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Estimation of the retention and unsaturated hydraulic conductivity functions is essential to effectively provide input for water flow and transport simulation and prediction. A parameter optimization procedure is shown as a promising tool to estimate inversely these hydraulic function parameters from transient soil matric potential and cumulative s...
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... 3.0-cm-long ceramic ring of the extraction device (l ) was in- serted in the center of the soil column (r 0), with its center located 6.3 cm below the soil surface (d). Three hypothetical tensiometers were installed (see also in Figure 2) at the fol- lowing positions: r 4.0 cm and z 18 cm (T 1 ); r 6.0 cm and z 18 cm (T 2 ); and r 6.0 cm and z 0.3 cm (T 3 ). Forward hypothetical simulations were done using a sandy loam and silt soil, for which Carsel and Parrish [1988] presented the hydraulic parameters. ...
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... measure- ments yielded K cer 8.334 10 4 cm h 1 . A schematic of the laboratory experiment, which includes the burette assembly for vacuum extraction and the boundary conditions, is presented in Figure 2. The soil used was a Co- lumbia fine sandy loam. ...
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... applying vacuum to the air phase in the burette, the extracted soil water flows into the burette with the pressure of the inflow end equal to the applied vacuum. The volume of extracted water was measured both manually and using a pressure transducer in the bottom of the burette (Figure 2). A film of oil to prevent water loss by evaporation covered the water in the burette. ...
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... is therefore anticipated that the sensitivity of soil matric potential measurements will increase using step increments in vacuum (multistep extraction) rather than using a single vac- uum step, since a multitude of vacuum increments create a series of periods with increased soil matric potential gradients near the extraction device. Figure 5 shows the sensitivity (s) (Equation (11)) of soil matric potential (h 2 ) at T 2 (Figure 2) and cumulative extraction volume (Q) as a function of time for all optimized parameters for the loamy soil. When correcting for differences in absolute magnitude between Q and h, it becomes clear that the sensitivity of Q to any of the listed parameters is at least 5 times as large than the sensitivity of h. Figure 5 demonstrates that both cumulative extraction vol- umes and matric potentials are most sensitive to parameters and n and least sensitive to r and K cer . ...
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Citations
... However, uncertainties and limitations in terms of prolonged testing times, expensive equipment, and limitations in measuring range make the determination of HCF through direct measurements very rare [19,43,48]. To overcome these difficulties, many researchers have proposed different estimation methods or indirect methods to obtain the HCF of the soil [21,36,52,65,66,74]. Herein, a new methodology is defined aiming at calibrating the unsaturated hydraulic parameters of the soil in a slope subjected to rainfall, when monitoring data of soil water content are available. ...
Numerous studies have looked at rainfall infiltration as a triggering factor for rainfall-induced landslides. In addition to rainfall characteristics, soil hydraulic properties are recognized to play a crucial role in instability mechanisms. This study proposes a methodology for assessing the soil-water characteristic curve and hydraulic conductivity function through finite-element seepage modelling of physical model tests. The approach is applied to an instrumented, small-scale slope model built with uniformly graded sand with a 30 degree inclination, exposed to homogeneous rainfall until the occurrence of failure. In a first stage, a sensitivity analysis is carried out to assess the influence of the Mualem–van Genuchten model parameters on the slope response. For this purpose, six physically based indicators are utilized to compare the numerical modelling results with the experimentally obtained data regarding the hydraulic response of the slope model. In the subsequent stage, a trial-and-error calibration stage is conducted to determine the set of parameters for which the difference between the numerically and experimentally acquired data is minimized. Ultimately, the suggested methodology facilitates the assessment of the optimal set of hydraulic parameters, to which both the sensitivity analysis and the trial-and-error calibration phase are anchored. The approach has demonstrated its effectiveness in calibrating the unsaturated hydraulic properties of the considered soil, as it properly addresses the physical mechanisms associated with rainfall infiltration in a slope.
... Interestingly, for known characteristic volumetric water contents, only the saturated hydraulic conductivity, K s , is required to apply the described procedure in dimensional terms, indicating that such procedure could be used as an inverse method to determine K s , according to an objective function to be minimized, on the basis of monitored soil water content profiles in the field or in the lab, and on covariance (weighting) matrices, which provide information about the measurement accuracy, as well as any possible correlation between measurement errors and/or parameters involved (Clausnitzer et al. 1995;Inoue et al. 1998;Šimůnek et al. 2011). ...
... In conclusion, this simple simplified approach could even open doors to estimate as an inverse method the saturated hydraulic conductivity, by monitoring water content profiles in the field or in the lab (Inoue et al. 1998). It needs to remark that (Table 3.1), for a time-variable rainfall intensity, i(t), indicated in (a), (c), (e), (g) (secondary axis), water content profiles (θ), at the depths 10, 30, 50, 70 and 90 cm, versus the time t, and related runoff (i−K s ), and drainage (K) fluxes. ...
In the hydrologic literature, to model water flow in unsaturated soils, the Richards equation is usually applied, allowing the main components of the hydrologic cycle, as rainfall partitioning into surface runoff and infiltration, to be determined. The Richards equation is highly nonlinear, making it very challenging to derive analytical solutions. Recently, for constant rainfall intensity, under the simplified hypothesis of gravity-driven infiltration, and by assuming a capacitance framework, a simplified solution of the Richards equation that considers the Brooks and Corey hydraulic conductivity function, was suggested. By maintaining the assumption that the infiltration process is dominated by gravity, the objective of this paper is to relax the capacitance sketch applied to only one reservoir, by replicating the internal water content travel times through the discretization of the soil profile into multiple tanks connected in series. First, the previous analysis is briefly summarized, which is useful for the further developments. Then, for a fixed soil pore connectivity index (c = 0.5), which could be assumed for sandy soils, the same approach is extended to multiple non-linear reservoirs to model water balance components, achieving more reliable conditions. The presented approach could be not affected by uncertainty, since it is simply hydraulic, provided the hypotheses c = 0.5 and the assumption of a gravity-driven infiltration are satisfied. The suggested solution was compared with that derived by the Richards equation (via Hydrus-1D), where the gravity-driven hypothesis is relaxed the effect of the number of reservoirs was analyzed, and applications for both constant and time-variable rainfall intensity were performed.KeywordsGravity-driven infiltrationNon-linear reservoirsSandy soilsSimplified solutionsWater balance components
... Moreover, considering that the adopted hydraulic sketch can lead to the drainage and runoff excess volume and intensity, the transportation of the runoff generated could also be modelled by using the aforementioned solutions, where also hyperbolic tangent and the hyperbolic cotangent functions appeared (Agnese et al. 2001), which verified those introduced by Horton (1939), for dry antecedent conditions. Interestingly, for known characteristic volumetric water contents, only the saturated hydraulic conductivity, K s , is required to apply the described procedure in dimensional terms, indicating that such procedure could be used as an inverse method to determine K s , according to an objective function to be minimized, on the basis of monitored soil water content profiles in the field or in the lab, and on covariance (weighting) matrices, which provide information about the measurement accuracy, as well as any possible correlation between measurement errors and/or parameters involved (Clausnitzer et al. 1995;Inoue et al. 1998;Šimůnek et al. 2011). Thus, this approach could have relevant implications in determining the field saturated hydraulic conductivity, especially for high spatial variability conditions (Leij et al. 2004;Fan et al. 2016), both in the lab and in the field . ...
... In conclusion, this simple simplified approach could even open doors to estimate as an inverse method the saturated hydraulic conductivity, by monitoring water content profiles in the field or in the lab (Inoue et al. 1998). It needs to remark that (Table 3.1), for a time-variable rainfall intensity, i(t), indicated in (a), (c), (e), (g) (secondary axis), water content profiles (θ), at the depths 10, 30, 50, 70 and 90 cm, versus the time t, and related runoff (i−K s ), and drainage (K) fluxes. ...
