Saturated Water Flow Research Articles

Effect of CO2 on the water slip flow at silica surfaces for nanometer slit pores of talc

In our previous study, Molecular Dynamics (MD) simulated water flow with no dissolved gas in nanometer slit pores of the hydrophobic talc surfaces revealed a slip length of about 0.5 nm, which is close to the size of “water exclusion zone” but much less than experimental slip length. Atomic Force Microscopy (AFM) imaging confirmed the presence of pancake shape nanobubbles at the hydrophobic talc (001) surface (size from tens to hundreds of nanometers). The effect of CO2 on water slip flow in talc nanopores is reported to reveal the importance of dissolved gas for confined fluid flow. MD simulated 7 nm CO2 nanobubbles were found to attach and spread at the talc (001) surface, consistent with the AFM observation. Simulated CO2 saturated water flow in the slit pores of talc (001) surfaces predicted the generation of CO2 nanobubbles at the end of the slit pore, due to the stabilization of a CO2 film at the talc (001) surfaces and a water barrier at the edge surfaces of talc. A “critical thickness” of about 1.5 nm was found for CO2 nanobubbles to be stabilized at the end of the talc (001) surface. With 1.5 nm CO2 nanobubbles at the talc (001) surface of a 6 nm slit pore, a water slip length of 1.8 nm was determined. The nanometer slit pore simulations with dissolved CO2 in water revealed an increased slip length. It is expected that an increased slip length value would be found with an increased CO2 film thickness.

Saturated water flow boiling heat transfer and pressure drop in scalably microstructured plain and finned copper tubes

Well established understanding of flow boiling heat transfer and its hydrodynamic driving mechanisms have led to the inception of surface geometry augmentation techniques that can enhance thermal-hydraulic performance. Enhancing the flow boiling heat transfer at a reasonable pressure drop enables the deployment of more compact and efficient heat exchangers and thermal systems. To enable ease of manufacturing, simplicity, and reliability, passive augmentation techniques that do not require external stimuli are preferred. In this study, a scalable copper microstructuring technique was developed on both smooth and internally finned 0.25” tubes to investigate how it affects the thermofluidic behavior of relatively higher surface tension water during saturated flow boiling. The internally finned tubes used in this study comprised of 50 fins with a helical angle of 13°. To apply the conformal microstructures on the internal tube surfaces, chemical oxidation via an alkaline mixture was used, resulting in structures having characteristic length scales approaching 200 nm −1 µm. Our results show that microstructuring of plain copper tubes provides a water flow boiling heat transfer coefficient enhancement ranging from 10 % to 90 % compared to untreated specimens for vapor qualities ranging from 0 to 0.1 and mass flow rates ranging from 255 to 485 kg/(m2·s). Augmentation is attributed to the increased roughness of the plain copper tubes that creates additional nucleation sites for enhanced liquid entrapment and increases wettability. Associated with this heat transfer augmentation is an increased pressure drop ranging from 0.5 % to 38 % relative to untreated tubes due to the increased skin friction as well as add fluid flow disruption. Overall, the performance factor ranged between 0.86 to 1.81 demonstrating that the augmentation in heat transfer overshadowed the increase in pressure drop. Interestingly, applying the conformal microstructures on internally finned copper tubes decreased the heat transfer coefficient and pressure drop by as much as 75 % and 45 %, respectively, when compared to the un-structured finned copper tubes counterparts. The decrease in heat transfer performance and pressure drop was attributed to partial wetting of the fin roots due to the presence of a vapor layer near the inner tube walls. Our work develops a mechanistic understanding of the role that microstructures play during flow boiling of water on industrially applicable smooth and finned tube geometries and designs.

Managing climate change impacts on the Western Mountain Aquifer: Implications for Mediterranean karst groundwater resources

