Changes in 20th century streamflow regimes of the Bow and Athabasca Rivers, Alberta, Canada. Presented by Brian Luckman at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

1. Changes in 20th century streamflow regimes in the
central Canadian Rockies
Brian Luckman and Heather Haines
University of Western Ontario, Department of Geography
Athabasca River at Jasper
October 2008
Global Change and the World’s Mountains
Perth ,Scotland 29th September 2010

2. Outline
Examine evidence for
hydrological changes in the
flow of Athabasca and Bow
Rivers during the 20th century.
Columbia Glacier,
source of the Athabasca
Evaluate the effect of glacial cover River
on hydrologic responses
Determine the possible
influence of the Pacific
Decadal Oscillation (PDO) on
flow variability

3. Previous Studies in the Canadian Rockies
Bow River at Banff
longest natural flow record 1909-2009
Hopkinson and Young (1998) Bow
River at Banff (1951-93) baseline flow
decreasing due to glacier wastage Map
North Saskatchewan River
Demuth and Petroniro 2003 Athabasca
Most data fragmentary (mainly post `
ca. 1970) except Mistaya 1950-2000
Peyto Glacier in headwaters Decrease
in mean and minimum flow volume
during Aug-October but increase in
maximum volume

4. Source
Why Athabasca?
Previously ignored
Longest proglacial record (Sunwapta)
Significant glacier record
Provides headwater source for the
Alberta tar sands downstream

5. HYDAT data ( Environment Canada),
Daily monthly and seasonal discharge
Guage stations, Upper Athabasca Watershed
Looks
good,
But…
Mountain
Front

6. Data for the Upper Athabasca Watershed
Data are fragmentary
often only seasonal
±

7. Bow River vs. Athabasca River
Julian day
Bow River at Banff Athabasca River near Jasper
Data from 1909-2005 Data from 1913-1931,1970-2005
Complete daily data:1911-2005 Complete daily data:1914-21, 1924, 1926-
Drainage Area = 2209.6 km2 30, 1971-2005
Mean discharge 39.3 m3/s Drainage Area = 3872.7 km2
Mean 1971-2005 38.0 m3/s Mean discharge 87.3 m3/s
Mean 1971-2005 86.1m3/s

8. Seasonality of Flow
Both rivers have >80%
of flow between
May-September
Largest contributions
during JJA summer
season
Athabasca has greater
relative flows in August
and lesser component
in June
May

9. 20th century annual flow record
Mean discharge for Athabasca River is 87.3 m3/s, for Bow is 39.3m3/s
For the common 1971-2005 period they are 86.1 m3/s, and 38.0m3/s

10. Peak discharges for the 20th century record

11. Dates of peak discharge
Athabasca
anomaly
1978

12. Total precipitation in Jasper in September 1978 was the greatest in 70 years of record
It was 3.67 standard deviations above the mean

13. 20th century date of peak discharge
Between 1971-2005 the mean dates are June 23rd (Athabasca) and June 14th (Bow).
The trend lines suggest peak discharges are becoming later (8 days for Athabasca and 11
days for the Bow) over the 1977-2005 period

14. Date of the center of Mass of flow for the 20th century record
Mean CT date from 1971-2005 is June 4th (Bow) and June 16th (Athabasca)
CT Decreases
1971-2005 A 5 days 1977-2004 A 3 days
Bow 1911-2005 6 days B B 7 days B B 3 days

15. Hydrologic change in the 20th century
The continuous Bow record allows the trends in
the discontinuous Athabasca record to be placed in
perspective
Temporal pattern between the Bow and
Athabasca rivers are very similar
Both records show long term linear trends of
decreasing flow and earlier timing of peak flow and
center of mass over the 20th century
Differences exist between the magnitude of the
change between the two rivers

16. Effects of differences in glacier cover
LIA (ca. 1840s)
lateral moraine of
Athabasca (left)
and Dome ( right)
Glaciers
Stewart, et al (2004, 2005) found snowmelt dominated alpine basins are trending
towards earlier peak and center of mass flows while those that are non-snowmelt
dominated have later flow trends
Rood, et al (2006) found that several rivers in the Canadian Cordillera had
significant decreasing trends of annual discharge but some rivers with large
glacial melt contribution did not show significant change

17. Basin area glacier discharge discharge
km2 % m3/s per km2
Athabasca at Jasper 3872 6.8 86 0.022
Athabasca-Miette 3243 8.1 75.6 0.023
Miette at Jasper 629 0.3 10.4 0.017
Sunwapta 29.3 75 2.5 0.085
Bow 2210 2.6 38 0.017
Sunwapta is May-October only

18. Effect of Glacial Cover on Hydrological Change
Upper Athabasca Watershed provides an additional perspective to this
discussion
Athabasca River and (its tributary) Miette River have
significantly different degrees of glacier cover
Athabasca
Sunwapta River at Athabasca Glacier is the longest discharge record for
a pro-glacial river in Canada
Miette Junction of the Athabasca and Miette rivers
near Jasper (August 2010)

19. 1954
1938
Sunwapta River at Athabasca Glacier
Area 29.3 km2 Discharge 2.5m3/sec (May 1-Oct 31)
1948-1995, 2005-
Estimated Glacier cover 75%

20. Summer half year flows
(May 1- October 31 only)
Common period of record
Flow Duration Curve
Mean Daily flows
(Percentage of total
discharge)

21. Athabasca River vs. Miette River
Athabasca River above Jasper
ca, 8% glacial cover including
parts of the Columbia, Chaba
and Hooker Icefields
Complete daily data: 1914-21,
1924, 1926-30, 1971-2005
Drainage Area = 3872.7 km2
Mean discharge 75.6 m3 /s
Miette River near Jasper
little glacial cover (< 0.2%)
Complete daily data:
1915-20, 1976-2005
Drainage Area = 628.5 km2
Mean discharge 10.4 m3 /s

