Seawater intrusion simulation using proper orthogonal decomposition method as a surrogate model. Presented at AGU Annual Meeting 2023 San Francisco, CA (11-15 December 2023)

We address some of the challenges posed by seawater intrusion (SWI) in coastal aquifers and the use of 'variable-density' models to simulate groundwater flow and dissolved salt transport. These models, solving coupled partial differential equations, are computationally expensive, limiting their practicality for rapid and repetitive model runs needed in scenarios like risk analysis and groundwater management. The study proposes a surrogate model for SWI using the proper orthogonal decomposition (POD) method, a projection-based technique. The POD method, applied with a finite difference numerical method, reduces the computational burden by mapping the coefficient and right-hand side matrices onto a reduced space. This results in solving a smaller system of linear equations, significantly improving computational efficiency. The surrogate model is tested on the Santa Barbara aquifer, demonstrating notable speed improvements while maintaining acceptable accuracy levels in simulating SWI.