https://scholars.wlu.ca/etd/2317

Faber, Jelle André (2020) Reconstructing Hydrologic Conditions and Metals Supplied by the Peace River to the Peace-Athabasca Delta, Scholars Commons Laurier - Theses and Dissertations, https://scholars.wlu.ca/etd/2317

The Peace-Athabasca Delta (PAD) in northern Alberta, Canada, is recognized internationally for its ecological, historical, and cultural significance. The delta is mostly within Wood Buffalo National Park, a UNESCO World Heritage Site, and is a Ramsar Wetland of International Importance. The construction of the WAC Bennett Dam (1967) and the Site C Dam (ongoing, 2024) on the Peace River, and expansion of the Alberta Oil Sands industry along the Athabasca River have raised concerns over water quantity and quality in the delta. When industry operations began, effective monitoring had not been implemented. Consequently, pre-industrial reference conditions are unknown and can be difficult to define. Paleolimnological techniques provide means to assess current environmental conditions of the PAD in the context of a pre-industrial baseline. Research focuses on lakes very near to the Peace River to reconstruct past hydrological conditions and to characterize sediment metal deposition derived from Peace River floodwaters. Results from sediment core analysis at lakes ‘PAD 65’ and ‘PAD 52’ show that organic matter content and d13Corg increase while C/N ratios decrease after 1970, suggesting a decrease in flood frequency. The timing of this stratigraphic shift aligns with changes in the Peace River hydrograph caused by river regulation as a result of the construction of the Bennett Dam. Notably, these are the first lakes (of >30 in the PAD) with paleolimnological evidence to attribute hydroecological change in the PAD to the Bennett Dam, which suggests these effects are evident in very close proximity to the Peace River. These two lakes lie in regions and perhaps at elevations that are highly sensitive to changes in the Peace River hydrograph that have occurred during the open-water season. Other lake sediment stratigraphic records examined in this study from the northern part of the PAD, and just downstream along the Slave River, show drying trends since the early twentieth century, likely due to climate change, consistent with previously published paleolimnological records. Sediment metal concentrations were analyzed at two lakes in the Peace River sector of the PAD, lakes ‘PAD 65’ and ‘PAD 67’, where metal-normalizer relationships and enrichment factors show no evidence of anthropogenic influence, although post-1920 metals at PAD 67, especially cadmium, copper, nickel, and zinc, did have an enrichment factor of up to 1.4. However, these concentrations fall below the minimum threshold of influence of 1.5 (Birch 2017) and are closely correlated with percent organic matter. This suggests the influence of metals scavenging by primary producers, as aquatic productivity increased. These findings will be of interest to multiple stakeholders, and will inform stewardship and lake ecosystem monitoring of the delta.

https://scholars.wlu.ca/cgi/viewcontent.cgi?article=3447&context=etd