Climate Toolbox Activities

FUTURE STREAMFLOW

In this activity, we will explore future streamflow in watersheds near Portland, Oregon by utilizing the Future Streamflow Tool in the Climate Toolbox.

Hydrograph Peaks

Rain-dominant watersheds in the Pacific Northwest typically experience peak streamflow during the winter, when precipitation falling as rain is heaviest.

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Climate Effects

Streamflow

Streamflow is the rate at which a volume of water moves downstream. It is often represented in units of cfs = cubic feet per second and is shown on a hydrograph of monthly average streamflows.

Streamflow is a combination of surface runoff, groundwater and snowmelt.

EXPLORE FUTURE STREAMFLOW

NEAR PORTLAND, OREGON

ClimateToolbox.org

Monthly Hydrograph.

Source: Amy Snover

Drinking water and hydropower

Portland maintains two reservoirs in the Bull Run watershed to supply drinking water to the City and its suburbs, and to generate regional hydropower. Winter rains fill up the reservoirs and water is stored to meet demands through the dry summer months. Hydropower generation is highest in winter when flows are higher. The City has a secondary groundwater supply during dry summers and emergency events when the Bull Run supply is shut off.

Warmer winter temperatures in a watershed can cause precipitation to fall as rain instead of snow or can cause snow to melt earlier.

Water Management

Transient watersheds receive both rain and snow during the winter, and display a double-peak in their hydrographs.

Snow-dominant watersheds have higher elevations with a winter snowpack, essentially a mountain reservoir of water. As the snowpack melts in the spring and summer, the water runs off into streams so that peak streamflows occur in late spring or early summer.

The two reservoirs in Bull Run Watershed drain into the Sandy River and provide water for Portland.

ClimateToolbox.org

Data

FUTURE STREAMFLOW

The future streamflow data used in this activity was produced by routing watershed modeled runoff and snowmelt from grid cells in a hydrology model into streams. The hydrology model used here decides how precipitation falling on each grid cell evaporates, soaks the soil surface, runs off the surface or is stored as snow on the ground. The hydrology model uses inputs of daily future climate projections from 10 different global climate models and 2 future greenhouse gas emission scenarios (RCP 4.5, 8.5) from CMIP5. The raw streamflow data represents waterways in their natural state due to only climate and without the regulation from dam and reservoir operations. The bias corrected streamflow data has adjustments to match observed flows.

Activity

Create a climate data story on future streamflow in watersheds near Portland.

Prepare a 3-5 min presentation (2 slides) on your story.

To Do

To Do

Prepare Slide

Prepare Talking Points

The Facts (Slide 1)

The Meaning (Slide 2)

• Go to the Future Streamflow Tool in the ClimateToolbox.org.
• Uncheck the box for ‘Use Bias Corrected data’. Click the button for Future Scenario and choose RCP 8.5.
• Choose location ’Sandy River at Bull Run Reservoir’ to look at drinking water supplies. View the map to see where this is.
• On the hydrograph, click on the future time periods to remove them from the graph leaving only historical. Download screenshot.
• Go to TopoBuilder to identify a high elevation region in the watershed where water likely flows to Sandy River.
• Go to the Climograph Tool in the ClimateToolbox.org. Choose a location at the Bull Run Reservoir and one that is high elevation in the Bull Run watershed. Generate a climograph for both locations.
• Analyze climograph and hydrograph together. What months are likely snowfall? Why does the peak occur in the month it does? Determine if it is a snow or rain dominated watershed.

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• Tell a story about projected changes in the Bull Run watershed’s precipitation.
• What challenges do you see in Portland’s management of drinking water? Which months will have the greatest impacts?
• The large dams along the rivers provide us a lot of control to save water for dry summer months but there may be challenges.
• The future is not set in stone. If we reduce

emissions (esp. coal), our future could be the RCP 4.5 scenario not the RCP 8.5.

• Include a screenshot of hydrograph w/ future.
• Find a picture of the Bull Run Reservoir

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• Go back to the Future Streamflow Tool in the ClimateToolbox.org. This time take a screenshot of the hydrograph with the future lines on the graph.
• Analyze the hydrograph to see what it says about changes in the watershed for the amount and timing of monthly precipitation.

Prepare Slide

• Include a screenshot of historical hydrograph.
• Include a screenshot of a climograph. Label.