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Changes in 20th century streamflow regimes in the central Canadian Rockies [Brian Luckman]


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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.

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Changes in 20th century streamflow regimes in the central Canadian Rockies [Brian Luckman]

  1. 1. Changes in 20th century streamflow regimes in the central Canadian Rockies Brian Luckman and Heather Haines University of Western Ontario, Department of GeographyAthabasca River at Jasper October 2008 Global Change and the World’s Mountains Perth ,Scotland 29th September 2010
  2. 2. OutlineExamine evidence forhydrological changes in theflow of Athabasca and BowRivers during the 20th century. Columbia Glacier, source of the AthabascaEvaluate the effect of glacial cover Riveron hydrologic responsesDetermine the possibleinfluence of the PacificDecadal Oscillation (PDO) onflow variability
  3. 3. Previous Studies in the Canadian RockiesBow River at Banfflongest natural flow record 1909-2009Hopkinson and Young (1998) BowRiver at Banff (1951-93) baseline flowdecreasing due to glacier wastage MapNorth Saskatchewan RiverDemuth and Petroniro 2003 AthabascaMost data fragmentary (mainly post `ca. 1970) except Mistaya 1950-2000Peyto Glacier in headwaters Decreasein mean and minimum flow volumeduring Aug-October but increase inmaximum volume
  4. 4. SourceWhy Athabasca? Previously ignoredLongest proglacial record (Sunwapta)Significant glacier record Provides headwater source for the Alberta tar sands downstream
  5. 5. HYDAT data ( Environment Canada), Daily monthly and seasonal discharge Guage stations, Upper Athabasca WatershedLooksgood,But… Mountain Front
  6. 6. Data for the Upper Athabasca Watershed Data are fragmentary often only seasonal±
  7. 7. Bow River vs. Athabasca River Julian day Bow River at Banff Athabasca River near Jasper Data from 1909-2005 Data from 1913-1931,1970-2005Complete 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. 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 JuneMay
  9. 9. 20th century annual flow recordMean 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. 10. Peak discharges for the 20th century record
  11. 11. Dates of peak discharge Athabasca anomaly 1978
  12. 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. 13. 20th century date of peak dischargeBetween 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. 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 daysBow 1911-2005 6 days B B 7 days B B 3 days
  15. 15. Hydrologic change in the 20th centuryThe continuous Bow record allows the trends inthe discontinuous Athabasca record to be placed inperspectiveTemporal pattern between the Bow andAthabasca rivers are very similarBoth records show long term linear trends ofdecreasing flow and earlier timing of peak flow andcenter of mass over the 20th centuryDifferences exist between the magnitude of thechange between the two rivers
  16. 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. 17. Basin area glacier discharge discharge km2 % m3/s per km2Athabasca at Jasper 3872 6.8 86 0.022Athabasca-Miette 3243 8.1 75.6 0.023Miette at Jasper 629 0.3 10.4 0.017Sunwapta 29.3 75 2.5 0.085Bow 2210 2.6 38 0.017 Sunwapta is May-October only
  18. 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. 19. 1954 1938 Sunwapta River at Athabasca GlacierArea 29.3 km2 Discharge 2.5m3/sec (May 1-Oct 31) 1948-1995, 2005- Estimated Glacier cover 75%
  20. 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. 21. Athabasca River vs. Miette RiverAthabasca 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 /sMiette 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. 22. Comparison of annual flow of Athabasca and Miette Rivers (1978-2005) Athabasca Mean 75.6 m3/s, Miette 10.4 m3/sLittle change in mean annual flows or mean peak discharge values
  23. 23. Comparison of center of mass of Athabasca and Miette RiversStewart, et al (2005) show 5-10 day decrease over a 55 year period for westernNorth 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 ofglacier melt
  24. 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. 25. Four late season (September) rainfall peaks replaced 1957, 1968, 1978,1982
  26. 26. Effect of Glacial Cover on Hydrological ChangeResults from the Athabasca and Miette rivers near Jasper indicatethat glacial cover has only a minor effect on hydrological changeBoth rivers are showing little decrease in annual flow with timing ofcenter of mass decreasing but the date of peak discharge isbecoming 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 inflow timing that are contributing to the differences between theAthabasca and Miette RiversRivers dominated by glacial melt are reacting differently thanthose with little glacial input
  27. 27. Potential Influence of the PDO Several studies have shown the effects of the PDO on 20th centurystreamflow 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 1890-19241977-mid-1990s 1947-1976 Nate Mantua web site, September, 2005; JIASO, U. Washington
  28. 28. 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.
  29. 29. Streamflow for the Bow River54% of annual precipitation and 76% of flow are from April-August melt of winter snowpack is important contributor to flow Snowpack recordsReconstructed annualflow Bow River atBanff PDO ( inverted)and April 1 snowpack
  30. 30. Athabasca River near Jasper 1975-2000 Mean Runoff Dec NovFlow visualization OctMean flow calculated from a“ box” of 7 years (horizontal) Sepand 15 days ( vertical) 5.8 5.4weighted using a Hanning Aug 5 4.6filter 4.2 Jul 3.8Plotted in “surfer” mm/day 3.4 3 Jun 2.6Runoff in mm/day 2.2 1.8Courtesy C.C. Smart May 1.4 1 0.6 Apr 0.2 Mar Feb Jan 1980 1990 2000
  31. 31. Bow River at Banff 1914-2000 Mean RunoffDecNovOctSep 5.8 5.4 5Aug 4.6 4.2 3.8 mm/dayJul 3.4 3 2.6Jun 2.2 1.8 1.4May 1 0.6 0.2AprMarFebJan 1920 1940 1960 1980 2000
  32. 32. Bow River, Centre of Mass (CT) with PDO Phases
  33. 33. There has been little changein summer temperaturesbut the biggest changes inwinter temperatures andsnowfallCentre of mass does notchange much, the mainchange 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
  34. 34. 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 levelThe Bow has only 2.5% glacial cover so its main flow contribution is fromsnowmelt runoff with lower winter precipitation after 1976.
  35. 35. Dates of peak discharge , Bow River at Banff 1947-76 vs 1977-2005Mean 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.
  36. 36. Data for the Upper Athabasca WatershedIs 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
  37. 37. Mean value 3.12 m3/s, Mean Value3.50 m3/s.
  38. 38. Influence of the PDOAfter 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.
  39. 39. Conclusions & Future WorkThe PDO has major step change effects on winter precipitation and thusglacier and snowmelt runoff that dominate any analysis of trends inthese records. This problem complicated the short or broken records ofmany of these rivers. Thus short term trends may not be indicative oflong term patterns.These analyses are preliminary and do not examine changes inprecipitation and temperatures directly. Future work will attempt tolink these changes more directly with the available instrumentalclimate records Athabasca at Athabasca Falls
  40. 40. Thank you for your attention Athabasca Glacier