Climate Change Impacts on Groundwater Recharge in Gulf Islands, Canada

With significant changes expected in the earth's global climate over the next century, due to global warming, and its resulting changes in the frequency and amount of precipitation, there has been growing concerns on climate change impacts on water resources. Especially concerned to water managers and governments is the potential impacts on groundwater aquifers since they are the main available source of potable water supply worldwide. This research, therefore, investigates the potential impacts of climate change on groundwater recharge to the fractured bedrock aquifers, which serve as the main source of potable water supply to the inhabitants of Gulf Islands in BC, Canada. Using Statistical DownScaling Model (SDSM) in combination with the LARS-WG stochastic weather generator, daily current and future (i.e., 2010-2039, 2040-2069, and 2070-2099) climate data were generated from CGCM1 predictions of the study location. These predictions were used as input to the HELP hydrologic model for estimation of recharge for the different climate change periods. The main properties of the aquifer -soil permeability, aquifer permeability and water table depth- used for recharge modeling were linked to ArcGIS for generating recharge zones, which allowed spatial and temporal integration of the recharge results. The combination of SDSM and LARS-WG in downscaling and predicting both the observed monthly temperature and precipitation was very successful. Mean annual precipitation downscaling with SDSM is predicted to increase by 52%, 65% and 88% relative to the observed for 2020s, 2050s and 2080s, respectively. On the other hand, the mean monthly temperature is predicted to rise by 1.14 ºC in 2020s, 2.05 ºC in the next 30 years and up to 3.5 ºC by the end of the century. According to HELP, the current mean annual recharge is about 44 % of the annual precipitation and is predicted to increase progressively by 7%, 8% and 9% in the 2020s, 2050s and 2080s, respectively, from the current. (Detta examensarbete är utfört vid Avd Teknisk vattenresurslära, TVRL)