Abstract
Tidal influences are rarely considered in parameter estimation procedures for coastal groundwater flow models. Yet, considering tides adds to the already high computational burden associated with such models due to the presence of density‐dependent flow. Our objective was to present a parameter estimation procedure that includes tidal overheight in coastal groundwater flow models and to analyze the appropriateness of the chosen model, process setup, and its simplifications. As an example, the procedure was applied to a model for the barrier island Norderney (Germany). The focus of the model was to replicate seasonal groundwater recharge dynamics and the influence of storm surges on the freshwater lens as well as the freshwater/saltwater interface. We applied an iterative‐ensemble smoother (PESTPP‐IES) for history matching with a model chain of a constant‐density freshwater‐lens model and a density‐dependent submodel around the island's water works. An adequate match between measured and simulated observations was obtained from history matching. Model verification was performed using a density‐dependent model of the entire island. Additional verification runs focusing on the transient dynamics of a single boundary condition each (i.e., the sea level or recharge) were compared to deconvoluted signal components of monitored, high‐resolution hydraulic head time series. This revealed that seasonal recharge patterns and the magnitude of storm surge influences were replicated well. However, the simulated hydraulic heads and interface depth underestimated observed data. We attribute this to the scarce information available regarding salinity observations and a possibly too pronounced focus on an accurate representation of tidal influences in the modeling setup.