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{{Short description|Ability of water to flow through a porous material}}

In [[science]] and  [[engineering]], '''hydraulic conductivity''' ({{mvar|K}}, in [[SI unit]]s of [[meter]]s per second), is a property of [[porous material]]s, [[soil]]s and [[Rock (geology)|rocks]], that describes the ease with which a [[fluid]] (usually water) can move through the [[porosity|pore space]], or fracture network.<ref> https://www.preene.com/blog/2014/07/what-is-hydraulic-conductivity#:~:text=DEFINITIONS%20OF%20HYDRAULIC%20CONDUCTIVITY&text=In%20theoretical%20terms%2C%20hydraulic%20conductivity,the%20material%20is%20less%20permeable. Hydraulic conductivity definition </ref> It depends on the [[intrinsic permeability]] ({{mvar|k}}, unit: m{{sup|2}}) of the material, the degree of [[Water content|saturation]], and on the [[density]] and [[viscosity]] of the fluid. Saturated hydraulic conductivity, {{math|''K''<sub>sat</sub>}}, describes water movement through saturated media.
By definition, hydraulic conductivity is the ratio of volume flux to [[Hydraulic head#Hydraulic gradient|hydraulic gradient]] yielding a quantitative measure of a  saturated soil's ability to transmit water when subjected to a hydraulic gradient.

==Methods of determination==
[[File:HydrCondTable.GIF|thumb|450px|Overview of determination methods]]
There are two broad approaches for determining hydraulic conductivity:
*In the ''empirical'' approach the hydraulic conductivity is correlated to soil properties like [[Porosity|pore-size]] and [[particle-size (grain-size)]] distributions, and [[soil texture]].
*In the ''experimental'' approach the hydraulic conductivity is determined from hydraulic experiments that are interpreted using [[Darcy's law]].

The experimental approach is broadly classified into:
*[[Laboratory]] tests using soil samples subjected to hydraulic [[experiment]]s
*''Field tests'' (on site, in situ) that are differentiated into:
**small-scale field tests, using observations of the water level in cavities in the soil
**large-scale field tests, like [[pumping test]]s in [[Water well|wells]] or by observing the functioning of existing horizontal [[drainage]] systems.
The small-scale field tests are further subdivided into:
*[[Infiltration (hydrology)|infiltration]] tests in cavities ''above'' the [[water table]]
*[[slug test]]s in cavities ''below'' the [[water table]]

The methods of determining hydraulic conductivity and other hydraulic properties are investigated by numerous researchers and include additional empirical approaches.<ref>{{cite journal | url=https://doi.org/10.2113/gseegeosci.22.4.319 | doi=10.2113/gseegeosci.22.4.319 | title=Empirical Methods and Estimation of Hydraulic Conductivity of Fluvial Aquifers | year=2016 | last1=Sahu | first1=Sudarsan | last2=Saha | first2=Dipankar | journal=Environmental & Engineering Geoscience | volume=22 | issue=4 | pages=319–340 | bibcode=2016EEGeo..22..319S }}</ref>

==Estimation by empirical approach==
===Estimation from grain size===
[[Allen Hazen]] derived an [[Empirical method|empirical]] formula for approximating hydraulic conductivity from grain-size analyses:
:<math>K = C (D_{10})^2</math>
where
:<math>C</math> Hazen's empirical coefficient, which takes a value between 0.0 and 1.5 (depending on literature), with an average value of 1.0.  A.F. Salarashayeri & M. Siosemarde indicate C is usually between 1.0 and 1.5, with D in mm and K in cm/s.{{Citation needed|date=October 2022|reason=Source referenced (A.F. Salarashayeri & M. Siosemarde) but never given}}
:<math>D_{10}</math> is the [[diameter]] of the 10 [[percentile]] grain size of the material.

===Pedotransfer function===
A [[pedotransfer function]] (PTF) is a specialized empirical estimation method, used primarily in the [[soil science]]s, but increasingly used in hydrogeology.<ref>{{cite journal |author=Wösten, J.H.M., Pachepsky, Y.A., and Rawls, W.J. |title=Pedotransfer functions: bridging the gap between available basic soil data and missing soil hydraulic characteristics |year=2001 |volume=251 |issue=3–4 |pages=123–150 |doi=10.1016/S0022-1694(01)00464-4 |journal=[[Journal of Hydrology]] |bibcode = 2001JHyd..251..123W }}</ref> There are many different PTF methods, however, they all attempt to determine soil properties, such as hydraulic conductivity, given several measured soil properties, such as soil [[particle size]], and [[bulk density]].

