BeerBorg

Lake Pontchartrain is not a true lake but an estuary connected to the Gulf of Mexico via the Rigolets strait (known locally as "the Rigolets") and Chef Menteur Pass into Lake Borgne, another large lagoon, and therefore experiences small tidal changes. It receives fresh water from the Tangipahoa, Tchefuncte, Tickfaw, Amite, and Bogue Falaya rivers, and from Bayou Lacombe and Bayou Chinchuba. It is one of the largest wetlands along the Gulf Coast of North America.[2] It comprises more than 125,000 ha of wetland, including bottom land hardwoods and cypress swamps (although these have been severely degraded by past logging) along with a complex mixture of herbaceous wetlands including fresh, intermediate and brackish marsh.[3]

Salinity varies from negligible at the northern cusp west of Mandeville up to nearly half the salinity of seawater at its eastern bulge near Interstate 10. Lake Maurepas, a true freshwater lake, connects with Lake Pontchartrain on the west via Pass Manchac. The Industrial Canal connects the Mississippi River with the lake at New Orleans. Bonnet Carré Spillway diverts water from the Mississippi into the lake during times of river flooding.