A Dendroclimatic Investigation of Southwestern Saskatchewan

Date
2013-11
Authors
Kerr, Samantha Alicia
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Faculty of Graduate Studies and Research, University of Regina
Abstract

Water resources of the southwestern Canadian Prairies are limited and sensitive to changes in climate and land cover. An increasing demand for water resources has increased vulnerability to hydrological drought. Because few instrumental records exceed 100 years, climate proxies are used to extend the historical record of natural variability. Understanding the frequency, magnitude, and duration of past climate extremes allows researchers to better forecast the probability of future extreme hydrological events. Through standard dendrochronological methods, fifteen moisture sensitive tree-ring chronologies (Pinus albicaulis, Pinus ponderosa, Pinus contorta, Picea glauca, and Pseudotsuga menziesii) were collected and updated from the Sweet Grass Hills and Bears Paw Mountains (Montana, USA), and the Cypress Hills (Alberta and Saskatchewan, Canada). Correlation analysis was used to identify significant relationships between tree-ring chronologies (annual, earlywood, and latewood) and streamflow data, and multiple linear regression techniques were used to create robust multi-proxy reconstructions of mean summer (June – August) and average water-year (October – September) streamflow of the Frenchman River, Battle Creek, and Swift Current Creek in southwestern Saskatchewan, Canada, back to the late 1600s. Reconstructions developed for southwestern Saskatchewan explain approximately 40-55% of the instrumental variance for summer, and water-year streamflow. Hydrological extremes (droughts and floods) were quantified, classified and ranked on their severity (25th and 75th percentiles respectively; periods of critical hydrologic drought were defined by the lowest 10th percentile), and periods of extreme low flow were identified for the early 1700s, mid 1700s, early 1800s, mid to late 1800s, early 1900s, and late 1900s. Spectral analyses (Multi-taper and Wavelet) of the reconstructed streamflow revealed common cycles of variability at the inter-annual (~2-6 year) and multi-decadal (~20-30 year) scales of ocean-atmosphere oscillations, specifically the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). The level of uncertainty for each reconstruction was assessed, and results were compared to other dendroclimatological reconstructions for the western regions of Canada and the USA. Results show the large natural variability of prairie water levels, with cycles of decades with high flow followed by decades of low flow, and more extreme flows than in the instrumental records.

Description
A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Geography, University of Regina. viii 148 p.
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