Results from the City of Atlanta Water-quantity and Water-quality Monitoring Program: Suspended Sediment, Trace Element, and Nutrient Fluxes, 2004–2005

During 2003, the U.S. Geological Survey established a major long-term water-quantity and qualitymonitoring network for the City of Atlanta (COA). During 2004 and 2005, suspended sediment fluxes from the COA to downstream receiving waters amounted to about 150,000 t y; ≥94% of the transport occurred in conjunction with stormflow, which also accounted for ≥65% of the annual discharge. This occurred despite the relatively short duration of most runoff events, which cumulatively ranged from a minimum of 6 to a maximum of 35% of the year, depending on the drainage basin. Based on annual median chemical concentrations for baseflow and stormflow, the annual fluxes of ≥75% of trace elements (e.g., Cu, Pb, Zn,), major elements (e.g., Fe, Al), and total P occurred in association with suspended sediment; in turn, ≥90% of the transport of these same constituents occurred in conjunction with stormflow. As such, baseflow sediment-associated and all dissolved contributions represent a relatively insignificant portion of the total annual load. One of the few exceptions is total N, whose sediment-associated fluxes range from 50 to 60%; even so, the annual storm-related transport of this constituent typically exceeds 80.