Classification of river discharge and nutrient export from the tributaries to Chesapeake Bay: Cluster analysis of monitoring data from 1985-2016
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Nutrient and discharge patterns from the Chesapeake Bay watershed are a management focus due to their impacts on ecosystem functioning of the estuary. Effective management of watersheds is augmented by the Chesapeake Bay Program partnership’s non-tidal monitoring network, which provides large amounts of water quality data from subbasins of varying size, land use, and physiographic province. To assess patterns in water quantity and quality and their similarities among watersheds, we synthesized monitoring and discharge data using cluster analysis. Specifically, mean monthly river discharge, nitrogen concentration, and phosphorus concentration between 1985-2016 were compiled and analyzed using hierarchical clustering to identify spatial clusters of stations. Furthermore, different temporal periods and seasons were considered to explore variations in the clusters. In addition, land uses and physiographic provinces for these subbasins were analyzed to investigate their ability to explain the spatial patterns of clusters. Results from this work are useful to watershed management in the Chesapeake Bay region toward communicating spatial patterns of clusters, identifying hotspots of nutrient export, and possibly predicting nutrient export from ungaged watersheds. The views presented here are those of the authors and do not represent official views or policy of the U.S. Environmental Protection Agency.