Many studies highlight the decrease in precipitation due to climate change in the Mediterranean region, making it a prominent hotspot. This study examines the combined impacts of climate change and three groundwater demand scenarios on the water resources of the Western Mountain Aquifer (WMA) in Israel and the West Bank. While commonly used methods for quantifying groundwater recharge and water resources rely on regression models, it is important to acknowledge their limitations when assessing climate change impacts. Regression models and other data-driven approaches are effective within observed variability but may lack predictive power when extrapolated to conditions beyond historical fluctuations. A comprehensive assessment requires distributed process-based numerical models incorporating a broader range of relevant physical flow processes and, ideally, ensemble model projections. In this study, we simulate the dynamics of dual-domain infiltration and precipitation partitioning using a HydroGeoSphere (HGS) model for variably saturated water flow coupled to a soil-epikarst water balance model in the WMA. The model input includes downscaled high-resolution climate projections until 2070 based on the IPCC RCP4.5 scenario. The results reveal a 5% to 10% decrease in long-term average groundwater recharge compared to a 30% reduction in average precipitation. The heterogeneity of karstic flow and increased intensity of individual rainfall events contribute to this mitigated impact on groundwater recharge, underscoring the importance of spatiotemporally resolved climate models with daily precipitation data. However, despite the moderate decrease in recharge, the study highlights the increasing length and severity of consecutive drought years with low recharge values. It emphasizes the need to adjust current management practices to climate change, as freshwater demand is expected to rise during these periods. Additionally, the study examines the emergence of hydrogeological droughts and their propagation from the surface to the groundwater. The results suggest that the 48-month standardized precipitation index (SPI-48) is a suitable indicator for hydrogeological drought emergence due to reduced groundwater recharge.

Predicting bacterial transport through saturated porous media using an automated machine learning model.

Escherichia coli, as an indicator of fecal contamination, can move from manure-amended soil to groundwater under rainfall or irrigation events. Predicting its vertical transport in the subsurface is essential for the development of engineering solutions to reduce the risk of microbiological contamination. In this study, we collected 377 datasets from 61 published papers addressing E. coli transport through saturated porous media and trained six types of machine learning algorithms to predict bacterial transport. Eight variables, including bacterial concentration, porous medium type, median grain size, ionic strength, pore water velocity, column length, saturated hydraulic conductivity, and organic matter content were used as input variables while the first-order attachment coefficient and spatial removal rate were set as target variables. The eight input variables have low correlations with the target variables, namely, they cannot predict target variables independently. However, using the predictive models, input variables can effectively predict the target variables. For scenarios with higher bacterial retention, such as smaller median grain size, the predictive models showed better performance. Among six types of machine learning algorithms, Gradient Boosting Machine and Extreme Gradient Boosting outperformed other algorithms. In most predictive models, pore water velocity, ionic strength, median grain size, and column length showed higher importance than other input variables. This study provided a valuable tool to evaluate the transport risk of E.coli in the subsurface under saturated water flow conditions. It also proved the feasibility of data-driven methods that could be used for predicting other contaminants' transport in the environment.

Spatial relationship of the saturated hydraulic conductivity and rock fragments on the soil surface in an Andean microwatershed

ABSTRACT Saturated hydraulic conductivity (Ks) is an important soil variable. Multiple investigations have analysed the influence of rock fragments on saturated hydraulic conductivity, but they hardly involve the spatial component. This research spatially modelled the Ks and its relationship with the contents of rock fragments, organic carbon, and total porosity in the surface horizon of the soils of a tropical Andean micro-basin. Hydrologic response units were used to run a stratified-type sampling. Ks was determined using the constant head method and the total porosity using the tension table. Disturbed samples were used to determine rock fragments and organic carbon content. Results showed that the Ks had an exponential distribution, with high values located in areas of the middle and upper parts of the basin. The distribution was spatially related to the content of rock fragments, the total porosity and the organic carbon content using the spatial autocorrelation model with which it was obtained the best fit results between the observed values of Ks and their predicted values on the soil surface (r = 0.883). The inclusion of these three variables in pedotransfer functions and hydrological models would reduce the uncertainty in estimating the saturated flow of soil water in stony soils.

Variably saturated dual-permeability flow modeling to assess distributed infiltration and vadose storage dynamics of a karst aquifer – The Western Mountain Aquifer in Israel and the West Bank

Available methods to quantify the recharge of karst aquifers usually rely on spatially and temporally aggregated precipitation measurements and simplified recharge models, employing transfer functions to account for the delay in infiltration and the distribution in time and space. They generally neglect the non-linear nature of infiltration dynamics through the vadose zone, characterized by dual flow behavior with slow diffuse and rapid focused recharge components. Here, we present a methodology that accounts for the physics of flow by employing a variably saturated dual-permeability flow model to simulate diffuse and preferential infiltration in a large-scale carbonate aquifer. The Western Mountain Aquifer (WMA) in Israel and the West Bank was selected as a suitable groundwater basin because of the large thickness of the vadose zone, extending over several hundred-meters, the availability of long-term data as well as the catchment size, stretching across a catchment area of circa 9000km2. Together, these characteristics allow the identification and quantification of the spatio-temporal distribution of the infiltration/recharge component, assessed at the level of the groundwater table. The presented methodology allows for improved water resources planning and generalization of the results, i.e., the robustness of large-scale model results with respect to local hydraulic parameter variations and data uncertainty. Semi-arid climate regions with a highly pronounced seasonality of precipitation and intense short-duration rainfalls, such as the Mediterranean region, represent a prime study location because of the clear and pronounced recharge input signals that are not superimposed by summer rainstorms. We simulate the complex dynamics of the dual-domain infiltration and partitioning of the precipitation input signal by employing HydroGeoSphere (HGS) for transient variably saturated water flow. Flow in the limestone rock matrix and high porosity system (i.e., conduits and fractures) is modeled by overlapping individual continua based on the bulk-effective Richards’ equation with van Genuchten (VG) parameters.

