Climate Change and Streamflow in the Columbia Basin

Ben M. PeltoUniversity of Northern British Columbia

Changing Streamflow

Major Controls

• Precipitation • Amount• Timing• Phase

• Temperature• Snow melt timing• Glacier melt• Evapotranspiration

Temperature

• Around 1.6˚C warming in the Basin over the last century

• Basin temperature will continue to rise by 2 to 4˚C by 2100

• Days of extreme heat (>30˚C) will increase

ourtrust.org

Temperature and moisture

Jackson (2017)

• Increased summer temperature = more energy available to evaporate water and therefore higher potential evaporation

• The deficit between potential evaporation and actual evaporation is the climate moisture deficit

• This deficit is expected to grow in the Basin.

• Snow decrease at low elevations

• Snow line will rise• rain at low elevations

Snow

Carver/CBT, 2017

Columbia snow and runoff change

High

elevation,

increased

snow?

Reduced runoff

May-September

Schnorbus et al. (2014)

Earlier loss of snowpack, and

shrinking glaciers

Low

elevation,

decreased

snow

1961-1990 vs. 2050s

Snow

• Poorly monitored at high elevations• Some models project

increased snow up high

• Middle elevations underrepresented as well• Rising snow lines make

middle elevations even more important

Mid-elevations

High-elevations

Basin snow monitoring

Frank Weber, BC Hydro

Snow

• Measure snow depth with airborne laser surveys --LiDAR

Streamflow monitoring

• River discharge monitoring has focused on downstream sites, with a focus on power generation

• Understanding the source (snow, rain, groundwater) requires gauging tributaries.

Dave Hutchinson, Env. CAN

Measuring Glaciers

2014‒2015 2015‒2016 2016‒2017 2017‒2018 2014‒2018

Glaciers

• Area loss: 1985-2018 20% ice area loss in the Basin

• Thinning: -0.42 m ice yr-1 2000-2018,

-0.68 m yr-1 2013-2018

• Runoff = melt rate x glacier area• Even with increased melt rate, area loss will reduce glacier

runoff

Peak Water

Huss and Hock (2018)

• The Basin is at or near peak water

Projected glacier runoff

• June : increase • Earlier loss of snow

• July – October: decrease• Smaller glaciers negate increased

rate

Huss and Hock (2018)

Changing hydrograph

Rahman et al. (2015)

Earlier Peak in runoff

• Earlier spring freshet

• Earlier peak runoff

• Decreased summer and fall runoff

Climate variability

• Is climate variability in the Basin increasing?

• The link between climate indices, like El Niño and La Niña and streamflow are weakening (Brahney et al. 2017).

• Less predictability makes forecasting streamflow from climate indices problematic, increasing the importance of real-time data to help project seasonal runoff.

Changing Streamflow

• What do we need to know more about?• Streamflow in tributaries

• Stream temperature

• Glacier runoff

• Snow at high elevation

• How do we meet these needs?

• How do we adapt for these changes?

Works Cited

• Brahney, J., Weber, F., Foord, V., Janmaat, J. and Curtis, P. J.: Evidence for a climate-driven hydrologic regime shift in the Canadian Columbia Basin, Can. Water Resour. JournalRevue Can. Ressour. Hydr., 42(2), 179–192, 2017.

• Carver et al. 2017, Water Monitoring and Climate Change in the Upper Columbia Basin

• CBT, Climate Action in the Columbia Basin

• Huss, M. and Hock, R.: Global-scale hydrological response to future glacier mass loss, Nat. Clim. Change, 8(2), 135, 2018.

• Rahman, K., da Silva, A. G., Tejeda, E. M., Gobiet, A., Beniston, M. and Lehmann, A.: An independent and combined effect analysis of land use and climate change in the upper Rhone River watershed, Switzerland, Appl. Geogr., 63, 264–272, 2015.

• Schnorbus, M., Werner, A. and Bennett, K.: Impacts of climate change in three hydrologic regimes in British Columbia, Canada, Hydrol. Process., 28(3), 1170–1189, doi:10.1002/hyp.9661, 2014.