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Archive - June 2021

What are Rivers?
Rivers and streams are aquatic habitats contained within a channel. They have water in motion. If water flows through the channel all year, the river or stream is called a perennial stream. An intermittent stream has water flowing only part of the year. The smaller streams that feed into larger rivers and streams are called tributaries. The land next to a river or stream that is periodically flooded is called the flood plain.

What are Some Rivers in Illinois? 
The major rivers in Illinois are the Mississippi River, Illinois River, Kaskaskia River, Little Wabash River, Wabash River, Embarras River, Sangamon River, Big Muddy River, Rock River, Spoon River, Des Plaines River, Ohio River, Fox River and Cache River. If you go to this document and scroll to page five, you can see a map of the rivers of Illinois.

How Big Are They?
Illinois has 106,900 miles of rivers and streams within its borders. The list below shows the length of some of the major rivers in the state. Some of these rivers flow through more than one state. The numbers below represent only the Illinois portion of those rivers.
Source: Illinois Environmental Protection Agency, 1995.

581 miles Mississippi River
332 miles Illinois River
292 miles Kaskaskia River
237 miles Little Wabash River
230 miles Wabash River
220 miles Embarras River
206 miles Sangamon River
166 miles Big Muddy River
163 miles Rock River
163 miles Spoon River
156 miles Des Plaines River
133 miles Ohio River
115 miles Fox River
93 miles Cache River

What Lives in and Along a River?
Plants growing along flowing water provide shade to the river or stream, cooling it and allowing it to hold more oxygen. They also slow the rate of soil loss along the river, decreasing the amount of silt in the water. Characteristic plants growing along rivers in Illinois include willows (Salix spp.), cottonwood (Populus spp.), sycamore (Platanus occidentalis), box elder (Acer negundo), sedges, bulrushes, cattails (Typhus spp.), buttonbush (Cephalanthus occidentalis) and touch-me-not (Impatiens spp.).

Aquatic organisms are often categorized by where they live in the water. Benthic organisms live on the bottom and feed on plant and animal materials that collect there. Crayfish, mussels and stonefly and mayfly larvae are examples of benthic organisms. Pelagic organisms live within the water column. These organisms may float or swim and include fishes, frogs, snakes, turtles, salamanders, water lilies and insects. Surface-dwelling organisms live on the top of or just above the water level and include water striders, duckweeds and adult dragonflies and damselflies. Other organisms, like birds and mammals, come to the water for drinking and/or feeding or live in and raise their young in burrows or other shelters along the river. Examples include the American beaver Castor canadensis, the North American river otter Lontra canadensis and the wood duck Aix sponsa.

What are the Values of Rivers?
Rivers provide a home for many species of plants and animals as well as drinking water and a source of food for animals that live near it. Life in swift water provides abundant food supplies flowing downstream and water with high amounts of dissolved oxygen.

River flooding helps to improve the soil quality of the flood plain along the river.

Rivers provide recreational opportunities such as boating, canoeing, fishing, hunting, trapping, skiing and wildlife observation.

Rivers are used for shipping many types of goods.

Rivers and streams that have a dam built across them may generate electricity, provide a water supply for people to use and store flood waters. While dams help people, they cause problems for aquatic organisms.

What are Some Threats to the Rivers of Illinois?
Illinois’ rivers are threatened by dredging, damming, pollution, siltation and/or the presence of exotic plants and animals.

Though soil erosion is a natural process, many human activities speed up the process, thus increasing the amount of soil that enters rivers and streams. Clearing or removing native habitats makes soil particles more easily moved by wind or water. Soil particles in water can kill bottom-dwelling organisms, clog the gills of fishes and mussels and destroy habitat used for reproduction. Chemical pollutants attached to soil particles can kill or severely injure aquatic organisms.

When water movement slows, soil particles can fall out of the water column and build up in the river channel, a process called sedimentation. Sediment may need to be removed through dredging, a very expensive process.

Damming of rivers results in the loss of aquatic habitats. While dams help people, they cause problems for aquatic organisms.

Illinois’ agricultural landscape impacts aquatic habitats. The chemicals used to increase crop production and kill crop pests wash into rivers and streams with rainfall and other precipitation. Contaminants that enter the water eventually enter the body of organisms living in it. Often these contaminants make fishes unfit to eat. Pollution from other sources enters rivers as well.

Invasive species, such as the zebra mussel, cause serious threats to native aquatic life by taking away habitats and/or food sources for native species.

What Else Should I know about Rivers?
Rivers and streams change over time. Young rivers and streams flow swiftly. Their channel is usually straight, with a v-shaped bottom. Older streams have a wide, flat-bottomed or u-shaped channel. The water flows slower in these rivers than in young streams.

Every river has a watershed or drainage basin. The watershed is the total land area that provides water to the river.

Running water helps support aquatic life because its movement increases the amount of oxygen available in the water. The moving water brings nutrients to organisms and flushes wastes further downstream.

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