Authors: Lauren K. Farmer*, University of Victoria, Dan J. Smith, University of Victoria, Bethany Coulthard, University of Nevada Las Vegas, Biing T. Guan, National Taiwan University
Topics: Paleoenvironmental Change, Water Resources and Hydrology, Canada
Keywords: precipitation, drought, reconstruction, dendrochronology, tree rings, detrending: EEMD
Session Type: Paper
Presentation File: No File Uploaded
Climate change is projected to make summers in British Columbia drier, leading to more frequent and severe droughts. On southern Vancouver Island, in particular, summer droughts are no longer unusual and have become commonplace in recent years. For instance, the Sooke Watershed, which supplies the majority of drinking water required by communities in the Greater Victoria area, experienced five historical droughts (1928-1930, 1940-1942, 1991-1995, 2001-2003, 2015) since 1916. The frequency and intensity of these droughts were severe enough to warrant the implementation of a drought management action plan that prompted the expansion of reservoir storage by 70% in 2002. To effectively assess the past, present, and future supply systems of the Sooke Watershed, we used Douglas-fir tree-rings collected in 2006 and 2016 to reconstruct precipitation and extend the instrumental record. Using a novel detrending method called Ensemble Empirical Mode Decomposition, a model was created which explained 28% of the precipitation variance. Results from the dendrohydroclimatic analyses extend the water supply area precipitation record to 1591. While the most severe interval of continuous drought within the instrumental record occurred between 2015 and 2016, it was exceeded in duration by five events that include extended drought episodes in 1662-1665 and 1705- 1708. The 2015-2016 drought event was also exceeded in intensity by seven events within the reconstruction, including the severest drought identified in 1594-1596. The findings of the research ensure that the water managers of the Sooke Watershed have insights into long-term water availability.