Subsurface Flow Research Articles

Exploring the Effects of Fissures on Hydraulic Parameters in Subsurface Flows from the Perspective of Energy Changes

Reynolds number (Re), pore water pressure (P), and water flow shear force (τ) are primary indicators reflecting the characteristics of subsurface flow. Exploring the calculation of these parameters will facilitate the understanding of the hydrodynamic characteristics in different subsurface flows and quantify their differences. Hence, we conducted a study to monitor soil water content, matrix potential, and pore water pressure in two typical soil profiles (with and without fissures). The distribution of Re, P, and τ in both matrix flow (MF) and preferential flow (PF) were calculated with an improved calculation method, focusing on their energy changes. Results showed that these hydrologic parameters are quite different between MF and PF. Re values in MF remained below 0.1, indicating lower water flow velocities, while the Re values ranged from 0.8 to 2 in PF, indicating higher flow velocities. The P values in PF was tens to hundreds of times higher than that in MF, which is mainly due to the rapid accumulation and leakage of water within soil fissures. Additionally, the larger hydraulic radius and gradient in PF also resulted in higher τ values in PF (2~6 N m−2) than in MF (0~1.5 N m−2). In PF, the pressure potential was the significant factor for τ, while τ in MF was dominated by the matrix potential and varies with the magnitude of the matrix potential gradient. This study suggests that Re, P, and τ could be considered as the major indexes to reflect dynamic characteristics of subsurface flow.

A comparison of sea-level rise and storm-surge overwash effects on groundwater salinity of a barrier island

Coastal fresh groundwater is threatened by salinization due to both sea-level rise and storm-surge overwash. Most studies of subsurface saltwater intrusion focus on sea-level rise, but storms that are becoming more frequent and intense with climate change could have more imminent and permanent effects on aquifer salinity. Few studies directly compare saltwater intrusion due to sea-level rise with saltwater intrusion due to storm-surge overwash, and no studies address this issue on barrier islands. In this study, a hydrological model simulating coupled, variable-density, surface and subsurface flow and salt transport was developed and calibrated to water level and specific conductance data at Assateague Island, MD. The calibrated model was used to calculate the mass of salt and the total volume of aquifer salinized in 2080 due to both sea-level rise and more frequent storm surges. The results suggest that the total mass of salt that intrudes into the aquifer due to changes in the 2-year storm surge height is approximately equal to that of sea-level rise (∼300 kg), and the surges salinize nearly the entire aquifer, exceeding the volume salinized by sea-level rise (∼80 %). The influence of aquifer properties and unsaturated zone thickness was investigated by reducing aquifer hydraulic conductivity, resulting in greater salinization from storm-surge overwash (100 % of aquifer volume) than from sea-level rise (∼20 %). Higher storm surges are expected to overtop the dunes on Assateague by 2080 causing a 75 % decline in areas above the 2-year storm event while sea-level rise will only inundate ∼ 40 % of the land area on Assateague. This analysis suggests that groundwater is likely more vulnerable to storm-surge overwash than to sea-level rise induced salinization, even in systems where sea-level rise is expected to be most severe.

Study on the fatigue performance and Residual Stress of subsurface fluid flow of 2519a aluminum alloy based on water jet peening

In this study, the influence mechanism of water jet (WJ) strengthening on the surface integrity and fatigue properties of 2519 aluminum alloy was investigated by using finite element software Abaqus 2023 and fatigue analysis software Fe-safe. The effects of jet velocity and transverse velocity on the development of surface roughness and residual stress in different strengthening stages were studied, and the fatigue properties of WJ strengthened samples were analyzed by Fe-safe fatigue software. Finally, the fatigue life and fracture morphology of WJ strengthened specimens were analyzed by fatigue test, and the accuracy of finite element analysis was verified. Results indicate that surface roughness post-WJ enhancement displays a “W” shaped distribution, positively correlated with jet velocity. Conversely, increased roughness negatively correlates with higher traverse speeds, with optimal values recorded between 400 and 600 mm/min at WJ-290 mm/s, ranging from 1.10322 to 1.41167 μm. Additionally, the study reveals that maximum residual compressive stress during the WJ-Ip phase correlates positively with jet velocity, peaking at 302 MPa for WJ-290 mm/s. The research also notes that while higher jet velocities enhance residual compressive stress, they simultaneously elevate surface roughness, potentially introducing damage and increasing the variability of stress magnitudes. The study underscores the necessity of meticulously calibrating WJ parameters to enhance surface quality effectively while minimizing adverse effects. This balance is critical to optimizing the treatment process and achieving desired material properties.

