1. An Assessment of Historical and Future Hydro-Climatic Extremes Over Key Watersheds Within Western Canada
Barrie Bonsal1 and Charles Cuell2
1Environment Canada, Saskatoon, SK, Canada
2Selkirk College, Castlegar, BC, Canada

2. Outline Background Objectives Data & Methods
Past Hydro-Climatic Trends, Variability, & Atmospheric Causes
Future Hydro-Climatic Changes
Summary

3. Climate Impacts on Hydrology: Water Resources of Western Canada

4. Climate Impacts on Hydrology: Extremes and Variability
Western Canada: Region of high natural hydro-climatic variability – Daily, Seasonal, Inter-Annual, Decadal
Recent decades: Several high-impact extremes

5. Objectives
Identify, quantify, and predict the impacts of past and future climate variability and change on western Canadian water supply
Focus on key/vulnerable watersheds
Focus on extremes and variability on longer time scales (seasonal to annual)
Understand the drivers (e.g., atmospheric circulation) associated with variability and extremes

6. Quantification of Hydro-Climatic Extremes
Drought/Moisture Indices
Standardized Precipitation Index (SPI): Precip only
Palmer Drought Severity Index (PDSI): Temp & Precip; Shortcomings
Standardized Precipitation Evapotranspiration Index (SPEI): Temp & Precip; Standardized for region in question
SPEI: Based on Monthly CANGRD ( ); 50 km resolution; Focus on summer (JJA) values

7. Atmospheric Circulation: Synoptic Typing
Daily 500 hPa geopotential heights for summer period (NCEP/NCAR reanalysis) from 40°N to 60°N, 130°W to 100°W from
Based on kmeans clustering
Identify 6 types with corresponding temp & precip anomalies

8. Future Projections
North American Regional Climate Change Assessment Program
; 6 RCMs
Future summer SPEI
Future 500 hPa circulation

9. Summer SPEI over Oldman & Swift Current Watersheds

10. Summer Synoptic Catalogue
Warm & Dry
Regional
Cool P

11. Summer Synoptic Catalogue (cont’d)
Wet
Warm & Dry
Cool & Wet P

12. Dry Summers: % Frequency of Types
More Dry Types: 1 and 5
Fewer Wet Types: 4 and 6

13. Wet Summers: % Frequency of Types
More Wet Types: 4 and 6??
Fewer Dry Types: 1 and 5

14. Trends/Variability in Relevant Types
Dry: Type 5
Wet: Type 6

15. Future SPEI

16. Future Atmospheric Circulation
Dry Types

17. Future Atmospheric Circulation
Wet Types

18. Summary
500 hPa synoptic patterns explain temperature and precipitation patterns over Oldman and Swift Current watersheds
Occurrence of key synoptic types associated with extreme low and to a lesser extent extreme high SPEI summers
Trends and variability in key synoptic types reveal some interesting trends and variations
Preliminary analysis suggests much drier conditions in the future; Associated with more dry, and less wet atmospheric circulation patterns

19. Questions?