22. Comparison of annual flow of Athabasca
and Miette Rivers (1978-2005)
Athabasca Mean 75.6 m3/s, Miette 10.4 m3/s
Little change in mean annual flows or mean peak discharge values

23. Comparison of center of mass of
Athabasca and Miette Rivers
Stewart, et al (2005) show 5-10 day decrease over a 55 year period for western
North America. Above record shows 3 (Athabasca) or 7 days (Miette)
decreases over the 30 year period.
Athabasca shows a smaller trend possibly reflecting the buffering effect of
glacier melt

24. Changes in the center of mass
Sunwapta River at Athabasca Glacier
Sunwapta River ( drainage area ca. 29.3km2 is fed directly by drainage from
Athabasca Glacier.
Seasonal data (normally May 1 to October 31 but 48 complete years June 1-Sept 30th

25. Four late season (September) rainfall peaks replaced 1957, 1968, 1978,1982

27. Effect of Glacial Cover on Hydrological
Change
Results from the Athabasca and Miette rivers near Jasper indicate
that glacial cover has only a minor effect on hydrological change
Both rivers are showing little decrease in annual flow with timing of
center of mass decreasing but the date of peak discharge is
becoming slightly later.
Trends are not as prominent as in previous studies [see Stewart, et al
(2004, 2005)
Sunwapta River at Athabasca Glacier shows strong trends in
flow timing that are contributing to the differences between the
Athabasca and Miette Rivers
Rivers dominated by glacial melt are reacting differently than
those with little glacial input

28. Potential Influence of the PDO
Several studies have shown the effects of the PDO on 20th century
streamflow and snowfall in western Canada [Demuth and Petroniro (2003) ,
Mote (2006), Rood et al (2006), St Jacques et al ( 2010) ]
“warm” PDO "cool" PDO
1925-1946 1890-1924
1977-mid-1990's 1947-1976
Nate Mantua web site, September, 2005; JIASO, U. Washington

29. Peyto Glacier Mass balance 1966-2007
PDO shift observed
as a decrease in
winter mass
balance after 1976.
Winter mass
balance is highly
correlated to
winter snowfall.

30. Streamflow for the Bow River
54% of annual precipitation and 76% of flow are from April-August
melt of winter snowpack is important contributor to flow
Snowpack records
Reconstructed annual
flow Bow River at
Banff PDO ( inverted)
and April 1 snowpack

31. Athabasca River near Jasper 1975-2000 Mean Runoff
Dec
Nov
Flow visualization
Oct
Mean flow calculated from a
“ box” of 7 years (horizontal) Sep
and 15 days ( vertical) 5.8
5.4
weighted using a Hanning Aug 5
4.6
filter 4.2
Jul 3.8
Plotted in “surfer”
mm/day
3.4
3
Jun 2.6
Runoff in mm/day 2.2
1.8
Courtesy C.C. Smart May 1.4
1
0.6
Apr 0.2
Mar
Feb
Jan
1980 1990 2000

32. Bow River at Banff 1914-2000 Mean Runoff
Dec
Nov
Oct
Sep 5.8
5.4
5
Aug 4.6
4.2
3.8
mm/day
Jul 3.4
3
2.6
Jun 2.2
1.8
1.4
May 1
0.6
0.2
Apr
Mar
Feb
Jan
1920 1940 1960 1980 2000

33. Bow River, Centre of Mass (CT) with PDO Phases

34. There has been little change
in summer temperatures
but the biggest changes in
winter temperatures and
snowfall
Centre of mass does not
change much, the main
change is in flow volumes
Mean discharge CT date
1911-1924 41.11 June 8
1925-1945 39.01 June 5
1947-1976 40.69 June 4
1977-2005 37.31 June 3

35. Flow volumes, Bow River at Banff
1947-76 (“cool” PDO) vs 1977-2005 (“warm” PDO)
The mean discharges are 40.7m3/s (1947-19780 and 37.3 m3/s (1977-2005)
They are significantly different at the 0.013 level
The Bow has only 2.5% glacial cover so its main flow contribution is from
snowmelt runoff with lower winter precipitation after 1976.

36. Dates of peak discharge , Bow River at Banff
1947-76 vs 1977-2005
Mean peak date during cool phase is June 17th and warm phase is June 12th.
Despite a similar trend direction there is clearly a shift at 1976.

37. Data for the Upper Athabasca Watershed
Is there evidence of the 1976 shift in the Athabasca records?
Sunwapta River at Athabasca
Glacier is the best available
data set in this area
1976

38. Mean value 3.12 m3/s, Mean Value3.50 m3/s.

39. Influence of the PDO
After 1976 shift the PDO causes lower winter precipitation which is evident in the
Bow River as a decrease in available summer runoff .
In the Sunwapta River it shows as an increase in glacial melt with longer exposure
The Bow River shows a date shift in 1976 but it does not match clearly the effect
seen in the Sunwapta River.

40. Conclusions & Future Work
The PDO has major step change effects on winter precipitation and thus
glacier and snowmelt runoff that dominate any analysis of trends in
these records. This problem complicated the short or broken records of
many of these rivers. Thus short term trends may not be indicative of
long term patterns.
These analyses are preliminary and do not examine changes in
precipitation and temperatures directly. Future work will attempt to
link these changes more directly with the available instrumental
climate records
Athabasca at Athabasca Falls

41. Thank you for your attention
Athabasca Glacier