A modification of the constant-head permeameter to measure saturated hydraulic conductivity of highly permeable media

The saturated hydraulic conductivity (K(s)) is a key characteristic of porous media, describing the rate of water flow through saturated porous media. It is an indispensable parameter in a broad range of simulation models that quantify saturated and/or unsaturated water flow. The constant-head permeameter test is a common laboratory method to determine K(s) on undisturbed soil samples collected from the field. In this paper we show that the application of this conventional method may result in a biased K(s) in the case of highly permeable media, such as the top layer of Sphagnum peat and gravel. Tubes in the conventional permeameter, that collect water under the sample, introduce a hydraulic head-dependent resistance for highly permeable media and result in an underestimation of K(s). We present a simple and low-budget alternative of the constant-head permeameter test that overcomes the disadvantages of conventional permeameters. The new method was successfully tested on intact highly permeable peatmoss collected from a northern peatland. • Conventional constant-head permeameters underestimate K(s) of highly permeable media due to flow resistance in tubing systems; • We developed the low-resistance permeameter to overcome this disadvantage. • Testing of the low-resistance permeameter demonstrated no systematic bias and successful application for highly permeable media.