In hydrogeology, the coastal aquifers of Kerala frequently experience saltwater intrusion. Which physical process under natural equilibrium conditions prevents seawater from migrating inland into freshwater aquifers?

💡 Solution & Explanation

Under natural equilibrium conditions, the hydrostatic pressure head generated by the seaward-flowing freshwater lens creates a sufficient hydraulic gradient to prevent denser saline water from migrating inland into coastal aquifers. Physical barriers or tidal actions do not provide the primary counterpressure necessary to maintain this freshwater-saltwater interface.