Analysis of Temperature Effect on Saturated Hydraulic Conductivity of the Chinese Loess

Saturated hydraulic conductivity (Ks) is a significant basic hydraulic parameter in the field of soil science. However, it is typically used as a constant, and that will lead to some inaccurate results in numerical simulations of water movement. In this study, a laboratory experiment was conducted to investigate the effect of temperature on Ks of Chinese loess. The results indicated that Ks had a special relationship with temperature for this soil: Ks increased in the range of temperatures (t) from 7 to 44 °C. A formula in Forest Standard of China LY/T 1218-1999 can well describe the distribution characteristics of the experimental data, but it may not apply if bulk density changes. The study improved the formula by analyzing another set of published experimental data. In the improved formula, the influence of bulk density and temperature on Ks is fully considered. The results show that the improved formula can be applied to the simulation of saturated water flow by accurately describing Ks variation with temperature and bulk density.

Review of Rain or Shine: An Introduction to Soil Physical Properties and Processes. Tyson Ochsner. Published by Oklahoma State University Libraries under the Creative Commons Attribution 4.0 International License. Version 6. Last updated 19 Jan. 2022. DOI: https://doi.org/10.17605/OSF.IO/Z4RBT

Review of <i>Rain or Shine: An Introduction to Soil Physical Properties and Processes</i>. Tyson Ochsner. Published by Oklahoma State University Libraries under the Creative Commons Attribution 4.0 International License. Version 6. Last updated 19 Jan. 2022. DOI: https://doi.org/10.17605/OSF.IO/Z4RBT

Mechanism of coalbed methane migration and production based on micro-pore overpressure environment

A complete understanding of the mechanism and characteristics of the migration and output of coalbed methane (CBM) is of great significance for CBM development. For the coal reservoir in a micropore overpressure environment, the “Reservoir inner surface desorption-micropore diffusion-natural fracture seepage” cannot completely describe the CBM production process. To this end, starting from the three stages of CBM production, based on the microporous overpressure environment of coal reservoirs to reveal CBM's migration and production mechanism. The results show that: (1) In the stage of saturated single-phase water flow, CBM was transported by “solution mass transfer”; (2) At the single-phase unsaturated water flow stage, CBM become “microporous drainage”; (3) At the two-phase gas-water flow stage, CBM is transported and produced traditionally.

Hybrid modelling of saturated water flow in percolating and non-percolating macroporous soil media