==Determination by experimental approach==
There are relatively simple and inexpensive laboratory tests that may be run to determine the hydraulic conductivity of a soil:  constant-head method and falling-head method.

===Laboratory methods===
====Constant-head method====
The [http://www.geotechdata.info/geotest/constant-head-permeability-test constant-head method] is typically used on granular soil. 
This procedure allows water to move through the soil under a steady state head condition while the volume of water flowing through the soil specimen is measured over a period of time.  
By knowing the volume {{math|Δ''V''}} of water measured in a time {{math|Δ''t''}}, over a specimen of length {{mvar|L}} and cross-sectional area {{mvar|A}}, as well as the head {{mvar|h}}, the hydraulic conductivity ({{mvar|K}}) can be derived by simply rearranging [[Darcy's law]]:
:<math>K = \frac{\Delta V}{\Delta t}\frac{L}{ A h}</math>

''Proof: ''
Darcy's law states that the volumetric flow depends on the [[Pressure gradient|pressure differential]] {{math|Δ''P''}} between the two sides of the sample, the [[Permeability (earth sciences)|permeability]] {{mvar|k}} and the [[dynamic viscosity]] {{mvar|μ}} as: <ref>[https://imechanica.org/files/JCIS-2019-Tailoring%20porous%20media%20for%20controllable%20capillary%20flow_0.pdf Controlling capillary flow] an application of Darcy's law </ref>
:<math>\frac{\Delta V}{\Delta t}=-\frac{k A}{\mu L}\Delta P</math>
In a constant head experiment, the head (difference between two heights) defines an excess water mass, {{mvar|ρAh}}, where {{mvar|ρ}} is the density of water. 
This mass weighs down on the side it is on, creating a pressure differential of {{math|1=Δ''P'' = ''ρgh''}}, where {{mvar|g}} is the gravitational acceleration.
Plugging this directly into the above gives 
:<math>\frac{\Delta V}{\Delta t}=-\frac{k \rho g A}{\mu L}h</math>
If the hydraulic conductivity is defined to be related to the hydraulic permeability as
:<math>K = \frac{k\rho g}{\mu},</math>
this gives the result.

====Falling-head method====
In the falling-head method, the soil sample is first saturated under a specific head condition. 
The water is then allowed to flow through the soil without adding any water, so the pressure head declines as water passes through the specimen. 
The advantage to the falling-head method is that it can be used for both fine-grained and coarse-grained soils.
.<ref>Liu, Cheng "Soils and Foundations." Upper Saddle River, New Jersey:  Prentice Hall, 2001  {{ISBN|0-13-025517-3}}</ref> 
If the head drops from {{mvar|h{{sub|i}}}} to {{mvar|h{{sub|f}}}} in a time {{math|Δ''t''}}, then the hydraulic conductivity is equal to 
:<math>K = \frac{L}{\Delta t}\ln\frac{h_f}{h_i}</math>
''Proof: '' As above, Darcy's law reads
:<math>\frac{\Delta V}{\Delta t}=-K\frac {A}{L}h</math>
The decrease in volume is related to the falling head by {{math|1=Δ''V'' = Δ''hA''}}.
Plugging this relationship into the above, and taking the limit as {{math|Δ''t'' → 0}}, the differential equation
:<math>\frac{dh}{dt} = -\frac{K}{L}h</math>
has the solution
:<math>h(t) = h_ie^{-\frac{K}{L}(t-t_i)}.</math>
Plugging in <math>h(t_f)=h_f</math> and rearranging gives the result.

===In-situ (field) methods===
In compare to laboratory method, field methods gives the most reliable information about the permeability of soil with minimum disturbances. In laboratory methods, the degree of disturbances affect the reliability of value of permeability of the soil.

====Pumping Test====
Pumping test is the most reliable method to calculate the coefficient of permeability of a soil. This test is further classified into Pumping in test and pumping out test.

