Automated In Situ Measurement of Unsaturated Soil Water Flux

Abstract

Abstract A device is presented which, based on new operation principles, intercepts unsaturated soil water fluxes within an error of 10% and can yield samples for subsequent chemical analysis and calculation of convective solute fluxes. Operation is controlled by a microprocessor which automatically adjusts the vacuum imposed on a porous filter cloth such that identical matric potentials are maintained just above the cloth and at the same depth in the neighboring soil. Contact resistances and internal resistance of the device are implicitly corrected by adjustment of suction. Laboratory and field tests in a loamy sand under steady and transient flow conditions showed that cumulative water fluxes could be measured within 10% of those calculated from storage changes, and from numerical and analytical flow models.