Two widely used measurement techniques of saturated hydraulic conductivity are the Guelph Permeameter (GP) method and the Constant Head Permeameter (CHP) method. A study was conducted to investigate variations in saturated hydraulic conductivity as related to two factors which can influence GP and CHP results. To begin, the influence of the antecedent soil water content on the GP measurements was studied. Then, the effect of the size of the soil core on the laboratory estimates was examined. Finally, a comparison between results of the two methods was carried out. The study was conducted in a sandy clay soil. Experiments with the GP produced decreasing estimates of saturated hydraulic conductivity with increasing antecedent soil wetness; this result was mainly due to the influence of the soil water content at the time of augering the well on the permeability characteristics of the well wall. Laboratory results were influenced by the size of the soil core. In particular, large cores produced lower and less variable estimates of saturated conductivity than small cores, in which the potential for preferential flow increases greatly. On the average, results of the comparison between the two methods were satisfactory only when GP results obtained in the initially dry soil and laboratory estimates obtained on large cores were selected.
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Bagarello et al. (1996) studied this question.