Residual moisture content is the amount of soil moisture that cannot be removed from the soil by drainage or evapotranspiration. Values are provided to the model as soil moisture contents (volume of residual soil moisture content / total volume of soil) [mm/mm]. When residual soil moisture is defined as 0 mm/mm the soil hydraulic conductivity relationship collapses to Campbell (1974), otherwise it follows Brooks and Corey (1964).
Brooks, R. H. and A. T. Corey, Hydraulic Properties of Porous Media, Hydrology Paper 3, Colorado State University, Fort Collins, Colo, 1964.
Campbell, G. S., A Simple Method for Determining Unsaturated Conductivity from Moisture Retention Data, Soil Sci., vol. 117, pp. 311-314, 1974.