Streamflow Chloride Concentration Trends in the Dorset Catchments, ON Canada, and Efforts to Harness High-Frequency Specific Conductivity-Chloride Monitoring for Event Chloride Load and Flowpath Investigations
Abstract
Recent analyses of thirty-six years of streamflow and inlake monitoring in the Dorset catchments in central Ontario, Canada are showing increasing trends in chloride concentrations attributed to human disturbance (road management) in contrast to decreasing trends in minimally disturbed catchments. For disturbed headwater lakes, estimated load contributions from ungauged shoreline are particularly high, suggesting important contributions from local groundwater along longer and slower pathways. In other regions of Ontario, very rural watersheds (5% total impermeable area) are also showing longterm increases in chloride, and both urban and rural systems can show evidence of multiple pathways of delivery (legacy groundwater versus shorter-term overland flow). Using a combination of longterm monitoring records (36 years of weekly water quality grab samples), and more recent (2011-2019) high frequency monitoring of both streamflow and specific conductivity, we examine changes in streamwater chemistry for stream gauging stations located above (undisturbed) and below road crossings (disturbed) in the Dorset catchments (Dickie and Harp lake catchments). Bivariate regression relationships between chloride and specific conductivity are evaluated for undisturbed and disturbed streamflow and where appropriate, used in combination with high frequency data to estimate seasonal and event loadings with the aim to improve understanding of road salt movement, storage and to inform modeling approaches. The long history of monitoring and hydrologic and geochemistry studies at the Dorset catchments makes for an ideal setting in which to examine new questions related to the wide ranging concern over impacts of road management and road salt application on ecological systems, and specifically in Canadian Shield watersheds.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H43G2082J
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1806 Chemistry of fresh water;
- HYDROLOGY;
- 1848 Monitoring networks;
- HYDROLOGY;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY