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[1] Thirty one hydrological time series of shallow groundwater levels, precipitation, and moisture-sensitive tree ring chronologies were analyzed and related to two climate indices: Niño 3.4 and PDO. Spearman rank correlation and spectral analyses (multitaper method, continuous wavelet transform, and wavelet coherence) were used to document the influence of El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) on shallow (depth < 20 m) groundwater level records from the Canadian Prairies. Modes of variability in the 2-7, 7-10, and 18-22 year bands were detected and reconstructed. Correlations and wavelet coherence between these oscillation modes and the climate indices suggest that variability in the 2-7 and 7-10 year bands is highly influenced by ENSO. The oscillation modes in the 18-22 year band reflect a negative correlation with the PDO index. When either of these teleconnections (ENSO/PDO) is in their respective positive phases, groundwater levels reflect the effect of associated warmer and drier winters experienced over much of interior Canada and the US, affecting important resource inputs to the hydrological cycle and groundwater recharge.

In this paper the mean water year (October through September) flow of the North Saskatchewan River (NSR) at Edmonton, Alberta is reconstructed back to 1063 A.D. using a new network of moisture-sensitive tree-ring chronologies from limber pine and Douglas fir at seven sites in the headwater sub-basins of the North Saskatchewan River Basin (NSRB). Over the full extent of the proxy hydrometric record (1063Á2007), we examined 1) the duration and severity of low flow, 2) the dominant frequencies of periodic variability and 3) the correlation between these significant periodicities in proxy streamflow and climate indices, specifically sea surface temperature oscillations, which are known drivers of regional hydroclimatic variability. This new record of the paleohydrology of the NSRB is compared to previous tree-ring reconstructions of the annul flow of the North and South Saskatchewan Rivers. Extending the reference hydrology for the basin from decades to centuries changes perceptions of the reliability of the water supply and understanding of the hydroclimatic variability. The gauge record not does represent the full extent of interannual to multidecadal variability in the tree-ring data; there are periods of low flow in the pre-instrumental record that are longer and more severe than those recorded by the gauge.Ré sumé : Dans la présente communication, le débit moyen de l'année hydrologique (d'octobre à septembre) de la riviaère Saskatchewan Nord (RSN) à Edmonton, en Alberta est reconstitué jusqu'à 1063 de notre ére à l'aide d'un nouveau réseau de dendrochronologies sensibles à l'humidité, grâce au pin flexible et au douglas de Menzies, à sept sites dans les sous-bassins du cours supérieur du bassin de la rivière Saskatchewan Nord (BRSN). Pour la durée compléte des relevés hydrométriques indirects (de 1063 à 2007), nous avons examiné 1) la durée et l'intensité des débits d'étiage, 2) les fréquences dominantes de la variabilité périodique et 3) la corrálation entre les périodicités importantes dans les indices climatiques et d'écoulement fluvial substitutifs, plus particulièrement les oscillations de température de surface de la mer, qui sont des facteurs connus de la variabilité hydroclimatique régionale. Ce nouveau relevé de la paléohydrologie du BRSN est comparé aux reconstitutions dendrométriques antérieures du débit annuel des riviéres Saskatchewan Nord et Sud. Le fait d'ètendre

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