Reconstructing river discharge trends from climate variables and prediction of future trends

•Significant declines of river discharges in Canada were reported.•There are challenges to extract accurate trends in basins with short periods of record.•A correlation model between river flow and climate variables was established to reconstruct natural modes of river discharge.•The proposed model is applied to Athabasca River discharge trend analysis.

SummaryA number of studies suggest a significant decline of river discharge in the Canadian Plains that drain the eastern slopes of the Canadian Rocky Mountains, and elsewhere in Canada. Analyses of these trends suggested that apparent decline rates may represent long-term discharge variation as a result of anthropogenic induced change in seasonal flow and/or may also represent true long-term declines in annual flow. Potential for significant declines in river discharge raises concern over future water supply for this region. However, extracting accurate trends in river discharge is challenging for basins with relatively short periods of record as quasi-periodic decadal and multi-decadal oscillations are found to be important components of long-term natural variability. In order to reconstruct historic river flows, a correlation model between river flow and climate variables (that normally have longer periods of record) was developed. This empirical relationship was used as a proxy to reconstruct natural modes of river discharge, allowing a means to extend short term discharge records further back in time. The Athabasca River was used as an example to demonstrate the application of the proposed methods. The resulting long-term Athabasca River flow trends show variation is strongly related to the Pacific Decadal Oscillation. Previous studies suggesting decline flows on this river have been biased by examining short-term records of flow, that by chance corresponded with the down limb of a long term cycle.