Climate change and New Zealand's groundwater resources: A methodology to support adaptation

Study region: Hawke's Bay and Otago regions, North and South Islands, New Zealand (NZ). 

Study focus: Evidence that climate change affects groundwater is emerging, but a complete understanding of the processes and impacts on the resources remains limited in most countries, including NZ. This paper presents a methodology to explore the potential effects of climate change on groundwater for an envelope of future climate scenarios (i.e., low and high greenhouse gas emissions; mid- and end-century). The methodology uses national and sub-national datasets and models and is applied to two case studies (Hawke's Bay and Otago). Its structure allows for future implementation in other NZ regions.

New hydrological insights for the region: Results are provided as projected changes in precipitation minus evapotranspiration, rainfall recharge to groundwater (RR) and water table elevation. General water quantity reductions are projected for Hawke's Bay (e.g., RR reduced by up to −1.5 mm/d), and more limited and variable changes for Otago (e.g., RR varying between +/- 0.4 mm/d). We then present a discussion about furthering the science of climate change effects on groundwater, characterisation of climate change uncertainty and unique effects, and adaptation in the NZ context. We anticipate that our results, despite limitations and uncertainty, can enable adaptation actions without delay. We recommend integrated and adaptive approaches, including action effectiveness monitoring and community engagement, to develop resilience to climate change threats.