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

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

Climate Impacts on Hydrology: Water Resources of Western Canada

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

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

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 (1900-2011); 50 km resolution; Focus on summer (JJA) values

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 1950-2011 Based on kmeans clustering Identify 6 types with corresponding temp & precip anomalies

Future Projections North American Regional Climate Change Assessment Program 2041-2070; 6 RCMs Future summer SPEI Future 500 hPa circulation

Summer SPEI over Oldman & Swift Current Watersheds

Summer Synoptic Catalogue Warm & Dry Regional Cool P

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

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

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

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

Future SPEI

Future Atmospheric Circulation Dry Types

Future Atmospheric Circulation Wet Types

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

Questions?