MEASUREMENT OF HYDRAULIC CONDUCTIVITY OF PEATS

1973 ◽  
Vol 53 (1) ◽  
pp. 21-26 ◽  
Author(s):  
T. S. DAI ◽  
J. H. SPARLING
Keyword(s):  
Hydraulic Conductivity ◽  
Darcy’S Law ◽  
Vertical Component ◽  
Darcy's Law ◽  
Horizontal Component ◽  
Chamber Length ◽  
Poor Fen ◽  
The Poor

The measurement of hydraulic conductivity of peats in a northeastern Ontario peatland is described. Several sizes of piezometer were tested and revealed little effect on the hydraulic conductivity. Various lengths of piezometer chamber were used to measure both vertical and horizontal components of hydraulic conductivity at a number of sites. Open bog sites had a higher vertical component of hydraulic conductivity than the poor fen site. The poor fen site exhibited a greater dependence of the hydraulic conductivity on piezometer chamber length than the open bog site, indicating a greater horizontal component of the hydraulic conductivity. A significant correlation between the differential heads and hydraulic conductivity is demonstrated. This indicates a deviation of Darcian flow in the peatland. The ratios of differential heads in piezometer are constant, however, and therefore the proportionality of Darcy's Law is exhibited by the piezometer method.

Incorporation of Interfacial Areas in Models of Two-Phase Flow

1999 ◽  
Author(s):  
William G. Gray ◽  
Michael A. Celia
Keyword(s):  
Porous Media ◽  
Hydraulic Conductivity ◽  
Single Phase ◽  
Darcy’S Law ◽  
Darcy's Law ◽  
Hydraulic Gradient ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Α Phase ◽  
Flow Through

The mathematical study of flow in porous media is typically based on the 1856 empirical result of Henri Darcy. This result, known as Darcy’s law, states that the velocity of a single-phase flow through a porous medium is proportional to the hydraulic gradient. The publication of Darcy’s work has been referred to as “the birth of groundwater hydrology as a quantitative science” (Freeze and Cherry, 1979). Although Darcy’s original equation was found to be valid for slow, steady, one-dimensional, single-phase flow through a homogeneous and isotropic sand, it has been applied in the succeeding 140 years to complex transient flows that involve multiple phases in heterogeneous media. To attain this generality, a modification has been made to the original formula, such that the constant of proportionality between flow and hydraulic gradient is allowed to be a spatially varying function of the system properties. The extended version of Darcy’s law is expressed in the following form: qα=-Kα . Jα (2.1) where qα is the volumetric flow rate per unit area vector of the α-phase fluid, Kα is the hydraulic conductivity tensor of the α-phase and is a function of the viscosity and saturation of the α-phase and of the solid matrix, and Jα is the vector hydraulic gradient that drives the flow. The quantities Jα and Kα account for pressure and gravitational effects as well as the interactions that occur between adjacent phases. Although this generalization is occasionally criticized for its shortcomings, equation (2.1) is considered today to be a fundamental principle in analysis of porous media flows (e.g., McWhorter and Sunada, 1977). If, indeed, Darcy’s experimental result is the birth of quantitative hydrology, a need still remains to build quantitative analysis of porous media flow on a strong theoretical foundation. The problem of unsaturated flow of water has been attacked using experimental and theoretical tools since the early part of this century. Sposito (1986) attributes the beginnings of the study of soil water flow as a subdiscipline of physics to the fundamental work of Buckingham (1907), which uses a saturation-dependent hydraulic conductivity and a capillary potential for the hydraulic gradient.

