Climate Change in the Bow River Basin
Covering more than 25,000 square kilometres, the Bow River Basin (BRB) begins in the Rocky Mountains where snow and melting glaciers feed the headwaters of the Bow River. From the mountains, the Basin extends through Banff National Park into the Foothills and Grasslands regions until it terminates just west of Medicine Hat, Alberta1.
Most of the water in the BRB originates in the Rocky Mountains where large amounts of snow accumulate. Because the mountains are steep, runoff and snow melt travels quickly down the tributary streams and into the Bow River itself.
The Foothills and Grassland regions receive less reliable precipitation than the Rocky Mountains, but they are home to ecosystems that depend on the cold water originating from melting mountain snow.
The BRB is the most densely populated region in Alberta, with the population growing by more than a quarter of a million people in the last ten years3. Although approximately 20% of the BRB is forest reserve, the Basin also supports industries such as agriculture, manufacturing, and oil and gas4.
To determine the climate of a region, scientists compile data from various instruments including air temperature sensors and precipitation gauges. As can be seen in the instrument record, the average amount of precipitation in the BRB is between 511 millimeters per year near Banff, to 312 millimeters per year near Hays. The average maximum daily temperature in summer ranges by area from 21 to 25 degrees Celsius, and in the winter it ranges from -1 to -2 degrees Celsius. The data are from the instrument record compiled by Environment Canada.
Because the instrument record is relatively short (only approximately 100 years), scientists use information from the natural world to gain a better understanding of what the climate looked like thousands of years ago. Old trees, for example, provide a record of wet and dry years because the amount of growth each year is dependent on the amount of water available to the tree.
In the BRB, tree ring data from the past 800 years shows that there was much more variability and greater climate extremes than can be seen in the relatively short instrument record5. This information is significant because what happened in years past could theoretically happen again. Because of climate change, people living and working in the BRB need to be prepared for the possibility of even greater climate variability and extremes, as well as an overall trend of increasing temperatures.
Climate change is projected to increase air temperatures in the BRB. This is important because the natural pattern of flow in the Bow River is largely determined by when the snow in the Rocky Mountain headwaters melts. Right now, melting snow creates high river levels in the spring which taper off as the snow disappears, and the river flow is low in the late summer, sustained by glacier meltwater and intermittent rainfall events.
Warmer air temperatures will likely result in snow melting earlier in the spring. Due to this warming, researchers estimate that the spring snow melt in the Bow River could happen an average of two weeks earlier in the 2080s compared to now6. It will also likely cause precipitation to fall as rain instead of snow at some points in the year, particularly in the fall and spring.
Along with earlier spring runoff and rain instead of snow, scientists expect the BRB could have drier late summer months and increasing variability in precipitation from year to year7. Researchers also project that the BRB will experience more frequent and severe intensive storms that could potentially cause flooding8.
Because of the changing climate in the BRB, there will likely be several impacts on water users in the region. Specific challenges include the following:
- Snow melting earlier in the year will mean spring flood events happen earlier in the spring as well as low river flow in the later part of the summer.
- The wild animals and plants may need more water in warmer temperatures, and aquatic ecosystems may be impacted by changing stream flow. For example, fish that rely on higher river levels to spawn in the fall may face challenges, and species that need cold water may not thrive in warming creeks. Warm-water adapted species may become more common.
- The changing frequency of precipitation events could result in a reduced water supply for municipalities when they are experiencing longer, hotter summers.
- Hydroelectric power generation could be impacted if there is not enough water in the reservoirs to turn turbines during periods of low precipitation. This scenario is increasingly likely if there is less precipitation during the summer and more evaporation from reservoir surfaces as a result of higher temperatures.
- Irrigation districts in the BRB rely on upstream precipitation to come down the river and provide enough water to irrigate crops. Less precipitation during the growing season may increase the need for irrigation but there may not be enough water available to meet this demand due to low river flow.
