Heterogeneous saltwater intrusion patterns and drivers among multiple outlets in a complex estuary

Area of Science:

• Environmental Science
• Hydrology
• Coastal Engineering

Background:

• Saltwater intrusion in estuaries poses a global threat to ecosystems and freshwater supplies.
• Existing research often overlooks the impact of factors beyond magnitude, such as variability and timing, on intrusion patterns.

Purpose of the Study:

• To investigate heterogeneous saltwater intrusion patterns in a complex estuary.
• To analyze the dominant drivers influencing these patterns using explainable artificial intelligence (XAI).

Main Methods:

• Utilized an estuary hydrodynamic and salinity transport model.
• Developed a comprehensive indicator system for river runoff, tide, and wind characteristics.
• Applied XAI techniques to identify key influencing factors.

Main Results:

• Identified significant variations in salinity across multiple estuary outlets, with some exceeding national standards even in wet seasons.
• Revealed that river runoff dynamics, particularly extremes, significantly influence temporal saltwater intrusion.
• Demonstrated the importance of wind duration and tidal rate of change in intrusion dynamics.

Conclusions:

• Heterogeneous saltwater intrusion patterns are driven by complex interactions of runoff, tide, and wind characteristics.
• XAI analysis provides critical insights into dominant drivers for improved forecasting.
• Findings support enhanced saltwater intrusion management and mitigation strategies in estuaries worldwide.