Potential impacts of climate change on water availability for crops in the Okanagan Basin, British Columbia. Can. J. Soil Sci. 86: 921-936. 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 CO 2 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 scenarios coincided. In one sub-basin, supply and demand thresholds were exceeded 1 yr in 6 (HadCM3) in the 2050s and at least 1 yr in 4 for all GCMs by the 2080s, and existing water supply infrastructure may be inadequate. Crop growing seasons were defined empirically from growing degree days or threshold temperatures. The growing season lengthened up to 30-35% leading to higher demand in fall and shortages due to low stream flows. Les auteurs n'ont pas pris en compte les effets éventuels de la hausse de la concentration de CO 2 sur la conductance des stomates qui pourrait réduire la demande d'eau. Lorsqu'on compare les résultats avec les eaux de captage modélisées du lac Okanagan, on constate généralement la concordance des scénarios indiquant une demande d'eau plus élevée et des réserves moindres. Dans un bassin secondaire, les seuils de l'apport et de la demande d'eau seront dépassés une année sur six (HadCM3) au cours des années 2050 et au moins une année sur quatre pour tous les modèles avant les années 2080. L'infrastructure actuelle des réserves hydriques pourrait donc s'avérer inadéquate. La période végétative a été définie de manière empirique d'après le nombre de degrés-jours de croissance et les seuils de température. La saison de croissance se prolongera de jusqu'à 30 à 35 %, ce qui entraînera une hausse de la demande à l'automne et des pénuries, consécutivement au niveau plus bas des cours d'eau.

The effects of xenon-arc radiation, using an Atlas Weather-Ometer and a clear glass pyrex filter system, on the breaking strength, extension-to-break, and the energy-to-break for several nylon, polyester, and polyester/cotton yarns were compared to these of outdoor exposure behind window glass. Both types of exposure resulted in similar, related rates of loss for these properties for all yarns. Lamp age in the Weather-Ometer intluenced degradation rates in some cases. All nylon yarns degraded slowly during Weather-Ometer exposure and rapidly outdoors behind window-glass, in comparison to polyester, while the polyester/cotton yarns degraded at similar rates in both locations. Yarn-denier variation and the presence of an optical, brightener had no detectable effect on degradation rates. Sensitization by anatase in nylon and polyester yarns occurred during outdoor exposure, but not during Weather-Ometer exposure.

The spectral distributions of xenon-arc radiation using several filter systems were compared to August sun-sky radiation measured behind window glass. By locating the main bond-dissociation energies of polyester and nylon at their equivalent photon energies on the spectral distribution curves it was possible to explain the discrepancies in degradation rates, reported in Part I of this work, which occurred between the xenon-arc and outdoor exposures. These differences in spectra may also account for degradation sensitization by anatase during the outdoor exposures.