National hydrological and water resource impacts of climate change

Using the New Zealand Water Model, we have explored how climate change-driven changes in hydrology will impact agriculture, hydropower and flood hazards.

As part of this project, we have identified where New Zealand’s water cycle is most vulnerable to change.

Shifts in hydropower generation under climate change in relation to growing electricity demand
Daniel Collins, Roddy Henderson, and Laurence Fischer

Hydropower generation is projected to expand over the course of the 21st century to meet growing global electricity demand, in part driven by the need to mitigate climate change. At the same time, hydropower is sensitive to climate changes. This research found there will be “significant increases” in winter precipitation in major hydropower catchments which will shift the low hydropower supply to summer, rather than the peak demand time of winter. By mid-century, an extra 1 TWh or a 5 per cent increase in power generation potential is projected. 

Emergence of increasingly extreme floods within New Zealand under climate change
Daniel Collins

One of the challenges for flood risk management is the question of when to adapt. A useful indicator of the growing significance of climate change effects is the Time of Emergence, when a signal becomes detectable above background variability. This study investigated when and where climate change will have a detectable impact on 100-year flood events, finding that most locations show no robust emergence this century. When changes in the 100-year flood do emerge, they tend to lie within the south and west of the South Island, with Times of Emergence towards the end of the century.

Impacts of 21st century climate change on water stress and availability across New Zealand
Daniel Collins

This research assessed how climate change in this century will alter the water cycle, and, therefore, water stress and water availability, critical to land-based primary industries. It found higher water stress and longer restrictions in river abstraction projected for the north and east of the North and South Islands. Lower water stress and fewer restrictions on abstraction were projected for the west and south of both islands. However, under higher emissions scenarios, most of the country would experience increased water stress and longer restrictions.