The Heart of Cajun Country: Atchafalaya River

atchafalaya-mapAs I’ve mentioned in previous posts, my research at LSU will focus primarily on hydrology and the biogeochemistry of the Atchafalaya River, a 137 mile distributary of the Mississippi River. The Atchafalaya River Basin is home to the United States’ largest continuous wetland/swamp ecosystem and has a very interesting past that I believe plays an important role in its ecology and chemical processes.

Geomorphologists, or scientists that study the relationship between physical land features and the earth’s structure, believe the Atchafalaya formed in the 15th century as a product of the Red River’s channel naturally intercepting the Mississippi. As a result the Atchafalaya began draining water from the Mississippi River. Over time the Atchafalaya continued to intercept more and more water from the Red and Mississippi Rivers, so much in fact that it would have completely re-routed the majority of the flow of the Mississippi through it’s channel, which would not have been good for transport and commerce up the Mississippi. However, in the 1960s the U.S. Army Corps of Engineers intervened and built a control structure to regulate the amount of flow the Atchafalaya receives from the Mississippi. This structure, along with several others, is still used today to ensure the Atchafalaya is receiving around 30% of the flow of the Mississippi and may be used as a flood-release gate if water levels are to get too high in the Mississippi.

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The Red and Mississippi Rivers once ran paralell to one another. The natural convergence of the two rivers in the 15th century formed the Atchafalaya River. The construction of leveels, addtional channels, and flow control mechanisms between the three rivers has greatly altered the ecology of southern Louisiana. Picture courtesy of the U.S. Army Corps of Engineers

It’s amazing that engineering has been able to prevent the overtake of the Mississippi River by the Atchafalaya. There’s no doubt these engineering feats have preserved the larger channel necessary for moving large freight and commerce up the Mississippi. Additionally, the flood-release structures have been opened multiple times to prevent flooding along the Mississippi downstream in Baton Rouge and New Orleans. However, it has not been without consequences in the Atchafalaya River Basin.

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Atchafalaya River – Calumet, LA – photo cred to my grad student colleague, Emily DelDuco

Prior to the intervention of humans, the Atchafalaya River Basin was composed of numerous small braided streams that were interconnected by wetlands. These wetlands were home to multiple species of waterfowl, fish, and plants and assisted in preventing the loss of Louisiana’s coastline via  coastal erosion. In the mid 20th century many of these wetlands water sources were diverted due to construction of water control structures, levees along the main channel of the river, and canals/pipelines  to support oil and gas exploration. Consequently, these wetlands were segregated, deprived of a water, and have dried up. We are fortunate that a stretch of 1.4 million acres of wetlands still exists today where the Atchafalaya drains into the Gulf of Mexico, however, it is only a portion of what existed merely 200 years ago.

Now, this brief post has been simply a snippet of the history of human intervention in the Atchafalaya River. It is by no means  a comprehensive analysis of how these ecosystems have been altered or the consequences of those alterations. But it is information like this that will hopefully allow me to tell a more comprehensive story of the hydrologic and chemical processes occurring in the Atchafalaya River today. Louisiana’s stories, politics, management, issues, and community views relating to water resources are so very different from Indiana’s, and I’m just happy to be a part of it.

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