Scaling field‐measured soil hydraulic properties using a similar media concept

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Abstract
With a view toward developing techniques for studying water flow in spatially varying soils, field data for soil water characteristic relationships and unsaturated hydraulic conductivity are scaled by using the concept of similar media. Data observed by different investigators at three geographic areas are used. The soil water characteristic data consisted of 840, 900, and 512 observations, while those for the unsaturated hydraulic conductivity (available from only one of the three sources) consisted of 2640 observations. In the process of scaling the data a best fit for the scaled data is defined in terms of a sum of squares about an ‘average’ curve using one value for the scaling parameter for each sampling location. Comparisons made between curves fitting the data and those fitting the scaled data show that scaling reduces the sums of squares by amounts varying from 34 to over 90%. For similar media the scaling parameter determined at a given sampling location for the soil water characteristic relationship (α from h(S)) should be identical to that for the unsaturated hydraulic conductivity (αr from K(S)). Although these parameters were highly correlated (r = 0.91 ) for the only set of data available, α r from h(S) values are shown to be more effective in scaling the unsaturated hydraulic conductivity data than are αr from K(S) values in scaling soil water characteristic data.