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

Abstract

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.