Oral Presentation Symposium on Urbanization and Stream Ecology 2025

Interactions between hydrologic drivers, land cover, and population characteristics control E. coli in urban streams (#25)

Sarah H. Ledford 1 , Richard Milligan 1 , Zakia Riaz 1 , Jessica Sterling 2 , Michael Meyer 2 , Jacqueline Echols 3
  1. Georgia State University, GA, United States
  2. Chattahoochee Riverkeeper, Atlanta, GA
  3. South River Watershed Alliance, Atlanta, GA

Urban streams and rivers have chronic bacteria contamination in the United States, coming from multiple sources, following a variety of flowpaths to the waterway, and with differing downstream fates. However, bacteria from human sewage, estimated through measures of Escherichia coli, are the highest risk to human health. We analyzed four years of E. coli monitoring by community science groups to look for spatial and temporal drivers of E. coli densities in watersheds in Atlanta, GA, with a wide range of racial and economic diversity. These watersheds already have environmental injustices towards Black communities around flooding, soil contamination, and air quality, and our goal was to understand if this extended to E. coli. While there were minimal differences in E. coli between watersheds with different Black and white populations, individual sites could be identified as hot and cold spots of contamination. Storm events did increase E. coli at most sites, indicating a combination of runoff and sediment-sorbed E. coli explain about 50% of the variability in E. coli densities. Long-term median E. coli levels were not strongly correlated to land cover or socio-demographic characteristics of the contributing watershed, but E. coli variability was lower in less urbanized areas. Temporal and spatial distributions of E. coli are controlled by complex interactions between sources that vary across watersheds and hydrologic transport. While direct correlations to minority populations were not observed, the interactions between sewage as one environmental harm and the many others (air quality, soil quality, prison-industrial complex, etc.) present in minority and low-income urban communities emphasize the oversized burden environmental justice communities carry.