Does afforestation increase soil water buffering? A demonstrator study on soil moisture variability in the Alpine Geroldsbach catchment, Austria

This study employed an operational monitoring network to measure soil moisture and runoff behaviour continuously in the Alpine catchment Geroldsbach-Götzens, Austria. We hypothesize that afforestation can have a positive impact on soil water buffering. To analyse the impact of soil properties and vegetation cover changes on soil water dynamics, four experimental plots were established on grassland and monitoring stations were installed in the forest. The rainfall test site is equipped with an automatic weather station to obtain meteorological observations, and weirs to measure surface runoff of natural occurring precipitation events and artificial rainfall simulations. In the plots, 200 soil moisture sensors were installed at five different depths, aimed to track and visualize infiltration and subsurface flow processes. Another twenty sensors monitored soil moisture at different afforestation stages in the forested part of the catchment. The measurements show that soils covered with young and old-growth forest have a higher and more stable soil moisture content than grassland and soils with a lack of vegetation throughout the seasons. We observed large spatial differences at plot scale, where the spatial variability of soil moisture increases with depth and is highest during convective precipitation. The initial conditions and rainfall characteristics play an important role in infiltration processes and soil water storage. Our rainfall test site demonstrated the challenges of innovative monitoring techniques and that it offers opportunities for more experiments to gather evidence-based data as input for flood models. Overall findings confirm the sponge effect of forest soils and indicate that afforestation as Nature-Based Solution reduces the temporal soil moisture variability, buffering soil water during precipitation events, which can be beneficial for runoff reduction in Alpine catchments.

A Statistical Analysis of Fluid Interface Fluctuations: Exploring the Role of Viscosity Ratio.

Understanding multiphase flow through porous media is integral to geologic carbon storage or hydrogen storage. The current modelling framework assumes each fluid present in the subsurface flows in its own continuously connected pathway. The restriction in flow caused by the presence of another fluid is modelled using relative permeability functions. However, dynamic fluid interfaces have been observed in experimental data, and these are not accounted for in relative permeability functions. In this work, we explore the occurrence of fluid fluctuations in the context of sizes, locations, and frequencies by altering the viscosity ratio for two-phase flow. We see that the fluctuations alter the connectivity of the fluid phases, which, in turn, influences the relative permeability of the fluid phases present.

Characterizing Flow Dynamics in a Two-dimensional Flow Cell: Developing Methodologies for Enhanced Subsurface Contaminant Remediation Research

This study used a two-dimensional (2-D) flow cell apparatus (25 cm × 25 cm × 1 cm) to characterize water flow and contaminant transport in porous media. The primary objective was to enhance the understanding of flow dynamics and contaminant behavior in controlled 2-D environments, which is crucial for optimizing the application of remediation technologies to treat contaminants in saturated and unsaturated soil conditions. The 2-D cell was designed with transparent walls to simulate subsurface conditions using medium grained sand, allowing for precise control and observation of fluid movement under saturated and quasi-saturated (trapped air) conditions. Visualization techniques and flow measurement tools were employed to capture detailed data on flow patterns, velocities, and dispersion characteristics. Analysis of breakthrough curves for salt tracer tests using electrical conductivity measurements, alongside varying flow rates, flow fractions, and port configurations, provided significant insights into fluid behavior and contaminant transport. The study also explored the effects of varying salt concentrations (and solution densities) on flow dynamics, contributing to a better understanding of the role of contaminant concentration in contaminant plume development and remediation processes. Visual analysis using dyed contaminant complemented the quantitative data, offering real-time observations of flow patterns and contaminant distribution. A custom-built apparatus was used to control the hydraulic head of multiple outlet ports to sample water from different depths. The experiments demonstrated that gravity plays a crucial role in solute (salt) breakthrough, with lower ports showing earlier breakthrough. Flow fields formed vertically, from bottom-to-top, and horizontally, from inlet-to-outlet, with lower portions advancing sooner. However, multi-port configurations, especially involving five ports, disrupted the sequential breakthrough order, possibly due to convection in the clear well that formed the outlet boundary of the flow cell. These findings will support research students in conducting similar experiments with flow and transport that varies with depth, with future insights for professionals in developing and optimizing remediation strategies related to subsurface contaminant flow. Special thanks are extended to Liam Price, Julia-Barnes James, and Brooke Belfall who were helpful during the research and the experimentation process.

