Abstract

During 2003–2008, the U.S. Geological Survey sampled 13 sites in the Indianapolis metropolitan area in Indiana for benthic invertebrates, fish communities, and streambed-sediment chemistry. Data from seven White River sites and six tributary sites complement surface-water chemistry data collected by the Indianapolis Department of Public Works. The information is being used to assess changes in water quality in conjunction with the City’s programs to reduce combined sewer overflows and other point and nonpoint sources of pollution in the Indianapolis area.

During the study, 233 benthic-invertebrate taxa were identified from which the Ephemeroptera, Plecoptera, and Trichoptera (EPT) Index, the Hilsenhoff Biotic Index (HBI), and the Invertebrate Community Index (ICI) were calculated. EPT index scores ranged from 2 to 16 on the White River and from 2 to 17 on the tributaries. EPT index scores indicate that these pollution-intolerant taxa are more prevalent upstream from and away from the combined-sewer areas of Indianapolis. HBI scores from sites on the White River ranged from 4.67 (good) to 9.55 (very poor), whereas on the tributaries, scores ranged from 4.21 (very good) to 8.14 (poor). Lower HBI scores suggest that less organic pollution was present and, like the EPT scores, indicate better conditions where combined-sewer overflows (CSOs) are not present. Similarly, ICI scores indicated better conditions upstream from the CSO outfalls on the White River. White River scores ranged from 12 to 46, where higher ICI scores indicate better conditions in the benthic-invertebrate community. ICI scores at the tributary sites ranged from 12 to 52, with the highest scores on streams without CSOs.

Fish-community data collected during 2006 and 2008 identified 65 taxa (51 on the White River and 53 on tributaries). The Centrarchidae (sunfishes) were the predominant fishes collected on the White River, while the Cyprinidae (carps and minnows) were predominant on the tributaries. Index of Biotic Integrity (IBI) scores ranged from 20 to 52 on the White River and from 26 to 52 on the tributaries. White River scores all improved from 2006 to 2008.

Streambed sediments were collected at the study sites in 2005 and 2007. The number of chlorinated pesticides detected in those samples increased in 2007, with trans-nonachlor, cis-chlordane, dieldrin, trans-chlordane, and PCBs being most frequently detected. Three organophosphate insecticides were detected. More than 30 semivolatile organic compounds (SVOCs) were detected at more than half the sites sampled. Sites below CSO outfalls had higher concentrations of SVOCs, whereas sites not near CSOs had lower concentrations.

Historical biological data consistently indicated that the Nora site—upstream from CSO influence—showed the least impairment among the White River sites. The data also indicated that the Morris and Harding sites—closest to the CSOs—showed the poorest biological conditions on the White River. The Buck Creek site, followed by the Williams Creek site, scored best among the tributaries, whereas the most urban sites—Fall Creek, Pleasant Run, and Pogues Run—scored the poorest.

Historical numbers of pollution-tolerant and pollution-intolerant organisms in the White River reflect changes at the wastewater treatment facilities in 1983 to tertiary treatment, including ozonation, and in 1994 to chlorination. The advent of ozone treatment of the effluents had a positive effect on the benthic-invertebrate communities downstream from the wastewater treatment facilities. The benthic-invertebrate communities at the upstream site exhibited minor yearly variations until a chemical spill in 1999 had a dramatic impact on the biological communities in the river, including the killing of thousands of fish.

Historical IBI data collection began in 1999 and show that fairly stable fish communities are present in the study area. Like the benthic-invertebrate data, the IBI scores reflect more pollution-tolerant fish communities near the CSO-affected sites. Only the Waverly site on the White River and the Pogues Run site appear to have slightly decreased IBI scores with time, whereas the remaining sites showed only minor year to year variations.

Posted July 31, 2012