# The influence of climate change on the river discharge of the Lower Athabasca River and its implications for navigation   - Maxime de Bekker


## Abstract

Climate change is expected to alter discharge patterns in cold region river basins, affecting both low flow conditions and river ice processes. This study investigates how climate exchange may impact discharge in the Lower Athabasca River in Alberta, Canada and what implications this has for navigation. The river is important for Indigenous communities who use navigation for transportation of resources, hunting and fishing. 

To assess navigation constraints, a critical discharge threshold of 500 m3/s at Fort McMurray was used, representing conditions where navigation is restricted at 8 critical locations throughout the rivers. An algorithm was developed to identify when the river breaks and freezes up. This defined the narrowest fixed open water season to occur from 18 May to 17 October. The hydrological HBV model was calibrated and validated using observed discharge data and ERA5 forcing data. The model was then run using CMIP6 MPI-ESM1-2-HR forcing data under future climate scenarios SSP126, SSP245 and SSP370 for the period 2025-2099, where:

- SSP126: Optimistic climate approach, global temperatures expected to increase by 1,8 ℃.
- SSP245: Limited climate action, global temperatures expected to increase by 2,7 ℃.
- SSP370: Large global disparities, global temperatures expected to increase by 3,7 ℃.

The results show that annual low flow days are generally higher in the future compared to the historical period. The observed period contains an average of 27 annual low flow days, while future periods range between 31 and 49 annual low flow days depending on the climate scenario. SSP370 shows a weak increasing trend over time. Extreme low flow years become more frequent in all future scenarios. The open water season is also projected to expand, with earlier river ice break up and later freeze up.

These results indicate that climate change is expected to increase navigation constraints in the Lower Athabasca River, especially under SSP370.