The hydraulic conductivity‐water content relationship, as used in the differential equation describing unsteady flow in unsaturated porous materials, is determined from measurements obtained during the drainage of an initially saturated sand column. The approach utilizes instantaneous profiles of the macroscopic flow velocity, the potential gradient, and the water content. The derived relationship exhibits a direct proportionality between the instantaneous velocity and the corresponding potential gradient, thus lending strong support to the contention that Darcy's Law is applicable to flow in unsaturated porous materials of the size range considered in this study.

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An experimental arrangement for measuring soil‐water suctions with rapid response is described and the operating characteristics of the tensiometer‐transducer system discussed. The equations relating to the response of the equipment are given, and a dynamic correction procedure using an iterative approach is illustrated.

A tensiometer-pressure transducer system using nylon hydraulic leads was found to be sensitive to small temperature fluctuations. A suitable model to describe the effect was developed, and the appropriate differential equation was solved in terms of the pressure variation occurring in the system for a sinusoidal pattern of temperature change. Experiments are described in which the measuring system is subjected to a sinusoidal temperature variation and the induced pressure changes recorded. From such records the amplitude and phase shift of the pressure are determined and compared with those obtained from the model solution.