====Augerhole method====
There are also in-situ methods for measuring the hydraulic conductivity in the field.<br />
When the water table is shallow, the augerhole method, a [[slug test]], can be used for determining the hydraulic conductivity below the water table.<br />
The method was developed by Hooghoudt (1934)<ref>S.B.Hooghoudt, 1934, in Dutch. Bijdrage tot de kennis van enige natuurkundige grootheden van de grond. Verslagen Landbouwkundig Onderzoek No. 40 B, p. 215-345.</ref> in The Netherlands and introduced in the US by Van Bavel en Kirkham (1948).<ref>C.H.M. van Bavel and D. Kirkham, 1948. Field measurement of soil permeability using auger holes. Soil. Sci. Soc. Am. Proc 13:90-96.</ref><br />
The method uses the following steps:
#an augerhole is perforated into the soil to below the water table
#water is bailed out from the augerhole
#the rate of rise of the water level in the hole is recorded
#the {{mvar|K}}-value is calculated from the data as:<ref name="Oost">Determination of the Saturated Hydraulic Conductivity. Chapter 12 in: H.P.Ritzema (ed., 1994) Drainage Principles and Applications, ILRI Publication 16, p.435-476. International Institute for Land Reclamation and Improvement, Wageningen (ILRI), The Netherlands. {{ISBN|90-70754-33-9}}. Free download from: [http://www.waterlog.info/articles.htm], under nr. 6, or directly as PDF : [http://www.waterlog.info/pdf/chap12.pdf]</ref>

#:<math>K=F \frac{H_o-H_t}{t}</math>

where: 
*{{mvar|K}} is the horizontal saturated hydraulic conductivity (m/day)
*{{mvar|H}} is the depth of the water level in the hole relative to the water table in the soil (cm):
**{{math|1=''H{{sub|t}}'' = ''H''}} at time {{mvar|t}}
**{{math|1=''H{{sub|o}}'' = ''H''}}  at time {{math|1=''t'' = 0}}
*{{mvar|t}} is the time (in seconds) since the first measurement of {{mvar|H}} as {{mvar|H{{sub|o}}}}
*{{mvar|F}} is a factor depending on the geometry of the hole:
*:<math>F=\frac{4000r}{h'}\left(20+\frac{D}{r}\right)\left(2-\frac{h'}{D}\right)</math>

where: 
*{{mvar|r}} is the radius of the cylindrical hole (cm)
*{{mvar|h'}} is the average depth of the water level in the hole relative to the water table in the soil (cm), found as <math>h'=\tfrac{H_o+H_t}{2}</math>
*{{mvar|D}} is the depth of the bottom of the hole relative to the water table in the soil (cm).

[[File:PANAZ1.JPG|thumb|200px|Cumulative frequency distribution ([[lognormal]]) of hydraulic conductivity (X-data)]]

The picture shows a large variation of {{mvar|K}}-values measured with the augerhole method in an area of 100 ha.<ref>Drainage research in farmers' fields: analysis of data. Contribution to the project “Liquid Gold” of the International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. Free download from : [http://www.waterlog.info/articles.htm], under nr. 2, or directly as PDF : [http://www.waterlog.info/pdf/analysis.pdf]</ref> The ratio between the highest and lowest values is 25. The cumulative frequency distribution is [[lognormal]] and was made with the [[cumulative frequency analysis|CumFreq]] program.

==Related magnitudes==
===Transmissivity===
The transmissivity is a measure of how much water can be transmitted horizontally, such as to a pumping well.<br />
:<small>''Transmissivity'' should not be confused with the similar word [[transmittance]] used in [[optics]], meaning the fraction of incident light that passes through a sample.''</small>
An [[aquifer]] may consist of {{mvar|n}} soil layers. The transmissivity {{mvar|T{{sub|i}}}} of a horizontal flow for the {{mvar|i}}th soil layer with a ''saturated'' thickness {{mvar|d{{sub|i}}}} and horizontal hydraulic conductivity {{mvar|K{{sub|i}}}} is:
:<math>T_i = K_i d_i</math>
Transmissivity is directly proportional to horizontal hydraulic conductivity {{mvar|K{{sub|i}}}} and thickness {{mvar|d{{sub|i}}}}. Expressing {{mvar|K{{sub|i}}}} in m/day and {{mvar|d{{sub|i}}}} in m, the transmissivity {{mvar|T{{sub|i}}}} is found in units m<sup>2</sup>/day.<br />
The total transmissivity {{mvar|T{{sub|t}}}} of the aquifer is the sum of every layer's transmissivity:<ref name="Oost" />
:<math>T_t = \sum T_i</math>

