Impacts of climate and forest change to streamflow in Southern Alberta
Authors: Vinod Mahat and Axel Anderson
Rivers in Southern Alberta are vulnerable to climate change because much of the river water originates as snow in the eastern slopes and Rocky Mountains. Changes to the likelihood of forest disturbance (wildfire, insects, logging, etc.) may also have compounding impacts with climate change. This project is evaluating the impacts of climate change and forest disturbance on streamflow in the upper parts of the Oldman. Here we present the results for future climate change scenarios, which were evaluated with HBV-EC in combination with a stochastic weather generator (LARS-WG) driven by GCM output climate data. Three climate change scenarios (A1B, A2 and B1) were selected to cover the range of possible future climate conditions (2020, 2050, and 2080). GCM projected less than 10 % increase in precipitation in winter and about same amount of precipitation decrease in summer. These small changes in projected precipitation resulted in up to 200% (9.3 mm) increase in winter streamflow in February and up to 63% (31.2 mm) decrease in summer flow in June. This amplification is mostly driven by the projected increase in temperature that melted winter snow earlier in winter and spring suggesting possible future water scarcity in the snow melt dominated regions during the summer. A “guided” GLUE (generalized likelihood uncertainty estimation) approach was used to obtain best100 parameter sets to produce the ranges of streamflows for uncertainty analysis. The impacts of uncertainty were found to be higher in spring and summer flows compared to winter and fall flows.
Rivers in Southern Alberta are vulnerable to climate change because much of the river water originates as snow in the eastern slopes and Rocky Mountains. Changes to the likelihood of forest disturbance (wildfire, insects, logging, etc.) may also have compounding impacts with climate change. This project is evaluating the impacts of climate change and forest disturbance on streamflow in the upper parts of the Oldman. Here we present the results for future climate change scenarios, which were evaluated with HBV-EC in combination with a stochastic weather generator (LARS-WG) driven by GCM output climate data. Three climate change scenarios (A1B, A2 and B1) were selected to cover the range of possible future climate conditions (2020, 2050, and 2080). GCM projected less than 10 % increase in precipitation in winter and about same amount of precipitation decrease in summer. These small changes in projected precipitation resulted in up to 200% (9.3 mm) increase in winter streamflow in February and up to 63% (31.2 mm) decrease in summer flow in June. This amplification is mostly driven by the projected increase in temperature that melted winter snow earlier in winter and spring suggesting possible future water scarcity in the snow melt dominated regions during the summer. A “guided” GLUE (generalized likelihood uncertainty estimation) approach was used to obtain best100 parameter sets to produce the ranges of streamflows for uncertainty analysis. The impacts of uncertainty were found to be higher in spring and summer flows compared to winter and fall flows.
