Fig. 4. Time domain reflectometry (TDR) measured bulk electrical conductivity (EC) (EC_b) as a function of solution EC_w, measured independently with an EC meter. Effluent EC_e was also measured using the same meter and is compared to EC_w with a 1:1 line. The saturated sand (0.18–0.295 mm) porosity was 0.45 and model prediction is from Eq. [2]. Inset displays time to equilibrium with changes in EC_b.