Application of high frequency surrogate modeling of instream chloride to improve understanding of chloride mobilization in cottage country, Ontario
Estimating Chloride (Cl) concentration and loading in streams is important to the management of salt application in cold regions because of potential influence on both aquatic species and humans. Traditional Cl monitoring based on lab analysis of instream samples does not have sufficient temporal resolution to evaluate acute water quality. This research examines the relationship between instream specific conductivity (SC) and Cl concentration, builds high-resolution SC-Cl surrogate models, and evaluates Cl mobilization for several of the Dorset Environmental Science Centre (DESC) Precambrian shield catchments located in south-central Ontario, Canada. SC-Cl surrogate models are used to generate high frequency (10-min) instream Cl concentration and loading, improving the temporal resolution of Cl loading estimation for up to a 10-year period. High frequency instream Cl estimates are then used to investigate Cl mobilization with autocorrelation (ACF), cross-correlation (CCF), the continuous wavelet transform (CWT), and wavelet transform coherence (WTC). This work shows that high frequency Cl estimates can result in large differences in the estimation of Cl loading, especially for the month of April, when large daily temperature differences promote daytime melt on roadways. While most previous studies focus on study of instream Cl in urban regions, this study demonstrates that application of SC-Cl models are feasible in rural regions with low instream Cl concentration.