Aquifer Test Forum--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 = V_v/V_T

where V_v is void volume and V_T 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 (S_y)

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

Aquifer Properties

Hydraulic Conductivity (K)

Porosity (n)

Specific Yield (Sy)

Specific Yield (S_y)