Extreme Event Reconstructions for the Upper Fraser River Basin, British Columbia, Canada
Spring freshets and summer droughts have recently worsened in the Fraser River Basin, British Columbia, Canada, with significant impacts to the keystone Pacific salmon populations, the food and economic sovereignty of over eighty First Nations, and the western Canadian economy. These extreme events...
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| Format: | Text |
| Language: | English |
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Digital Scholarship@UNLV
2021
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| Online Access: | https://digitalscholarship.unlv.edu/thesesdissertations/4151 https://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=5155&context=thesesdissertations |
| Summary: | Spring freshets and summer droughts have recently worsened in the Fraser River Basin, British Columbia, Canada, with significant impacts to the keystone Pacific salmon populations, the food and economic sovereignty of over eighty First Nations, and the western Canadian economy. These extreme events present a potential risk since, unlike many large and less hydroclimatically-complex and/or empounded watersheds, the Fraser River Basin is susceptible to a combination of unregulated spring freshet and summer drought events even within the same year. A major limitation for understanding past and future extreme event risk in the Fraser River Basin is that observational streamflow datasets are both short in duration and potentially forced by anthropogenic warming. They therefore provide a potentially incomplete record of natural hydrological variability and inaccurate benchmarks of long-term natural runoff extremes. While longer-term, highly-resolved (annual), tree ring (TR) based paleohydrological reconstructions are increasingly being used worldwide by water managers and stakeholders to extend short observational streamflow records, this approach is difficult in complex temperate watersheds like the Fraser. For this study I developed the first multi-century, sub-annual resolution (seasonal), paired freshet and drought reconstructions within a single watershed. I targeted the Upper Fraser Basin since it represents the headwaters and primary runoff source of the greater Fraser Basin. By focusing on sub-annual streamflow seasons, I was able to both independently reconstruct seasonal extreme flow events, and also overcome methodological limitations that precluded prior attempts to reconstruct total water-year runoff in this watershed. Newly developed and existing TR chronologies from multiple species were used as proxies for seasonal temperature and cool-season precipitation which are, in turn, drivers of streamflow in each reconstruction season. I analyzed the magnitudes, durations, and statistical probabilities of high ... |
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