Author(s)

R Vedom

Abstract

On the heavy urbanized Etobicoke Creek watershed salt crystals and other chlorides are used for roads deicing in winter and for suppressing dust in summer. How are the chlorides from these two sources distributed between surface and ground waters; how subsequently ends up in Lake Ontario, which tributary Etobicoke Creek is? Can surface water monitoring results be interpreted this way? Is it possible to assess daily dynamics of surface and groundwater chlorides based on the available monitoring database? An attempt to quantitatively estimate daily contamination of direct, inter- and baseflow of a highly urbanized watershed (209 km2) was done using the only source of quality data - the monitoring database of Environment Canada (~1 sample/month). Average daily load of chloride by Etobicoke Creek into Lake Ontario was 71.9, highest - almost 1500 tons. Shares of the base, inter- and direct flow in the monthly loads fluctuated in 18-64, 23-53 and 2-40% ranges, respectively. The overall year average of chloride loads of the total flow for examined period was 26990 tons breaking into mentioned above components in amounts of 7899, 11252 and 7840 tons, respectively. The result has revealed the predominant contamination of the interflow pathway for Etobicoke Creek. Introduction The simple approach to interpret the monitored chloride concentrations of total flow as a certain combination of flow components at the moment of sampling was considered. An idea that chemical composition of the flow is conditioned by its pathway [10] was exploited here based on heavily impacted watershed. There was the following consequence of procedures made in this investigation: 1. daily proportions of base-, inter- and direct components of total flow using a flow

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