Typhoon Ulysses (Vamco) brought about more than 300 flooding incidents in the Philippines in November 2020. The Cagayan Valley Region was reported with the highest worth of damage to infrastructure and agriculture. In this study, synthetic aperture radar images were used to analyze the effect of Typhoon Ulysses in the region. The VV and VH bands of Sentinel 1 were used to detect the flooded areas before (November 1) and after (November 13) the typhoon. The VH band was found more effective at detecting flooded and agricultural areas (72,722.30 ha and 37,736.70 ha, respectively) than the VV band (69,501.12 ha and 35,606.59 ha, respectively). The VV polarization was found to be more suited for monitoring vegetation, whereas the VH polarization is more suited for estimating flood extent, as based on the backscatter intensity of the two polarizations before and during flooding on representative places. The significantly high amount of rainfall (200–300 mm) received, low elevation and slope of the affected areas, and the volume of water released from Magat Dam were noted as the contributing factors to the massive flooding event. More than 35,000 ha of rice areas were flooded in Alcala town. Results showed that the standing crops I n Alcala increased after the typhoon (from 660.55 to 923.16 ha) when the flood subsided. This was determined using MODIS, Sentinel 1 and 2, and a 0.3 NDVI threshold. It was also noted that before the typhoon, most of the rice crops were at a stage of maturity and were ready for harvest a few days later.KeywordsGISRemote sensingFlood assessmentTyphoon UlyssesNDVI
... Moreover, considering that the adopted hydraulic sketch can lead to the drainage and runoff excess volume and intensity, the transportation of the runoff generated could also be modelled by using the aforementioned solutions, where also hyperbolic tangent and the hyperbolic cotangent functions appeared (Agnese et al. 2001), which verified those introduced by Horton (1939), for dry antecedent conditions. Interestingly, for known characteristic volumetric water contents, only the saturated hydraulic conductivity, K s , is required to apply the described procedure in dimensional terms, indicating that such procedure could be used as an inverse method to determine K s , according to an objective function to be minimized, on the basis of monitored soil water content profiles in the field or in the lab, and on covariance (weighting) matrices, which provide information about the measurement accuracy, as well as any possible correlation between measurement errors and/or parameters involved (Clausnitzer et al. 1995;Inoue et al. 1998;Šimůnek et al. 2011). Thus, this approach could have relevant implications in determining the field saturated hydraulic conductivity, especially for high spatial variability conditions (Leij et al. 2004;Fan et al. 2016), both in the lab and in the field . ...
... In conclusion, this simple simplified approach could even open doors to estimate as an inverse method the saturated hydraulic conductivity, by monitoring water content profiles in the field or in the lab (Inoue et al. 1998). It needs to remark that (Table 3.1), for a time-variable rainfall intensity, i(t), indicated in (a), (c), (e), (g) (secondary axis), water content profiles (θ), at the depths 10, 30, 50, 70 and 90 cm, versus the time t, and related runoff (i−K s ), and drainage (K) fluxes. ...
