Jr. Nimmo et al., THE FEASIBILITY OF RECHARGE RATE DETERMINATIONS USING THE STEADY-STATE CENTRIFUGE METHOD, Soil Science Society of America journal, 58(1), 1994, pp. 49-56
The establishment of steady unsaturated flow in a centrifuge permits a
ccurate measurement of small values of hydraulic conductivity (K). Thi
s method can provide a recharge determination if it is applied to an u
nsaturated core sample from a depth at which gravity alone drives the
flow. A K value determined at the in situ water content indicates the
long-term average recharge rate at a point. Tests of this approach hav
e been made at two sites. Unsaturated K values were measured easily fo
r sandy core samples from a site in the San Joaquin Valley of Californ
ia. The results indicate that a better knowledge of the matric pressur
e profiles is required before a recharge rate can be determined. Fine-
textured cores from a site in southeastern Washington required new dev
elopments of apparatus and procedures, especially for making centrifug
e measurements with minimal compaction of the samples. Measured K valu
es led to preliminary recharge rate determinations that are reasonable
considering the known hydrology and topography of the site.