Accurately forecasting saltwater intrusion through navigation locks requires nautical traffic simulation modelling

• Salinity measurements enable validation of analytical lock exchange models. • Cycle-averaged computation without calibration can misestimate salt intrusion. • Coupling vessel traffic and lock exchange models enables time-varying computation. • Time-varying lock exchange models can yield accurate results without calibration. • Our method improves future lock design and operation under varying conditions. Navigation locks enable vessel transit between separated water bodies but also induce water exchange, leading to saltwater intrusion. During droughts, operational strategies that limit this intrusion cause vessel delays. Consequently, accurate estimation of the salt intrusion is essential for optimising these strategies. Current analytical lock exchange models, such as the Sea Lock Formulation, are a suitable and computationally efficient option for this purpose. However, the performance of these models relies on scarce gate-status data of the lock operation. To overcome this challenge, we present a novel method integrating the Sea Lock Formulation with the nautical traffic model OpenTNSim to derive time-varying lock operation parameters from accessible vessel data. This approach uniquely enables simultaneous evaluation of mitigation strategies on both saltwater intrusion and traffic performance. Applied to the world’s largest lock at IJmuiden, the model is validated against measured salt concentration and operation records. When forecasting, our method significantly improves the accuracy of the analytical models, reducing long-term salt intrusion errors from + 22.2 % to − 2.6 %. This marks a critical advancement toward a systematic exploration of tradeoffs between hydraulic and nautical objectives, enabling, for the first time, integrated lock management strategies that balance hydraulic protection with nautical efficiency in closed waterway systems.