The ''apparent'' horizontal hydraulic conductivity {{mvar|K{{sub|A}}}} of the aquifer is:
:<math>K_A = \frac{T_t}{D_t}</math>
where {{mvar|D{{sub|t}}}}, the total thickness of the aquifer, is the sum of each layer's individual thickness: <math display="inline">D_t = \sum d_i.</math>

The transmissivity of an aquifer can be determined from [[pumping test]]s.<ref name="Boon">J.Boonstra and R.A.L.Kselik, SATEM 2002: Software for aquifer test evaluation, 2001. Publ. 57, International Institute for Land reclamation and Improvement (ILRI), Wageningen, The Netherlands. {{ISBN|90-70754-54-1}} On line : [http://content.alterra.wur.nl/Internet/webdocs/ilri-publicaties/publicaties/Pub57/Pub57.pdf]</ref>

''Influence of the water table''<br />
When a soil layer is above the [[water table]], it is not saturated and does not contribute to the transmissivity. When the soil layer is entirely below the water table, its saturated thickness corresponds to the thickness of the soil layer itself. When the water table is inside a soil layer, the saturated thickness corresponds to the distance of the water table to the bottom of the layer. As the water table may behave dynamically, this thickness may change from place to place or from time to time, so that the transmissivity may vary accordingly.<br />
In a semi-confined aquifer, the water table is found within a soil layer with a negligibly small transmissivity, so that changes of the total transmissivity ({{mvar|D{{sub|t}}}}) resulting from changes in the level of the water table are negligibly small.<br />
When pumping water from an unconfined aquifer, where the water table is inside a soil layer with a significant transmissivity, the water table may be drawn down whereby the transmissivity reduces and the flow of water to the well diminishes.

===Resistance===
The ''resistance'' to vertical flow ({{mvar|R{{sub|i}}}}) of the {{mvar|i}}th soil layer with a ''saturated'' thickness {{mvar|d{{sub|i}}}} and vertical hydraulic conductivity {{mvar|K{{sub|v{{sub|i}}}}}} is:
: <math>R_i=\frac{d_i}{K_{v_i}}</math>
Expressing {{mvar|K{{sub|v{{sub|i}}}}}}  in m/day and {{mvar|d{{sub|i}}}} in m, the resistance ({{mvar|R{{sub|i}}}}) is expressed in days.<br />
The total resistance ({{mvar|R{{sub|t}}}}) of the aquifer is the sum of each layer's resistance:<ref name="Oost" />
:<math>R_t=\sum R_i=\sum \frac{d_i}{K_{v_i}}</math>
<br />
The ''apparent'' vertical hydraulic conductivity ({{mvar|K{{sub|v{{sub|A}}}}}}) of the aquifer is:
:<math>K_{v_A}=\frac{D_t}{R_t}</math>
where {{mvar|D{{sub|t}}}} is the total thickness of the aquifer: <math display="inline">D_t=\sum d_i.</math>

The resistance plays a role in [[aquifer]]s where a sequence of layers occurs with varying horizontal permeability so that horizontal flow is found mainly in the layers with high horizontal permeability while the layers with low horizontal permeability transmit the water mainly in a vertical sense.