Samples of leachate from the Osisioma open dumpsite and water from four boreholes from the surrounding residence were collected using the four cardinal point model. The sampled boreholes were assigned BH 1, BH 2, BH 3, and BH 4 with distances of 80, 251, 348, and 455 (m) respectively from the location of the dumpsite which is at the center as regards to the cardinal point model used. Physicochemical and microbiological parameters were analyzed to determine the quality of the water. pH, Conductivity, Temperature, TDS, Colour, alkalinity, DO, BOD, COD, Nitrate, Nitrate-Nitrogen, Iron, Chlorine, Chromium, Copper, Arsenic, Lead, Zinc, total bacterial count, E. coli and total coliform count were analyzed. pH ranged from 5.2 to 6.3 in borehole water indicating toxic pollution and was neutral (7.1) in the leachate sample. The temperature of borehole water and leachate ranged from 26.70 to 29.70 °C, Colour (Platinum Cobalt Unit) ranged from 13 to 13850PCU in borehole water and leachate. The concentrations of, Lead, Chromium, Copper, Nitrate, Chlorine, Zinc and Iron ranged from; Lead 0.001 in BH 3 to 0.125 in BH 1, Copper 0.00 in BH 3 to 0.08 in BH 4, Chromium 0.014 in BH 3 to 0.037 in BH 2, Nitrate 234.2 in BH 4 to 343.0 in BH 1, Chlorine 0.35 in BH 3 to 1.71 in BH 4, Zinc; 0.09 mg/L in BH 3 to 0.25 in BH 4 and Iron 0.19 in BH 3 to 0.42 in BH 4 respectively. Alkalinity in water sample was below the WHO permissible limit. Arsenic and Iron were above the permissible limits in BH 1 (0.031 and 0.40 mg/L) and BH 4 (0.020 and 0.42 mg/L). Lead also exceeded the limit in BH 1 at 0.125 mg/L. DO, nitrate, nitrate-nitrogen and chlorine exceeded the limits across all the boreholes water sampled. In the microbiological analysis, Total Bacteria Count, E. coli, and Total Coliform Count were analyzed with mean values of 62.00, 6.50 and 23.75 respectively. All the microbial parameters analyzed exceeded WHO permissible limits which make the water unfit for direct consumption. The variations in concentration of microbiological parameters were in respect to distance from the dumpsite and elevation of the sampling points. There is therefore a need for major water treatment to be carried out on the borehole water before human consumption. Dumping of fresh refuse in the study area should be discouraged with the use of sanctions and fines on defaulters. Government should adopt eco-friendly solid waste disposal management systems such as sorting before disposal, incineration, landfill, waste conversion to biogas and compost as well as provision of portable water to reduce indiscriminate borehole construction to preserve the soil structure.KeywordsBoreholeDumpsiteGroundwaterLeachateLandfillPollutionWaste
... Moreover, considering that the adopted hydraulic sketch can lead to the drainage and runoff excess volume and intensity, the transportation of the runoff generated could also be modelled by using the aforementioned solutions, where also hyperbolic tangent and the hyperbolic cotangent functions appeared (Agnese et al. 2001), which verified those introduced by Horton (1939), for dry antecedent conditions. Interestingly, for known characteristic volumetric water contents, only the saturated hydraulic conductivity, K s , is required to apply the described procedure in dimensional terms, indicating that such procedure could be used as an inverse method to determine K s , according to an objective function to be minimized, on the basis of monitored soil water content profiles in the field or in the lab, and on covariance (weighting) matrices, which provide information about the measurement accuracy, as well as any possible correlation between measurement errors and/or parameters involved (Clausnitzer et al. 1995;Inoue et al. 1998;Šimůnek et al. 2011). Thus, this approach could have relevant implications in determining the field saturated hydraulic conductivity, especially for high spatial variability conditions (Leij et al. 2004;Fan et al. 2016), both in the lab and in the field . ...
... In conclusion, this simple simplified approach could even open doors to estimate as an inverse method the saturated hydraulic conductivity, by monitoring water content profiles in the field or in the lab (Inoue et al. 1998). It needs to remark that (Table 3.1), for a time-variable rainfall intensity, i(t), indicated in (a), (c), (e), (g) (secondary axis), water content profiles (θ), at the depths 10, 30, 50, 70 and 90 cm, versus the time t, and related runoff (i−K s ), and drainage (K) fluxes. ...
1.Provides the most updated references on water resources management in arid regions
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... In the absence of measured data, we used the Rosetta pedotransfer functions of Schaap et al. (2001) to estimate initial values of the VGM parameters from measured sand, silt, and clay percentages, and the bulk density. Previous studies have shown that the residual water content θr is generally the least sensitive of the VGM parameters to the calibration data (e.g., Inoue et al., 1998;Šimůnek et al., 1998;Vrugt et al., 2001). We note here that our tensiometers could not collect pressure head data below about -8 m. ...
