Phosphorus and sediment loading in a Boreal Shield River

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

Jane White, Nipissing University, [email protected]
April James, Nipissing University, [email protected]
Merrin Macrae, Univ. of Waterloo, [email protected]
Joel Harrison, North Bay-Mattawa Conservation Authority, [email protected]

Abstract

Estimating phosphorus (P) contributions entering source waters from tributaries is vital to P management. P concentrations in the Wasi River, a tributary of Lake Nipissing located in the headwaters of Lake Huron, regularly exceed the provincial water quality objective, a concern for residents who rely on Callander Bay, located at the river outlet, as a municipal drinking water source. Studies in similar climates have found that high-flow events (rainstorms and snowmelt) can contribute 80-90% of yearly loading, making accurate estimation of event flows vital to estimating P export. Streams in cold, humid climates are susceptible to under-estimation of P loads due to infrequent (< bi-weekly) sampling. From 2014–2018, base-flow sampling on the Wasi River was augmented with high-flow sampling during spring snowmelt and storm-events. In 2018, a “weekly +” strategy (weekly sampling plus event sampling) was implemented. Turbidity measurements were collected using an FTS DTS-12 probe during two summer periods and three continuous years (2016–2018); discharge is available from the Water Survey of Canada gauging station. Interpolation and regression-based approaches are used to estimate annual, event and seasonal P loading. It is expected that the use of high-frequency data will improve P loading estimates for the Wasi River.