Climate Change Streamflow Scenario Tool
Need for Climate Change Streamflow Scenarios
Magnitude of Projected Climate Change Impacts
Although some uncertainty remains in regional climate change projections, the magnitude of projected warming for the Pacific Northwest (PNW) and the region's strong reliance on mountain snowpack for water supply warrants consideration of climate impacts in water resource management and policy development. These impacts generally include the following for the PNW:
- Elevated winter snowline and decreased total winter snowpack;
- Increased winter streamflow;
- Decreased spring peak flows, summer and fall streamflow;
- Increased time between snowmelt and fall rains; and
- Increased competition among water users.
Specific impacts will vary to some degree depending on basin type and other distinguishing characteristics of the basin and water supply, including population and types of water use.
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Timing of Impacts
For watersheds at moderate elevations in the Cascade Mountains and in the southern interior of the Columbia River basin (e.g., the Snake River basin), significant climate change water resources impacts are likely to appear within the next few decades.
In large snow melt dominated systems like the northern headwaters of the Columbia River, climate change impacts may not become apparent for several more decades.
Given the long lead time required to change water resources infrastructure and policy, we argue that PNW policy makers and water management agencies need to begin to assess these potential impacts in their planning as soon as possible.