Moisture equilibrium in the vertical in swelling soils. II. Applications

Soil Research ◽  
1969 ◽  
Vol 7 (2) ◽  
pp. 121 ◽  
Author(s):  
JR Philip
Keyword(s):  
Hydraulic Conductivity ◽  
Water Table ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Moisture Distribution ◽  
Specific Yield ◽  
Swelling Soils ◽  
Total Potential ◽  
Equilibrium Distributions ◽  
Moisture Profiles

The paper discusses, with the aid of calculated examples, applications in hydrology and soil mechanics of the analysis developed in Part I. Various classical concepts of groundwater hydrology fail completely for swelling soils. The distributions of saturation and of hydraulic conductivity relative to the water table differ entirely from the conventional picture. Variations in surface topography affect moisture distribution in swelling soils. The theory of this effect is developed for topographies that are not too steep and is illustrated by examples. The equilibrium distributions found would be classically interpreted as disequilibrium states persisting because of small hydraulic conductivity; but, in fact, the moisture differentials are maintained, not by a lack of conductivity, but by a lack of difference in total potential. The variation of specific yield with water table elevation and stratum thickness in swelling soils is basically different from that in non-swelling soils. The analysis of Part I is used to discuss the following topics in soil mechanics: the variation of equilibrium soil levels with water-table depth, and with water depth over the soil; the effect of surface loading on equilibrium moisture profiles and on soil levels. Extension of the analysis to two- and three-dimensional systems is treated briefly.

Moisture equilibrium in the vertical in swelling soils. I. Basic theory

Soil Research ◽  
1969 ◽  
Vol 7 (2) ◽  
pp. 99 ◽  
Author(s):  
JR Philip
Keyword(s):  
Soil Mechanics ◽  
Scalar Potential ◽  
Moisture Ratio ◽  
Moisture Distribution ◽  
Soil Physics ◽  
Swelling Soils ◽  
Total Potential ◽  
Common Notion ◽  
Classical Behaviour ◽  
Equilibrium Profile

The classical methodology of the scalar potential is used to develop the theory of equilibrium moisture distribution in the vertical in swelling soils. In addition to the well-known moisture potential � and the gravitational potential -z (z being the vertical ordinate, taken positive downward), the total potential � includes a further component �, the overburden potential. It is shown that � = de/d� [P(Zo) + ?zzo] (A) where e is the void ratio, 6 is the moisture ratio, P(zJ is the load (if any) at the surface z = z,, and y is the apparent wet specific gravity. The equilibrium condition that � be constant in depth reduces to a first-order differential equation, the solutions of which represent equilibrium moisture profiles. The singular solution � = �pt for all z > zo (B) separates two distinct classes of non-singular solutions. �p, designated the pycnotatic point, is the moisture ratio at which � assumes its maximum value. Swelling soils satisfying certain conditions (which appear to be theoretically reasonable and agree with the data of soil physics and soil mechanics) possess one, and only one, pycnotatic point. In such soils, then, three distinct types of equilibrium profile occur: (i) Hydric profiles, for which the surface moisture ratio �o > �p. 6 decreases with increasing z, asymptotically approaching 8, at great depths. (ii) Pycnotaticprojiles, for which 8, = aP and equation (B) is satisfied. (iii) Xeric profiles, for which �o < �p. � increases with z, asymptotically approaching �p at great depths. The physical significance of this result is discussed with the aid of calculations for an illustrative example. The hydrology of swelling soils is entirely different in character from classical hydrological behaviour, which ignores the consequences of volume change. Contrary to a common notion, the effects of overburden potential manifest themselves right to the surface of the soil: it is not the magnitude of n, but that of d�/dz, which is important. The effect of swelling on the behaviour of the soil water may be crudely summarized as follows: Gravity operates completely in reverse to the expectations of classical theory in the 'normal' part of the hydric range; its effect diminishes to zero at the pycnotatic point; and it approaches classical behaviour at the dry end of the xeric range. Applications of the analysis to equilibrium states in hydrology and soil mechanics are treated in Part II. In later papers the concept of the overburden potential is applied to steady vertical flows and to infiltration in swelling soils.

scholarly journals A quasi-three-dimensional model for predicting rainfall-runoff processes in a forested catchment in Southern Finland

2000 ◽  
Vol 4 (1) ◽  
pp. 65-78 ◽  
Author(s):  
H. Koivusalo ◽  
T. Karvonen ◽  
A. Lepistö
Keyword(s):  
Soil Moisture ◽  
Water Table ◽  
Unsaturated Soil ◽  
Water Movement ◽  
Three Dimensional ◽  
Moisture Distribution ◽  
Richards Equation ◽  
Rainfall Runoff ◽  
Forested Catchment ◽  
Soil Moisture Distribution

