Lake Pontchartrain Basin Facts
The Pontchartrain Basin is a 4,700 square mile watershed in southeast Louisiana and southern Mississippi. Elevations range from over 300 feet mean sea level in the hills along the Mississippi state line to sea level throughout the coastal lowlands and occasionally below sea level in some urban areas. Many small rivers drain the Florida Parishes and introduce freshwater into Lakes Maurepas and Pontchartrain, the great mixing zone of fresh and saline water.
Lake Pontchartrain was formed 5,000 years ago, covering almost 630 square miles. The shallow Lake (average depth 12 feet) is brackish, receiving freshwater from Lake Maurepas, the Tangipahoa and Tchefuncte Rivers, Bayous Lacombe and Bonfouca, as well as drainage canals, and saltwater from the Gulf of Mexico. This combination and the resultant surrounding wetlands form a complex estuarine ecosystem.
The Basin experiences a variety of environmental stressors. Nonpoint source pollutants, sewage from humans and farm animals and industrial and agricultural discharges, comprise the majority of runoff problems. Shell dredging, oil and gas exploration and development, the Mississippi River Gulf Outlet (MRGO), and industrial activities along the Inner Harbor Navigation Canal (IHNC) also impact the environmental quality of the Basin.
Natural forces, such as hurricanes and land subsidence, affect change in the Basin. Subsidence and accompanying shoreline erosion has had significant consequences in low lying St. Bernard Parish.
For many years, the Basin's wetlands have been channelized, drained and filled, resulting in Lake Pontchartrain receiving a variety of contaminants. The cumulative effects of wetland degradation, shoreline erosion, saltwater intrusion, and discharge of contaminants have decreased grassbeds, diminished shellfish and fish harvests, closed beaches, and resulted in occasional occurrences of oxygen-deficient areas ("dead zones") in the Lake.
The Pontchartrain Basin is a complex system of physical elements where biological diversity is the rule. The picture of the Basin is further complicated by the rapid growth around Metropolitan New Orleans and Baton Rouge. Economic activities range from heavy industry along the Mississippi River, to forestry and agriculture in the upper reaches of the watershed, to fishing and trapping in the coastal wetlands.
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