Abstracts
Climate Change and Agricultural Water Management in the Okanagan Basin, B.C.
Denise Neilsen1, Scott Smith, Stewart Cohen and Bill Taylor
1Agriculture and Agri-Food Canada
NeilsenD@AGR.GC.CA
Agriculture accounts for 75% of consumptive water use in the Okanagan Basin and crop production is entirely dependent on irrigation. In order to examine the effects of long term climate change and variability on daily water demand for agriculture, a GIS based model was developed that estimates water demand based on crop type and spatial distribution, ET/canopy development calculations and 1x1 km gridded climate datasets. Regional hydrology was modeled using the UBC Watershed Model. Climate scenarios generated by three GCMs and two SRES scenarios, for three time slices, 2020s, 2050s and 2080s were compared with historic data 1961-90 and 1991-2003 for both 30 year normal and annual outcomes. A 20-40% increase in demand was projected by the 2080s. Licensed allocations would be able to meet this increased demand, but supply may be limiting as comparisons of basin wide demand and unregulated inflow into Okanagan Lake indicated that scenarios projecting increased demand also projected decreased supply.
Major risks to agriculture and basin water supply are associated with the annual occurrence of droughts and low flows. In a case study, supply and demand in a major sub-basin were modeled using the six climate scenarios and three time slices and compared to critical thresholds based on flow, and current allocations associated with the maintenance of fish flows. Risk of exceeding both thresholds was assessed for each 30 year data set and six scenario. Comparing the periods 1961-1990 and 2071-2100, risk of low flow increased from 1 year in 30 to 1 year in 3 and risks of high demand increased from 0 to 100%.
Demand/supply scenarios were used to inform stakeholder dialogue sessions and continue to form the basis for debate on basin-wide water management and planning for development. Adaptation options will require changes in both demand and supply management.
2005-04-05 |
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