Potential impacts of climate change on water availability for crops in the Okanagan Basin, British Columbia

Crop water demand in the Okanagan Basin was determined for 1961 to 1990, 2010 to 2039, 2040 to 2069, and 2070 to 2099. Daily station temperature data were spatially interpolated to a 1 × 1 km grid and adjusted for elevation. Daily precipitation data were estimated across four climatic regions. Output from three global climate models (GCM), CGCM2, CSIROMk2 and HadCM3 was used to create future daily climate. Daily potential evapo-transpiration (grass reference) was estimated from an empirical relationship between Bellani- plate atmometer readings, temperature and extra-terrestrial solar radiation, and then modified by crop coefficients for all crops except pasture. Depending on GCM, projected water demand increased by 12–20% (2010 to 2039), 24–38% (2040 to 2069) and 40–61% (2070 to 2099). Possible elevated CO2 effects on stomatal conductance, which may reduce water demand, were not accounted for. Comparisons with modeled Okanagan Lake inflows indicated that, on average, high water demand and low supply scen...