Properties

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Aquifer Properties

Hydraulic Conductivity (K)

The hydraulic conductivity of an aquifer is defined as a constant of proportionality relating the specific discharge of a porous medium under a unit hydraulic gradient. Hydraulic conductivity has units of length/time, L/T.

The following table shows representative values of hydraulic conductivity for various unconsolidated sedimentary materials, sedimentary rocks and crystalline rocks (from Domenico and Schwartz 1990):

Unconsolidated Sedimentary Materials
Material Hydraulic Conductivity
(m/sec)
Gravel 3x10-4 to 3x10-2
Coarse sand 9x10-7 to 6x10-3
Medium sand 9x10-7 to 5x10-4
Fine sand 2x10-7 to 2x10-4
Silt, loess 1x10-9 to 2x10-5
Till 1x10-12 to 2x10-6
Clay 1x10-11 to 4.7x10-9
Unweathered marine clay 8x10-13 to 2x10-9
 
Sedimentary Rocks
Rock Type Hydraulic Conductivity
(m/sec)
Karst and reef limestone 1x10-6 to 2x10-2
Limestone, dolomite 1x10-9 to 6x10-6
Sandstone 3x10-10 to 6x10-6
Siltstone 1x10-11 to 1.4x10-8
Salt 1x10-12 to 1x10-10
Anhydrite 4x10-13 to 2x10-8
Shale 1x10-13 to 2x10-9

Crystalline Rocks
Rock Type Hydraulic Conductivity
(m/sec)
Permeable basalt 4x10-7 to 2x10-2
Fractured igneous and metamorphic rock 8x10-9 to 3x10-4
Weathered granite 3.3x10-6 to 5.2x10-5
Weathered gabbro 5.5x10-7 to 3.8x10-6
Basalt 2x10-11 to 4.2x10-7
Unfractured igneous and metamorphic rock 3x10-14 to 2x10-10

To Convert From
m/sec To		 Multiply
By
cm/sec 100
gal/day/ft2 2.12x106
ft/sec 3.28

Porosity (n)

Porosity is defined as the void space of a rock or unconsolidated material:

n = Vv/VT

where Vv is void volume and VT is total volume.

The following tables show representative porosity values for various unconsolidated sedimentary materials, sedimentary rocks and crystalline rocks (from Morris and Johnson 1967):

Unconsolidated Sedimentary Materials
Material Porosity (%)
Gravel, coarse 24 - 37
Gravel, medium 24 - 44
Gravel, fine 25 - 39
Sand, coarse 31 - 46
Sand, medium 29 - 49
Sand, fine 26 - 53
Silt 34 - 61
Clay 34 - 57

Sedimentary Rocks
Rock Type Porosity (%)
Sandstone 14 - 49
Siltstone 21 - 41
Claystone 41 - 45
Shale 1 - 10
Limestone 7 - 56
Dolomite 19 - 33

Crystalline Rocks
Rock Type Porosity (%)
Basalt 3 - 35
Weathered granite 34 - 57
Weathered gabbro 42 - 45

Specific Yield (Sy)

Specific yield is defined as the volume of water released from storage by an unconfined aquifer per unit surface area of aquifer per unit decline of the water table.

The following table shows representative values of specific yield for various geologic materials (from Morris and Johnson 1967):

Material Specific Yield (%)
Gravel, coarse 21
Gravel, medium 24
Gravel, fine 28
Sand, coarse 30
Sand, medium 32
Sand, fine 33
Silt 20
Clay 6
Sandstone, fine grained 21
Sandstone, medium grained 27
Limestone 14
Dune sand 38
Loess 18
Peat 44
Schist 26
Siltstone 12
Till, predominantly silt 6
Till, predominantly sand 16
Till, predominantly gravel 16
Tuff 21


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Last modified: 19 January 2008