EFFECTIVE HYDRAULIC PARAMETERS FOR TRANSIENT INFILTRATION IN HETEROGENEOUS SOILS

This study is a focused effort on deriving effective hydraulic properties of transient infiltration into heterogeneous soils in terms of variabilities of the hydraulic parameters based on field-measured and re-generated hydraulic parameter data sets. The main goals are to investigate 1) how the effective hydraulic parameter schemes are sensitive to the time scale of hydrologic process, 2) how the hydraulic parameter correlation and variability significantly impact effective hydraulic parameter schemes, and 3) how the effective schemes can be better expressed in relation to local scale hydraulic parameter variability. An inverse procedure along with the HYDRUS-1D numerical program is used to find the effective hydraulic parameters for infiltration process in heterogeneous soils. Using various boundary pressure head and depth to water table conditions we illustrate the effects of ponding and depth to water table on the effective hydraulic parameters at different time scales. By comparing the effective hydraulic parameters of field-measured and re-generated hydraulic parameters data sets, we investigate the sensitivity of effective hydraulic parameters to the correlation of the saturated hydraulic conductivity and the shape parameter. Results show that the effective hydraulic parameters change with time scale of infiltration initially, and then approach nearly constant values, indicating an equivalent homogeneous medium is a more viable alternative for large temporal scale transient infiltration process. The effective hydraulic parameters are also found to be sensitive to the correlation between the saturated hydraulic conductivity and the shape parameter.