The cumulative effects on streamflow of surface water management for hydroelectric development, irrigation, and flood control and the effects of climate change on nival freshets, over-winter baseflow, and summer high-flow events are myriad, of interest to ecologic health and infrastructure security, and difficult to disentangle by studying historic observations alone. Inter-decadal, inter-annual, sub-annual, and sub-weekly variability and periodicity of streamflow are affected by both shifting climates and the growing regulation of freshwater for human uses. These changes to freshwater cycles at multiple temporal scales have had observed impacts on sea-ice formation and circulation in Hudson Bay, projected to increase in the future. Cyclicity, periodicity, and extrema of streamflow can be represented by a suite of flow signatures applied to historic and future modelled streamflow timeseries.
This presentation describes the present-day effects of water management by presenting the differences in multi-time-scale flow signatures between two hydrologic models (regulated and naturalized) forced by an ensemble of CMIP5 input and further characterizes these flow signatures’ parallel, divergent, and convergent behaviour by projecting the models using 50 years of climate change data as forcing. Flow signatures describing sub-annual dynamics are convergent for both models (due to climate change), where longer-term flow signatures are parallel under climate change regardless of regulation. These finding suggest that while regulation of streamflow affects sub-annual dynamics, decadal-scale changes to streamflow are principally driven by climate change regardless of any buffering effects by human intervention at the continental scale.
