Laboratory tests for hydraulic conductivity of unconsolidated sediments are presented and associated terminology used in groundwater literature and practice is discussed. Samples of unconsolidated sediments, i.e. gravels and sands deposited at two sites, Zagreb alluvial aquifer (Sava basin, Croatia) and Virovitica alluvial aquifer (Drava basin, Croatia) were tested in the laboratory using a constant head permeameter. Main features of the tests are presented and the results at two sites arc compared. Discussion on terminology used to denote the capacity of a medium to transmit water in groundwater literature and practice is presented, referring to the ambiguity of terms most often used to its denotation. Today's most often denotations in groundwater literature and practice are hydraulic conductivity, K [UT] (m/s in SI system) or coefficient of permeability, k [L/T] (m/s in SI system), the terms being used specifically for the flow of a single water phase through a porous media. In addition, discussion is broadened with the relation to the notation permeability, k [1,21 (m2 in SI system) i.e. intrinsic or absolute or specific permeability, also denoted as k [L2-I (m2 in SI system) when porous medium is 100% saturated with a single-phase fluid, i.e. water in considered case, and which are the property of the porous media only, not the fluid.
