Institute of Ecosystem Studies

2008 BES Annual Meeting Presentation and Poster Abstracts

Nutrient Input and Dynamics in a Restored Urban Stream Impacted by Mixed Sewer Systems
Sikora, Marion
Co-Authors: Emily Elliott Daniel Bain
Abstract: Nutrient cycling in urban watersheds remains poorly constrained. Although studies in Baltimore address the role of sewer inputs, the city does not have a combined sewer system. Combined sewer systems cause considerable water quality problems in many urban centers. We sampled biweekly baseflow (from April 2007 to present) and stormflow from Nine Mile Run, a restored urban stream in Pittsburgh, Pennsylvania (USA) impacted by both sanitary sewer and combined sewer systems. Analysis of post-restoration water quality data suggests that atmospheric deposition and sewage both contribute nutrient pollution to the stream. We estimate input of atmospheric nitrate deposition to the watershed is 19 kg NO3- ha-1yr-1, yet a preliminary nitrogen budget indicates that nitrate export from the basin is consistently higher (~30 kg NO3- ha-1yr-1). This suggests the water quality is consistently affected by substantial sewer inputs. Additionally, we determined baseflow nitrate concentrations were higher during wetter months suggesting increased stream/ sewer interactions during wet periods. These results document the effect of varied sewer systems on an urban stream and highlight the challenges inherent in improving urban water quality through physical stream restorations.