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Quantifying future changes to winter hydraulics and discharge potential in a large Canadian regulated river

Author(s): Kevin Lees; Shawn Clark; Jarrod Malenchak; Mike Vieira

Linked Author(s): Shawn Clark

Keywords: River Ice; Climate Change Impacts on River Ice Hydraulics

Abstract: Predicted long-term impacts of global climate change on the cryosphere are numerous and far-reaching. For hydropower operations in cold regions, the effects of multiple changing hydro-climatic variables on environmental conditions may present both risks and opportunities. In northern Manitoba, Canada, the Nelson River features a significant hydropower network that generates approximately 75% of the province’s electricity demand. Upper Nelson River discharge is supplied mainly by Lake Winnipeg’s outflow, which is routed through a complex lake-outlet system (Outlet Lakes Area; OLA). Several ice processes throughout winter lead to reduced hydraulic efficiency of the OLA when compared to open-water conditions, leading to a seasonal decline in Lake Winnipeg outflow. It is inevitable that these ice processes will be impacted by climate change. The objective of this study was to quantify the effects of climate change on OLA winter discharge using an ensemble of CMIP5 scenarios and simulated reservoir water levels from HYdrologic Predictions for the Environment (HYPE). Hydro-meteorological datasets (i.e., air temperature, precipitation and Lake Winnipeg water level) were sourced from a hydrologic investigation by the BaySys research team [Tefs, A., 2018]. For this study, BaySys datasets were combined with empirical equations, which were derived from historical datasets to quantify OLA hydraulics. Output variables of interest included ‘winter discharge potential’, which was calculated under a range of possible future conditions. Comparing ensemble results for reference (1981-2010), near future (2021-2050) and far future (2041-2070) periods, statistically significant changes were identified. Ensemble results indicate that relative to the reference period, a smaller decline in Lake Winnipeg outflow will occur in future winters. Further, increased variability between winters conditions is predicted for future periods. While disagreements between individual climate scenarios add uncertainty to study predictions, these findings yield valuable insight for future hydropower planning as part of climate change preparedness.


Year: 2022

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