Learning CO[formula omitted] plume migration in faulted reservoirs with Graph Neural Networks

Deep-learning-based surrogate models provide an efficient complement to numerical simulations for subsurface flow problems such as CO2 geological storage. Accurately capturing the impact of faults on CO2 plume migration remains a challenge for many existing deep learning surrogate models based on Convolutional Neural Networks (CNNs) or Neural Operators. We address this challenge with a graph-based neural model leveraging recent developments in the field of Graph Neural Networks (GNNs). Our model combines graph-based convolution Long-Short-Term-Memory (GConvLSTM) with a one-step GNN model, MeshGraphNet (MGN), to operate on complex unstructured meshes and limit temporal error accumulation. We demonstrate that our approach can accurately predict the temporal evolution of gas saturation and pore pressure in a synthetic reservoir with impermeable faults. Our results exhibit a better accuracy and a reduced temporal error accumulation compared to the standard MGN model. We also show the excellent generalizability of our algorithm to mesh configurations, boundary conditions, and heterogeneous permeability fields not included in the training set. This work highlights the potential of GNN-based methods to accurately and rapidly model subsurface flow with complex faults and fractures.

A juvenile journey: Using a highly resolved 3D mooring array to investigate the roles of wind and internal tide forcing in across‐shore larval transport

AbstractThe across‐shore transport of meroplanktonic larvae is predominantly driven by coastal physical processes, resulting in episodic recruitment of benthic species. Historically, due to the sampling challenges associated with resolving these advective mechanisms across the continental shelf, relevant components of larval transport have been difficult to isolate and understand. We use three‐dimensional temperature and velocity data from an array of 29 moorings to identify fundamental physical processes that could have generated successful across‐shore transport and settlement of meroplankton. The dense spatial and temporal sampling from this array allows us to use Lagrangian particle tracking to estimate the influences of wind conditions and the internal tide on the across‐shore transport of planktonic larvae. Settlement was found to be episodic at all depths studied. Above mid‐water, modeled larvae were successfully transported onshore by the internal tide during wind relaxations. Surprisingly, abundant pulses of shallow‐water larvae were supplied to the coast on occasions when strong, upwelling‐favorable winds (> 4 m s−1) drove offshore‐flowing surface waters, revealing a complex, potentially topographically influenced flow. These intense upwelling‐favorable winds also contributed to subsurface onshore flows that created large pulses of larval settlement in deeper waters (> 20 m). Our analyses from this highly resolved data set provide novel insights into the interactions of physical drivers in creating episodic pulses of coastal larval recruitment.

Studies of Wastewater Management through Microbiology of Constructed Wetland

Constructed wetlands are distinguished by certain environmental factors that let many physical and biological processes to occur simultaneously. This is the outcome of a particular habitat that supports the development of microbes and hydrophytes, which are plants that can live in aquatic and semiaquatic environments and are capable of anaerobic, anaerobic, and aerobic environments. Their combined activity amplifies the processes of oxidation and reduction, which are in charge of eliminating and holding onto contaminants. Sorption, sedimentation, and absorption all aid in these processes. Treatment wetland systems have been employed in community management for more than 50 years because of these benefits. Constructed wetlands are becoming more and more popular for treating or pre-treating many kinds of industrial wastewater because of their benefits, cheap operating costs, and high removal efficiency. The paper examines how these facilities are being used worldwide to treat industrial wastewater. With a focus on particular and distinctive pollutants from industries, the conditions of usage and efficacy of pollutants removal from wastewater that degrades quickly and slowly were described. The article addressed the use of subsurface horizontal flow beds for the treatment of wastewater from various industrial processes, including the manufacturing of paper, oil, and coffee, as well as the food sector, which includes wineries and distilleries. Constructed wetlands are used in Poland to treat wastewater and milk processing sludge on a pilot size or to dewater sewage sludge generated in municipal wastewater treatment plants that handle household sewage with around 40% of wastewater from the dairy and fish industries. Constructed wetlands provide the so-called ecosystem function in addition to an adequate degree of treatment in every instance.

