
Medicine
Abstract
In river ecological restoration, the mechanical and morphological properties of vegetation are critical modulators of hyporheic exchange, thereby influencing the broader fate of nutrients and contaminants. However, few studies have considered the effect of the dynamic interplay of vegetation flexibility on surface water-groundwater exchange, limiting our ability to predict the coupled dynamics of "flow-vegetation-hyporheic exchange". To address this concern, a coupled model integrating surface water-groundwater exchange and heavy metal transport was developed to investigate the synergistic regulatory mechanisms of river vegetation characteristics on hyporheic exchange at the sediment-water interface, and also the transport of copper ions. The results indicate that: (i) vegetation height significantly influences the surface flow field structure; higher vegetation creates a high-velocity zone above the canopy (approximately 0.35 m/s) and a low-velocity zone within the vegetation, forming a distinct velocity stratification that is considerably more pronounced than that observed with shorter vegetation; (ii) vegetation height is the dominant factor regulating hyporheic exchange, the hyporheic exchange flux under higher vegetation conditions are approximately 123% greater than that of the shorter vegetation, and rigid vegetation enhances flux by about 17% compared to flexible vegetation of the same height; (iii) vegetation height significantly promotes the transport of copper ions within the hyporheic zone; under higher vegetation conditions, the vertical transport depth of copper ions increases by up to 100% within 24 h, whereas the effect of vegetation flexibility on this process is fewer than that of the vegetation height. This study reveals the multi-scale regulatory mechanisms of vegetation mechanics and morphological parameters on hyporheic exchange processes, providing a theoretical basis for the rational configuration of vegetation and the integrated hydrological-ecological design in river ecological restoration.
Purpose: The aim of this study is to examine the effect of variations in groundwater table height on foundation settlement behaviour in arid-zone soils, where evaporation, restricted recharge and anthropogenic groundwater extraction are the dominant hydrologic conditions.
Design/Methodology/Approach: This research integrates field monitoring, laboratory testing, and numerical modelling to quantify settlement behaviour in response to changing groundwater levels. At an actual site, seasonal groundwater table depths between 1.2 m and 2.8 m BGL have been measured and implemented in hydro-mechanical simulations with PLAXIS 2D for the three common arid-region soil types (fine-grained, expansive soils and silty sands).
Research Limitation: The research focuses only on general desert soil types and the level of groundwater fluctuation present at the chosen site. Long-term climatic variations and extreme pumping scenarios seeded into the models, as well as three-dimensional groundwater flow effects, were not considered explicitly and potentially alter settlement behaviour under different field conditions.
Findings: The results show that groundwater depletion decreases effective stress and increases consolidation settlements, whereas fine-grained and expansive soils exhibit settlement up to ~38 mm for a groundwater drawdown of 2–3 m, and silty sands respond rapidly with lower settlement magnitudes. At footing edges, maximum differential footing settlement was near the footing edges and increased with depth due to the localised pumping hydraulic gradient. Deep foundations produced the highest reduction in differential settlement among all mitigation measures (up to 65%); lime–cement stabilisation was the next best alternative (reduction of 42%); and groundwater control systems provided only moderate improvement at relatively lower incremental costs.
Practical Implication: The results have immediate implications for foundation design in arid regions, highlighting the leading role of groundwater oscillations in settlement behaviour.
Social Implication: Better detection and tracking of groundwater-induced settlements can avoid damage to buildings and infrastructure in arid areas, increasing public safety, decreasing maintenance costs, and supporting reliable groundwater management practices.
Originality / Value: The combination of field data with hydro-mechanical numerical modelling offers a unifying approach for improving the outcome of large foundation designs and a useful input to researchers and practitioners alike.
K. A. Al-Abbas, S. A. Saadoon, A. Al-Robay· African Journal Of Applied R...· 0 citations
Accurate prediction of dissolved phosphorus (P) transport to groundwater, and especially to drain tiles, is a major challenge, particularly in structured soils where preferential flow dominates subsurface hydrology. Existing vadose zone models rely on advection–dispersion formulations that insufficiently represent macropore-driven transport, leading to underestimation of dissolved P losses. This study develops a simplified convective–preferential (CP) transport equation to describe event-scale movement of dissolved P through the vadose zone to groundwater. The equation conceptualizes the soil profile as a near-surface distribution zone that acts as a linear reservoir with a transmission zone below where preferential flow is activated when imposed fluxes exceed the effective matrix conductivity. Under these conditions, P-rich event water bypasses much of the soil matrix, rapidly reaching the groundwater. The CP equation uses a small set of physical parameters, based on partitioning the flux between the matrix and preferential pathways. Model results were validated against laboratory leaching experiments, published column studies of various soil textures, and tile-drained field soils. The CP equation reproduced observed dissolved P breakthrough patterns and flow-dependent concentration in tile drains. Model results confirm that significant P transport occurs during high-intensity rainfall on saturated soils with restrictive layers on structured soils with a low-permeable hardpan.
