HR: 0800h
AN: H11F-0841    [Abstracts]
TI: Modeling Spatial Recharge in the Arid Southern Okanagan Basin and Impacts of Future Predicted Climate Change
AU: * Allen, D M
AF: Simon Fraser University, Depatment of Earth Sciences TASC I Building 8888 University Drive, Burnaby, BC V5A 1S6, Canada
AU: Toews, M W
EM: mwtoews@sfu.ca
AF: Simon Fraser University, Depatment of Earth Sciences TASC I Building 8888 University Drive, Burnaby, BC V5A 1S6, Canada
AB: Groundwater systems in arid regions will be particularly sensitive to climate change owing to the strong dependence of evapotranspiration rates on temperature, and potential shifts in the precipitation amounts and timing. In this study, future predicted climate change from three GCMs (CGCM1 GHG+A, CGCM3.1 A2, and HadCM3 A2) are used to evaluate the sensitivity of recharge in the Oliver region of the Okanagan Valley, south- central British Columbia, where annual precipitation is approximately 300~mm. Temperature data were downscaled using Statistical Downscaling Model (SDSM), while precipitation and solar radiation changes were estimated directly from the GCM data. Results for the region suggest that temperature will increase up to 4°C by the end of the century. Precipitation is expected to decrease in the spring, and increase in the fall. Solar radiation may decrease in the late summer. Shifts in climate, from present to future-predicted, were applied to the LARS-WG stochastic weather generator to generate daily stochastic weather series. Recharge was modeled spatially using output from the HELP hydrologic model applied to one-dimensional soil columns. An extensive valley-bottom soil database was used to determine both the spatial variation and vertical assemblage of soil horizons in the Oliver region. Soil hydraulic parameters were estimated from soil descriptions using pedotransfer functions through the ROSETTA program. Leaf area index (LAI) was estimated from ground-truthed Landsat 5 TM imagery, and surface slope was estimated from a digital elevation model. Irrigation application rates were modified for each climate scenario based on estimates of seasonal crop water demand. Daily irrigation was added to precipitation in irrigation districts using proportions of crop types along with daily climate and evapotranspiration data from LARS-WG. The two dominant crop classes are orchard (including peaches, cherries and apples) and vineyards (grapes). Recharge in irrigated areas is significantly higher, with irrigation return flow between 25--58%. Recharge results show a general increase of annual recharge, with the peak recharge shifting from March to February. Lower recharge rates and higher potential evapotranspiration rates are expected in the summer. The minor increase of annual recharge in future predicted climate states is due the shift of peak recharge from increased temperature. Growing season lengths, as determined from growing degree day accumulation, are expected to lengthen by 3--4 weeks by the 2080s.
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1807 Climate impacts
DE: 1829 Groundwater hydrology
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting