With spillway closing, Lake Pontchartrain enters next phase

Bonnet Carre Spillway opening, hot weather is perfect storm for algae blooms

Last Saturday (June 11,) the U.S. Army Corps of Engineers began closing the Bonnet Carre spillway. Closing 20 to 30 bays per day (river stage permitting), the structure may be entirely closed in a couple of weeks.

With the closure comes the next phase of impacts to Lake Pontchartrain. Lake users are asked to contact the Lake Pontchartrain Basin Foundation if they happen to encounter anything out of the ordinary so the foundation can track locations of events.

With the high lake level and lack of rain, the foundation is noticing that many Northshore rivers are not flowing much. This is causing dissolved oxygen levels to be very low in the rivers, and can potentially lead to fish kills. This has already happened once or twice, according to the foundation.

If you see a number of dead, floating fish in a Northshore river (particularly near the lake), you are asked to contact the foundation. They will investigate and notify agencies.

With the flow from the Bonnet Carre stopped and no wind, the sediment in the Mississippi River water (that is now in Lake Pontchartrain) will begin to sink out of the water column. This will leave the water very clear and full of nutrients – a perfect situation for algae growth.

Some species of algae have toxins that can affect pets and humans, so it is best to avoid swimming in it. Once the algae grow and die, the bacteria that decompose them will use all of the oxygen in the water and could lead to fish kills.

From past Bonnet Carre openings, the foundation anticipates that the lake will return to normal conditions in about six months.

If you see indications of any water-quality problems or have any questions about the impacts of the spillway opening on the basin, contact the foundation at info@saveourlake.org or at 504.836.2215.