The saturated water flow phenomenon is determined by the soil pore transport processes occurring at a micro-scale. In this study, saturated water flow was modeled using two different approaches, depending on the existence of the percolating macropore network. The soil material comprised 26 undisturbed soil cores. Soil samples were scanned using an X-ray micro-CT scanner, and saturated hydraulic conductivity (Ksat), bulk density and particle size distribution were measured. The voxel size for X-ray CT scans of soil cores was 23.6 µm, which allowed soil macropore network discrimination. The macropore network was percolating in 11 samples, while the remaining cores were not. A typical approach based on Navier–Stokes (NS) equations was used for saturated water flow modeling in the case of a percolating samples. In the case of cores with a non-percolating macropore network, the NS modeling approach could not be used. An alternative method of modeling (NS/Darcy) was used in this case, blending: regular NS flow in the well-defined macropores with the Darcy–Forchheimer flow in the remaining part – the soil matrix. Soil matrix is treated by the NS/Darcy model as a pore medium without well-defined pore geometry but with some intrinsic permeability incorporated in the model using the Darcy–Forchheimer equation. Unlike the NS approach, the NS/Darcy model allowed for the simulation of water flow for all soil samples, including those where the macropore network was not percolating. Based on simulations, the Ksat was estimated used for model validation. The analysis of results leads to the proposal of a new hybrid modeling approach, mixing the NS and NS/Darcy modeling approaches. A good estimation of the Ksat was obtained using the proposed model (R2 = 0.61). The NS/Darcy modeling approach was used for the analysis of the macropore flow in the soil media. The simulations show that water permeates through the core, but macropores are a favorable flow path if they exist, even if they are not directly connected to each other. The areas of the soil cores taking part in the preferential, macropore flow were quantified, showing that only a small fraction of the macropores take part in water flow both for percolating and non-percolating cores. But generally, for most of the analyzed flow-related indices, apparent differences in results between percolating and non-percolating samples were observed. Effective flow area (EFA), i.e., the sample area used for water flow with a velocity higher than the threshold velocity (Utr) was analyzed. Considering the macropore flow, only ∼2% of sample volume is responsible for: 82% of the total flux in case of percolated and 34% in case of non-percolated samples. Also, for non-percolated samples, the dependence (R2 = 0.44) between relative flux participation and the effective flow area is observed. The simulation results for the non-percolating samples revealed the relationship between the simulated saturated conductivity of the whole soil sample and the saturated conductivity of the soil matrix and macroporosity. This allowed for developing a simple multiple linear regression model (R2 = 0.98) of the soil core’s hydraulic conductivity.

River Buffer Effectiveness in Controlling Surface Runoff Based on Saturated Soil Hydraulic Conductivity

In tropical Indonesia, rainforests are managed by an intensive forest management system (IFMS). The IFMS has promoted selective logging for timber harvesting and intensive line planting to enrich the standing stock. The implementation of the IFMS has reduced the forest canopy cover, disturbed the surface soil, changed the soil hydraulic properties, and increased direct runoff and soil erosion. Investigation of the IFMS impact on soil hydraulic properties and the generation of surface runoff using a saturated hydraulic conductivity model is needed. Soil hydraulic properties were investigated on 11 plots, including one virgin forest plot and 10 plots at different operational periods of the IFMS. A two-dimensional saturated soil water flow simulation was applied to generate surface runoff from different periods of the IFMS. The main parameters of canopy cover, net rainfall, and saturated hydraulic conductivity were used in the simulations. A simulation scenario of a surface runoff hydrograph in different forest operations was used to analyze the river buffer effectiveness. The results showed that fundamental IFMS activities associated with mechanized selective logging and intensive line planting have reduced the soil hydraulic conductivity within the near-surface profile. The recovery time for near-surface Ks on non-skidder tracks was between 10 and 15 years, whereas on the skidder tracks it was more than 20 years. Forest disturbances have altered the typical surface hydrological pathways, thereby creating the conditions for more surface runoff on disturbed surfaces than on undisturbed surfaces. Maintaining the buffer area is an effective means to reduce the peak discharge and surface runoff in the stream channel.

Thermodynamically consistent model for poroelastic rocks towards tectonic and volcanic processes and earthquakes

Summary A general-purpose model combining concepts from rational continuum mechanics, fracture and damage mechanics, plasticity, and poromechanics is devised in Eulerian coordinates, involving objective time derivatives. The model complies with mass, momentum, and energy conservation as well as entropy inequality and objectivity. It is devised to cover many diverse phenomena, specifically rupture of existing lithospheric faults, tectonic earthquakes, generation and propagation of seismic waves, birth of new tectonic faults, or volcanic activity, aseismic creep, folding of rocks, aging of rocks, long-distance saturated water transport and flow in poroelastic rocks, melting of rocks and formation of magma chambers, or solidification of magma.

Removal of Sulfate Ions by Precipitation and Flotation

The removal of sulfate ions from natural waters, as well as from industrial effluents of different origins, is a problem, considering that most of the proposed processes are inefficient and have a high cost, mainly when reducing the sulfate ion concentration to values below 500 mg.L−1 is required. The flotation technique, combined with precipitation, has proven to be efficient for the removal of heavy metal ions. However, there is not enough research to confirm its efficiency for the removal of sulfate ions. This article presents the results of sulfate ion removal from synthetic solutions prepared in an acidic medium, applying the co-precipitation techniques with polyaluminum chloride (PAC) and solid/liquid separation by dissolved air flotation (DAF). The effect of the pH, the [PAC: sulfate ions] ratio, the effect of saturated water flow with air, and the flocculant and collector doses were studied. The achieved results confirm that it is possible to reduce the concentration of sulfate ions from 1 800 to 350 mg.L−1 (80% removal) from synthetic solutions by applying the flotation technique combined with precipitation.

Empirical modeling of turbidity removal in a dissolved air flotation system: application of artificial neural networks

Abstract Dissolved air flotation (DAF) is a physical separation process that uses air microbubbles to remove suspended material dispersed in a liquid phase. Even though DAF is considered a well-established unit operation, modeling it is difficult due to the complexity of the phenomena involved, resulting in conceptual models with no practical application. Thereby, the objective of this work was to evaluate empirical modeling efficiency in predicting the turbidity removal dynamic using artificial neural networks applied to a DAF prototype. For the study of the neural network input variables, a two-level, full-factorial design was utilized to verify the statistical significance of the saturation pressure and the saturated water flow rate in relation to the turbidity removal. Using a time-delay recurrent neural network architecture, two empirical models were proposed to simulate the dynamic behavior of the turbidity removal promoted by the DAF prototype. The real-time model provided good predictions with R = 0.9717 and MSE = 1.0482, and the simulation model was also able to predict the process behavior presenting performance criteria equal to R = 0.9475 and MSE = 1.8640.

Distinguishing between rheophysical regimes of fluid-saturated granular-flows using dilatancy and acoustic emission measurements

Dry granular flows provide an ongoing challenge to physics and under saturation the multiphase physics is even more difficult to disentangle. A rich literature has elucidated the possible regimes achieved, however, the nonlinear nature of the multiphase process makes predicting the appropriate dynamic regime difficult. In this study, we introduce a new experimental strategy to identify the appropriate dynamical regimes by combining traditional methods with acoustic emission measurements. We sheared natural granular materials under dry, water and oil-saturated conditions while recording mechanical, acoustic and visual data. By applying alternate low and high velocity steps we respectively obtained quasi-static and inertial granular flow regimes. Dilation was observed for all high-velocity flows but its amount varied as did the degree of acoustic emission. At high velocities, the water-saturated flow dilated less and had reduced acoustic emissions relative to the dry case. In contrast, the oil-saturated flow dilated more while having even less acoustic emissions. This difference in trends of the dilation and acoustic emissions with increasing fluid viscosity suggests that oil and water granular flows achieved distinct dynamical regimes. Damping of granular pressure by reducing grain collisions and Dilatancy due to fully lubricated contacts are two competing processes influence the saturated shear physics and theoretically expected, but distinguishing between the regimes is difficult to anticipate. The acoustic emissions provide an extra piece of information that allows us to distinguish the physical regimes and determine the competition between processes that control the physics of saturated granular flows in the granular inertial regime.

Application of the Darcy and Richards equations for modelling of water capillary rise in building materials

This paper presents the application of the Darcy and Richards equations, describing water flow and dynamic changes of the water content in porous medium, for numerical modeling of water capillary rise in the selected building materials. The numerical simulations of unsaturated and variably saturated water flow in the studied materials were performed in FEFLOW commercial computational software, by DHI-Wasy, Germany. The developed model represented a wall section constructed of aerated concrete blocks, covered by mortar prepared using blended cement with biomass ash addition. The physical and water retention characteristics of the modeled materials were based on the previously performed laboratory measurements and literature research. The assumed initial conditions reflected air dry wall with limited moisture, while the boundary conditions allowed modeling of capillary rise due to direct contact of the studied materials with water with variable pressure head. The results of numerical calculations allowed observation of the time-dependent changes in the moisture content of building materials in relation to their physical properties and variable boundary conditions.

Numerical modeling of post-flood water flow in pavement structures

Water infiltration through pavement structures as a result of flooding and/or extreme rainfalls, can adversely influence the bearing capacity of the pavement and lead to its premature failure. Since the entire pavement system will not be always in saturated state, the post-flood water movement throughout its granular layers should be formulated based on unsaturated flow principles. This study is aimed at developing a practical numerical model for simulating the partially saturated water flow in pavements caused by surface infiltration. To this end, available numerical methods and software packages are evaluated based on the relative merits of availability and computational rigor. The selected method is validated with published data. Existing correlations are used to reduce the number of inputs required for modeling. Subsequently, a parametric study is carried out to investigate the influence of material properties, such as aggregate gradation, and environmental conditions, such as rainfall intensity and duration, on the pavement’s response. Special cases, such as anisotropic material and clogged drainage are also modeled. This study provides an insight into the hydraulic behavior of pavement structures subjected to severe precipitation. In addition, this model establishes a solid basis for subsequent structural analyses to fully understand the behavior of inundated pavements under traffic loadings.

