Climate Change and Streamflow in Ben M. Pelto the Columbia ...€¦ · University of Northern British Columbia. Changing Streamflow Major Controls •Precipitation •Amount •Timing

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.