Solute and heat transport experiments for estimating recharge rate

Abstract

In order to examine the relationship between mobile water content and water flux during infiltration, laboratory experiments were conducted for simultaneous transport of solute (bromide) and heat using columns of two soils, Bassendean sand and Collie loam. Within a limited water flux range, for the same flux the mobile water fraction was lower for the sand than for the loam. The mobile fraction of soil water increased with increasing water flux for sand but was relatively constant for loam. These results have significant implications in field estimations of deep drainage (recharge rate) using tracer techniques, and also in the development of empirical expressions for the relationship between unsaturated hydraulic conductivity and the effective saturation of specific soils. Estimates of water flux based on the analysis of soil temperature changes agreed well with those based on the solute tracer. This agreement was closest when water flux using solute was calculated using the mobile water content, and the heat capacity for the temperature method was calculated using the total water content.