The ecological health and quality of urban lakes and streams can be affected by stormwater runoff and sewage inflows. Tibbetts Brook (TB), which feeds into Van Cortlandt Lake (VCL), are an urban stream and lake located in the Bronx NY, where water quality issues such as fishkills, low dissolved oxygen, and extreme eutrophication have frequently occurred. Limited historical data has prevented the determination of the causes of these water quality problems. Currently, TB and VCL are culverted into the municipal sewer but there are plans to daylight TB, which will bring the stream aboveground (out of the sewer) and have it channeled into the Harlem River. However, the poor water quality and unknown sources of contamination has prevented this from occurring. A year-long baseline monitoring study of VCL and TB was conducted starting December 2015 with the goal of collecting water quality data that will inform stakeholders on the best management practices to improve water quality in VCL and TB. Weekly water quality data at 6 locations in TB and VCL was collected including dissolved oxygen, water temperature, conductivity, pH, nutrients (nitrate and total phosphorus), and turbidity. Findings confirm previous research that TB and VCL experience high eutrophication, especially during summer months, corresponding to a low dissolved oxygen. The cause of this eutrophication is likely due to high total phosphorus levels in the summer (June – September). Results also suggest that both systems are nitrogen limited. Additionally, it was found that that the direct, point load introduction of partially or untreated highway runoff into VCL is a major contributor of nutrients and sediment into the Lake. These results as well as statistical analyses and comparison of these results to the limited historical data will be presented.

Investigation of sources of eutrophication, sedimentation, and nutrient pollution in an urban watershed

254th National Meeting (2017)

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