Thursday, 13 February 2003
Modelling hydrologic conditions in present and future climates—model performances for recent conditions in coastal British Columbia
Variations in temperature and precipitation exert tremendous influence on the amount and form of water that reaches the surface of Georgia Basin, British Columbia. The form in which precipitation occurs in winter, either snow or rain, is the primary factor controlling the hydrology of the region. In previous work we delineated zones of homogenous hydrologic processes within the Georgia Basin. Watersheds were separated into three types: rainfall-driven streams, snow melt-driven streams, and hybrid (mixed rain and snow melt-driven) streams. Climate change could have major regional effects on these hydrologic types. To investigate, we used climate data downscaled from the Canadian Coupled Global Climate Model as inputs to hydrologic models for six watersheds. Results were used to determine the location of the hydrologic zones during the 21st century. Model output suggests changes occurring in each of the three zones: rainfall driven streams show increased winter flows, snow melt streams shown an increasingly early onset to spring snowmelt, and hybrid streams become increasingly rainfall-driven. To complement this analysis of mean streamflow conditions, an analysis of extreme events – droughts and floods – was completed using outputs from the hydrologic models. A thorough investigation of biases between observed streamflows, modelled streamflows based on data downscaled from reanalyzed climate fields, and modelled streamflows based on data downscaled from the GCM was completed prior to analysis of simulated streamflows for future time periods. Changes in droughts and floods that accompany future climates are assessed.