Modeling porosity and permeability evolution of burrow fillings with packstone fabric in the Upper Jurassic Hanifa Formation, central Saudi Arabia: A digenetic backstripping study

Understanding the development and characteristics of burrow fillings (BF) is crucial for predicting porosity, permeability, and fluid flow behavior in bioturbated carbonate reservoirs. Advanced imaging, digital rock modeling, and backstripping techniques offer valuable insights into this development. In this study, we examined the BF in the bioturbated strata of the Upper Jurassic Hanifa Formation (central Saudi Arabia) to understand how sedimentological and diagenetic processes—such as compaction, dolomitization, and dissolution—influence porosity and permeability over time.Backstripping results provide significant insights into the evolution of porosity and permeability within packstone BF of the studied strata. We found that compacted, grain-supported BF exhibit limited improvement in porosity and permeability post-compaction. In contrast, less compacted intervals with open fabric BF can achieve up to 20% porosity and >5000 mD permeability in their grainstone versions. Notably, even with over 10% mud content, open fabric BF maintained substantial permeability (>1000 mD) due to a connected pore network. Moreover, these BF have the potential to recover porosity and permeability after complete pore network occlusion by the mud matrix through diagenetic processes like preferential dolomitization of the mud matrix and subsequent dissolution.The findings underscore the dynamic evolution of porosity in packstones within BF of bioturbated strata. Initially, mud-rich packstones with low porosity and permeability can transform into more permeable packstones through dolomitization and dissolution. Conversely, initially high-quality, mud-poor packstones with high porosity and permeability may degrade due to compaction. The quantification of porosity and permeability using digital rock modeling and backstripping techniques provides an objective and comprehensive understanding of these evolving properties, highlighting key phases and processes affecting reservoir quality. The approach of integrating digital rock modeling and backstripping technique enhances the ability to predict subsurface storage and flow capacity in bioturbated strata.

Treatment of domestic wastewater and extracellular polymeric substance accumulation in siphon-type composite vertical subsurface flow constructed wetland.

In this study, the siphon-type composite vertical flow constructed wetland (Sc-VSsFCW) was constructed with anthracite and shale ceramsite chosen as the substrate bed materials. During the 90-day experiment, typical pollutant removal effects of wastewater and extracellular polymeric substance (EPS) accumulation were investigated. Meanwhile, X-ray diffraction and scanning electron microscopy were used to examine the phase composition and surface morphology to analyze adsorptive property. Additionally, we evaluated the impact of siphon effluent on clogging and depolymerization by measuring the EPS components' evolution within the system. The findings reveal that both the anthracite and shale ceramsite systems exhibit impressive removal efficiencies for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), chemical oxygen demand (COD), ammonium nitrogen (NH4 +-N), and nitrate nitrogen (NO3 --N). However, as the experiment progressed, TP removal rates in both systems gradually declined because of the saturation of adsorption sites on the substrate surfaces. Although the dissolved oxygen (DO) levels remained relatively stable throughout the experiment, pH exhibited distinct patterns, suggesting that the anthracite system relies primarily on chemical adsorption, whereas the shale ceramsite system predominantly utilizes physical adsorption. After an initial period of fluctuation, the permeability coefficient and porosity of the system gradually stabilized, and the protein and polysaccharide contents in both systems exhibited a downward trend. The study underscores that anthracite and shale ceramsite have good effectiveness in pollutant removal as substrate materials. Overall, the hydraulic conditions of the double repeated oxygen coupling siphon in the Sc-VSsFCW system contribute to enhanced re-oxygenation capacity and permeability coefficient during operation. The changes in EPS content indicate that the siphon effluent exerts a certain depolymerization effect on the EPS within the system, thereby mitigating the risk of biological clogging to a certain extent. PRACTITIONER POINTS: The system can still maintain good pollutant treatment effect in long-term operation. The re-oxygenation method of the system can achieve efficient and long-term re-oxygenation effect. The siphon effluent has a certain improvement effect on the permeability coefficient and porosity, but it cannot effectively inhibit the occurrence of clogging. The EPS content did not change significantly during the operation of the system, and there was a risk of biological clogging.