N. Brindt, B. Richards, T. Steenhuis· Water· 0 citations
The vadose zone (VZ) mediates contaminant migration to aquifers, yet its attenuation efficiency under transient conditions remains poorly understood. Most studies have employed batch experiments at a fixed saturation degree, which could not capture the coupled effects of water and oxygen content under transient conditions. This study evaluated nitrate behavior using unsaturated soil columns packed with sandy loam (SL) and loamy sand (LS) subjected to infiltration rates of 6.25-75 mm/h for simulating the VZ environment. Water and oxygen contents were continuously monitored, and pore-water samples were collected at multiple depths to characterize nitrate transport and fate. The presence and abundance of denitrifiers were analyzed to support apparent denitrification within the column. The modular 71.5-cm column packed with SL had a higher water content (∼0.3 v/v) and a capillary fringe of ∼22 cm, and retained 38.8-41.4% of introduced nitrate, predominantly at mid-depths (∼38.5 cm). Under a moderate infiltration rate (6.25 mm/h), 40.8% apparent denitrification occurred in SL. In contrast, coarser-textured LS with a shallower capillary fringe (∼10 cm) showed stronger vertical nitrate transport, with most nitrate remaining in the deeper ∼60.5 cm layer (25.5-47.7%). Although LS still showed 15.8% apparent denitrification at 6.25 mm/h, no apparent denitrification was detected under very heavy rainfall (75 mm/h) due to enhanced drainage, which inhibited stable microbial niche development. These results show that infiltration rate and soil texture control nitrate partitioning between apparent denitrification and leaching by regulating water residence time. Groundwater vulnerability to nitrate contamination may therefore vary with rainfall conditions.
Sungjik Oh, Jaeshik Chung, Man Jae Kwon et al.· Journal of Environmental Man...· 0 citations
Changes in fluvial environments and hydrogeological conditions critically govern biogeochemical processes in the hyporheic zone, with noticeable effects on nitrogen cycling. These environmental variations further govern the migration and transformation of nutrients and contaminants within riverine systems. This study established a two‐dimensional numerical model that couples hydrodynamic flow and reactive solute transport to explore the coupled hydrological and biogeochemical behaviours of the hyporheic zone beneath in‐stream restoration structures. A series of sensitivity tests were conducted to quantify how stream water quality, ambient temperature, as well as the hydraulic and solute transport characteristics of river sediments influence the rates of nitrification and denitrification. Numerical modelling outputs reveal that shifts in river surface water quality exert regulatory controls on nitrogen translocation and biological conversion in the hyporheic zone. Specifically, dissolved organic carbon (DOC) availability dominates the source‐sink function of the hyporheic zone for nitrate, exhibiting a stronger regulatory effect than ammonium (NH
4
+
) supply. Additionally, fluctuations in ambient temperature also serve as a key factor altering nitrogen transport and transformation processes in this critical interaction zone. As temperature increased, the penetration depth of solute fronts for four reactive species gradually decreased, nitrification rates increased by nearly two orders of magnitude, and denitrification rates first increased and then decreased. Conversely, elevated sediment hydraulic permeability accelerates hyporheic exchange flux across riverbed, which accordingly boosts the elimination efficiency of nitrate. This study deepens the current knowledge regarding the intricate coupling relationships between hydrodynamic behaviours and biogeochemical reactions in artificially modified river hyporheic zone. It provides a scientific basis for formulating adaptive river ecological restoration projects‐such as those addressing water quality regulation, temperature control andsediment property management in river systems ‐ultimately supporting fluvial system restoration and water quality improvement.
