Multi-Year Microbial Source Tracking Study Characterizing Fecal Contamination in an Urban Watershed

Area of Science:

• Environmental Microbiology
• Hydrology
• Water Quality Assessment

Background:

• Tributary streams can significantly impact the water quality of receiving rivers, particularly concerning bacterial contamination.
• Understanding bacterial contributions from urban subbasins is crucial for effective watershed management.
• Microbial Source Tracking (MST) markers aid in identifying the origins of fecal pollution.

Purpose of the Study:

• To rank tributary stream contributions of bacteria, including E. coli and MST markers, to the Little Blue River.
• To assess bacterial loads and yields during base flow and storm events in urban subbasins.
• To evaluate the impact of Independence, Missouri's tributaries on downstream river water quality.

Main Methods:

• Collected microbiological and hydrological data from five subbasins within Independence.
• Characterized concentrations, loadings, and yields of E. coli and MST markers.
• Analyzed data during both base flow and storm event conditions.
• Developed a ranking methodology based on daily loads and yields to prioritize subbasins.

Main Results:

• The E. coli water quality threshold was exceeded in 29% of base-flow and 89% of storm-event samples.
• Tributaries within Independence did not significantly increase median E. coli or MST marker concentrations downstream.
• Daily loads and yields were used to rank subbasins based on their bacterial contributions.
• A methodology was established for prioritizing subbasin remediation.

Conclusions:

• While individual subbasins contribute bacteria, their combined impact did not significantly degrade the overall water quality of the Little Blue River leaving the city.
• The developed ranking methodology provides a valuable tool for prioritizing remediation efforts in urban watersheds.
• Further research may focus on specific pollutant sources within the highest-ranking subbasins.