Sarah Kaykhosravi, Mahyar Shafii, Steph Slowinski, Yubraj Bhusal, Fereidoun Rezanezhad, Philippe Van Cappellen (2022). A novel approach for regionalization of SWMM to data poor regions for the estimation of urban phosphorus loads. Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

Calibration parameters of water quality models are specific to a particular study area with limited applicability in other areas. In our study, we developed a simplified parameter transfer approach to calibrate a Stormwater Management Model (SWMM) using data collected in two urban sewersheds located in the town of Ajax in the Greater Toronto Area (GTA). Together, the two sewersheds cover ~252 ha and encompass commercial, industrial, and residential land uses, as well as green spaces. The data consisted of discharge and a suite of operationally-defined phosphorus (P) pools – total P (TP), total dissolved P (TDP), and dissolved reactive P (DRP) – measured during precipitation events from October 2020 to October 2021. Our data analysis yielded meaningful and quantitative correlations between loadings of different P species exported from the two sewersheds and flow and land cover characteristics. We derived calibration parameters from these observations and applied them in a continuous SWMM model at the 5-minutes temporal scale. The model successfully reproduced annual, seasonal, and long-term (2011 to 2021) P export from both urban sewersheds demonstrating a good predictive performance for both the hydrology (NSE: 0.84 to 0.97) and P loadings estimates (NSE: 0.60 to 0.81). The approach can be used to quantify P loads under past and future precipitation regimes (temporal upscaling) and extrapolate the loads to the entire GTA (spatial upscaling). The proposed modeling approach can help inform the implementation of urban green infrastructure that reduces P loads from the GTA in order to mitigate eutrophication in the nearshore waters of the western basin of Lake Ontario. Moreover, the approach can be applicable to other urban environments in other regions of the world.

First Author: Sarah Kaykhosravi
Additional Authors: Mahyar Shafii, Steph Slowinski, Yubraj Bhusal, Fereidoun Rezanezhad, Philippe Van Cappellen/ Affiliation: Ecohydrology group, Department of Earth and Environmental Sciences, Faculty of Science, University of Waterloo