Paleo-hydrologic reconstruction of 400 years of past flows at a weekly time step for major rivers of Western Canada

摘要

The assumption of stationarity in water resources nolonger holds, particularly within the context of future climate change.Plausible scenarios of flows that fluctuate outside the envelope ofvariability of the gauging data are required to assess the robustness ofwater resource systems to future conditions. This study presents a novelmethod of generating weekly time step flows based on tree-ring chronologydata. Specifically, this method addresses two long-standing challenges withpaleo-reconstruction: (i) the typically limited predictive power oftree-ring data at the annual and sub-annual scale and (ii) the inflatedshort-term persistence in tree-ring time series and improper use ofpre-whitening. Unlike the conventional approach, this method establishesrelationships between tree-ring chronologies and naturalized flow at abiennial scale to preserve persistence properties and variability ofhydrological time series. Biennial flow reconstructions are furtherdisaggregated to weekly flow reconstructions, according to the weekly flow distribution ofreference 2-year instrumental periods, identified as periods with broadlysimilar tree-ring properties to those of every 2-year paleo-period. TheSaskatchewan River basin (SaskRB) in Western Canada is selected as a studyarea, and weekly flows in its four major tributaries are extended back tothe year 1600. The study shows that the reconstructed flows properlypreserve the statistical properties of the reference flows, particularly in terms ofshort- to long-term persistence and the structure of variability across timescales. An ensemble approach is presented to represent the uncertaintyinherent in the statistical relationships and disaggregation method. Theensemble of reconstructed weekly flows are publicly available for downloadfrom https://doi.org/10.20383/101.0139 (Slaughter and Razavi,2019).