The ability of a soil or rock to conduct water. The conductivity of dry soil or rock is low, as water must form a film of water around the soil particles before conduction occurs. Tuli and Hopmans (2004) Eur. J. Soil Sci. 55, 1 find that pore geometry and pore-size distribution determine the relations between saturation, hydraulic conductivity, and air conductivity. Saturated hydraulic conductivity refers to the maximum rate of water movement in a soil; see Lilly (2000) Soil Use Manag. 16.