A modified Green-Ampt infiltration model for muddy water

The Green-Ampt infiltration model has been widely used because of its simple structure and clear physical meaning of the parameters. The model parameters were improved using the equivalent saturated hydraulic conductivity to develop the Green-Ampt infiltration model for muddy water (MWGA). A saturated soil column infiltration test with muddy water was conducted to determine the influence of the soil texture (sandy soil and silt loam) and the sand content (S = 3 %, 6 %, 9 %, and 12 %) on the hydraulic conductivity of saturated soil columns. The equivalent saturated hydraulic conductivity was derived based on several assumptions and under different conditions. Eight one-dimensional vertical infiltration tests were conducted under the same conditions for verification. The MWGA was simplified according to the results, and four tests with different sand contents (S = 4 % and 10 %) were conducted to validate the MWGA for both soils (the simplified infiltration model was used for the sandy soil). The results indicated that the hydraulic conductivity trend of the saturated soil column during the infiltration of muddy water into sandy soil was in accordance with the physical model. The hydraulic conductivity of the silt loam was only influenced by the sand content and showed a significant linear relationship with the sand content. The root mean square error (SRMSE) obtained from the validation test under the same conditions was close to 0, and the absolute value of the relative error (SRE) was less than 15 %, indicating a good fit. The results of the validation tests for different sand contents showed that the simulated and observed values were close to the 1:1 line, demonstrating high model accuracy. Our results provide new insights into the infiltration of muddy water and the mechanism of reducing the infiltration rate due to the dense layer formed on the soil surface.