UZ investigations frequently need measurements of saturated hydraulic conductivity, because it establishes the limit of how great unsaturated K can be, and because media in UZ sometimes are saturated. In some ways a saturated K measurement is easier than an unsaturated K measurement: (1) it is a higher number, (2) there is only one saturated K number per sample as opposed to a rapidly varying function over a range of water contents, and (3) the method does not have to include a means of maintaining a particular unsaturated water content. In other ways saturated K is more difficult: it is particularly sensitive to mechanical disturbance of the sample, and is susceptible to water flow around the edge of the sample, a process that is an artifact of measurement rather than a sample characteristic.
We measure saturated K using the SSC with modified operation and different formulas for computing results (Nimmo and Mello, 1991) in addition to the more widely used benchtop falling head and constant-head methods as described in handbooks (e.g. Klute and Dirkson, 1986). It is important to make such measurements before a series of SSC unsaturated K measurements, in order to select operating fluxes and centrifuge speeds appropriately.
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