Monitoring suspended sediments and associated chemical constituents in urban environments: lessons from the city of Atlanta, Georgia, USA Water Quality Monitoring Program

Abstract

Background, aim, and scope The City of Atlanta, Georgia (COA) is part of the ninth largest metropolitan area in the USA and one of the fastest growing (e.g., >24% between 2000 and 2007). Since 2003, the US Geological Survey has been operating an extensive long-term water-quantity and water-quality monitoring network for the COA. The experience gained in operating this network has provided insights into the challenges as well as some solutions associated with determining urban effects on water quality, especially in terms of estimating the annual fluxes of suspended sediment, trace/major elements, and nutrients. Discussion and findings The majority (>90%) of the annual fluxes of suspended sediment and discharge (>60%) from the COA occur in conjunction with stormflow. Typically, stormflow averages ≤20% of the year. Normally, annual flux calculations employ a daily time-step; however, due to the "flashy" nature of the COA's streams, this approach can produce substantial underestimates (from 25% to 64%). Greater accuracy requires time-steps as short as every 2 to 3 h. The annual fluxes of ≥75% of trace elements (e.g., Cu, Pb, Zn), major elements (e.g., Fe, Al), and total P occur in association with suspended sediment; in turn, ≥90% of the transport of these constituents occurs in conjunction with stormflow. With the possible exception of nitrogen, baseflow sediment-associated and both baseflow and stormflow dissolved contributions represent relatively insignificant portions of the total annual load; hence, nonpoint (diffuse) sources are the dominant contributors to the fluxes of almost all of these constituents.

Suspended sediment transport dynamics in rivers: Multi-scale drivers of temporal variation

“…from vehicle combustion and industrial sources) as well as other particles originating from anthropogenic activities, are deposited on land. Large expanses of impervious surfaces in urban areas generate higher volumes of overland flow that will transport these particles to artificial drainage networks and rivers (Horowitz, 2009;Rossi et al, 2013;Taylor and Owens, 2009). …”

“…High-flow events generate a large proportion of the total annual SS load in rivers Horowitz, 2009;Lloyd et al, 2016;Pulley et al, 2015). Consequently, disentangling the factors that drive event-based SS dynamics is essential to improve our understanding of longer term SS trends, the importance of episodic events on those trends, and the impact of SS on ecology, geomorphology and infrastructure.…”

“…SS plays an essential role in structuring the landscape, creating ecological habitats and transporting nutrients (Dean et al, 2016;Koiter et al, 2013b). Despite being an indispensable part of the river system, SS is also linked to a range of problems related to pollution, ecological degradation, flooding and damage to infrastructure in an increasingly built-up world (Bilotta and Brazier, 2008;Horowitz, 2009;Taylor and Owens, 2009). To develop adequate management strategies, we must be able to quantify SS transport, and link these transport dynamics to drivers both within the channel and the wider catchment in order to accurately predict SS transport in rivers over management relevant timescales (Gao, 2008;García-Ruiz et al, 2015;Taylor and Owens, 2009;Vanmaercke et al, 2011).…”

Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring program in the Gironde fluvial-estuarine system

“…Thus, predicting response of estuarine system to global changes and local impacts is critical to protect or restore good water quality and ecosystem functioning (Johnson et al, 2009;Stevenson and Sabater, 2010). The importance of time series in aquatic system has been recognized long ago to better understand the long-term changes (Neal, 2004;Baborowski et al, 2004;Blain et al, 2004;Horowitz, 2009). …”

The use of bed sediments in water quality studies and monitoring programs

“…Utoy Creek is a small urban stream that flows through the City of Atlanta, Georgia as well as well as being a tributary of the Chattahoochee River (e.g., Horowitz and Hughes, 2006;Horowitz, 2009;West Atlanta Watershed Alliance, 2016). The creek is some 42 km long and the watershed encompasses some 89 km 2 (West Atlanta Watershed Alliance, 2016).…”