The Guardian - Severe drought torments British Columbia, a year after devastating floods
British Columbia is a case study on the paradoxical effects that climate change exerts on stressed hydrologic systems - a mixture of catastrophic flooding and severe drought. These see-sawing hydrologic conditions are discussed in a new article by The Guardian.
“The factors that cause a specific drought are randomly occurring over time. We simply cannot blame the current one on a lack of rain during the last several months. To do so would be a big mistake.
Ten months ago, when we lost 30 to 40cm of snow in 48 hours, that likely exacerbated the effects of droughts we’re seeing now. As a result, critical ground water recharge was far less than needed.”
Click here to read the article in the Guardian.
As temperatures rise across the globe, the atmosphere will tend to carry more moisture. This will have different effects in different areas, but in many parts of Canada the result is that we will expect more precipitation in the future.
However, this extra rain will likely fall in fewer, more extreme precipitation events. The increased temperatures also cause higher rates of evapotranspiration, so in between the rains the land surface will be drier. The end result is that when the rains do fall they will tend to runoff overland more than in the past , and less water will infiltrate into soil, through wetlands, and other pathways that slow the water down. With increased runoff and overland flow, water will flow directly into rivers and streams and resulting in higher peaks in river elevation (i.e. catastrophic flooding), but the decreased water in the 'slow' flow paths causes an overall decrease in water storage throughout watersheds (i.e. extreme drought).
And there are many additional processes which impact hydrologic conditions at a local scale, and it’s great to see this complexity represented in this article by the Guardian. In the case of British Columbia, the current drought is driven not only by very low levels of precipitation throughout the last summer. For example, the atmospheric rivers which passed over the Rocky Mountains and caused catastrophic flooding last November happened to melt 30-40cm of snowpack in the mountains over the course of just a few days. The melting of this snow contributed not only to the flooding in the Fraser Valley, but also resulted in a huge decrease in the groundwater recharge - recharge that is necessary to sustain critical groundwater baseflow to rivers and streams.
To quantify these trends the Canada1Water project is pairing regionally downscaled climate forecasts with highly advanced integrated hydrologic models (using HydroGeoSphere) for river basins across Canada. As a federally funded project, the results of this project will be published freely for water resources managers across the country. Understanding the impacts of climate change is the first step in effectively adapting to them. Canada1Water will provide the key foundational knowledge for Canadians to mitigate the impacts of climate change on our shared water resources.