Changes in 20th century streamflow regimes in the

central Canadian Rockies

Brian Luckman and Heather Haines University of Western Ontario, Department of Geography

Global Change and the World’s Mountains

Perth ,Scotland 29th September 2010

Athabasca River at Jasper

October 2008

Outline

Columbia Glacier,

source of the Athabasca

River

Examine evidence for

hydrological changes in the

flow of Athabasca and Bow

Rivers during the 20th century.

Evaluate the effect of glacial cover

on hydrologic responses

Determine the possible

influence of the Pacific

Decadal Oscillation (PDO) on

flow variability

Previous Studies in the Canadian Rockies

Map

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

Athabasca

`

North Saskatchewan River Demuth and Petroniro 2003

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

Why Athabasca? Source

Previously ignored

Longest proglacial record (Sunwapta)

Significant glacier record

Provides headwater source for the

Alberta tar sands downstream

Mountain

Front

Guage stations, Upper Athabasca Watershed

Looks

good,

But…

HYDAT data ( Environment Canada),

Daily monthly and seasonal discharge

Data for the Upper Athabasca Watershed

±

Data are fragmentary

often only seasonal

Bow River vs. Athabasca River

Bow River at Banff

Data from 1909-2005

Complete daily data:1911-2005

Drainage Area = 2209.6 km2

Mean discharge 39.3 m3/s

Mean 1971-2005 38.0 m3/s

Athabasca River near Jasper

Data from 1913-1931,1970-2005

Complete daily data:1914-21, 1924, 1926-

30, 1971-2005

Drainage Area = 3872.7 km2

Mean discharge 87.3 m3/s

Mean 1971-2005 86.1m3/s

Julian day

Seasonality of Flow

May

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

Ok so these are the mean annual flow values and the units are correct! The trendlines represent the entire data series.

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

This is the peak discharge for Ath and Bow with trendlines over the entire period

Peak discharges for the 20th century record

Date of peak discharge uncorrected for ath 1978 which is a rainfall peak – trendlines are for the entire data period including the anomalous day

Dates of peak discharge

Athabasca

anomaly

1978

Athabasca Discharge for 1978 showing the required date change

Total precipitation in Jasper in September 1978 was the greatest in 70 years of record

It was 3.67 standard deviations above the mean

Corrected date of peak discharge over the entire data period – trendlines are for the entire data periods

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

CT date over the H2O year using the Stewart et al method. Trendline is for the entire period

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

Bow 1911-2005 6 days

1971-2005 A 5 days

B B 7 days

1977-2004 A 3 days

B B 3 days

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

Hydrologic change in the 20th century

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

Effects of differences in glacier cover

LIA (ca. 1840s)

lateral moraine of

Athabasca (left)

and Dome ( right)

Glaciers

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

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

Sunwapta River at Athabasca Glacier is the longest discharge record for

a pro-glacial river in Canada

Athabasca

Miette Junction of the Athabasca and Miette rivers

near Jasper (August 2010)

Sunwapta River at Athabasca Glacier

Area 29.3 km2 Discharge 2.5m3/sec (May 1-Oct 31)

1948-1995, 2005-

Estimated Glacier cover 75%

1938

1954

Summer half year flows

(May 1- October 31 only)

Common period of record

Flow Duration Curve

Mean Daily flows

(Percentage of total

discharge)

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

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

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

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

Date of peak discharge before I corrected for the 4 major rainfall peaks

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

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

Potential Influence of the PDO

“warm” PDO

1925-1946

1977-mid-1990's

"cool" PDO

1890-1924

1947-1976

Nate Mantua web site, September, 2005; JIASO, U. Washington

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) ]

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.

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

Reconstructed annual

flow Bow River at

Banff PDO ( inverted)

and April 1 snowpack

Snowpack records

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

1980 1990 2000

Athabasca River near Jasper 1975-2000 Mean Runoff

0.2

0.6

1

1.4

1.8

2.2

2.6

3

3.4

3.8

4.2

4.6

5

5.4

5.8

mm

/da

y

Flow visualization

Mean flow calculated from a

“ box” of 7 years (horizontal)

and 15 days ( vertical)

weighted using a Hanning

filter

Plotted in “surfer”

Runoff in mm/day

Courtesy C.C. Smart

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

1920 1940 1960 1980 2000

Bow River at Banff 1914-2000 Mean Runoff

0.2

0.6

1

1.4

1.8

2.2

2.6

3

3.4

3.8

4.2

4.6

5

5.4

5.8

mm

/da

y

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

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

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.

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.

Data for the Upper Athabasca Watershed

1976

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

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

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.

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

Conclusions & Future Work

Athabasca at Athabasca Falls

Thank you for your attention

Athabasca Glacier