The hydroelectric power potential of New Zealand’s largest catchment (Clutha River) under 21st century climate change

摘要

© New Zealand Hydrological Society (2022).With major alterations in the regimes of snow-fed mid-latitude rivers projected for the end of this century, the output from hydroelectric river run-off schemes will potentially be affected to a similar extent. While resulting changes in the annual and seasonal power output have been investigated for a number of catchments, more transparency is needed in terms of dominant mechanisms driving these changes and model component-specific uncertainty. In this study an ensemble of 32 hydrological simulations is used to investigate the hydroelectric power potential of the Clutha River (Southern Alps, New Zealand) under 21st century climate change. The ensemble encompasses two emission scenarios, four General Circulation Models, two bias correction methods and two snow models. The fully distributed hydrological model WaSiM is used to model both the main natural processes and major forms of water management in the catchment. The catchment’s largest hydroelectric scheme is modelled by an external component. In the 2090s the results show substantial increases in the output for winter (18%) and spring (7%), followed by reductions in summer (-19%) and autumn (-4%). A net increase in annual streamflow does not lead to a corresponding increase in annual output, which is attributed to excess water being spilled during high flow events. The driving controls behind this are identified as more winter precipitation, a reduction in the solid fraction of precipitation and an increase in extreme precipitation events. The relatively large variation in the projected seasonal output is found to be primarily caused by the General Circulation Model and the emission scenario, while bias correction and the snow model made a smaller contribution to the overall uncertainty.