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The Rock River

The Rock River that European settlers encountered was surrounded by fertile soils, large forests, and ran with clear sparkling water that supported thousands of species of insects, fish, turtles, frogs, mussels, birds and mammals. Much has changed over the last 150 years. Today over 60% of the Rock River basin’s wetlands have been destroyed and nearly all of the oak savannas and prairies have been cut down and plowed to make way for agriculture.

The Rock River rises near West Bend, Wisconsin and flows south 130 miles into Illinois where it takes a southwest course for 155 miles past Rockford, Oregon, Dixon, Sterling and Rock Island to empty into the Mississippi. The river provides an aquatic resource of some 12,400 acres. Biologists who assess and manage the ecology of the Rock River divide it into two segments.  The Upper Rock River runs from south central Wisconsin through Ogle County, Illinois. The Lower Rock River flows through parts of Bureau, Carroll, Henry, Lee, Rock Island, and Whiteside counties.

From its headwaters in Wisconsin, the Rock River runs through major urban areas of Madison, Janesville, Beloit, Rockford and the Quad Cities. The majority of the land in the Rock River basin today is rural and the Rock and its tributaries are dramatically impacted by agricultural, as well as urban, land uses. Pollution is the greatest threat affecting the river’s water quality and ability to support natural plant and animal populations.

The pollutants of concern, nitrogen, phosphorus and sediment enter the river from many sources. Crop fields, pastures, municipal and industrial wastewater discharges, construction sites and urban areas all have contributed to the degradation of the Rock’s water quality. Excess phosphorus in the water leads to algae blooms that turn the water green, scummy, odorous and undesirable for recreation. Blue-green algae produce toxins that can cause rashes, illness and even death. When these plants die, the process of decomposition uses much of the available oxygen. This results in a severely depleted supply of oxygen in the water, endangering fish and other aquatic life. An excess amount of sediment causes many problems in water bodies, primarily destroying habitat, blocking sunlight and warming the water.

The entire main stem of the Rock River is designated as ‘impaired’. The federal Clean Water Act (CWA) requires that states adopt water quality standards to protect waters from pollution. The standards rely on criteria for a wide range of pollutants such as: phosphorus, sediment, bacteria, PCBs, and mercury. A river is ‘impaired’ if it does not support full use by humans, wildlife, fish and other aquatic life and it exceeds one or more of the pollutant criteria.

Historically, wetlands attached to the Rock River provided natural flood control, habitat for fish and waterfowl and natural water purification. Wetlands help to maintain stream and river flows during dry periods, thereby replenishing water supplies and maintaining aquatic habitat. Today less than 30% of the wetlands in the original Rock River’s ecosystem remain. Stream channelization, building of drainage ditches and draining of wetlands have contributed to flooding problems along the Rock.

Loss of floodplain wetlands has also had devastating effects on wildlife. Species such as blue-spotted salamanders, crayfish, yellow-headed black birds and Blanding’s turtles that historically bred in the shallow waters and vegetation in the Rock’s floodplains are now scarce. Many native fish species require the quiet shallow ponds and marshes that once fringed the Rock for spawning, feeding and refuge.

Wildlife habitat in the Rock River basin continues to be lost and fragmentation of habitat accelerates. Most of the original habitat was displaced by agriculture, but urban sprawl is now having major detrimental impacts as subdivisions, strip malls, and parking lots have begun replacing farms as dominant features in the Rock River watershed landscape.

The Illinois Department of Natural Resources has rated the Index of Biotic Integrity) of the Rock River based on the number of species found in its last sampling in 2008. Much of the Rock is scored in the A or B range.  Most of the Rock River is rated B which translates as fair to good.  A few sections are A, meaning good to excellent.  Just one section was rated C.

The Rock River in Illinois supports more than 50 fish species. They include Endangered Species,  also several species on the Illinois Wildlife Action Plan list of Species in Greatest Need of Conservation such as northern pike, muskie, small mouth bass, walleye, sauger. Blue gill, largemouth bass, black crappie, channel catfish, white crappie and carp round out the list of game fish present in the Rock River.

In many areas along its route to the Mississippi, the Rock River and its tributaries provide the last remaining undeveloped corridors providing wildlife with sheltered paths between habitats, for migration, food sources and breeding areas. Although dozens of species have vanished, an impressive array of wildlife can still be found inhabiting the Rock and in restored marshes and wetlands at its margins. Bald eagles have made a come-back in the last fifteen years because the river is supporting more aquatic life and they are finding abundant fish to feed on.  Commonly sighted are frogs, turtles, ducks, wading birds, muskrats, foxes and beavers. Visitors may see kingfishers and bald eagles fishing, and hear some of the 100+ species of song birds who use the Rock River as a migratory flyway. Because of the intensive agricultural land use in Illinois and Wisconsin and lost natural habitat, the Rock River’s riparian corridor is considered a critical oasis for resting and feeding migratory birds.

Forest Preserves containing restored natural areas on the Rock River include Mill Race Isle, Norman Jensen, Macktown and Hononegah.