Field tests were carried out to estimate effective unsaturated soil hydraulic properties of layered residual soils in Rio de Janeiro, southeastern Brazil. Data of this type are important for understanding the initiation of rainstorm-induced soil landslides, which often occur in the state of Rio de Janeiro as well as other areas having similar geologic settings and climate conditions. Tests were carried out using a simplified field approach, referred to as the Monitored Infiltration Test, which requires only a tensiometer to measure pressure heads below the wetting front, triggered by flow from a Mariotte bottle which maintains a constant pressure at the top edge of the soil profile. The data can then be analyzed by numerical inversion using the HYDRUS-2D software package. The test is relatively fast since no steady-state flow conditions are needed, and versatile since the test can be carried out quickly on steep slopes with the help of a manual auger. Soil water retention and the unsaturated hydraulic conductivity functions were obtained for a range of young, mature and saprolitic residual soils. The effective hydraulic properties of the distinct residual soil layers can be quite large, reflecting a need to provide a careful analysis of field-scale hydraulic heterogeneity in geotechnical analyses.
... For example, Kool et al. (1985), Eching and Hopmans (1993), van Dam et al. (1992, Šimunek et al. (1998), Wayllace and Lu (2012) used the parameter estimation method on experimentally obtained data in the laboratory. The same method was applied to in-situ measurements (e.g., Šimunek and van Genuchten, 1996;Gribb, 1996;Inoue et al., 1998;Nakhaei and Šimunek, 2014). Despite the possibility of estimating the HCF without the need for direct Table 1 Mean values of the basic properties of the residual soil samples used in the study (Peranić et al., 2018). ...
Rainfall is a major triggering factor of landslides in flysch deposits along Europe. Physical and mechanical changes of flysch rock masses caused by the weathering process, result in a complex soil profile with residual soil typically present at the slope surface. The research encompasses residual soils from the Rječina River Valley in Croatia. Built in flysch deposits, the valley is known for several deep-seated and shallow historical landslides. This manuscript presents the hydro-mechanical properties of the soil existing in unsaturated zone of the slope that could play an important role in landslide activation on flysch slopes. Presented unsaturated soil property functions are essential for modelling of the transient rainfall infiltration process and how it affects the stability of flysch slopes in time. For the first time, shear strength and hydraulic conductivity determination were performed in saturated and unsaturated soil conditions, using both the intact as well as remolded samples of the residual soil form flysch rock mass. The results indicate that, in order to correctly define hydraulic and mechanical properties of the in-situ soil, measurements have to be performed on intact samples. Also, the presented results highlight the importance of hysteresis effects and hydraulic paths that fine-grained residual soil has been subjected to in the past.
... However, these approaches may not be representative especially at large scale representation and are mostly robust only at large water content. Field measurement methods have proved also to be attractive especially for soil hydraulic properties determination (Gribb, 1996;Gribb et al., 1997;Inoue et al., 1998). Despite the prominence use of the method in industrial context, field measurements for transport problems are generally tedious, time consuming, and expensive (Abbasi et al., 2003;Ramos et al., 2006). ...