JAMES BUTTLE REVIEW: Interflow, subsurface stormflow and throughflow: A synthesis of field work and modelling

AbstractInterflow, throughflow and subsurface stormflow are interchangeable terms that refer to the lateral subsurface flow above a restricting layer of lower hydraulic conductivity that occurs during and following storm events. Interflow (used here) is a more dominant process in steeper catchments with high infiltration capacity soils overlying a more impermeable soil or geologic layer. Interflow as a runoff process was first recognised in the early 1900s, yet hydrologists still struggle to predict its occurrence, persistence, importance, interaction with other streamflow generation processes, and potential to connect to valleys and streams during and following storms. We review the history of interflow research and address some of the challenges in understanding its role in runoff production. We argue that characterising the controls on interflow initiation and occurrence relies on detailed field observations of subsurface properties, which exist only in limited experimental settings. This data shortcoming contributes to our inability to predict interflow or determine its contribution to streamflow more broadly. There remain many opportunities to advance our understanding of interflow that include both modelling and experimental or observational approaches in hydrology.

Forecasting of sub-surface flow velocity through a temporarily open/close estuary under closed condition using machine learning

TOCE or temporarily open/closed estuary is a complex estuary system created by interaction of longshore transport and river outflows. Under the closed condition when an estuarine sandbar is formed, river flow is impeded creating backwater rise that could result in floods. At present, there are no hydrological models that could cater for river flows under closed estuary conditions. This paper proposes the application of a machine learning (ML) approach to model flow velocity in an estuarine sandbar which is crucial for flow estimations. A TOCE located at Mengabang Telipot, Terengganu, Malaysia was chosen for model development where river water and groundwater levels (inside the sandbar) were measured and tidal levels from an existing station were used. Average flow velocities were calculated using Darcy’s equation to represent observed data. Multilayer perceptron (MLP) neural networks were trained by the Levenberg-Marquardt algorithm and developed concerning the parameters above to predict groundwater average velocity. In this study, the optimal model was a neural network with four neurons in the hidden layer and the degree of influence of each parameter was determined by the results of the sensitivity analysis, where the R2 was obtained to be about 97–99% when predicted data was compared to observed data. Hence, the results indicated that neural networks were able to predict groundwater mean velocity quite well. The developed model was further verified using data from another TOCE from a different time. The results were very good having a R2 of 0.990. Hence, it was concluded that the ML approach was able to model flow in a TOCE and has great potential application in such an environment seeing that it is simpler than complex physics-based models.

Water budgets in an arid and alpine permafrost basin: Observations from the High Mountain Asia

Ground freeze‒thaw processes have significant impacts on infiltration, runoff and evapotranspiration. However, there are still critical knowledge gaps in understanding of hydrological processes in permafrost regions, especially of the interactions among permafrost, ecology, and hydrology. In this study, an alpine permafrost basin on the northeastern Qinghai‒Tibet Plateau was selected to conduct hydrological and meteorological observations. We analyzed the annual variations in runoff, precipitation, evapotranspiration, and changes in water storage, as well as the mechanisms for runoff generation in the basin from May 2014 to December 2015. The annual flow curve in the basin exhibited peaks both in spring and autumn floods. The high ratio of evapotranspiration to annual precipitation (>1.0) in the investigated wetland is mainly due to the considerably underestimated ‘observed’ precipitation caused by the wind-induced instrumental error and the neglect of snow sublimation. The stream flow from early May to late October probably came from the lateral discharge of subsurface flow in alpine wetlands. This study can provide data support and validation for hydrological model simulation and prediction, as well as water resource assessment, in the upper Yellow River Basin, especially for the headwater area. The results also provide case support for permafrost hydrology modeling in ungauged or poorly gauged watersheds in the High Mountain Asia.