Abstract. Runoff generation in a forested catchment (0.18 km2) was simulated using a quasi-three-dimensional rainfall-runoff model. The model was formulated over a finite grid where water movement was assumed to be dominantly vertical in the unsaturated soil zone and horizontal in the saturated soil. The vertical soil moisture distribution at each grid cell was calculated using a conceptual approximation to the one-dimensional Richards equation. The approximation allowed the use of a simple soil surface boundary condition and an efficient solution to the water table elevation over the finite grid. The approximation was coupled with a two-dimensional ground water model to calculate lateral soil water movement between the grid cells and exfiltration over saturated areas, where runoff was produced by the saturation-excess mechanism. Runoff was an input to a channel network, which was modelled as a nonlinear reservoir. The proposed approximation for the vertical soil moisture distribution in unsaturated soil compared well to a numerical solution of the Richards equation during shallow water table conditions, but was less satisfactory during prolonged dry periods. The simulation of daily catchment outflow was successful with the exception of underprediction of extremely high peak flows. The calculated water table depth compared satisfactorily with the measurements. An overall comparison with the earlier results of tracer studies indicated that the modelled contribution of direct rainfall/snowmelt in streamflow was higher than the isotopically traced fraction of event-water in runoff. The seasonal variation in the modelled runoff-contributing areas was similar to that in the event-water-contributing areas from the tracer analysis.

Moisture profiles in swelling soils

Soil Research ◽  
1974 ◽  
Vol 12 (2) ◽  
pp. 71 ◽  
Author(s):  
T Talsma
Keyword(s):  
Water Table ◽  
Water Movement ◽  
Moisture Gradient ◽  
Clay Soils ◽  
Upward Flow ◽  
Swelling Soils ◽  
Equilibrium Profile ◽  
Moisture Profiles

In situ moisture profiles are examined, in two soils of clay texture and in a loam, for the condition of equilibrium about a water table. In addition, moisture profiles during periods of approximately steady upward flow are examined in one of the soils of clay texture. Equilibrium moisture profiles in the clay soils are typical of the 'hydric' profiles which have been predicted for swelling materials. Upward water movement occurs against the moisture gradient. The equilibrium profile in the loam is typical of those observed for non-swelling materials.

Drawdowns at the Free Water Table During Pumping Tests in Artesian and Semiartesian Aquifers

1980 ◽  
Vol 11 (3-4) ◽  
pp. 159-168 ◽  
Author(s):  
Henrik Kærgaard
Keyword(s):  
Water Table ◽  
Free Water ◽  
Pumping Test ◽  
Water Withdrawal ◽  
Specific Yield ◽  
Minor Role ◽  
Long Term Effects ◽  
Long Term Storage ◽  
Term Storage

In an earlier paper I have shown an example of how long term drawdowns can be used for the computation of long term storage in artesian and semiartesian areas. In most cases the long term storage is more or less equivalent to the specific yield at the water table; the storage mechanisms of consolidation playing a minor role in long term situations. The specific yield in artesian areas is a very important parameter in the prediction of long term effects of ground water withdrawal. Especially the stream depletion will often mainly be governed by draw-downs in upper nonpumped aquifers near the water table, and these drawdowns depend to a great extent on the specific yield at the water table. A determination of long term storage will often necessitate long term draw-down data, however, under certain circumstances a determination can be made on the basis of a pumping test of limited duration (3-5 weeks) provided drawdown observations at the water table can be made. In this paper some formulas dealing with water table drawdowns in different geohydrologic systems are reviewed, and two cases in which these formulas have been used in practice are presented.

EFFECT OF SPATIAL VARIABILITY IN HYDRAULIC CONDUCTIVITY ON WATER TABLE DRAWDOWN

1997 ◽  
Vol 40 (2) ◽  
pp. 371-375
Author(s):  
S. O. Prasher ◽  
M. Singh ◽  
A. K. Maheshwari ◽  
R. S. Clemente
Keyword(s):  
Hydraulic Conductivity ◽  
Spatial Variability ◽  
Water Table

scholarly journals Three-dimensional hydraulic conductivity upscaling in groundwater modeling

2010 ◽  
Vol 36 (10) ◽  
pp. 1224-1235 ◽  
Author(s):  
Haiyan Zhou ◽  
Liangping Li ◽  
J. Jaime Gómez-Hernández
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Modeling ◽  
Three Dimensional

scholarly journals Simulation and Assessment of Groundwater for Domestic and Irrigation Uses