Effect of Climate Change on a Monolithic Desulphurized Tailings Cover

A soil cover system can be viewed as a thin interface placed between the atmosphere and the underlying waste. Climate is a primary design variable in soil cover design; therefore, climate change poses a number of challenges to design, operation and long-term performance of covers. In this research climate change effects on the hydraulic behavior of soil covers at a Northern Ontario, Canada site were assessed. Covers were analyzed using historical and future climate datasets. Historical climate data were compiled from an Environment Canada weather station near the site. The future climate datasets were sourced for different Global Circulation Models (GCM) for various representative concentration pathways (RCP). The covers at the site were constructed with a single layer of desulphurized tailings. Soil covers were meant to limit oxygen ingress to the underlying reactive tailings by maintaining high water saturation in the covers. Oxygen flux through soil covers for current and future climates were predicted using variably saturated water flow and oxygen transport modeling using the finite element method. The results of this research indicate that the effect of climate change on soil cover depends on the hydraulic properties of the soil cover materials and that of the underlying tailings. The results of this study suggest that the effect of climate change on the coarse tailing covers could be marginal resulting in a maximum increase of 5% in oxygen flux at the cover surface for the future climates in comparison to the base climate. However, in the case of fine tailings covers, increases of up to 65% can be expected.

Multiphase and multicomponent simulation of acid mine drainage in unsaturated mine waste: Modeling approach, benchmarks and application examples

Acid mine drainage (AMD), caused by weathering of sulfide-rich mine wastes, is arguably the most critical environmental issue in the mining sector. Despite the fact that individual mechanisms responsible for the generation/propagation of AMD are fairly well-known, the prediction of overall dynamics in a mine waste system is challenging due to the nonlinearity and multilevel coupling associated with the key physico-chemical processes. This work presents a new three-phase multicomponent reactive transport model for AMD simulations, taking into account variably saturated water flow, multicomponent advective-dispersive transport both in aqueous and gaseous phase, and kinetic and equilibrium chemical reactions. The model is capable to capture the species-species coupling due to solute/surface charge or gas phase pressure by solving Nernst-Planck equation for the aqueous transport, and Maxwell-Stefan equation for the gaseous transport. Furthermore, the unsaturated flow and transport code is coupled with PHREEQC, utilizing the PhreeqcRM module, to simulate a wide range of geochemical reactions. The capabilities of the code are benchmarked against other software, previously published laboratory data, and pilot-scale drainage experiments in mica schist containing waste rocks performed in this study. The results are analyzed in terms of spatial and temporal profiles. The simulations reveal that the proposed model, called AMD-PHREEQC, is capable of accurately reproducing the experimental results, and thus it can be effectively used in environmental risk assessment, long-term drainage quality predictions, and data interpretations in mine waste.

Sensitivity of hydrologic and geologic parameters on recharge processes in a highly heterogeneous, semi-confined aquifer system

Abstract. An increasing reliance on groundwater resources has been observed worldwide during the past 50–70 years and has led to unsustainable groundwater abstraction in many regions, especially in semi-arid and arid alluvial groundwater basins. Managed aquifer recharge (MAR) has been promoted to replenish overdrafted groundwater basins and augment surface water supply. However, MAR feasibility in alluvial groundwater basins is complicated by complex geologic architecture that typically includes laterally continuous, fine-texture confining units that can impede both recharge rates and regional propagation of increases in the hydraulic head. A greater feasibility of MAR hinges on identifying locations where rapid, high-volume recharge that provides regional increases in pressure head are possible, but relatively little research has evaluated the factors that control MAR feasibility in alluvial groundwater basins. Here, we combine a transition probability Markov chain geostatistical model of the subsurface geologic heterogeneity of the eastern side of the northern Central Valley, California, with the three-dimensional, variably saturated water flow code ParFlow to explore the variability of MAR feasibility in this region. We use a combination of computationally efficient local- and global-sensitivity analyses to evaluate the relative importance of factors that contribute to MAR feasibility. A novel proxy parameter approach was used to describe the configuration and proportions of subsurface hydrofacies and the water table depth for sensitivity analyses, and results suggest that recharge potential is relatively more sensitive to the variability of this proxy parameter than to the variability of individual hydrofacies hydraulic properties. Results demonstrate that large variability of MAR feasibility is typical for alluvial aquifer systems and that outsized recharge rates are possible in select locations where interconnected, coarse-texture hydrofacies occur.