Scale dependency of hydraulic conductivity

From GeoClasses

From Kalbus et al., 2006

For measurements conducted in heterogeneous media, such as the subsurface, the measurement scale on which a selected technique operates may have a significant influence on the results, which has clearly been demonstrated for hydraulic conductivity in numerous studies. As Rovey and Cherkauer (1995) point out, hydraulic conductivity generally increases with test radius, because with a larger test radius the chance to encounter high-conductivity zones in a heterogeneous medium increases. Schulze-Makuch and Cherkauer (1998) found that hydraulic conductivity estimates increased during individual aquifer tests as the volume of aquifer impacted increased. Therefore, they concluded that scale-dependency of hydraulic conductivity is not related to the measurement method, but to the existence of high-conductivity zones within a low-conductivity matrix. Schulze-Makuch et al. (1999) observed no scaling effects for homogeneous media, whereas for heterogeneous media they found an empirical relation for the scaling behavior. The relationship is a function of the type of flow present (porous flow, fracture flow, conduit flow, double-porosity media) and the degree of heterogeneity, associated with pore size and pore interconnectivity. The relationship was found to be valid up to an upper boundary value, representing the scale above which a medium can be considered quasi-homogeneous. In many of the test results included in the study by Schulze-Makuch et al. (1999), hydraulic conductivities obtained by pumping tests were close to the upper boundary.