As the Mississippi River continues to rise higher and higher, the Army Corps of Engineers has been forced to blast levies along the river in an attempt to lower the water level. Unfortunately, while the destruction of levees has protected cities along the river, it has also led to the flooding of thousands of acres of farmland. (Those farmers are rather miffed, to say the least, and are now suing the government.) Frankly, it doesn't take a scientific study to guess the effects of flooding on nearby cropland, but what about the various water systems (lakes, estuaries, etc.) along the river?
Well, environmentalists know that, in fact, historically the Mississippi flooded those nearby water systems annually, bringing in restorative nutrients and sediment. The Mississippi was particularly important to the development of the Louisiana wetlands, which needed the nutrients and sediment. The construction of levees along the river, many believe, contributed heavily to the wetlands' decline in the past century. In 2009, scientists at Louisiana State, Boston University, and Shanghai Ocean University published an analysis of what happened when flooding in 2008 forced government officials to open the Bonnet Carre Spillway, which channels excess water from the Mississippi into Lake Ponchartrain, on the northern border of New Orleans. (Ponchartrain is actually an estuary, but residents no doubt decided that "Ponchartrain Estuary" had too many syllables for everyday use.) Contrary to expectations, the researchers found that the river did not leave significant amounts of nutrients or other particulates in the lake, nor did the river significantly affect the phytoplankton in the lake. "Essentially," they conclude, "the river water eventually flowed as a river through the lake," into the Gulf of Mexico. Perhaps the river water wanted to get to the Gulf of Mexico before it became all oily.