Sediment of The Mississippi River

Prior to 1900, the Mississippi River transported an estimated 400 million metric tons of sediment per year from the interior of the United States to coastal Louisiana and the Gulf of Mexico. During the last two decades, this number was only 145 million metric tons per year. The reduction in sediment transported down the Mississippi River is the result of engineering modification of the Mississippi, Missouri, and Ohio rivers and their tributaries by dams, meander cutoffs, river-training structures, and bank revetments and soil erosion control programs in the areas drained by them.

Discharge of The Mississippi River

The Mississippi river discharges at an annual average rate of between 200 and 700 thousand cubic feet per second (7,000–20,000 m³/s). Although it is the 5th largest river in the world by volume, this flow is a mere fraction of the output of the Amazon, which moves nearly 7 million cubic feet per second (200,000 m³/s) during wet seasons. On average, the Mississippi has only 9% the flow of the Amazon River.

Outflow of The Mississippi River

Fresh river water flowing from the Mississippi into the Gulf of Mexico does not mix into the salt water immediately. The images from NASA's MODIS to the right show a large plume of fresh water, which appears as a dark ribbon against the lighter-blue surrounding waters.

The images demonstrate that the plume did not mix with the surrounding sea water immediately. Instead, it stayed intact as it flowed through the Gulf of Mexico, into the Straits of Florida, and entered the Gulf Stream. The Mississippi River water rounded the tip of Florida and traveled up the southeast coast to the latitude of Georgia before finally mixing in so thoroughly with the ocean that it could no longer be detected by MODIS.

Drainage Area and Basin of The Mississippi Rriver

The Mississippi River drains the majority of the area between the Rocky Mountains and the Appalachian Mountains, except for the areas drained to the Hudson Bay via the Red River of the North, by the Saint Lawrence River and the Great Lakes, the Rio Grande (and numerous other rivers in Texas), the Alabama River-Tombigbee River, and the Chattahoochee River-Apalachicola River.

The Mississippi River empties into the Gulf of Mexico about 100 miles (160 km) downstream from New Orleans. Measurements of the length of the Mississippi from Lake Itasca to the Gulf of Mexico vary somewhat, but the United States Geological Survey's number is 2,340 miles (3,770 km). The retention time from Lake Itasca to the Gulf is about 90 days.

Watershed of The Mississippi River

The Mississippi River has the fourth largest drainage basin or "catchment" in the world. The basin covers more than 1,245,000 sq mi (3,220,000 km²), including all or parts of 31 states and two Canadian provinces. The drainage basin empties into the Gulf of Mexico. The total catchment of the Mississippi River covers nearly 40% of the landmass of the continental United States.