The parameter Ksat is the saturated hydraulic conductivity for each layer used in a VIC model. Ksat is approximated using data onsoil textures available for the basin.
Soil textures are from the STATSGO database (USDA NRCS), which has been compiled from a state-by-state format into a U.S. database, available through Penn State University at http://dbwww.essc.psu.edu/dbndx/tree/amer_n/us_48/data/soilprop/statsgo_geo.html
This reports 16 different soil texture classes for 11 layers, which cover a depth of 2.5 meters. The majority of data does not extend beyond 1.5 meters, which includes the first 9 of their 11 layers. The Penn State data is available in gridded form at a resolution of 30 arc-seconds.
The soil texture data is then imported into Arc/Info, where it is indexed to values of Ksat according to an index table soil hydraulic properties (see sample table here). The data in this table are placed into an INFO file in Arc/Info, and the individual relates are then created to be used in an Arc/Info macro to create the Ksat grid for each layer. An example Arc/Info macro can be downloaded here.