UBC Theses and Dissertations
Changing with the flow : an analysis of water supply and demand in a subwatershed of the Okanagan Basin, British Columbia Harma, Kirsten Joy
Surface water is critical for meeting water needs in British Columbia’s Okanagan Basin, but the timing and magnitude of its availability is being altered through climate and land use changes and growing water demand. WEAP, an integrated water management model, was used to consider future scenarios for water supply and demand in an unregulated and a reservoir-supported stream that supply the District of Peachland. Potential changes to the magnitude and timing of streamflow were evaluated in response to the following scenarios: (i) climate change (derived from the HadCM3 and CGCM2 GCMs for the 2020s and 2050s), (ii) a simulated prolonged drought, (iii) land cover change resulting from a Mountain Pine Beetle (MPB) outbreak, and (iv) combinations of these conditions. These changes, in combination with likely demand increases and reservoir operating rules were evaluated in terms of stress on water availability for human use and aquatic life. Results demonstrate that anticipated future climate conditions will critically reduce streamflow relative to demand (societal and ecological) in at least a few months of “normal” and “dry” years. On the unregulated creek, an earlier recession of peak spring snowmelt, accompanied by higher demands at the beginning of the summer outdoor watering season as early as the 2020s, reduced the ability to meet downstream needs. On the regulated stream, two “very dry” years under a climate change scenario resulted in deficits for municipal water users under a higher reservoir release scenario. In all scenarios, even with the higher flows expected under the MPB scenario, some combinations of demand, reservoir operations and climate variability resulted in less than optimal conditions for instream ecological flow needs. Beyond the implications for the District of Peachland, this work demonstrates a method of using an accessible modeling tool for integrating knowledge from the fields of climate science, forest hydrology, water systems management and stream ecology to aid in water and land management decision-making.
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