Optimal strategies for assigning prior boundary settings in Hydraulic Tomography analysis

Hydraulic tomography (HT) is a high-resolution method for identifying aquifer hydraulic property heterogeneity. Despite decades of development that have led to the relative maturation of HT, the influence of prior boundary information on HT estimations remains insufficiently explored. In this study, HT methods were applied to a synthetic heterogeneous aquifer to examine the impacts of boundary condition types, boundary sizes, and prescribed head values on parameter estimation. The results indicate that boundary size has a limited impact on HT outcomes, regardless of data adequacy, whereas boundary condition type plays a critical role in HT inversion. Increasing the boundary size can mitigate errors arising from incorrect assumptions about boundary type. The SimSLE-HCA iterative algorithm effectively estimates optimal boundary head values when sufficient HT survey data are available. For practical applications, when the boundary size is unknown, a moderate expansion of the simulation domain is recommended. When the boundary type is uncertain, specifying a constant-head boundary is a practical and robust choice.