The reconstruction of past streamflow events is of great interest to the water resources engineer to obtain the best possible estimates of extreme flow conditions for investment, decision making, and design. The tree ring data offer a unique way of addressing this problem. The pattern of growth rings of a tree reflects the environmental conditions experienced during each year. Tree rings are produced annually and can be precisely and reliably linked to climatic variations, which makes them ideal for correlation with annual climatic records. This paper demonstrates the utility of using the methods of dendroclimatology, the study of climate through tree rings, to extend streamflow records. The techniques developed were applied to the Athabasca River at Athabasca. The results reveal considerable benefits from the reconstruction through more precise, and more extreme, estimates of drought quantiles.Key words: drought, tree ring data, reconstruction, extreme flow quantiles, frequency analysis.

An approach was developed for combining streamflow drought information from synthetic (generated) data with data reconstructed based on palaeoclimatic information (tree ring widths). The tree ring data were used to reconstruct streamflow in periods when no streamflow data were collected. The reconstructed data were then used as a source of historical data for estimating drought severity quantiles. The generated data were obtained using a nearest neighbour resampling method while the tree ring reconstruction was accomplished using a regression model. The application of the approach was to data from the Athabasca River in Alberta, Canada. The results demonstrate the feasibility and the utility of the approach for obtaining more accurate and precise estimates of extreme drought severity quantiles.