DIRECT MEASUREMENT OF UNSATURATED HYDRAULIC CONDUCTIVITY USING TIME DOMAIN REFLECTROMETRY

Abstract

A method of determining the relationship between unsaturated hydraulic conductivity and volumetric water content of particulate moss peat is described which used vertically and horizontally installed time domain reflectrometry waveguides to determine the equilibrium water content of a column of particulate peat with respect to a known and constant surface flux. A layer of sand was used as a distributor for water pumped on to the top of the column and the change in water content with time was used to monitor the advance of a wetting front down the column. Once water content reached constant values throughout the column the particulate peat could be regarded as being in equilibrium with the rate of water application. The hydraulic conductivity as a function of water content was equal to the rate of water applied divided by the cross-sectional area of application and the volumetric water content was measured directly. By changing the surface flux, a curve of the relationship was obtained. To evaluate the method a core with both vertical and horizontal waveguides was used; the horizontal waveguides were used to establish that the water content at the top and bottom of the vertical waveguides to assess whether there was a unit hydraulic gradient in the column.