flooding along the Middle Raccoon River. The Middle Raccoon River flows into the South Raccoon River about south of Redfield. The South Raccoon River, about long, rises in northeastern Audubon County and flows generally southeastwardly through Guthrie and Dallas counties, past the town of Guthrie Center. South of Redfield, after the Middle Raccoon River flows into the South Raccoon River, a flow gauge operated jointly by the United States Army Corps of Engineers (Rock Island District), the United States Geological Survey (Iowa District), and the Iowa Department of Transportation provides data about potential flooding threats. The north and south forks join in Dallas County just west of Van Meter, and the Raccoon River flows generally eastward into Polk County, past Walnut Woods State Park and West Des Moines. It joins the Des Moines River just south of downtown Des Moines and is part of the watershed of the Mississippi River. Drinking water use Both the Raccoon and Des Moines rivers have been providing drinking water for the Des Moines metropolitan area through water utilities since the 19th century. During the Great Flood of 1993, the Raccoon River flooded the water treatment facility of Des Moines, shutting off the city's drinking water supply. Agricultural pollution Spring thaws, as in the spring of 2013, and rainy spells after drought wash nitrate from fertilizer into the river. On November 20, 2014 nitrates spiked at 13.7 parts per million (ppm), making the water unsafe for pregnant women and infants. (The US Environmental Protection Agency requires officials to inform the public about safety risks at 10 ppm.) At the time, these were the highest readings in the nation. See also List of Iowa rivers References Sources Columbia Gazetteer of North America entry DeLorme (1998). Iowa Atlas & Gazetteer. Yarmouth, Maine: DeLorme. . GNIS entries for , , , External links Map of Raccoon River basin - Iowa Department of Natural Resources (DNR) website South Raccoon River gage near Redfield - US Army Corps of Engineers website North Raccoon River at Perry - National Oceanic Atmospheric Administration (NOAA) website Middle Raccoon River at Panora - NOAA website South Raccoon River at Redfield - NOAA website Raccoon River at Van Meter - NOAA website Raccoon River at Des Moines Fleur Drive - NOAA website Rivers of Iowa Tributaries of the Des Moines River Geography of Des Moines, Iowa Rivers of Sac County, Iowa Rivers of Calhoun County,