==Anisotropy==
When the horizontal and vertical hydraulic conductivity (<math display="inline">K_{h_i}</math> and <math display="inline">K_{v_i}</math>) of the <math display="inline">i\mbox{-th}</math> soil layer differ considerably, the layer is said to be [[anisotropy|anisotropic]] with respect to hydraulic conductivity.<br />
When the ''apparent'' horizontal and vertical hydraulic conductivity (<math display="inline">K_{h_A}</math> and <math display="inline">K_{v_A}</math>) differ  considerably, the [[aquifer]] is said to be [[anisotropy|anisotropic]] with respect to hydraulic conductivity.<br />
An aquifer is called ''semi-confined'' when a saturated layer with a relatively small horizontal hydraulic conductivity (the semi-confining layer or [[aquitard]]) overlies a layer with a relatively high horizontal hydraulic conductivity so that the flow of groundwater in the first layer is mainly vertical and in the second layer mainly horizontal.<br />
The resistance of a semi-confining top layer of an aquifer can be determined from [[pumping test]]s.<ref name="Boon" /><br />
When calculating flow to [[Drainage|drains]]<ref>The energy balance of groundwater flow applied to subsurface drainage in anisotropic soils by pipes or ditches with entrance resistance. International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands. On line: [http://www.waterlog.info/pdf/enerart.pdf] {{Webarchive|url=https://web.archive.org/web/20090219221547/http://www.waterlog.info/pdf/enerart.pdf |date=2009-02-19 }} . Paper based on: R.J. Oosterbaan, J. Boonstra and K.V.G.K. Rao, 1996, “The energy balance of groundwater flow”. Published in V.P.Singh and B.Kumar (eds.), Subsurface-Water Hydrology, p. 153-160, Vol.2 of Proceedings of the International Conference on Hydrology and Water Resources, New Delhi, India, 1993. Kluwer Academic Publishers, Dordrecht, The Netherlands. {{ISBN|978-0-7923-3651-8}}. On line: [http://www.waterlog.info/pdf/enerbal.pdf]. The corresponding free EnDrain program can be downloaded from: [http://www.waterlog.info/endrain.htm]</ref> or to a [[Water well|well]] field<ref>Subsurface drainage by (tube)wells, 9 pp. Explanation of equations used in the WellDrain model. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. On line: [http://www.waterlog.info/pdf/wellspac.pdf]. The corresponding free WellDrain program can be downloaded from : [http://www.waterlog.info/weldrain.htm]</ref> in an aquifer with the aim to [[Watertable control|control the water table]], the anisotropy is to be taken into account, otherwise the result may be erroneous.

==Relative properties==
Because of their high porosity and permeability, [[sand]] and [[gravel]] [[aquifer]]s have higher hydraulic conductivity than [[clay]] or unfractured [[granite]] aquifers. Sand or gravel aquifers would thus be easier to extract water from (e.g., using a pumping [[Water well|well]]) because of their high transmissivity, compared to clay or unfractured bedrock aquifers.

Hydraulic conductivity has units with dimensions of length per time (e.g., m/s, ft/day and ([[gallon|gal]]/day)/ft<sup>2</sup> ); transmissivity then has units with dimensions of length squared per time. The following table gives some typical ranges (illustrating the many orders of magnitude which are likely) for ''K'' values.

Hydraulic conductivity (''K'') is one of the most complex and important of the properties of aquifers in hydrogeology as the values found in nature:
* range over many [[orders of magnitude]] (the distribution is often considered to be [[lognormal distribution|lognormal]]),
* vary a large amount through space (sometimes considered to be [[random]]ly spatially distributed, or [[stochastic]] in nature),
* are directional (in general ''K'' is a symmetric second-rank [[tensor]]; e.g., vertical ''K'' values can be several orders of magnitude smaller than horizontal ''K'' values),
* are scale dependent (testing a m³ of aquifer will generally produce different results than a similar test on only a cm³ sample of the same aquifer),
* must be determined indirectly through field [[pumping test]]s, laboratory column flow tests or inverse computer simulation, (sometimes also from [[Particle size|grain size]] analyses), and
* are very dependent (in a [[nonlinearity|non-linear]] way) on the water content,  which makes solving the [[vadose zone|unsaturated flow]] equation difficult. In fact, the variably saturated ''K'' for a single material varies over a wider range than the saturated ''K'' values for all types of materials (see chart below for an illustrative range of the latter).

==Ranges of values for natural materials==
'''Table of saturated hydraulic conductivity (''K'') values found in nature'''
[[File:Groundwater Freeze and Cherry 1979 Table 2-2.png|thumb|a table showing ranges of values of hydraulic conductivity and permeability for various geological materials]]
Values are for typical fresh [[groundwater]] conditions — using standard values of [[viscosity]] and [[specific gravity]] for water at 20&nbsp;°C and 1 atm.
See the similar table derived from the same source for [[permeability (fluid)|intrinsic permeability]] values.<ref>{{cite book |author=Bear, J. |year=1972 |title=Dynamics of Fluids in Porous Media |publisher=[[Dover Publications]] |isbn=0-486-65675-6}}</ref>

