Watersheds of Illinois - 1996

24. Middle Kaskaskia River/Shoal Creek River Watersheds

The Middle Kaskaskia River/Shoal Creek River Watersheds cover a total of 1,647,400 acres in Christian, Shelby, Montgomery, Fayette, Marion, Macon, Madison, Clinton, and Washington counties. The largest cities in the watersheds are Vandalia (6,144), Greenville (5,108), and Hillsboro (4,400). Major streams which comprise the Middle Kaskaskia River/Shoal Creek River Watersheds include Crooked Creek, Shoal Creek, Beaver Creek, Hurricane Creek, and East Fork Kaskaskia River. A total of 1,456 stream miles were assessed on the Middle Kaskaskia River and its tributaries. Overall resource quality is "good" on 751 stream miles (51.7%), "fair" on 701 stream miles (48%), and "poor" on four stream miles (0.3%). The primary causes of water quality problems are nutrients, siltation, and suspended solids due to the effects of agricultural runoff and hydrologic/habitat modifications. A total of 18 lakes covering 31,488 acres were also assessed in the watersheds. Overall resource quality is "good" on 2,368 acres (8%) and "fair" on 29,120 acres (92%). The primary causes of water quality problems are nutrients and siltation attributed to agriculture, contaminated sediments (sediment and/or phosphorus attached to sediment particles), and shoreline erosion.

Kaskaskia River

A total of 93 stream miles of the Kaskaskia River (O) were assessed in the Middle Kaskaskia River/Shoal Creek River Watersheds. Of the total, 68 miles were rated as "good," and the overall resource quality of 25 stream miles was rated as "fair." Siltation is the primary cause of pollution due to the effects of agricultural runoff.

Shoal Creek

Shoal Creek (OI) is located centrally in the Middle Kaskaskia River/Shoal Creek River Watersheds. A total of 75 stream miles were assessed on Shoal Creek. Of the total, 61 miles were rated as "good," and the overall resource quality of 14 stream miles was rated as "fair." Nutrients and siltation were the primary causes of pollution due to the effects of hydrologic/habitat modifications.

Crooked Creek

A total of 70 stream miles were assessed on Crooked Creek (OJ). Of the total, 14 miles were rated as "good," and the overall resource quality of 56 stream miles was rated as "fair." Causes of pollution include nutrients, siltation, ammonia, and organic enrichment (low dissolved oxygen) attributed to point sources and agriculture.

Lake Carlyle

Lake Carlyle (ROA), located in Clinton County, is a public lake managed by the U.S. Army Corps of Engineers. The lake was created by damming the Kaskaskia River in 1966. The surface area of the lake is 24,580 acres and receives its water from a large 1,738,880 acre watershed. Lake Carlyle is the largest inland lake in the state of Illinois. The overall resource quality of the lake is considered "fair." Causes of pollution to the lake include nutrients, suspended solids, siltation, noxious aquatic plants, and organic enrichment (low dissolved oxygen). Sources of pollution include agriculture, shoreline erosion, and recreational activities.

Centralia, Raccoon, and Salem Lakes

Centralia, Raccoon, and Salem Lakes are all public water supply lakes located in Marion County. These lakes were created by the damming of area streams (Martin Branch, Raccoon Creek, and Town Creek, respectively) in 1911, 1942, and 1912, respectively. The sizes of these lakes are 450 acres (4,480 acre watershed), 925 acres (30,974 acre watershed), and 74 acres (2,572 acre watershed), respectively. Lake Centralia's overall resource quality is considered "good," while Raccoon and Salem Lakes have a "fair" overall resource quality. Causes of pollution to these lakes include nutrients, siltation, organic enrichment (low dissolved oxygen leading to taste and odor problems), and suspended solids. Primary sources of pollution include agricultural runoff and shoreline erosion. Raccoon and Salem Lakes have been monitored since 1981 by citizen volunteers in order to document water quality trends.