The Mississippi River is one of the world’s major river systems in size, habitat diversity and biological productivity. It is the second longest river in North America, flowing 2,350 miles from its source at Lake Itasca through the center of the continental United States to the Gulf of Mexico. The Missouri River, a tributary of the Mississippi River, is about 100 miles longer. Some describe the Mississippi River as being the third longest river system in the world, if the length of Missouri and Ohio Rivers are added to the Mississippi's main stem.
When compared to other world rivers, the Mississippi-Missouri River combination ranks fourth in length (3,710 miles/5,970km) following the Nile (4,160 miles/6,693km), the Amazon (4,000 miles/6,436km), and the Yangtze Rivers (3,964 miles/6,378km). The reported length of a river may increase or decrease as deposition or erosion occurs at its delta, or as meanders are created or cutoff. As a result, different lengths may be reported depending upon the year or measurement method.
For reasons mentioned above there are competing claims as to the Mississippi's length. The staff of Itasca State Park at the Mississippi's headwaters say the main stem of the river is 2,552 miles long. The US Geologic Survey has published a number of 2,300 miles, the EPA says it is 2,320 miles long, and the Mississippi National River and Recreation Area suggests the river's length is 2,350 miles.
At Lake Itasca, the river is between 20 and 30 feet wide, the narrowest stretch for its entire length. The widest part of the Mississippi can be found at Lake Winnibigoshish near Bena, MN, where it is wider than 11 miles. The widest navigable section in the shipping channel of the Mississippi is Lake Pepin, where it is approximately 2 miles wide.
At the headwaters of the Mississippi, the average surface speed of the water is about 1.2 miles per hour - roughly one-third as fast as people walk. At New Orleans the river flows 3 miles per hour on average.
Mississippi River Watershed
The Mississippi River watershed is the fourth largest in the world, extending from the Allegheny Mountains in the east to the Rocky Mountains in the west. The watershed includes all or parts of 31 states and two Canadian Provinces. The watershed measures approximately 1.2 million square miles, covering about 40% of the lower 48 states.
Communities up and down the river use the Mississippi to obtain freshwater and to discharge their industrial and municipal waste. We don't have good figures on water use for the whole Mississippi River Basin, but we have some clues. A January 2000 study published by the Upper Mississippi River Conservation Committee states that close to 15 million people rely on the Mississippi River or its tributaries in just the upper half of the basin (from Cairo, IL to Minneapolis, MN). A frequently cited figure of 18 million people using the Mississippi River Watershed for water supply comes from a 1982 study by the Upper Mississippi River Basin Committee. The Environmental Protection Agency simply says that more than 50 cities rely on the Mississippi for daily water supply.
Agriculture has been the dominant land use for nearly 200 years in the Mississippi basin, and has altered the hydrologic cycle and energy budget of the region. The agricultural products and the huge agribusiness industry that has developed in the basin produce 92% of the nation's agricultural exports, 78% of the world's exports in feed grains and soybeans, and most of the livestock and hogs produced nationally. Sixty percent of all grain exported from the US is shipped on the Mississippi River through the Port of New Orleans and the Port of South Louisiana.
In measure of tonnage, the largest port district in the world is located along the Mississippi River delta in Louisiana. The Port of South Louisiana is one of the largest volume ports in the United States. Representing 500 million tons of shipped goods per year (according to the Port of New Orleans), the Mississippi River barge port system is significant to national trade.
Shipping at the lower end of the Mississippi is focused on petroleum and petroleum products, iron and steel, grain, rubber, paper, wood, coffee, coal, chemicals, and edible oils.
To move goods up and down the Mississippi, the U.S. Army Corps of Engineers maintains a 9-foot shipping channel from Baton Rouge, LA to Minneapolis, MN. From Baton Rouge past New Orleans to Head of Passes, a 45 foot channel is maintained to allow ocean-going vessels access to ports between New Orleans and Baton Rouge.
At Lake Itasca, the average flow rate is 6 cubic feet per second. At Upper St. Anthony Falls, the northern most Lock and Dam, the average flow rate is 12,000 cubic feet per second or 89,869 gallons per second. At New Orleans, the average flow rate is 600,000 cubic feet per second.
There are 7.489 gallons of water in a cubic foot. One cubic foot of water weighs 62.4 pounds. A 48 foot semi-truck trailer is a 3,600 cubic foot container.
At Lake Itasca, it would take 10 minutes for one semi-trailer of water to flow out of the lake into the Mississippi.
At St. Anthony Falls, the equivalent of 3 semi-trailers full of water go over the falls every second.
At New Orleans, the equivalent of 166 semi-trailers of water flow past Algiers Point each second.
The Mississippi River and its floodplain are home to a diverse population of living things:
At least 260 species of fish, 25% of all fish species in North America;
Forty percent of the nation's migratory waterfowl use the river corridor during their Spring and Fall migration;
Sixty percent of all North American birds (326 species) use the Mississippi River Basin as their migratory flyway;
From Cairo, IL upstream to Lake Itasca there are 38 documented species of mussel. On the Lower Mississippi, there may be as many as 60 separate species of mussel;
The Upper Mississippi is host to more than 50 mammal species;
At least 145 species of amphibians and reptiles inhabit the Upper Mississippi River environs.