Geostatistical simulation for upscaling field measurements of unsaturated hydraulic conductivity

Characterizing the water infiltration capability of surficial soils can be an important aspect of many geotechnical and environmental site evaluations. The recent development of field-usable tension infiltrometers now allows insitu measurements of unsaturated hydraulic conductivity (K-u) at a study site, thus avoiding much of the uncertainty associated with testing remolded soil specimens in the laboratory. If spatial dependence is observed in a reasonably sized sample of K-u (say, 20 observations or more), then geostatistical spatial simulations can be used to stochastically describe K-u across the site. By simulating to a fairly fine grid with nodes spaced at distances comparable to the scale of the actual field tests, the test results can be upscaled to larger areas (or volumes) by spatial averaging These upscaling procedures are demonstrated by a case study at a 700 sq.-meter site comprised of coarse soil material.