Fig. 4. Scaled frequency as a function of volumetric water content as measured in the field (dots) and as calculated with a combination of the electric circuit model for lossy media and the empirical () relationship of Malicki et al. (1996) (lines). Calculations assume no dielectric losses and _w = 30, 60, and 90 dS m^–1 combined with _s = 60 dS m^–1. The tortuosity factor of Rhoades et al. (1976) and the tortuosity factor derived from the gas diffusion model of Marshall (1959) are used to calculate bulk electrical conductivity.