Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Geography & Environmental Studies

Program Name/Specialization

<--Please Select Program Name/Specialization-->

Faculty/School

Faculty of Science

First Advisor

Homa Kheyrollah Pour

Advisor Role

Supervision and conceptualization

Second Advisor

Gifty Attiah

Advisor Role

Supervision and conceptualization

Abstract

Lake surface temperature (LST) and turbidity are key indicators of water quality and ecosystem dynamics in northern lakes, where climate-driven warming and river discharge jointly regulate thermal structure and sediment transport. Great Slave Lake in Canada’s Northwest Territories, the deepest lake in North America and a critical freshwater resource for Indigenous and settled communities, receives approximately 74% of its total inflow from the Slave River, making it an ideal system for investigating coupled hydrological and thermal controls on lake water quality. Despite its ecological and social significance, no integrated long-term satellite study has simultaneously characterized LST and turbidity dynamics for this system.

This study uses multi-decadal satellite observations processed in Google Earth Engine to quantify LST and turbidity dynamics in Great Slave Lake. The analysis focuses on the 40 km Slave River Plume Zone over a 40-year period from 1984 to 2024. Three satellite platforms were used: Landsat (TM/ETM+/OLI, 30 m, 16-day revisit), MODIS Aqua (MYD09GA/MYD11A1, 500-1000 m, daily), and Sentinel-2 MSI (10 m, 5-day revisit), all restricted to the June-October open-water season. Turbidity was characterized using the Normalized Difference Turbidity Index (NDTI) derived from red and green surface reflectance bands, classified into High, Moderate, and Low regimes using fixed thresholds. Daily Slave River discharge records from Water Survey of Canada station 07NB001 were used to assess hydrological controls on turbidity.

Both Landsat and MODIS Aqua independently detected statistically significant open-water warming of +0.07 °C yr⁻¹ over the full 1984 to 2024 record. Discharge and turbidity emerged as the dominant mode of variability, explaining 65% of total variance, while LST operated as an independent thermal signal accounting for a further 32%. The 2020 high-flow event produced the largest turbidity episode in the 40-year record, with high turbidity areal extent reaching 3,408 km². Monthly heatmap analysis revealed a discharge-dependent turbidity lag, with peak NDTI occurring within one month of peak discharge during high-flow years and extending to three to four months during low-flow years. Spatially, turbidity intensification was persistent near the river mouth, with elevated sediment plumes spreading outward in all direction.

These findings highlight the coupled roles of hydrological forcing and thermal variability in regulating turbidity dynamics in subarctic lake systems, with direct implications for operational water quality monitoring, drinking water management and long-term environmental monitoring in the Northwest Territories.

Convocation Year

2026

Convocation Season

Fall

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Available for download on Saturday, July 24, 2027

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