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Peatlands comprise of approximately half of the Athabasca oil sands region, many of which overlay some of the world’s largest bitumen deposits where surface mining for this resource has permanently altered the landscape. By law, companies must reclaim disturbed landscapes into functioning ecosystems including integrated upland-wetland systems with the objective of forming sustainable peat-forming wetlands. This thesis presents six years (2013 – 2018) of water balance and associated salinity data from one of the two existing constructed upland-wetland systems, the Sandhill Fen Watershed (SFW), a 52-ha upland-wetland built on soft tailings to evaluate the hydrological and hydrochemical performance and its potential to be self-sustaining. Following a considerable decrease in hydrological management, the dominant water balance components changed from primarily horizontal (inflow and outflow) to vertical fluxes (precipitation and evapotranspiration) which increased inundation, encouraged salt accumulation and changed plant communities. Results suggest that current conditions are not favourable for fen-peatland development as marsh-like conditions have developed, limiting water conserving functions and the ability to persist long-term in a changing climate. In terms of winter processes, topography currently controls snow accumulation, redistribution and melt at SFW while the role of vegetation in these processes is expected to increase as it continues to develop. Runoff ratios of snowmelt from hillslopes were drastically different than those previously reported for reclaimed peatland watersheds highlighting the influence of different soil materials used during construction. Under various climate change scenarios of a warmer and wetter climate, results from the Cold Regions Hydrological Model indicate that the influence of winter processes will decrease, potentially putting reclaimed systems at greater risk of moisture stress. Substantial hydrochemical changes have occurred as salinity was relatively low at the study onset as high volumes of inflow and outflow prevented ion accumulation. Over time, salinity continued to increase year-over-year throughout SFW from 2013 to 2018 in the wetland and margin areas. This increase in site-wide salinity was attributed to the shift in dominant water balance fluxes, changes in water table position and increased mixing of SFW waters with deeper saline groundwater that underlies the system. Based on its current conditions, it is unlikely that SFW will support peat-forming vegetation. It is recommended that design strategies shift to incorporate characteristics found in undisturbed saline peatlands that are capable of supporting peat-forming vegetation in a saline environment. Thesis Doctor of Philosophy (PhD) A better understanding of the hydrological functioning of reconstructed peatlands in the Athabasca oil sands region is required as it is a novel approach in this region and there is potential for thousands of hectares of land that will require this reclamation in the future. Due to their recent establishment potential trajectories of constructed peatlands have yet to be fully analyzed as only recently has sufficient data been collected to evaluate the hydrological and hydrochemical functioning and provide insight on its overall success. While design strategies may seem sound, these constructed systems are completely human-made and it is unclear how they will develop and function in a highly disturbed landscape. Thesis results suggest that current conditions are not favourable to sustain a peatland as marsh-like conditions have developed which will limit its ability to persist long-term in a dry and changing climate. It is recommended that design strategies shift to incorporate characteristics found in undisturbed saline peatlands that are capable of supporting peat-forming vegetation in a saline environment. Due to the many challenges associated with reclamation in this region, lessons learned from this pilot project will help guide future peatland construction.

Bitumen extraction in the Athabasca oil sands causes significant disturbance of landscapes originally rich in wetland and forest ecosystems, which now require reclamation as mandated by the Alberta Government. However, most research to date has focused on upland-forest ecosystems with little attention on wetland-peatland ecosystems, which are considered more challenging to construct due to salinization potential from ubiquitous salts used in the oil sands extraction and treatment processes; with particular focus on elevated Na+ due to its detrimental ecological effects. Syncrude Canada Ltd. (SCL) has constructed an upland-wetland system, the Sandhill Fen Watershed (SFW), to advance the understanding of wetland reclamation in the oil-sands region. The SFW is a highly engineered and managed system. Water is supplied from an artificial fresh water source and drainage is enhanced through a constructed surface outlet and an under-drain system intended to provide a downward hydraulic gradient to inhibit the upward movement of salts from the underlying waste material. The objective of this research is to understand the hydrochemical response of the SFW to variations in hydrological management with respect to sources, flow pathways and major chemical transformations of water as it moves throughout SFW. Through surface and pore water sampling, the electrical conductivity and major ions were measured throughout the growing season of 2013 and 2014. Results indicate that the combination of freshwater inflow, flushing of the system with the outflow pump and open underdrains in 2013 kept the overall salinity within the SFW relatively low, with most lowland sites under 1000 µS/cm. Major ion results indicate that most water throughout the SFW classified as Ca-HCO3 or Ca-SO4 in 2013, with higher concentrations in the uplands however Na+ concentrations did not exceed 250 mg/L at any sampling sites. With minimal management in 2014 and consequent limited freshwater input and flushing of the system, the overall salinity of the SFW increased considerably and EC at most sites in lowlands exceeded 1000 µS/cm. Na+, Ca+2, SO4-2 and HCO3- concentrations increased across the SFW, with higher concentrations in the uplands than the lowlands. Although most sites classified as Ca-SO4, the most notable change in 2014 was the presence of several Na+ “hotspots” along the southern hummocks in the SFW, where water samples classified as Na-SO4 and Na+ concentrations reached as high as 886 mg/L. Results provides evidence of modelled upward movement of Na+ from underlying waste materials and subsequent seepage from hummocks with limited pump management in the SFW. Thesis Master of Science (MSc)