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Publication Abstract

Watershed Monitoring and Land Use Evaluation for the Vermilion River Watershed Keefer, Laura, Misganaw Demissie, Dan Mayer, Ken Nichols, and Susan Shaw, 1996  Illinois State Water Survey, Champaign, IL,  ISWS MP-176    Full Text Available

The Vermilion River, located in north-central Illinois, serves as a source of drinking water for the cities of Pontiac and Streator. Northern Illinois Water Corporation (NIWC) continuously withdraws water from the river for distribution to these communities. The annual water usage in 1994 and 1995 was 0.85 and 0.8 billion gallons for Streator and 0.74 and 0.76 billion gallons for Pontiac, respectively. The drainage area of the Vermilion River at the confluence with the Illinois River is 1,322 square miles. The watershed includes portions of seven counties in north-central Illinois as shown in figure 1. Agriculture is the predominant land use in the watershed, and some of the major urban areas are Streator, Pontiac, Fairbury, Forrest, and Chatsworth.

In recent years, NIWC has experienced problems related to nutrients in the water supply and had to implement measures to manage these problems. At the present time the major problem is related to high levels of nitrates during certain periods of the year. The nitrate problem is not unique to the Vermilion River and has become a major drinking water quality problem in central Illinois communities such as Decatur, Bloomington-Normal, and Danville. NIWC was able to address the nitrate problem in Pontiac's drinking water supply by storing river water with low nitrate concentration in old quarries for blending when nitrate exceeds the 10 milligram per liter (mg/1) maximum contamination level (MCL) in the river. In August of 1993, NIWC signed a Letter of Commitment (LOC) with the Illinois Environmental Protection Agency (IEPA) in which NIWC agreed to analyze the nitrate problem at Streator and implement a solution. One requirement of the LOC specifies that a two-year watershed monitoring study be conducted to determine nitrate sources and make recommendations that will reduce nitrate to levels below the MCL at the Streator water intake.

The Illinois State Water Survey (ISWS) conducted the two-year watershed monitoring and land use evaluation study for NIWC to monitor and identify the sources and causes of high nitrate concentrations in the Vermilion River basin. The watershed monitoring component of the study established seven stations at selected locations to monitor the nitrogen in the river system and flow of water at six of those stations. This technical report is the product of that study. It discusses the background of the nitrate issue and land uses in the Vermilion River watershed and nitrogen transformations. It also presents the hydrologic and water quality monitoring data collected during the study.

Based on the data collected in the Vermilion River basin and additional information from the literature review and other similar projects, the ISWS will prepare a set of recommendations for implementation in the watershed to reduce the nitrate concentrations in the Vermilion River below the maximum allowable contamination level (MCL) of 10 mg/1.

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