Climate Change and Streamflow in Ben M. Pelto the Columbia ...€¦ · University of Northern...
Transcript of Climate Change and Streamflow in Ben M. Pelto the Columbia ...€¦ · University of Northern...
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.