Hydraulic conductivity assessment for a variably-saturated rock matrix

Abstract

Water flow through unsaturated rock has received increasing attention recently. In order to solve unsaturated flow problems, it is necessary to determine the unsaturated hydraulic conductivity, K. A model which predicts K from water retention data was evaluated for rock matrices. It includes three unknown parameters to be determined from experimental data. To verify the model, K was measured by the outflow method. Water retention data were determined by two methods, the pressure plate extractor and the psychrometer. Near saturation, the water retention curve was best estimated by the pressure extractor method. The outflow method gave reliable measurements of K at low negative pressure heads (≥ -1000 cm of water). The predicted K deviated from the experimental values when only the water retention data were used to estimate the model parameters. When the measured K was incorporated in the parameter estimation process, the deviation was reduced considerably.