Measuring the saturated hydraulic conductivity of peat substrates in nursery containers

1994 ◽  
Vol 74 (4) ◽  
pp. 431-437 ◽  
Author(s):  
S. E. Allaire ◽  
J. Caron ◽  
J. Gallichand
Keyword(s):  
Hydraulic Conductivity ◽  
Correction Factor ◽  
Darcy’S Law ◽  
Water Flux ◽  
Darcy's Law ◽  
Saturated Hydraulic Conductivity ◽  
Disruptive Effect ◽  
Flow Measurements ◽  
Flux Measurements ◽  
Made In

Pore size, distribution and continuity are important characteristics for the exchange and storage of air and water in artificial mixes. Saturated hydraulic conductivity (Ks) measurements can be used to obtain such a characterization. However, two difficulties are encountered when using Ks in potting media. First, the validity of Ks may be limited because it may not apply in media composed of coarse material or peat. Second, the structure of peat substrates is very sensitive and in situ measurements of potted peat substrates (i.e. measurements made directly in the pots) should be carried out to avoid any disruptive effect due to handling. Such a measurement, when made in pots, may require the evaluation of the water flux reduction resulting from the container outflow configuration. The objectives of this study were therefore to check the validity of Darcy’s law for peat substrates and to propose an approach for estimating the saturated hydraulic conductivity from flow measurements made in nursery containers. For three different substrates, water flow in artificial mixes followed Darcy’s law for hydraulic gradients ranging from 1.1 to 1.6 cm cm−1. Experimental results showed that the measured fluxes in 5-L nursery container filled at five different substrate heights (9, 11.5, 14, 16.5 and 19 cm) with laterally located drainage holes were significantly different from those measured in pots with the bottom removed (therefore equivalent to measurement currently made in cylinders) at P = 0.0022. Fluxes in containers with bottoms removed were 7–31% higher than in intact pots. Water flux measurements may therefore need to be corrected for this flux reduction in order to accurately estimate hydraulic conductivity from flow experiments run in pots. A correction factor based on the results obtained from a finite difference model was derived and calibrated. Then, this correction factor was used to convert flux measurements made in pots with lateral holes into equivalent flux that would have been obtained had the pot had an open bottom. After correction, no significant flux reductions were found between pots with open bottoms and pots with lateral holes (P = 0.55). A correction factor estimated from Laplace’s equation, once calibrated, can therefore be applied to flux measurements obtained from pots to obtain estimates of Ks of undisturbed potted media. Key words: Hydraulic conductivity, peat substrates, container

scholarly journals Comparison between different infiltration models to describe the infiltration of permeable brick pavement system via lab-scale experiment

2021 ◽  
Author(s):  
Jianying Song ◽  
Jianlong Wang ◽  
Wenhai Wang ◽  
Liuwei Peng ◽  
Hongxin Li ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Darcy’S Law ◽  
Infiltration Rate ◽  
Darcy's Law ◽  
Optimal Model ◽  
Experiment Data ◽  
Runoff Volume ◽  
Infiltration Models ◽  
Scale Experiment ◽  
Horton Model

Abstract Permeable brick pavement system (PBPs) is one of a widely used low impact development (LID) measures to alleviate runoff volume and pollution caused by urbanization. The performance of PBPs on decreasing runoff volume is decided by its permeability, and it was general described by hydraulic conductivity based on Darcy's law. But there is large error when using hydraulic conductivity to describe the infiltration of PBPs, and which infiltration process is not following to the Darcy's law, so it is important to found a more accurate infiltration models to describe the infiltration of PBPs. The Horton, Philip, Green-Ampt, and Kostiakov infiltration models were selected to found an optimal model to investigate infiltration performance of PBPs via lab-scale experiment, and the maximum absolute error (MAE), Bias, and coefficient of determination (R2) were selected to evaluate the models' errors via fitting with experiment data. The results showed that the fitting accuracy of Kostiakov, Philip, and Green-Ampt models was significantly affected by the monitoring area and hydraulic gradients. Meanwhile, Horton model is fitting well (MAE = 0.25–0.32 cm/h, Bias = 0.07–0.11 cm/h, and R2 = 0.98–0.99) with the experiment data, and the parameters of Horton model often can be achieved by monitoring, such as the maximum infiltration rate and the stable infiltration rate. Therefore, the Horton model is an optimal model to describe the infiltration performance of PBPs, which can also be adopt to evaluate hydrological characterization of PBPs.

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