Also referred to as the Coefficient of Permeability, the conductivity is a measure of a liquid's ability to move through a porous media. Conductivity is derived from the relationship between specific discharge (v = Q/A) and the hydraulic gradient (dh/dl) defined in Darcy's law. The coefficient K is expressed in units of [L]/[T], commonly as m/d, cm/s or ft/d.
Source: Adapted from Domenico and Schwartz (1990).
How to use it:
Single Effective Value
Assign spatially-constant, effective horizontal (Kxx) values and implicitly assign vertical (Kzz) and north-south (Kyy) conductivities through prescribing vertical and horizontal anisotropy ratios (Kxx/Kzz and Kxx/Kyy, respectively) - more on this below. The value is applied throughout the model domain, expect in areas where zone-based refinement is being applied.
Server Data
Hydraulic Conductivity can be represented with a spatially variable 2D data-layer available on the IGW-NET server. The quality/resolution of this layer depends on location, e.g., for the State of Michigan a high resolution conductivity raster is available for use, generated by interpolating estimates of K from records in the Wellogic database, public water supply and U.S. Geological Society aquifer-tests, and aquifer properties reported in literature. (Similar data layers will be available for other states/provinces soon.)
Globally, lower resolution/quality data layers are available for both the surficial aquifer layer and the underlying rock. Although the global K layers are somewhat crude/low resolution, they provide a useful starting point for model development.
DataNET WCS layer
This option allows users to import from MAGNET4WATER DataNET a WCS data layer as a raster file of aquifer recharge. A "linked" DataNET page needs to be opened to be able to send a WCS layer from DataNET into IGW-NET (a prompt will appear if that is the case, allowing the user to open a new DataNET page to be linked).
Once the WCS layer is transferred into IGW-NET, it will be converted into a geotiff raster file uploaded to your user folder.
User raster files can be used to assign Kxx values across the model domain. To do this, check the box next to the "Import" link, then select the link to open a file browser.
The following raster file formats are supported for import of user hydraulic conductivity data layers:
1 - Ascii format with the same projection (PRJ) as your model PRJ
2 - Geotiff (.tif) format with PRJ information embedded in the .tif file
3 - IMG format with PRJ information embedded in the .tif file
Anisotropy Ratios
This section also allows assigning anisotropy ratios in both the horizontal and vertical directions, i.e., Kxx/Kyy and Kxx/Kzz, respectively, where Kxx is the X- (west-east) direction horizontal conductivity, Kyy is the Y- (north-south) direction horizontal conductivity, and Kzz is the vertical hydraulic conductivity within the current conceptual / aquifer layer.
Note that the ratios are assumed to be 1 if these checkboxes are not selected.
Also note that the anisotropy ratios apply to both a single value or a raster approach for assigning hydraulic conductivity.
Zone-based Option: TP Geostatistical Simulation
It is also possible to utilzie detailed characterizations of intra-aquifer geologic variability using zone features in IGW-NET. Specifically, IGW-NET can read the results from a Transition Probability (TP) "Markov chain" geostatistical simulations built from detailed lithology borehole records compiled by states/provinces and convert the TP results into a hydraulic conductivity field. See more in the Real-time Help page for Hydraulic Conductivty in the Zone Attributes menu (after drawing a zone and selecting 'SaveShape').