Abstract
This study aims at furthering our understanding of the Modified Philip–Dunne Infiltrometer (MPDI), which is used to determine the saturated hydraulic conductivity Κs and the Green–Ampt suction head Ψ at the wetting front. We have developed a forward-modeling algorithm that can be used to simulate water level changes inside the infiltrometer with time when the soil hydraulic properties Κs and Ψ are known. The forward model was used to generate 30,000 water level datasets using randomly generated values of Κs and Ψ values. These model data were then compared against field-measured water level drawdown data collected for three types of soil. The Nash–Sutcliffe efficiency (NSE) was used to assess the quality of the fit. Results show that multiple sets of the model parameters Κs and Ψ can yield drawdown curves that can fit the field-measured data equally well. Interestingly, all the successful sets of parameters (delineated by NSE ≥ the threshold value) give Κs values converged to a valid range that is fully consistent with the tested soil texture class. However, Ψ values varied significantly and did not converge to a valid range. Based on these results, we conclude that the MPDI is a useful field method to estimate Κs values, but it is not a robust method to estimate Ψ values. Further studies are needed to improve the experimental procedures that can yield more sensitive data that can help uniquely identify Κs and Ψ values.
Highlights
Saturated hydraulic conductivity Ks is one of the most important parameters that control the water seepage processes through the soil profile [1,2,3,4,5]
Results showed that the Modified Philip–Dunne Infiltrometer (MPDI) gave the correct trend of decreasing Ks values by increasing the fine content of the media
Our review indicates that several recent studies, including Weiss and Gulliver [29], García-Serrana et al [30], Kristvik et al [31], and Taguchi et al [32], have used the MPDI approach to measure the in situ soil hydraulic parameters
Summary
Saturated hydraulic conductivity Ks is one of the most important parameters that control the water seepage processes through the soil profile [1,2,3,4,5]. The soil core method has some challenges including macropores created by insertion of the ring, and relatively small sample size that may not yield a representative Ks value [5,13]. To overcome these disadvantages, several field techniques have been developed to measure the in situ saturated hydraulic conductivity of the soil. Natural variability of the soil properties and limitations of the field techniques such as sample size and flow geometry could result in inaccurate estimation of the field-scale hydraulic properties [5,14,15]
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