Primary INTERA Participants: Mohamed Hayek, Banda RamaRao, Marsh Lavenue, Jeremy White, Katie Markovich, Ed DeSousa, Abhishek Singh

Challenge: To address the shortcomings of traditional perturbation methods through development of a powerful sensitivity analysis tool for understanding the relationships between model parameters and important simulation results. The adjoint method for calculating parameter sensitivities to observations virtually eliminates the computational burden associated with traditional perturbation methods, but it requires intrusive access to model quantities during the simulation that is not generally available with compiled software like MODFLOW. The release of the MODFLOW application programming interface (API) has enabled INTERA to develop Mf6Adj, a lightning fast adjoint sensitivity tool that readily couples to MODFLOW 6 models.

Method: Dr. Mohamed Hayek, a renowned applied mathematician based in the INTERA Swiss office, is carrying forward the pioneering work by Drs. Banda RamaRao and Marsh Lavenue, and others on the adjoint state method in groundwater modeling by extending it to accommodate the Newton formulation, variable conductance approaches, and boundary condition packages available in MODFLOW 6. Dr. Jeremy White, with support from Drs. Katie Markovich and Edward DeSousa are leading the effort to build, test, and verify the Mf6Adj software package based on Dr. Hayek’s adjoint solutions. A beta version of Mf6Adj is expected to be released in an open-source GitHub repository in early 2024. Continuous and iterative development from implementation by INTERA scientists and members of the groundwater modeling community will bolster further improvement of the tool.

Primary Impact: A tool that readily couples to MODFLOW 6 models to enable sensitivity analysis at a trivial computational cost.