OPTICAL BRIGHTENERS AND SPECIFIC CONDUCTANCE AS INDICATORS OF LEAKY INFRASTRUCTURE IN ATLANTA, GA

Subwatersheds of Peachtree Creek (340 km²) drain a range of urbanization conditions within Atlanta, GA, and near suburbs, including intensely urbanized sectors and suburban areas with established forest cover. The watershed also contains a range of water infrastructure types of varied ages. This exploratory study incorporates multiple synoptic sampling events at 25 locations throughout Peachtree Creek, as well as analyses of longer-term flow patterns at the five USGS flow gauges located within the watershed, with the primary objective of developing a preliminary picture of interactions between infrastructure and stream baseflow in this watershed. The presence of optical brightening agents (OBAs) in streamflow is diagnostic of interaction with treated or untreated waste water, as OBAs are common additives to laundry detergents and personal care products. Freshwater SC values increase with added treated or untreated wastewater, but SC may be affected by multiple factors. Thus, a secondary objective of this study was to determine the correlation between OBA presence and SC values within the Peachtree Creek system. Synoptic point measurements of water fluorometry (to detect OBAs) and specific conductance (SC) were collected during baseflow conditions within the annual low flow season. Observed hot spots of OBAs and SC were qualitatively related to infrastructure networks, with interpretations of relationships to infrastructure type and age. Baseflow dynamics at five nested gauges within the watershed were quantitatively linked to watershed impervious surface cover and infrastructure networks, using standard statistical techniques and analyses derived from network theory. Interpretations using the separate approaches were combined to develop a preliminary understanding of wastewater infrastructure contributions to baseflow in Peachtree Creek.