The impact of flow displacement patterns on hydraulic tortuosity for unsaturated flow

In order to create a tool to help hydrologists and authorities to have good understanding about occurrences in stream flow regime together with its variation in the future under the impact of climate change in the Vu Gia Thu Bon catchment, a deterministic distributed hydrological model has been developed and constructed. This model covers the major processes in the hydrologic cycle including rainfall, evapotranspiration, overland flow, unsaturated flow, groundwater flow, channel flow, and their interactions. The model is calibrated and validated against the daily data recorded at seven stations during 1991–2000 and 2001–2010, respectively. The quality of results is demonstrated by Nash–Sutcliffe and correlation coefficients that reach 0.82 and 0.92, respectively, in discharge comparison. With water levels, the obtained coefficients are lower but the quality of results still remains high; Nash–Sutcliffe and correlation coefficients reach 0.77 and 0.89, respectively, in the upstream part of the catchment. This analysis demonstrates the performance of the deterministic distributed modeling approach in simulating hydrological processes one more time; it also confirms the usefulness of this model with ungauged catchments or large catchments. Additionally, this analysis proves the role of multi-calibration in increasing the accuracy of hydrological models for large catchments.

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Sensitivity Analysis of Clay Barriers

Water Science & Technology ◽

10.2166/wst.1991.0356 ◽

1991 ◽

Vol 24 (11) ◽

pp. 229-238

Author(s):

M. M. Nobre ◽

J. F. Sykes

Keyword(s):

Finite Element Method ◽

Sensitivity Analysis ◽

Unsaturated Flow ◽

Adjoint Operator ◽

Pressure Head ◽

Theoretical Modelling ◽

Operator Technique ◽

The Finite Element Method ◽

The Impact ◽

Clay Barriers

This paper illustrates the importance of sensitivity analysis in the design of clay barriers. Theoretical modelling simulations are performed using the finite element method in which realistic scenarios for unsaturated flow are conceived. Results show that the adjoint operator technique can be an efficient component to evaluate the impact of the thickness of the clay barriers as well as in the values of hydraulic conductivity values on pressure head distribution and integrated travel time.

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Controls on subsurface transport of sorbing contaminant

Hydrology Research ◽

10.2166/nh.2016.170 ◽

2016 ◽

Vol 48 (5) ◽

pp. 1226-1239 ◽

Cited By ~ 2

Author(s):

Ali A. Ameli

Keyword(s):

Unsaturated Flow ◽

Transport Model ◽

Infiltration Rate ◽

Water Systems ◽

Subsurface Transport ◽

Vertical Heterogeneity ◽

Kinetic Sorption ◽

The Impact ◽

Sorption Potential ◽

Sorption Characteristics

Subsurface transport of a sorbing contaminant is poorly understood and characterized. Here, a new semi-analytical saturated–unsaturated flow and transport model is coupled to a kinetic sorption algorithm to assess the impact of changes in the subsurface permeability architecture and flow rate on sorption characteristics. The model outputs reveal the pronounced effect of the rate of vertical decline in Ks on the frequency of occurrence and spatial distribution of subsurface sorption as well as the timing and rate of sorbing contaminants discharged into stream. Sorption potential is weakened with infiltration rate. The impact of infiltration rate on the decline in sorption potential becomes more accentuated as the degree of subsurface vertical heterogeneity in saturated hydraulic conductivity increases. Porosity pattern also impacts sorption characteristics; but its effects highly depend upon the degree of vertical heterogeneity in Ks. The results and methodology presented in this paper have potential implications for assessing water quality in integrated groundwater–surface water systems as well as designing remediation systems.

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Reclamation for aspen revegetation in the Athabasca oil sands: Understanding soil water dynamics through unsaturated flow modelling

Canadian Journal of Soil Science ◽

10.4141/cjss2010-035 ◽

2012 ◽

Vol 92 (1) ◽

pp. 103-116 ◽

Cited By ~ 16

Author(s):

J. J. Carrera-Hernández ◽

C. A. Mendoza ◽

K. J. Devito ◽

R. M. Petrone ◽

B. D. Smerdon

Keyword(s):

