oa Hydraulic Parameter Estimation using Geophysically-Constrained Analytical Flow Models

Hydraulic parameters used in constitutive relationships describe how water moves through the soil and are necessary to formulate hydrogeological models that track infiltration, evaporation, and redistribution. the hydraulic parameters are often difficult to obtain directly at a scale that is useful for modeling engineering projects such as aquifer recharge, contaminant remediation, or waste repository performance. Geophysical methods sensitive to changes in water content, however, can be used more easily to indirectly obtain the hydraulic parameters at a variety of scales. in particular, methods that measure the electrical conductivity or dielectric permittivity can be used in a time lapse sequence to track the position of the wetting front during an infiltration event. When directly coupled with a hydrogeological model with the appropriate boundary conditions, the need for extraneous geophysical modeling such as Tomography becomes unnecessary, as the measured, unprocessed geophysical data become the constraining variable for inverse hydraulic parameter estimation. This paper shows two geophysical methods that, when coupled with analytical flow models, can be used to obtain estimates of the parameters that define the unsaturated hydraulic conductivity function. Both model development and field examples are discussed to show the practical applications of the approach.