2019 ◽  
Vol 5 (9) ◽  
pp. 1877-1892 ◽  
Author(s):  
Majed Rodhan Hussain ◽  
Basim Sh. Abed
Keyword(s):  
Cross Sections ◽  
Three Dimensional ◽  
Water Quality Assessment ◽  
Alluvial Fan ◽  
Water Levels ◽  
Specific Yield ◽  
Annual Rainfall ◽  
Steady State Condition ◽  
Groundwater Samples ◽  
One Year

The alluvial fan of Mandali located between latitude 30˚45’00” N longitude 45˚30’00” E in east of Diyala Governorate, Iraq. Thirty-five wells were identified in the study area with average depth of 84 m and estimated area of 21550 ha. A three-dimensional conceptual model was prepared by using GMS program. From wells cross sections, four geological layers have been identified. The hydraulic conductivity of these layers was calculated for steady state condition, where the water levels for nine wells distributed over the study area were observed at same time. Afterward, PEST facility in the GMS was used to estimate the aquifer hydraulic characteristics. Other characteristics such as storage coefficient and specific yield have been determined from one year field observations that were collected by General Authority of Groundwater, Diyala Governorate. Also, the observations were used for calibration of unsteady state model. Then wells were hypothetically redistributed and increased to 103 wells, assuming a distance of 1500 m between the wells, a well productivity rate of were 7 l/s, annual rainfall rate was used for recharging. Three different wells operating times were suggested and these 6, 12, and 18 hr/day with total discharge of 150, 300, 450 m3/day and maximum drawdown of 7, 11, and 20 m respectively. For water quality assessment, the collected groundwater samples were analysed at the laboratory.  Results showed that the TDS in all wells was ranged from 1000-3000 mg/l but TDS in well number 18 was exceeded 3000 mg/l which indicate that the groundwater in this well is not recommended to be used for irrigation. According to Iraqi standard for drink (IQS 2009), it can be used for drinking if saline treatment units were provided.

scholarly journals Soil water management problems using fuzzy arithmetic

2013 ◽  
Vol 11 (4) ◽  
pp. 556-565
Keyword(s):  
Hydraulic Conductivity ◽  
Uncertain Data ◽  
Triangular Fuzzy Number ◽  
Effective Porosity ◽  
Specific Yield ◽  
Fuzzy Arithmetic ◽  
Two Dimensional ◽  
Fuzzy Analysis ◽  
Management Problems ◽  
Α Level

Drainage management problems are usually very hard to simulate due to the uncertainty of the hydraulic parameters involved. Fuzzy analysis is one of the available tools that can be used for such problems, involving uncertain data. A fuzzy analysis approach usually involves the consideration of several α-level cuts and an analytical approach or an explicit scheme approach for the PDE's discretization. Several application examples of this approach are listed in the literature, including uncertainty in hydraulic conductivity, specific yield, transmissivities, porosities, dispersivities, and deoxygenation rate coefficient. A methodology for the simulation of drainage problem having vague values of hydraulic parameters is introduced in this paper, and an analytical solution for a two-dimensional drainage application is presented. The two-dimensional problem of drainage is handled using fuzzy analysis by defining the hydraulic conductivity K as a triangular fuzzy number (TFN). The method of interval analysis is used in all the α-level cut examples. A solution is obtained using eleven α-level cuts and also solutions for two, three, and five α-level cuts are presented. Trials for different values of effective porosity are also performed. Finally conclusions on the necessary number of α-cuts utilized for drainage problems are drawn.

scholarly journals Large-scale lateral saturated soil hydraulic conductivity as metric for the connectivity of the subsurface flow paths at hillslope scale

2021 ◽  
Author(s):  
Mario Pirastru ◽  
Massimo Iovino ◽  
Hassan Awada ◽  
Roberto Marrosu ◽  
Simone Di Prima ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Hydraulic Conductivity ◽  
Spatial Scale ◽  
Water Table ◽  
Subsurface Flow ◽  
Lateral Flow ◽  
Saturated Soil ◽  
Flow Paths ◽  
Soil Hydraulic Conductivity ◽  
Hillslope Scale

