Oral Presentation Society for Freshwater Science 2026 Annual Meeting

Redlined water bodies are smaller and more polluted  (136093)

Anika R Bratt 1 , Alexandra Jabbarpour 1 2 , CJ Denney 1 3 , Ahmed Abdallah Ahmed 1 , Georgia Akins 1 , Ollie Branch 1 , Mara Pirone 1 , Lucia Zuvela 1 , Sophie Carpenter 1
  1. Macalester College, Saint Paul, MN, United States
  2. Friends of the Mississippi River, Minneapolis, Minnesota, US
  3. Yale University, New Haven, Connecticut, USA

Redlining was a racist, discriminatory practice developed by the Home Owners Loan Corporation (HOLC) in the mid-1930s that assigned grades to residential neighborhoods based on their perceived “mortgage security”. Neighborhoods were graded A (“best”), B (“still desirable”), C (“definitely declining”), or D (“hazardous”), with minoritized neighborhoods rated C or D. D neighborhoods were colored red on maps, thus the term redlining. While this policy ended in the mid-1950s, numerous studies have connected redlining to disparities in temperature, air quality, and green space between graded neighborhoods. There is, however, limited research exploring the connections between surface water and redlining. This study investigated how water quality and water body size varied across HOLC grades in Saint Paul and Minneapolis, MN. Stream data from the United States Geological Survey (USGS) was also used to assess stream flashiness across graded neighborhoods throughout the US. We show that water bodies in redlined neighborhoods are significantly smaller, but also had significantly cooler water temperatures. Further, our data demonstrate that this translates into less of a cooling effect in redlined neighborhoods during summer months. Long term records of water quality show that phosphorous was also significantly higher in C and D neighborhoods. USGS data suggest that streams and rivers in A and B ranked neighborhoods exhibit flashier discharge patterns. Overall these results show important disparities in water quality and ecosystem services in urban landscapes.