Note: The following article was written by Brady Barksdale, our summer intern and a student in the IU School of Public Health.
Lake Monroe, located in Brown and Monroe Counties, is the largest man-made body of water in all of Indiana coming in at 10,750 acres and has an average depth of 25 feet with a maximum of 54 feet deep. The lake was built in 1964 and filled with water in 1965 by the Louisville District of the Army Corps of Engineers with the original intention of being a method of flood control for the white river. Creation of this lake cost approximately $16.5 million but since its creation has prevented an estimated $38 million in flood damage. It was not until 1967 that the City of Bloomington decided to use Lake Monroe as a source of drinking water. Before Lake Monroe, the city used Lake Griffy as a source of drinking water, but with the creation of a much larger lake, the city found Lake Monroe to be a much better source of water. Currently, the Monroe Water Treatment Plant is pumping on average 15 million gallons of water per day, with amounts fluctuating as high as 23 million gallons per day in the warmer months.
Lake Monroe is divided into two basins, the upper and lower basin, which are divided by the State Highway 446 causeway. There are distinct differences in water quality from the upper to lower basin. Much of this is due to the fact that the upper basin, which is much shallower than the upper basin, is receiving upwards of 90% of the total runoff that is entering the lake. All of this runoff causes changes in the turbidity and overall water chemistry of this portion of the lake. The dissolved oxygen levels from each basin also vary. Higher dissolved oxygen levels are seen in the lower basin while lower levels of dissolved oxygen are seen in the upper basin. This has an effect on the fish in these areas given that fish need oxygen to survive. In the lower basin, the dissolved oxygen levels allow for fish to live at depths of 16 to 20 feet deep while the upper basin, with lower dissolved oxygen levels, only allows for most fish to live at depths up to 15 feet. Analysis from the Department of Natural Resources showed lake average surface dissolved oxygen levels ranging from 5.26 ppm to 7.02 ppm with the levels slowly dropping down as the depth increases.