Baltimore Ecosystem Study Institute of Ecosystem Studies

2017 BES Annual Meeting Presentation and Poster Abstracts

The Influence of Gray and Green Infrastructure on Water Quality Change in the Gwynns Falls Watershed, Baltimore, Maryland
Majcher, Emily
Co-Authors: Emily H. Majcher, Ellen Woytowitz, Alexander J. Reisinger, Peter Groffman

Abstract: Stakeholders in the Baltimore region identified that factors influencing water quality trends in urban streams are not well understood at the watershed scale, despite current regulatory requirements and considerable investments in gray and green infrastructure. To address this gap, long-term water quality trends and proposed factors of influence were examined in the Gwynns Falls watershed over the Baltimore Ecosystem Study (BES) timeframe. Variability in climate and land cover can mask signals in water quality improvements and can present challenges for meeting regulatory goals. Analysis of land cover in 2001-2011 in the Gwynns Falls watershed indicated minimal change during the study timeframe indicating that land cover change is likely not a factor of water quality change. However, an increase in annual and winter precipitation was apparent in the region. A higher proportion of runoff producing storms was observed in the winter, and less in the summer. These precipitation changes may exacerbate the inflow and infiltration to gray infrastructure and reduce the effectiveness of green infrastructure. Sanitary sewer overflows (SSOs, gray infrastructure) and best management practices (BMPs, green infrastructure) were identified as factors influencing water quality change. An increase in number, volume, and duration of SSOs were correlated to an increase in annual loads of nutrients and bacteria. An increase in number, storage volume and drainage area of BMPs were correlated to a decline in annual loads of phosphate, sulfate, and total suspended solids. Results suggest that continued investments in both gray and green infrastructure are necessary for urban water quality improvement.