Nutrient-rich river water flowed for a total of 123 days out of the river and into Lake Pontchartrain. The fresh water displaced the usually brackish lake water, and officials in Mississippi say it spread to Mississippi Sound, causing blooms of toxic algae in both the sound and the lake.
The excess fresh water also led to an abundance of midges, non-biting flies that look a lot like mosquitoes. Although they don't bite, they did swarm in numbers dense enough to coat the windshields of vehicles traveling across the Lake Pontchartrain Causeway.
Here is more information from a Corps news release: