Flood and drought extremes in southeastern Alberta

OBSERVATION: John Michalopoulos, Student, Royal Roads University

I have noticed a change in the timing of seasons and the increasing frequent occurrence of weather extremes in southeastern Alberta. I have lived in Medicine Hat Alberta for 26 years. This region is considered a semi arid climate with warm dry summers and fairly temperate winters.

Photo 1: Medicine Hat neighborhood beside the free flowing South Saskatchewan river January 2016

BACKGROUND:

Global change is becoming an increasing problem throughout the world and is evidenced by the ever cumulative appearance of extreme climate events witnessed globally. Although the Earth System is in constant change these changes usually occur very slowly over thousands or millions of years. This has been documented through ice core and ocean bed core analyses. What we are currently observing through the review of recorded history since the start of the industrial revolution is an unprecedented increase in the levels of CO2 in the atmosphere leading to global warming. This in turn causes surface temperatures to rise which increases moisture levels in the atmosphere causing more heavy rain patterns and often severe overland flooding episodes. Conversely the warmer atmosphere also causes higher surface temperatures leading to extreme heat waves and droughts in susceptible areas.

In southeastern Alberta recent weather history bears out this cycle and there is growing body of evidence of the drought / flood intensity becoming more extreme. Tree ring analysis showed that the three year period of 1999-2001 being the hottest three years in the past 150 with southeastern Alberta suffering from low surface water supplies leading to agricultural disasters. I have noted that we appear to be entering another drought phase in 2015-2016. Reservoir and irrigation districts are bracing for the worst with this past winter experiencing extremely low snow cover and precipitation. Ground moisture levels are at all time recorded lows in the spring of 2016.

Photo 2: Flows in South Saskatchewan River m3/sec Link

Photo 3: The chart below illustrates the trend of decreasing snow pack cover in the last 50 or so years. This lack of snow pack affects the amount of spring melt and runoff which contributes to storable water for agricultural irrigation and human consumption.

At the other extreme, southeastern Alberta specifically the Medicine Hat area has endured two 1 in 100 year flood events on the South Saskatchewan River (1995 and 2013) and a one 1 in 1000 year event with the flooding of headwaters flowing out of the Cypress Hills in 2010.

Photo 4: Flooding in Medicine Hat June 2013

Photo 5: Cypress Hills headwaters flooding east of Medicine Hat on the TransCanada highway 2010