The potential of Source-responsive Method in representing macropore structural characteristics within soil profiles

The source-responsive method (SRM), which accounts for film flow in macropores and matrix absorption phenomena, is an advanced dual-domain modeling framework and has been successfully applied in catchment scale. It also provides a parameter-predictive approach by introducing a parameter, M, to represent macropore area density. However, the capability of this parameter to accurately reflect macropore structure remains unclear. In this study, a 1-D infiltration model based on SRM was developed to simulate soil water dynamics across six experiments, and obtained calibrated M values. The results demonstrate that the SRM performs well (NSE>0.88) in most cases, except for two artificial-macropore experiments with low M values. Measured M values were extracted from horizontal image slices of dyeing experiments. In experiments with good infiltration simulation performance, the measured values align closely with calibrated values (RE<35%), though they are consistently slightly higher. Conversely, in poorly simulated experiments, significant deviations were observed, with RE exceeding one order of magnitude. Further analysis using HYDRUS-2D revealed that limited lateral water propagation from macropore walls contributed to poor simulation accuracy when M values were excessively low.

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