| Water resources planning requires the best possible estimates of extreme flow conditions for investment, decision making and design. The multi-year nature of drought events reduces the available sample size making estimates of extreme droughts very difficult.; Tree ring data offer a unique way of addressing this problem. The pattern of a tree's growth rings reflect the environmental conditions experienced during each year. In addition, trees are relatively long lived (up to 500 years) and well distributed in North America. Tree rings are produced annually and can be precisely and reliably linked to climatic variations. This makes them unique and ideal for correlation with annual climatic records.; The purpose of this thesis is to show the utility of using the methods of dendroclimatology, the study of climate through tree rings, to extend streamflow records. These methods use the principle that during drought periods moisture stress proportionally limits tree growth. This limitation is reflected in the width variation of annual growth rings. The climatic information inherently present in ring widths can then be used to extend historical records of low flow back the entire lifetime of the tree.; Three case studies were completed, one in the MacKenzie River Basin and two in the South Saskatchewan River Basin. Two of the case studies verified very well using split sample techniques, one was questionable. The reconstructions extended streamflow records from 59 to 190 years, from 60 to 420 years and from 65 to 352 years.; The results of a comparison between extreme droughts estimated from the gauged data and the reconstructed data showed a decrease in drought severity at all return periods. (Abstract shortened by UMI.)... |