Microplastic removal and risk assessment framework in a constructed wetland for the treatment of combined sewer overflows

Combined sewer overflows (CSOs) release a significant amount of pollutants, including microplastics (MPs), due to the discharge of untreated water into receiving water bodies. Constructed Wetlands (CWs) offer a promising strategy for CSO treatment and have recently attracted attention as a potential solution for MP mitigation. Nevertheless, limited research on MP dynamics within CSO events and MP removal performance in full-scale CW systems poses a barrier to this frontier of application. This research aims to address both these knowledge gaps, representing the first investigation of a multi-stage CSO-CW for MP removal. The study presents one year of seasonal data from the CSO-CW upstream of the WWTP in Carimate (Italy), evaluating the correlation of MP abundance with different water quality/quantity parameters and associated ecological risks. The results show a clear trend in MP abundance, which increases with rainfall intensity. The strong correlation between MP concentration, flow rate, and total suspended solids (TSS) validates the first flush phenomenon hypothesis and its impact on MP release during CSOs. Chemical characterization identifies acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), and polypropylene (PP) as predominant polymers. The first vertical subsurface flow (VF) stage showed removal rates ranging from 40 % to 77 %. However, the unexpected increase in MP concentrations after the second free water surface (FWS) stage suggests the stochasticity of CSO events and the different hydraulic characteristics of the CW units have diverse effects on MP retention. These data confirm filtration as the main retention mechanism for MP within CW systems. The MP ecological risk assessment indicates a high-risk category for most of the water samples, mainly related to the frequent presence of ABS fragments. The results contribute to the current understanding of MPs released by CSOs and provide insights into the performance of different treatment units within a large-scale CSO-CW system, suggesting the requirement for further attention.

The Effect of the Number of Equisetum hyemale Plants on the Efficiency of Horizontal Sub-Surface Flow Constructed Wetlands in Processing Liquid Laundry Waste

Laundry businesses in Indonesia have high economic development opportunities. However, laundry liquid waste in Indonesia does not yet have a good environmental culture and regulations for service users. Constructed wetland can be used as a sustainable biological processing technology, uses low energy, and does not require high costs to process liquid laundry waste. The aim of this research is to analyze the ability of horizontal sub-surface flow constructed wetlands in a batch system with different numbers of aquatic bamboo plants (Equisetum hyemale) in degrading chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) in laundry liquid waste. The research results showed that reactor 2 HSSF CW with a total of 200 E. hyemale plants produced higher removal efficiency compared to reactor 1 HSSF CW with a total of 120 E. hyemale plants where reactor 2 produced COD and BOD5 removal efficiency respectively. amounted to 88.22% and 90.30% while reactor 1 produced COD and BOD5 removal efficiencies of 86.04% and 88.10% respectively. Based on these results, reactor 1 and reactor 2 horizontal sub-surface flow constructed wetlands with E. hyemale plants produced effective performance in reducing COD and concentrations in laundry liquid waste.

Hydrological control of rock carbon fluxes from shale weathering

Shale bedrocks hold Earth’s largest carbon inventory. Although water is recognized for cycling elements through terrestrial environments, understanding how hydrology controls ancient rock carbon (Crock) release is limited. Here we measured depth- and season-dependent subsurface water fluxes and pore-water and pore-gas geochemistry (including radiocarbon) over five vastly different water years along a hillslope. The data reveal that the maximum depth of annual water table oscillations determines the weathering depth. Seasonally varying subsurface water fluxes determine the export forms and rates of weathered Crock. Eighty percent of released Crock is emitted as CO2 to the atmosphere primarily during warmer and lower water table seasons and 20% of released Crock as bicarbonate exports mostly during months of snowmelt to the hydrosphere. Thus, the rates and forms of Crock weathering and export are clearly controlled by climate via hydrologic regulation of oxygen availability and subsurface flow. The approaches developed here can be applied to other environments.

Nonlinear Tissue Permeability Drives Tissue Pressure and Injection Distribution: A Computational Investigation of Subcutaneous Injections.

