UNCERTAINTY QUANTIFICATION OF AQUIFER HETEROGENEOUS STRUCTURES

Aquifer heterogeneous structures are often large sources of uncertainty in contaminant remediation and risk assessment. Typically, when building a conceptual model for groundwater flow and solute transport in subsurface system, we assume that the aquifer heterogeneous structures are fixed and just perform uncertainty analysis on hydraulic parameters. In this study an uncertainty quantification method is presented for a coupled modeling of aquifer heterogeneous structures and pumping test data (or tracer test data) utilizing a response surface-based optimization technique. Borehole geological descriptions and geophysical log data are used to characterize the aquifer facies transition probability models. Structure inversion here is performed by estimating the aquifer-structure parameters of a transition probability model and updating the aquifer multi-scale facies distributions with the indicator cokriging simulator. The stochastic property of the structure parameters are demonstrated with the plots of response surfaces, which are used for determining the optimal structure parameters. The Bayesian inference theory is used to quantify the uncertainty of the identified aquifer structures. This methodology is illustrated by two synthetic data sets: a set of pumping test data and a set of tracer test data.