Increasing Air Temperatures:
Although the climate model used in Phase 2 suggests that the average total annual precipitation won’t change significantly in future, air temperatures are expected to increase, which means that more winter precipitation will fall as rain rather than as snow.
Furthermore, the future high elevation snowpack would melt sooner – by roughly one week over the 2011-2040 period, and 2-3 weeks over the 2041-2070 period. This will increase the importance of reservoir storage.
Less Water Stored as Snow:
Although average annual precipitation will not change too dramatically, winter precipitation will come more often as rain and on average there will be less water stored as snow.
Snow storage is an important component of water supply, so there may be less water available for summer use.
According to the computer models, climate change alone or in combination with increased irrigation and population growth is not expected to significantly affect average annual stream-flows.
Stream-flows will be increased in the fall and winter. However, between June and September, stream-flows could decrease by roughly 1/3 over the 2011-2040 period, and 2/3 by the 2041-2070 period (relative to current conditions) unless winter stream-flows are captured to augment summer flows.
Three Year Drought:
Under the future three-year drought scenario, average annual net inflows to Okanagan Lake are expected to be roughly half of what they are presently. Assuming such a scenario with current operating procedures, Okanagan Lake levels would drop below normal operating ranges, and could affect the ability to keep water flowing in Okanagan River.
Increased Risk of Flooding:
Flood risk may also increase as a result of more intense storm events.
- Summary Report – Part Four – Scenarios (555Kb PDF)