Comparing two methods of analysis of single-ring infiltrometer data for a sandy – loam soil

Abstract

The single-ring pressure i n filtrometer (PI) with the steady-state Two-Ponding-Depth (TPD) applic ation method were developed to simulta neously determine the saturated soil hydraulic conductivity, K , and the α ⁎ -parameter in the fi eld. Methods of analysis of transient PI data are also available but they have received little testing so far. The transient WU method and the TPD method were compared for a sandy-loam soil. A linearization technique o f the in filtration curve yielded more reliable K fs fs and α ⁎ results (i.e., falling within expected ranges) than a non-linear optimization technique. The WU method gave both positive and reasonable K and α ⁎ values for all infi ltration tests. Using the mean soil water content for all tests instead of the locally measu red ones did not affect substantially the calculations because the maximum absolute discrepancy between two estimates of a given variable ( K fs or α ⁎ ) a t a location wa s equal to 22%. In some cases, the TPD method yielded negative results or excessively low α ⁎ values. The mean results of the TPD method and the WU method with the linearization technique were similar for both K fs fs and α ⁎ (K : 175.1– 214 .1 m m h − 1 ; α ⁎ : 3.32 –3.94 m − 1 fs ). The differences between these two methods were reduced, also in terms of relative variability of the data (coef fi cient of variation = 76.9 – 81.3% for K and 126.1 –14 9.4% for α ⁎), when locations yielding both positive and reasonable results with the TPD method were considered. It wa s concluded that the WU method is a valid alternative t o the TPD method. The transient method should be preferred especially when time available for the test is limited and flow rates can easily be monitored at short time intervals from the beginning of the test. fs