Lateral saturated soil hydraulic conductivity, Ks,l, is the soil property governing subsurface water transfer in hillslopes, and the key parameter in many numerical models simulating hydrological processes both at the hillslope and catchment scales. Likewise, the hydrological connectivity of lateral flow paths plays a significant role in determining the intensity of the subsurface flow at various spatial scales. The objective of the study is to investigate the relationship between Ks,l and hydraulic connectivity at the hillslope spatial scale. Ks,l was determined by the subsurface flow rates intercepted by drains, and by water table depths observed in a well network. Hydraulic connectivity of the lateral flow paths was evaluated by the synchronicity among piezometric peaks, and between the latter and the peaks of drained flow. Soil moisture and precipitation data were used to investigate the influence of the transient hydrological soil condition on connectivity and Ks,l. It was found that the higher was the synchronicity of the water table response between wells, the lower was the time lag between the peaks of water levels and those of the drained subsurface flow. Moreover, the most synchronic water table rises determined the highest drainage rates. The relationships between Ks,l and water table depths were highly non-linear, with a sharp increase of the values for water table levels close to the soil surface. Estimated Ks,l values for the full saturated soil were in the order of thousands of mm h-1, suggesting the activation of macropores in the root zone. The Ks,l values determined at the peak of the drainage events were correlated with the indicators of synchronicity. The sum of the antecedent soil moisture and of the precipitation was correlated with the indicators of connectivity and with Ks,l. We suggest that, for simulating realistic processes at the hillslope scale, the hydraulic connectivity could be implicitly considered in hydrological modelling through an evaluation of Ks,l at the same spatial scale.

Simultaneous identification of contaminant source location, initial contaminant concentration, horizontal and vertical hydraulic conductivity in a three-dimensional coastal aquifer via ensemble Kalman filter 

2021 ◽  
Author(s):  
Arezou Dodangeh ◽  
Mohammad Mahdi Rajabi ◽  
Marwan Fahs
Keyword(s):  
Kalman Filter ◽  
Hydraulic Conductivity ◽  
Coastal Aquifers ◽  
Ensemble Kalman Filter ◽  
Coastal Aquifer ◽  
Three Dimensional ◽  
Source Location ◽  
Contaminant Concentration ◽  
Contaminant Source ◽  
Vertical Hydraulic Conductivity

&lt;p&gt;In coastal aquifers, we face the problem of salt water intrusion, which creates a complex flow field. Many of these coastal aquifers are also exposed to contaminants from various sources. In addition, in many cases there is no information about the characteristics of the aquifer. Simultaneous identification of the contaminant source and coastal aquifer characteristics can be a challenging issue. Much work has been done to identify the contaminant source, but in the complex velocity field of coastal aquifer, no one has resolved this issue yet. We want to address that in a three-dimensional artificial coastal aquifer.&lt;/p&gt;&lt;p&gt;To achieve this goal, we have developed a method in which the contaminant source can be identified and the characteristics of the aquifer can be estimated by using information obtained from observation wells. First, by assuming the input parameters required to simulate the contaminant transfer to the aquifer, this three-dimensional coastal aquifer that is affected by various phenomena such as seawater intrusion, tides, shore slope, rain, discharge and injection wells, is simulated and the time series of the output parameters including head, salinity and contaminant concentration are estimated. In the next step, with the aim of performing inverse modeling, random values &amp;#8203;&amp;#8203;are added to the time series of outputs obtained at specific points (points belonging to observation wells) in order to rebuilt the initial conditions of the problem to achieve the desired unknowns (contaminant source and aquifer characteristics). The unknowns estimated in this study are the contaminant source location (x, y, z), the initial contaminant concentration, the horizontal and vertical hydraulic conductivity of the aquifer. SEAWAT model in GMS software environment has been used to solve the equations of flow and contaminant transfer and simulate a three-dimensional coastal aquifer. Next, for reverse modeling, one of the Bayesian Filters subset (ensemble Kalman filter) has been used in the Python programming language environment. Also, to reduce the code run time, the neural network model is designed and trained for the SEAWAT model.&lt;/p&gt;&lt;p&gt;This method is able to meet the main purpose of the study, namely estimating the value &amp;#8203;&amp;#8203;of unknown input parameters, including the contaminant source location, the initial contaminant concentration, the horizontal and vertical hydraulic conductivity of the aquifer. In addition, that makes it possible to achieve a three-dimensional numerical model of the coastal aquifer that can be used as a benchmark to examine more accurately the impact of different phenomena simultaneously. In conclusion, we have developed an algorithm which can be used in the world's coastal aquifers to identify the contaminant source and estimate its characteristics.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Key words: coastal aquifer, seawater intrusion, contaminants, groundwater, flow field, parameter estimation, ensemble kalman filter&lt;/p&gt;

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