How big is Lake Pontchartrain?

Lake Pontchartrain, located in southeastern Louisiana, is one of the largest inland bodies of water in the United States. Despite being commonly referred to as a lake, it is technically an estuary — a brackish water body that connects to the Gulf of Mexico through a series of natural and man-made waterways. Its size, geographic importance, and ecological role make it a significant feature of Louisiana’s landscape.

Size and Dimensions

Lake Pontchartrain covers an area of approximately 630 square miles (1,630 square kilometers), making it the second-largest inland saltwater body in the United States after the Great Salt Lake in Utah. It stretches about 40 miles (64 kilometers) from east to west and about 24 miles (39 kilometers) from north to south at its widest point. Despite this vast surface area, the lake is relatively shallow, with an average depth of only 12 to 14 feet (3.7 to 4.3 meters). Its deepest point is around 65 feet (20 meters), located near the southern shore.

Geography and Hydrology

Lake Pontchartrain is bounded by several parishes, including Orleans, Jefferson, St. Tammany, St. John the Baptist, St. Charles, and Tangipahoa. It is part of a larger estuarine system that includes Lake Maurepas to the west and connects to the Gulf of Mexico via the Rigolets Strait and Chef Menteur Pass to the east. The lake is also linked to the Mississippi River through the Bonnet Carré Spillway, which is used to divert floodwaters into the lake during high river events.

The basin receives freshwater inflow from numerous rivers and bayous, such as the Tchefuncte, Tangipahoa, Amite, and Bogue Falaya rivers, which help moderate its salinity levels. As a result, Lake Pontchartrain contains brackish water — a mix of salt and freshwater — and supports a diverse aquatic ecosystem.

The Lake Pontchartrain Causeway

One of the most remarkable human-made features associated with Lake Pontchartrain is the Lake Pontchartrain Causeway, a dual-span bridge that stretches about 24 miles (38.5 kilometers) across the lake, connecting the cities of Metairie (near New Orleans) on the south shore and Mandeville on the north shore. It holds the Guinness World Record for the longest continuous bridge over water in the world. The causeway is not only a vital transportation link but also a symbol of human engineering across a massive natural water body.

Ecological and Economic Significance

Lake Pontchartrain plays an essential role in the region's ecology and economy. It serves as a habitat for numerous fish species, crustaceans, and birds, making it important for both commercial and recreational fishing. The lake and its surrounding wetlands also provide storm surge protection to nearby communities, including the city of New Orleans.

However, Lake Pontchartrain has faced significant environmental challenges over the years, including pollution from urban runoff, industrial discharge, and the effects of hurricanes such as Katrina in 2005. Conservation efforts, led by organizations like the Lake Pontchartrain Basin Foundation (now known as Pontchartrain Conservancy), have contributed to improving water quality and restoring the health of the lake.

Conclusion

In summary, Lake Pontchartrain is an expansive and shallow estuarine lake that spans approximately 630 square miles in southeastern Louisiana. It is a critical geographic feature with far-reaching implications for ecology, transportation, flood control, and the regional economy. Though it has faced environmental pressures, ongoing restoration efforts aim to preserve the lake’s natural beauty and utility for future generations.