{| border="1" width="600"
|  bgcolor="#FAEBD7" | ''K'' (cm/[[second|s]])
| 10²
| 10<sup>1</sup>
| 10<sup>0</sup>=1
| 10<sup>−1</sup>
| 10<sup>−2</sup>
| 10<sup>−3</sup>
| 10<sup>−4</sup>
| 10<sup>−5</sup>
| 10<sup>−6</sup>
| 10<sup>−7</sup>
| 10<sup>−8</sup>
| 10<sup>−9</sup>
| 10<sup>−10</sup>
|-
|  bgcolor="#FAEBD7" | ''K'' (ft/[[day]])
| 10<sup>5</sup>
| 10,000
| 1,000
| 100
| 10
| 1
| 0.1
| 0.01
| 0.001
| 0.0001
| 10<sup>−5</sup>
| 10<sup>−6</sup>
| 10<sup>−7</sup>
|-
|  bgcolor="#FAEBD7" | Relative Permeability
|  colspan="4" align="center" | Pervious
|  colspan="4" align="center" | Semi-Pervious
|  colspan="5" align="center" | Impervious
|-
|  bgcolor="#FAEBD7" | [[Aquifer]]
|  colspan="5" align="center" | Good
|  colspan="4" align="center" | Poor
|  colspan="4" align="center" | None
|-
|  bgcolor="#FAEBD7" | Unconsolidated [[Sand]] & [[Gravel]]
|  colspan="2" align="center" | Well Sorted Gravel
|  colspan="3" align="center" | Well Sorted Sand or Sand & Gravel
|  colspan="4" align="center" | Very Fine Sand, Silt, [[Loess]], [[Loam]]
|  colspan="4" |
|-
|  bgcolor="#FAEBD7" | Unconsolidated Clay & Organic
|  colspan="4" |
|  colspan="2" align="center" | [[Peat]]
|  colspan="3" align="center" | Layered [[Clay]]
|  colspan="4" align="center" | Fat / Unweathered Clay
|-
|  bgcolor="#FAEBD7" | Consolidated Rocks
|  colspan="4" align="center" | Highly Fractured Rocks
|  colspan="3" align="center" | [[Petroleum geology|Oil Reservoir]] Rocks
|  colspan="2" align="center" | Fresh [[Sandstone]]
|  colspan="2" align="center" | Fresh [[Limestone]], [[Dolomite (rock)|Dolomite]]
|  colspan="2" align="center" | Fresh [[Granite]]
|}

Source: modified from Bear, 1972

{| class="wikitable"
|+ Hydraulic conductivity at Liquid Limit for several Clays<ref>Table 4.4 James K. Mitchell, Kenichi Soga, Fundamentals of SoilBehavior, third ed., John Wiley & Sons Inc., Hoboken, NJ, 2005, 577 pp., ISBN 0-471-46302-7.</ref><ref>Nagaraj, T. S., Pandian, N. S., and Narasimha Raju, P. S. R. 1991. An approach for prediction of compressibility and permeability behaviour of sand-bentonite mixes, Indian Geotechnical Journal, Vol. 21, No. 3, pp. 271–282</ref>
|-
! Soil Type !! Liquid Limit, LL (%) !! Void Ratio at Liquid Limit, <math>e_L</math> (%) ||  Hydraulic conductivity, <math>10^{-7}</math> cm/s
|-
! Bentonite 
| 330|| 9.24 || 1,28
|-
! Bentonite <math>+</math> sand
| 215 || 5,91 || 2,65
|-
! Natural marine soil
| 106 || 2,798 || 2,56
|-
! Air-dried marine soil
| 84 || 2,234 || 2,42
|-
! Open-dried marine soil
| 60 || 1,644 || 2,63
|-
! Brown soil
| 62 || 1,674 || 2,83
|}

==See also==
* [[Aquifer test]]
* [[Hydraulic analogy]]
* [[Pedotransfer function]] – for estimating hydraulic conductivities given soil properties

==References==
<references />

== External links ==
*[http://www.fxsolver.com/solve/share/jZLNM1J9bHMGTCqIglfgmQ==/ Hydraulic conductivity calculator]

{{Aquiferproperties}}
{{Geotechnical engineering|state=collapsed}}

{{DEFAULTSORT:Hydraulic Conductivity}}
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