This paper studies the estimation of unsaturated soil parameters based on thermal, moisture, and solute characteristics, which are important factors that affect productivity and the environment. The objective of this investigation was to determine optimal hydraulic parameters in unsaturated soil. The soil thermal, moisture, and solute transport processes are approached using one‐dimensional isothermal models characterized with nonlinear permeability effects, sorption, and reaction that generally cause considerable experimental and numerical difficulties. The spectral element method is presented for space discretization while the time scheme is constructed along the fully implicit approach with the modified Picard iterative procedure. The iterative Levenberg‐Marquardt optimization algorithm is adopted for the inverse process. The reliability and performance of the studied model is conducted using refinement indicators based on error, residual, and variance analyses, which allow drawing more representative uncertainty of model parameters estimation. Good agreement with the nonlinear optimization of soil hydraulic parameters estimated and true values is obtained. The estimated responses from respective shape curves show relatively small variability. A consideration of ionic diffusional and average temperature effects was revealed, indicating that the change of one of these factors might not necessarily improve parameter identification responses. For soil moisture content ranges between 0.04 and 0.5 cm³ cm⁻³, average temperature input from 20 to 40 ° C as well as when the ionic molecular diffusion coefficient is greater than 10 cm² hr⁻¹, a rough representation of moisture, thermal, and hydrochemical characteristics might be sufficient to estimate soil hydraulic parameters.
... 8 ⋅ 10 −5 m ∕ s and capillary pressure head | ini | of − 30 cm are adjusted to match the experimental data, and are in good agreement with other studies using this type of soil (e.g. Inoue et al., 1998 ). Further values used in our numerical simulation are presented in Table 1 . ...
A realistic temperature estimation is crucial for many earth-science applications, ranging from hydro-thermal systems to plant physiology. The most common approach to calculate the temperature in multi-phase systems assumes immediate local thermal equilibrium (LTE) between the phases. However, local thermal equilibrium between the phases is not applicable in various scenarios like during the infiltration of rain or melt water in frozen soil, limiting the applicability of the approach and inhibiting the implementation of separate initial and boundary conditions for non-equilibrium situations. In local thermal non-equilibrium (LTNE) models, phase temperatures are described separately to the cost of additional differential equations and an explicitly formulated heat transfer between the phases. Especially a cumbersome parameterization of the explicit heat transfer restricts the use of the LTNE models in multi-phase conditions so far. In this work, we derive a general local thermal non-equilibrium model for dynamic, partly saturated porous media. Heat transfer between the phases is described explicitly using well-known semi-empirical parameterization accounting for velocity changes of the mobile phases. The change in volume fraction introduces an additional term in the heat equation, causing a coupling with the hydraulic model. We validate our model with a numerical simulation of historic experimental data from soil infiltration experiments of warm and cold water into drained soil, posing a perfect example of local thermal non-equilibrium conditions between the phases. Experimentally obtained mixture temperatures are reproduced within experimental accuracy. We further show the benefits of our model by applying it to rainwater infiltration into cold soil. Besides a consistent formulation of initial and boundary conditions, the derived model allows physically based conclusions about the thermal state of the separate phases.
... MSE has become the standard efficiency criterion of inverse modeling to estimate soil property parameters, especially for the dynamics-based groundwater model [7,15,37]. However, many studies together with the results of this study show that inverse modeling with only the soil seepages/outflows cannot yield accurate model parameter estimates [6,[38][39][40][41]. In theory (i.e., excluding any model inadequacy and input and observation errors), however, it is possible to obtain accurate estimates via inverse modeling [42]. ...
A practical formal likelihood function (L) is developed to separate model structure errors and observation errors by the separation of correlated and uncorrelated model residuals. L overcomes the time-consuming problem of likelihood functions proposed by previous studies, and combines the Mean Square Error (MSE) and first-order Auto-Regression (AR(1)) models. For comparison of the effect of different error models, MSE, AR(1), and L are used as efficiency criteria to calibrate the three-dimensional variably saturated ground-water flow model (MF2K-VSF) based on the soil tank seepages of rainfall–runoff experiments. Results of L are nearly the same as those of AR(1) due to negligible observational errors. Although all calibrated models well mimic the seepage discharges, MF2K-VSF with MSE cannot capture the groundwater level and soil suction processes because of the considerable autocorrelation of model residuals owing to model inadequacies (e.g., neglect of the soil moisture hysteresis), which obviously violates the statistical assumption of MSE. By contrast, L accounts for the model structural errors and thus enhances the reliability of hydrological simulations.