There is a significant opportunity to expand the understanding of subcutaneous injection mechanics with an aim to increase injectable volume while controlling tissue strain and associated subject pain. Computational modeling can evaluate the mechanics of subcutaneous injections as a supplement to experimental, animal and clinical studies. The objectives of this study are to (1) develop a computational model for subcutaneous injection in tissue, (2) investigate the influence anisotropic tissue permeability has on bolus formation, and (3) explore the effects that injection flow rate and viscosity have on injection flow and tissue strain. Poroelastic models with subsurface flow were implemented in finite element software (COMSOL, ABAQUS). Pore pressure and injectate distribution showed excellent agreement with experimental results when evaluated at multiple injection rates (20 ml/hr, 120 ml/hr and 360 ml/hr). Including the anisotropy of tissue permeability causes the injectate to preferentially spread horizontally, similar to experimentally observed bolus distributions. Cases are presented to provide additional insight into injection mechanics, including variations on the delivery rate, the injection volume, viscosity and the thickness of the subcutaneous layer. The results support the use of computational modeling as a valid tool for understanding tissue strains and injectate distributions for large volume injections.

Testing the hydrological performance of live pole drains (LPD) for mitigation of slope instability

Nature-based solutions (NbS) and soil bioengineering techniques have gained considerable attention due to their relevant hydrological functions and ability to mitigate slope instability. Live pole drains (LPD), a lesser-known NbS, have traditionally been deployed on slopes to drain the excess surface water and regulate the soil's water budget, making it a suitable technique for stormwater management and landslide prevention. However, neither the LPD performance as a plant-based drainage system nor its potential to regulate the soil-water budget through hydrological processes have been thoroughly studied. This paper presents a novel pilot, lab-based approach for testing the hydrological performance of LPD under different soil hydrological conditions. We built three different treatments and investigated their hydrological performance under multiple storm events. We explored how LPD regulate the soil-water budget by partitioning the water inputs (i.e., rainfall precipitation) into water outputs (i.e., surface runoff, subsurface flow, and percolation). The study revealed that LPD can effectively manage stormwater by draining excess runoff and buffering water in the soil, outperforming fallow soil. Subsurface flow and percolation were significantly higher under LPD treatments when compared to fallow ground, suggesting that the presence of an enhanced structure in the soil results in high soil hydrological performance. The presence of a secondary species with the LPD showed a more efficient hydrological performance than an LPD alone, which aligns with the current implementation of NbS fostering biodiversity. Antecedent soil moisture impacted the hydrological performance of LPD by altering the relative infiltration capacity of the soil and by potentially modifying the availability of channels for preferential flow. Our findings provide a sound basis for future research to improve our understanding of the hydrological performance of LPD for slope instability mitigation and encourage their reproduction and upscaling.

Subsurface complexity controls the aquifer heterogeneity: A case study from the Al-Hassa oasis, Eastern Saudi Arabia

Al-Hassa region in the eastern part of Saudi Arabia is well-known for its geological and hydrogeological importance since it has historically hosted over 280 natural springs, which were used to irrigate the largest oasis in the world. Al-Hassa is located near the renowned Ghawar oil field, the largest conventional oil field globally, which represents a potential pollution source. This study utilizes and integrate hydrochemical investigations and geophysical gravity surveys to understand and reconstruct the subsurface heterogeneity in the Al-Hassa area. The dataset encompasses 113 groundwater wells distributed across the Al-Hassa Oasis which have been analyzed for salinity major ions, and isotopic (oxygen and hydrogen) compositions. A total of 571 gravity stations covering the broader oasis area (approximately 350 km2) are collected, processed, and modeled. The combined hydrochemical and geophysical results show a good agreement between groundwater quality and density (gravity anomalies) distribution within the study area. The southeastern part of the study area exhibits distinctive positive gravity anomalies, indicating denser rock formations alongside high total dissolved solids (TDS) in groundwater, reflecting poor water quality. Conversely, the southwest displays significant negative gravity anomalies, suggesting basins filled with loose sediments and low TDS values, signifying good water quality. Furthermore, the study reveals a certain pattern in groundwater temperature distribution, with cooler waters in the areas characterized by negative gravity anomalies (basins), and hotter waters emerging from areas with positive gravity anomalies. These findings suggest that groundwater quality differences may stem from varying sub-basins and interactions with distinct geological substrates. Temperature variations may also be attributed to differing subsurface flow pathways. This study attempts to explain the controlling factors for groundwater heterogeneity in the Al-Hassa Oasis area, emphasizing the role of geological, tectonic, and hydrogeological elements in shaping the Oasis's hydrological and hydrochemical pattern.