Soil Water ◽

Water Table ◽

Oil Sands ◽

Unsaturated Flow ◽

Water Dynamics ◽

Soil Water Dynamics ◽

Natural Conditions ◽

Athabasca Oil Sands ◽

Flow Modelling ◽

The Impact

Carrera-Hernández, J. J., Mendoza, C. A., Devito, K. J., Petrone, R. M. and Smerdon, B. D. 2012. Reclamation for aspen revegetation in the Athabasca oil sands: Understanding soil water dynamics through unsaturated flow modelling. Can. J. Soil Sci. 92: 103–116. Reclamation of mined areas in the Athabasca oil sands region is required by law, with the ultimate goal of revegetating to species characteristic of predisturbance native plant communities. To develop adequate reclamation strategies, an analysis of soil water dynamics is of utmost importance, as is understanding the impact of the thickness of the reclamation cover. In this work, soil water dynamics and fluxes at the water table were simulated for three reclamation scenarios and compared with the fluxes obtained for natural conditions assuming that aspen is the target reclamation species. According to the simulations, a reclamation thickness between 0.5 and 1.0 m can be used to provide water for revegetation. The numerical simulations show that the reclaimed landscapes have fluxes at the water table that exhibit less fluctuation than natural conditions. To limit the interaction between the water table and atmospheric fluxes, and to limit upward flux, the water table should be deeper than 2.0 m on reclaimed landscapes that use aspen for revegetation, particularly when reclamation takes place during a dry climatological cycle.

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An experimental study of the effect of motile bacteria on the fluid displacement in porous media

E3S Web of Conferences ◽

10.1051/e3sconf/202020508008 ◽

2020 ◽

Vol 205 ◽

pp. 08008 ◽

Cited By ~ 1

Author(s):

Boyoung Jeong ◽

Yumeng Zhao ◽

Dong-Hun Kang ◽

Sheng Dai

Keyword(s):

Porous Media ◽

Microfluidic Chip ◽

Interfacial Properties ◽

Time Lapse ◽

Flow In Porous Media ◽

Fluid Displacement ◽

Multiphase Fluid Flow ◽

Multiphase Fluid ◽

Displacement Patterns ◽

The Impact

Multiphase flow patterns in porous media largely depend on the properties of the fluids and interfaces such as viscosity, surface tension, and contact angle. Microorganisms in soils change the fluid and interfacial properties, and thus can alter multiphase fluid flow in porous media. This study investigates the impact of motile bacterium Escherichia coli (E. coli) on fluid displacement patterns in a microfluidic chip. The fluid displacement is observed during the saturation and the desaturation processes of the microfluidic chip with and without E.coli suspension. Time-lapse photography results show that the presence of E.coli alters the displacement patterns during the wetting and drying process and changes the residual saturation of the chip. Although studies of the impacts of motility on interfacial properties remain elusive, these results bring the expectation to the manipulation of multiphase transport in porous media and the adaptive control of industrial and environmental flow processes using active particles.

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The effect of ionic strength on surfactant-induced unsaturated flow

Canadian Geotechnical Journal ◽

10.1139/t10-096 ◽

2011 ◽

Vol 48 (4) ◽

pp. 644-654 ◽

Cited By ~ 6

Author(s):

Rashid Bashir ◽

James E. Smith ◽

Dieter E. Stolle

Keyword(s):

Surface Tension ◽

Ionic Strength ◽

Soil Water ◽

Unsaturated Flow ◽

Water Solution ◽

Pure Water ◽

Soil Column ◽

Time Domain Reflectometry ◽

Induced Flow ◽

The Impact

The effect of ionic strength of soil water on surfactant-induced unsaturated flow is investigated for the anionic surfactant DOWFAX 8390. Instrumented infiltration experiments were performed to study the impact of surfactant and ionic strength of the soil-water solution on unsaturated flow. A solution having a measured surface tension of 68 mN/m was prepared with 0.014% w/w DOWFAX using distilled water and applied to the soil column instrumented with time domain reflectometry probes and pressure transducer equipped tensiometers. Results of the experiment were compared with those of pure water to investigate surfactant-induced flow and the corresponding influence of the ionic strength of soil water. The DOWFAX solution behaved like a solution having a surface tension of 49 mN/m, which was directly attributed to the interaction between the surfactant and soil water. Soil-moisture characteristic curves for soil wetted with water and DOWFAX were also measured, and a scaling relationship as a function of reduced surface tension is proposed.

