Finding the signal in the noise; distinguishing point and non-point sources in the Detroit River

Session: Nutrient Sources, Transport, and Internal Cycling (3)

Timothy Maguire, Great Lakes Institute for Environmental Research, University of Windsor, [email protected]
Courtney Spencer, University of Windsor, Great Lakes Institute for Environmental Research, [email protected]
Alice Grgicak-Mannion, University of Windsor, [email protected]
Ken Drouillard, University of Windsor, Great Lakes Institute for Environmental Research, [email protected]
Bernhard Mayer, University of Calgary, [email protected]
Scott Mundle, Great Lakes Inst. for Environmental Research, [email protected]

Abstract

Water quality impacts to the Laurentian Great Lakes create bi-national issues that have been subject of investigation since the 1970s. However, disaggregating upgradient sources of riverine nutrients throughout the region remains a challenge. Nutrients are derived from multiple (point and non-point) sources and flows are high. This is especially pertinent in the Lake Huron to Lake Erie corridor and the Detroit River. The Detroit River supplies 90% of the water to the western basin of Lake Erie (5,300 m3/s) with a variety water quality indicators and limited clearly identifiable sources. To find the source signal in the noise we used dissolved aqueous constituents and isotopic tracers with sediment chemical, isotopic, and contaminant indicators in a principal component analysis paired with a hierarchical clustering of loadings to identify sources. Our approach combined archival and contemporaneous data to distinguish point sources, non-point sources, and upgradient water bodies as sources of nutrients and contaminants to the Detroit River and ultimately the western basin of Lake Erie. Our results characterize the primary source of PO₄ in the Detroit River and highlights the need for continued research on broader best management practices protecting Lake Erie.