Jinghong Feng, X. Cai, Ying Liu et al.· Hydrological Processes· 0 citations
In cold and arid regions, climate change has altered precipitation patterns and accelerated glacierized retreat, which imposes severe risks on the stability of regional hydrological systems. Combined with the strong interactions between surface water (SW) and groundwater (GW) regulated by distinctive geological conditions, clarifying the baseline hydrological regime and predicting future hydrological changes is critical to maintaining local ecosystem stability. The headwater catchment of the Bortala River in Northwest China represents a typical glacierized watershed dominated by spring-fed discharge. Under the continuous influence of climate change, quantitative investigations into surface water-groundwater interactions in this catchment are still inadequate. In this study, a coupled SWAT-MODFLOW model embedded with a glacier module was developed to clarify the surface water-groundwater interactions relationship. Based on the Budyko framework, under CMIP6 climate scenarios, to establish an optimized decomposition and reconstruction simulation system, furthermore, to explore the changing characteristics of temperature, precipitation, and runoff. Observed hydrometeorological parameters were utilized to calibrate and validate the established model. A set of statistical indices was employed to assess the modeling performance, and the coupled model attained favorable simulation accuracy. The main results indicated that although surface water served as the dominant recharge source for groundwater from 1971 to 2020, representing a cumulative reduction of 26.7% from the initial value of the historical period, and an increased average annual decline rate of 0.45%. Future scenario projections revealed an increasing trend in total watershed runoff under both SSP2-4.5 and SSP5-8.5, with growth rates of 13.6% and 14.2%, respectively. A runoff inflection point is projected to occur around the 2070s (± 10 years), which will appear approximately 10 years earlier under the high-emission SSP5-8.5 scenario. In addition, intensified precipitation extremes may trigger severe hydrological risks, which are expected to concentrate around the 2040s and 2070s. The SWAT-MODFLOW model quantifies surface water-groundwater interactions in the glacial-snowmelt recharge system of the spring river, advancing hydrological modelling in cold-arid regions. Within the Budyko framework, the modified Choudhury-Yang equation combines temperature change and glacial-snowmelt recharge to analyze the spring river. CMIP6-driven SWAT-MODFLOW enhances runoff forecasting for the spring river. Combined with the SSP2-4.5 and SSP5-8.5 scenarios, it predicts future variations in temperature, precipitation, and runoff, identifies hydrological change inflection points, and provides a basis for flood prevention and water resources management. The SWAT-MODFLOW model quantifies surface water-groundwater interactions in the glacial-snowmelt recharge system of the spring river, advancing hydrological modelling in cold-arid regions. Within the Budyko framework, the modified Choudhury-Yang equation combines temperature change and glacial-snowmelt recharge to analyze the spring river. CMIP6-driven SWAT-MODFLOW enhances runoff forecasting for the spring river. Combined with the SSP2-4.5 and SSP5-8.5 scenarios, it predicts future variations in temperature, precipitation, and runoff, identifies hydrological change inflection points, and provides a basis for flood prevention and water resources management.
Wenjun Wang, Aihua Long, Jiawen Yu et al.· Applied Water Science· 0 citations
Summary Surface water-groundwater interactions are complex in the Great Bend region of the Yellow River. Clarifying water exchange and source differences among geomorphic units is important for understanding regional hydrological processes and improving water resources management. In this study, the Wulanmulun River Basin, a typical tributary of the Yellow River, was selected as the study area. A total of 90 water samples were collected, including 25 river water samples, 43 groundwater samples, and 22 precipitation samples. Gibbs diagrams, multivariate statistical analysis, PMF, and MixSIAR models were used to investigate the hydrochemical and isotopic characteristics, source contributions, and transformation relationships of surface water and groundwater. The results showed that, under the combined effects of rock weathering dissolution and evaporation concentration, the hydrochemical types of surface water and groundwater in the study area were dominated by Cl-Na and HCO3-Ca types, respectively. The source contributions of hydrochemical components differed between surface water and groundwater. Groundwater was mainly controlled by geological processes (41.1%), followed by agricultural input (31.3%); surface water was also dominated by geological processes (36.1%), but the influence of domestic input was enhanced (34.1%). In the hilly regions, groundwater discharge mainly recharged surface water, with an average contribution rate of 32.4%. In the plain and built-up areas, surface water infiltration mainly recharged groundwater, with average contribution rates of 34.2% and 25.0%, respectively. These results enhance understanding of surface water-groundwater transformation in the Yellow River’s “Great Bend” and support scientific management and efficient utilization of basin water resources.
