Evaluation of Paleo-Hydrologic Extremes and Their Uncertainties

English Abstract:

Natural proxy records of hydroclimatic behaviour, such as tree-ring chronologies, are a rich source of information of past climate-driven changes and non-stationarities in hydrologic variables. They are typically directly related to available water in respective years, thereby providing a means to go beyond the limited observational records. In this study, we investigated the tree-ring chronologies that demonstrate significant correlations with streamflows, with the objective of identifying the spatiotemporal patterns and extents of changes and non-stationarities in climate and hydrology, which are essentially representations of past “climate changes”. To this end, we developed a framework that also quantifies uncertainties around the reconstructions of paleo-hydrologic extremes. The major headwater tributaries of the Saskatchewan River basin (SaskRB), the main source of surface water in the Canadian Prairie Provinces, are used as the case study. Results confirm that stationarity has never existed in the hydrology of the region, as the statistical properties of annual paleo-hydrologic proxy records across the basin, i.e., the mean and autocorrelation structure, have consistently undergone significant changes at different points in the history of the region. This study identified paleo-hydrologic extremes (e.g., severe droughts) in the past four centuries that are well beyond recorded hydrologic extremes in the observational period of this region. This presentation highlights the need to broaden the understanding of hydrologic extremes in the Saskatchewan River Basin beyond the limited observational records, as an improved understanding is essential for more reliable assessment and management of available water resources.