Lake Borgne

Lake Borgne
A strip of marsh separates the MRGO (left) from the lake (right)
Location	Orleans / St. Bernard / St. Tammany parishes, Louisiana / Hancock County, Mississippi, United States
Coordinates	30°01′41″N 89°37′03″W / 30.02806°N 89.61750°W / 30.02806; -89.61750Coordinates: 30°01′41″N 89°37′03″W / 30.02806°N 89.61750°W / 30.02806; -89.61750
Type	lagoon
Primary inflows	MRGO and Mississippi River
Primary outflows	Gulf of Mexico
Catchment area	38,000 km2 (15,000 sq mi)
Basin countries	United States
Surface area	730 km2 (280 sq mi)
Average depth	3 m (9.8 ft)
Settlements	New Orleans
References

Lake Borgne is a lagoon of the Gulf of Mexico in southeastern Louisiana. Due to coastal erosion, it is no longer actually a lakebut rather an arm of the Gulf of Mexico. Its name comes from the French word borgne, which means "one-eyed."

The three large lakes -- Maurepas, Pontchartrain, and Borgne—cover 55% of the Pontchartrain Basin. A brackish marsh land bridge and Lake St. Catherine separate Lake Pontchartrain from Lake Borgne. The Rigolets and Chef Menteur Pass are the two open water connections between Pontchartrain and Borgne.

Due to coastal erosion, Borgne is now a lagoon connecting to the Gulf of Mexico, but early 18th century maps show it as a lake largely separated from the Gulf by a considerable extent of wetlands which have since disappeared. In a 1902 case before the United States Supreme Court over the oyster banks at the boundary between Louisiana and Mississippi, the State of Mississippi argued that at the time of Louisiana's admission into the Union, there probably was no such "Lake Borgne" or "Mississippi Sound".

The basin contains 483,390 acres (1956 km²) of wetlands, consisting of nearly 38,500 acres (156 km²) of fresh marsh, 28,600 acres (116 km²) of intermediate marsh, 116,800 acres (473 km²) of brackish marsh, 83,900 acres (340 km²) of saline marsh, and 215,600 acres (873 km²) of cypress swamp. Since 1932, more than 66,000 acres (267 km²) of marsh have converted to water in the Pontchartrain Basin — over 22% of the marsh that existed in 1932.

The primary causes of wetland loss in the basin are the interrelated effects of human activities and the estuarine processes that began to predominate many hundreds of years ago, as the Mississippi River delta was abandoned.