Exploring the Trends in Sediment and Phosphorous Concentration and Loads: Case Study over Part of the Great Lake Basin (Ontario, Canada)

In this study, trend analysis of total suspended solids (TSS) and total phosphorus (TP) concentrations and loads are performed, combining bootstrapping with the Weighted Regressions on Time, Discharge, and Season i.e., WRTDS_BT technique. The technique is used at ten selected monitoring stations of Northern Lake Erie, Eastern Lake Huron, and Lake Ontario & Niagara Peninsula in Ontario, Canada. Trend analysis over major tributaries reveals that trends in TSS concentrations and loads were highly variable, while there was a significant decline in TP concentrations and loads. However, in most tributaries, TSS and TP concentration levels are significantly higher than the provincial and national guidelines and objectives. To be precise, TSS concentration levels are significantly higher than Canadian Water Quality Guidelines (CWQG) for the TSS concentration in tributaries of 30 mg/L (following Toronto Region Conservation Authority (TRCA), Ontario) and TP concentration levels are significantly higher than the Ontario’s provincial water quality objectives (PWQO) guidance for the TP concentration in tributaries of 0.03 mg/L. Moreover, our findings suggest that changes in land management practices in agricultural areas, such as tillage, tile drainage and fertilizer/manure application may play an important role for the analysed trend.