It is becoming widely recognized that solute transport in heterogeneous soils are extremely difficult to predict. Factors, which complicate the prediction, include geological heterogeneity and data limitations. This project will investigate a new approach to predict field-scale flow and solute transport which accounts for variability and uncertainty in a systematic way. The new approach is based on the distributed stochastic estimation theory which combines field measurements with predictions from a stochastic groundwater model. The approach can be applied to characterize the extent and severity of groundwater contamination at hazardous waste sites before remediation begins and to evaluate the progress of cleanup techniques during remediation. The stochastic model provides prior estimates of the mean and variance of head and solute concentration throughout a contaminated site. These estimates are updated whenever new measurements of hydraulic conductivity, head and/or concentration become available. These estimates may be used to guide the placement of sampling wells and to evaluate the accuracy of the site characterization.
The research project is intended to be methodological in orientation and address tough conceptual and computational problems. The project will develop a new algorithm for coupled flow and transport conditioning that is not restricted by the assumptions of linearity, stationarity, or ergodicity. Specifically, the project will extend the PI's nonstationary spectral approach to iterative measurement conditioning and present a novel technique for its efficient implementation. The approach should greatly improve the estimation accuracy and dramatically increases the size and complexity of the site characterization problems that can be analyzed with stochastic methods.
The proposed research will proceed in two phases. The first phase will test nonstationary spectral conditioning on a groundwater flow problem. The objective of phase 1 study is to 1) demonstrate the new theory and specific objective phase is to application procedure using a concrete example, 2) demonstrate the accuracy, efficiency, and robustness of the new approach by comparing it with existing solution techniques, and 3) demonstrate the feasibility of the new approach for large groundwater systems. The second phase will test the new approach for coupled three-dimensional flow and transport problems and apply it to predict and characterize groundwater flow and contamination at a real field site. As suggested by NSF implementation of phase 2 will be deferred until phase 1 is successfully completed. We will later submit a revised proposal to NSF with a refined research plan for the second phase based on phase 1 results and make a compelling case for phase 2 investigation.
