Saline intrusion (SI) in coastal aquifers is a global problem with the potential to contaminate groundwater
used by over a billion people. Numerical modelling of SI in coastal aquifers is a key tool for risk assessment,
aquifer management and resource regulation, but is extremely challenging because the mixing zone across the
saline front is often very narrow, extending over metres or 10’s metres, yet the saline front itself may extend
laterally over a large (i.e. many km) three-dimensional (3D) domain. Moreover, the aquifer may be highly
heterogeneous, further complicating the movement and geometry of the front. We test here the use of dynamic
mesh optimization (DMO) in a parallel computational framework to simulate SI with higher accuracy and lower
computational cost compared to fixed-mesh approaches. The framework uses a double control-volume-finite element (DCVFE) method and is implemented in the open-source Imperial College Finite Element Reservoir
SimulaTor (IC-FERST), but could be implemented in other FE-based simulators. We confirm accuracy and
convergence using test cases based on the classic ’Henry’ SI problem, demonstrating that solutions obtained
using DMO require significantly fewer elements and therefore have much lower computational cost compared
to equivalent fixed mesh solutions. We apply the framework to a realistic 3D case study simulating saline
intrusion in a heterogeneous chalk aquifer, demonstrating simulation speed-up in excess of 120×. We suggest
that parallelized DMO offers significant advantages over existing methods to simulate SI.