Lake Pontchartrain, St. Tammany Parish, Louisiana
Lake Pontchartrain, an estuary located in southeastern Louisiana, is a prominent geographical feature in the United States. With a surface area of 630 square miles, it is the largest lake in Louisiana and holds a significant place in the region’s ecology, culture, and history.
Geography and Hydrology
Lake Pontchartrain is an estuary connected to the Gulf of Mexico, mainly fed by the Tangipahoa, Tchefuncte, Tickfaw, Amite, and Bogue Falaya rivers, along with Bayou Lacombe and Bayou Chinchuba. The lake’s oval shape measures approximately 40 miles west to east and 24 miles south to north. It is located in parts of six Louisiana parishes: St. Tammany, Orleans, Jefferson, St. John the Baptist, St. Charles, and Tangipahoa.
Toponymy
The lake is named after Louis Phélypeaux, comte de Pontchartrain, a French statesman during the reign of Louis XIV. The name ‘Pontchartrain’ originates from the location of Phélypeaux’s château in France, where a bridge (French: pont) crossed the river Mauldre on the route from Lutèce to Chartres (chartrain).
Description
Lake Pontchartrain is characterized by its shallow depth, averaging 12 to 14 feet, with some deeper shipping channels maintained through dredging. Salinity in the lake varies, with negligible levels at its northern end and increasing towards the east. The lake’s connection to the Gulf of Mexico via the Rigolets strait and Chef Menteur Pass into Lake Borgne makes it subject to tidal changes.
Infrastructure
The lake is famously crossed by the Lake Pontchartrain Causeway, the world’s longest continuous bridge over water. Additionally, a notable power line crosses the lake, its towers standing on caissons in Lake Pontchartrain.
Geology
The lake sits in a shallow geological trough also underlying the Everglades and the Kissimmee River Valley. This trough was formed by clay deposits over limestone and sand, and the area became a lake around 6,000 years ago due to rising sea levels and increased rainfall. The lake’s basin, primarily limestone, contributes to its shallow nature.
Limnology
Lake Pontchartrain is known for its dynamic ecosystems, including more than 125,000 acres of wetland. The lake comprises various habitats, including bottomland hardwoods, cypress swamps, and diverse marshes. It is part of the larger Pontchartrain Basin, one of the Gulf of Mexico’s largest estuarine systems.
Conservation and Restoration
Efforts are ongoing to conserve and restore the ecosystems around Lake Pontchartrain, given the stress from past exploitation. Various animal species indicate the health of these ecosystems, including the rangia clam, gulf sturgeon, paddlefish, and the alligator snapping turtle. The future of the lake hinges on restoring annual floods, controlling urban sprawl, and reducing harvesting of selected species.
Northshore
The area north of Lake Pontchartrain, known as the North Shore, encompasses several cities and parishes in Louisiana. This region, characterized by uplands and pine savannas, contrasts with the south shore areas of Lake Pontchartrain, which include New Orleans and its suburbs.