This metadata record document contains 7 tables used to assess factors influencing long-term water quality changes in the Gwynns Falls, Baltimore, MD, 1998-2016. Included are daily discharge measurements (source: United States Geological Survey (USGS), 2016), weekly nutrient sampling concentrations (source: Baltimore Ecosystem Study (BES), 2015), and approximately monthly bacteria, ammonia, TKN, and TSS sampling concentrations (source: Baltimore City Department of Public Works (DPW), 2016; Baltimore County Department of Environmental Protection and Sustainability (DEPS), 2016). Annual loads were calculated for each Gwynns Falls subwatershed from the discharge measurements and sampling concentrations. Green infrastructure data (Best Management Practices (BMPs), rain barrels) and gray infrastructure data (Sanitary Sewer Overflows (SSOs), sewer repairs, water main breaks & leaks) were obtained from Baltimore City DPW and Baltimore County DEPS and summarized annually for each Gwynns Falls subwatershed. Land cover change data (source: National Land Cover Dataset (NLCD), 2011 and 2015) was created for each Gwynns Falls subwatershed over the time period of 2001-2011. Regional climate data (source: National Oceanic and Atmospheric Administration (NOAA), 2016) was obtained from the Baltimore Washington International (BWI) Airport meteorological station.