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The importance of preferential flow in controlling groundwater recharge in tropical Africa and implications for modelling the impact of climate change on groundwater resources

Journal of Water and Climate Change ◽

10.2166/wcc.2010.040 ◽

2010 ◽

Vol 1 (4) ◽

pp. 234-245 ◽

Cited By ~ 24

Author(s):

M. O. Cuthbert ◽

C. Tindimugaya

Keyword(s):

Soil Moisture ◽

Preferential Flow ◽

Unsaturated Flow ◽

Uniform Flow ◽

Richards Equation ◽

Tropical Africa ◽

Lateritic Soils ◽

Flow Models ◽

Spatial Coverage ◽

The Impact

An improved water table fluctuation technique for estimating recharge is applied to a sustained (10-year) groundwater level monitoring record in Uganda, a rare dataset for tropical Africa, and compared against results from soil moisture balance models (SMBMs) and unsaturated flow models. The results show that recharge is directly proportional to rainfall (long-term average rainfall is around 1200 mm/a), even during times when high soil moisture deficits are anticipated. This indicates that preferential and/or localized flow mechanisms dominate the recharge behaviour. SMBMs and unsaturated flow models, based on uniform flow governed by the Richards equation, are shown to be inappropriate for estimating recharge in this location underlain by lateritic soils. Given the large spatial coverage of lateritic soils both globally and in tropical Africa, and despite the convenience of physically based uniform flow models and, in particular, SMBMs, concern is raised over the use of such models for recharge estimation, and thus for exploring future trends due to climate or land use change, unless backed up by sufficient hydraulic data to enable the recharge processes to be confirmed. More research is needed to assess how widespread preferential flow may be within other major soil groups and climate zones.

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Rainfall-triggered slope instabilities under a changing climate: comparative study using historical and projected precipitation extremes

Canadian Geotechnical Journal ◽

10.1139/cgj-2015-0602 ◽

2017 ◽

Vol 54 (1) ◽

pp. 117-127 ◽

Cited By ~ 37

Author(s):

Joe D. Robinson ◽

Farshid Vahedifard ◽

Amir AghaKouchak

Keyword(s):

Upper Bound ◽

Extreme Precipitation ◽

Unsaturated Flow ◽

Precipitation Extremes ◽

Statistics Of Extremes ◽

Precipitation Patterns ◽

Extreme Precipitation Events ◽

Local Strength ◽

Precipitation Estimates ◽

The Impact

This study aims to quantitatively assess the impact of extreme precipitation events under current and future climate scenarios on landslides. Rainfall-triggered landslides are analyzed primarily using extreme precipitation estimates, derived using the so-called stationary assumption (i.e., statistics of extreme events will not vary significantly over a long period of time). However, extreme precipitation patterns have shown to vary substantially due to climate change, leading to unprecedented changes in the statistics of extremes. In this study, a nonstationary approach, applied to climate model simulations, is adopted to project the upper bound of future precipitation extremes. Future precipitation estimates are obtained from the coupled model intercomparison project phase 5 (CMIP5) simulations. Baseline (historical) and projected (future) precipitation extremes are obtained for a study area near Seattle, Washington. The precipitation patterns are integrated into a series of fully coupled two-dimensional stress – unsaturated flow finite element simulations. The responses of the baseline and projected models at a 7 day rainfall duration obtained for a 50 year recurrence interval are compared in terms of the local strength reduction factor, displacements, matric suctions, and suction stresses. The results indicate that the usage of historical rainfall data can lead to underestimations in the hydromechanical behavior of natural slopes where locally increased transient seepage rates occur from the upper bound of future extreme precipitation estimates.

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Impact of density on the hydraulics of peat filters

Canadian Geotechnical Journal ◽

10.1139/t01-047 ◽

2001 ◽

Vol 38 (6) ◽

pp. 1213-1219 ◽

Cited By ~ 8

Author(s):

Paula L Kennedy ◽

Paul J Van Geel

Keyword(s):

Unsaturated Flow ◽

Mine Drainage ◽

Effective Porosity ◽

Septic Tank ◽

Dry Density ◽

Model Simulations ◽

Septic Tank Effluent ◽

Commercial Sources ◽

The Impact ◽

Soil Moisture Retention

Peat filters have been used to treat septic tank effluents from domestic and commercial sources, landfill leachate, and acid mine drainage. A better understanding of the hydraulics and impact of the organic loading on these types of systems will enhance the application of peat filter systems. This paper presents the results of a field study to evaluate the hydraulics of a peat filter used to treat the septic tank effluent from a public school west of Ottawa, Ontario, Canada. The filter was instrumented with tensiometers and transducers to monitor the pore-water pressures in response to a pulse of septic tank effluent. Samples of peat were collected to determine the dry density profile with depth. The soil moisture retention curve, effective porosity, and hydraulic conductivity as a function of dry density were determined in laboratory experiments. A one-dimensional unsaturated flow model was used to predict the pressure response due to a pulse. Two model scenarios were evaluated to demonstrate the impact of density variations on model simulations. Model simulations that accounted for dry density variations with depth measured in the field more accurately simulated the pressure responses measured in the field.Key words: unsaturated flow, peat, filters, septic, modelling, density.

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