- Warmer spring and fall temperatures could mean a longer growing season; however if the amount of precipitation or the available water in the river results in drought conditions, crops will not flourish regardless of the growing season.
- Warmer temperatures and increased precipitation in the spring months could lead to more flooding, with a quicker snowmelt also playing a role. In June 2013, several days of consistently heavy rain led to devastating floods in southern Alberta. Should the frequency of precipitation change and result in wetter springs, these flood events could become more common. Learn more about the 2013 floods here9.
- Some climate models of the BRB indicate that under certain climate conditions, very little snow will fall and instead precipitation will fall as rain. In these conditions, spring water levels will be reduced but winter water levels could be increased. Current water management planning in the Bow River is based on the highest river flows being in the spring from melting snow. The system of managing the Bow River would need to change significantly to capture water at different times of the year.
Due to increased climate variability and extremes, steps must be taken to help make communities more resilient and adaptable to changes in water availability. The growing population and increased economic activity in the BRB will also make it challenging to ensure there is enough water for everything that needs it. It will be important to ensure water is not wasted and that everyone works to increase their water efficiency.
The positive impacts of water conservation can already be seen through the City of Calgary’s Water Efficiency Plan which aims to reduce water consumption by 30 per cent over 30 years10. The strategy has already reduced consumption in the city from 518 litres per person per day in 2003 to 356 litres per person per day in 2019. This conservation has enabled the population of the city to grow but to still consume less water in total!
Read about how you can improve your water efficiency here11.
Using less water is not the only answer to future water availability. We can also use water smarter. Greywater reuse, for example, is when we reuse water from activities such as doing the laundry to flush toilets or to irrigate our lawns and gardens. You can read more about greywater here12.
Finally, it may be possible to build more water storage in the BRB to capture and store water for crop irrigation and other activities when it is needed during drier periods. Reservoirs are an example of a storage system that may help ensure there is enough water through inconsistent and changing annual precipitation to support activities in the BRB.
- Bow River Water Council. (n.d.). Bow River Basin State of the Watershed. Retrieved from https://www.brbc.ab.ca/ecr/
- Ibid, Bow River Basin State of the Watershed
- CGEN Archive. (n.d.) Waterscape – Bow River Basin. Retrieved from https://www.cgenarchive.org/bow-river-river-basin.html
- Ibid, Bow River Basin State of the Watershed
- Journal of the American Water Resources Association. (2016). Adaptative Water Resource Planning in the South Saskatchewan River Basin: Use of Scenarios of Hydroclimatic Variability and Extremes. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1111/1752-1688.12378
- Climatic Change. (2011). Potential impact of climate change on the water availability of South Saskatchewan River Basin. Retrieved from https://link.springer.com/article/10.1007/s10584-011-0221-7
- Journal of the American Water Resources Association. (2018). Projecting Canadian Prairie Runoff for 2041-2070 with North American Regional Climate Change Assessment Program (NARCCAP) Data. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1111/1752-1688.12642
- International Journal of Climatology. (2016). Possible Impact of Climate Change on Future Extreme Precipitation of the Oldman, Now and Red Deer River Basins of Alberta. Retrieved from https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.4338
- Alberta Water Portal Society. (2013). Southern Alberta Flood 2013. Retrieved from https://albertawater.com/southern-alberta-flood-2013
- City of Calgary. (n.d.). City of Calgary – Water Efficiency. Retrieved from https://www.calgary.ca/UEP/Water/Pages/Water-conservation/Water-efficiency-strategy.aspx#update
- Volusia County Florida. (n.d.). 25 Ways to Save Water. Retrieved from https://www.volusia.org/services/growth-and-resource-management/environmental-management/natural-resources/water-conservation/25-ways-to-save-water.stml
- WaterSMART Solutions. (2011). Grey Water Recycling and Reuse in Alberta. Retrieved from https://watersmartsolutions.ca/wp-content/uploads/2018/08/Greywater-Recycling-and-Reuse-in-Alberta-2011.pdf