Adhanom, G.T.Stirzaker, Richard JohnLorentz, Simon A.Annandale, John GeorgeSteyn, Joachim Marthinus2012-02-272012-02-272012-01Adhanom, GT, Stirzaker, RJ, Lorentz, SA, Annandale, JG & Steyn, JM 2011, 'Comparison of methods for determining unsaturated hydraulic conductivity in the wet range to evaluate the sensitivity of wetting front detectors', Water SA, vol. 38, no. 1, pp. 67-75.0378-4738 (print)1816-7950 (online)10.4314/wsa.v38i1.9http://hdl.handle.net/2263/18240The design of passive lysimeters or wetting front detectors determines the tensions at which they collect a water sample from an unsaturated soil. When deployed in the field to help manage irrigation, it is necessary to know the minimum flux of water that can be sampled by a passive lysimeter and how this relates to the drainage flux at field capacity. This requires a good estimate of the unsaturated hydraulic conductivity characteristic, K(h), in the wet range (< 10 kPa). We compared various field, laboratory and theoretical approaches for obtaining the K(h) function and compared these to a reference K(h) function derived by applying inverse modelling approaches to field drainage experimental data. The Van Genuchten model and three of the pedotransfer models produced K(h) functions with a root mean square error of less than 5% compared to the reference, and appear to be simple methods of obtaining a reasonable estimate of unsaturated hydraulic conductivity. However, despite the goodness of fit, there can be a 10-fold difference in conductivity at a given tension < 10 kPa estimated from the different methods. Moreover, water content at field capacity depends entirely on whether field capacity is defined as time elapsed after saturation, a set tension or a minimum flux.enWater Research CouncilInverse modellingInstantaneous profile methodPedotransfer functionsWetting front detectorField capacityHYDRUS-2DSoil permeabilityLysimeterIrrigation -- ManagementArticle