Saltwater intrusion is the dominant oceanographic threat, affecting over 1.7 million hectares of agricultural land in severe dry seasons. The mechanism is a classic salt wedge: dense saline seawater sinks to the bottom of the channel and advances inland along the bed, while lighter freshwater rides on top. The boundary between them — the halocline — is the critical surface. When upstream discharge falls (dry season, ENSO drought), the wedge advances; when discharge rises (wet season), it is flushed back toward the coast.

Try setting discharge to "dry" and switching to "flood tide" — you'll see the wedge advance furthest inland, which is exactly the scenario Mekong Delta experiences during La Niña–modulated dry seasons (e.g. 2015–2016, 2019–2020). During those events, intrusion exceeded 90 km into the Tiền and Hậu river branches, reaching stations like Vàm Kênh and Bình Đại in Bến Tre — areas historically considered safe.