The most polluted bodies of water in the US Part 5: Mississippi River
Maryella Begley-Garmon, P.E.
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The Mighty Mississippi might seem like an odd nickname for a river until you look at it. The Mississippi River runs from Lake Itasca near Minneapolis, MN for 2,340 miles through 10 states (Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana), finally emptying into the Gulf of Mexico in Louisiana. It drains 41 percent of the continental United States, including all or part of 32 states, and part of 2 Canadian provinces, and carries more water than any other American river. The total drainage basin is 1,151,000 square miles. It is the 13th largest river in the world with the 4th largest drainage basin. The Mississippi River discharges between 200 and 700 thousand cubic feet per second. That’s pretty mighty.
The Mississippi River is divided into 3 sections. The Upper Mississippi starts at the headwaters and goes to the confluence with the Missouri River at St. Louis. The Upper Mississippi has 43 dams and locks, and multiple lakes created by these dams. These are used for recreation and power generation, and control the flow of the upper river. The Middle Mississippi is downriver from the Missouri to the Ohio River at Cairo, Illinois. This section of the river is relatively free flowing. The Lower Mississippi is from the Ohio River to the Gulf of Mexico. The Lower River has massive engineering works, including the Old River Control Structure, to prevent the river from shifting into the channel of the Atchafalaya River and bypassing New Orleans. The Atchafalaya River is a major distributary taking 30% of the combined flow of the Mississippi and Red Rivers to the Gulf of Mexico.
There are 375 fish species known from the full Mississippi basin. Upper River is home to 120 fish species. Additionally, 60% of all migratory birds in North America (326 species) use the river basin as their flyway.
The Mississippi River is an important avenue in world wide shipping carrying 500 million short tons of goods every year including 60% of the grain exported from the US. The river supports approximately 1.3 million jobs and $400 billion in ecosystem services annually. The river supplies drinking water for 20 million people in more than 50 municipalities. It is one of the greatest water highways on earth. Native Americans have lived along the Mississippi since at least the 4th millennium BCE.
Because of the size of the river, it is hard to look at the pollution in the river without breaking it into sections. Overall, most of the pollution today is from elevated nutrient and chemical levels from agricultural runoff. Elevated levels of nitrogen and phosphorus cause algae blooms that block sunlight and suffocate anything below the surface of the water.?
To start at the beginning, research by the Army Corps of Engineers in 1881 reported that many of the sand bars were filled with sawdust instead of sand as the lumber industry in Minnesota took off with the Industrial Revolution and started dumping sawdust and other waste from factories into the Mississippi River. At least 144 million gallons of sewage and garbage were being tossed into the river every single day by the 1930's, leading to disease outbreaks such as typhoid. This same polluted water was used as the drinking water source, infecting nearly 1000 and killing nearly 100 people in Minneapolis each year. One advocacy group estimated that for every 6 gallons of water in the river, there was 1 gallon of sewage. These, combined with industrial waste from coal gasification, waste from slaughter houses, and oil spills combined to all flow down stream. Currently, stretches of the river within the National River & Recreation Area in MN exceed water quality standards for mercury, bacteria, sediment, PCBs (polychlorinated biphenyl), and nutrients, which make the water unsuitable for drinking, swimming, and fishing.?
To learn more about the pollution flowing into the Middle Mississippi, refer back to Part 4 of this series on the Ohio River.
Studies from Louisiana DEQ and LSU have shown that changes made since the passage of the Clean Water Act have been tremendously effective at decreasing the amount of industrial and urban pollution. Wastewater treatment plants and a reduction of industrial chemical discharges are of particular note in these reductions. This does not mean that all of the things dumped into the river previously are gone. There are many chemicals trapped in the sediment at the bottom of the river.? There are also some organic wastes still being discharged into the river. However, pollution from nonpoint sources like farming are now the main identified pollutants for the river. Plastic waste is another growing concern. Being fed by the Mississippi River, the Gulf of Mexico has one of the highest concentrations of plastic waste in the world.?