Examining the spatial and temporal variability of historical drought events to inform future climate risk in Canterbury

Abstract

Droughts are severe and unpredictable climate hazards that are challenging to predict and quantify. They are widely regarded as one of the most destructive natural hazards due to their unpredictability and far-reaching impacts, which extend across both time and space. Droughts affect socioeconomic and environmental systems, with their impacts often cascading beyond the initially impacted areas and systems. With climate change projected to increase the frequency and intensity of drought events globally, there is a growing need to further knowledge and understanding of drought characteristics to mitigate their impacts and develop effective adaptation strategies. Canterbury, a key agricultural region in New Zealand, is particularly vulnerable to drought. This study explores the spatiotemporal variability of historical summer droughts in Canterbury using long-term rainfall records from 1950–2022 at twenty five weather stations. The analysis reveals significant spatial and temporal variability in drought rarity and severity, identifying five sub-regional clusters with similar rainfall experiences. Further investigation of the temporal characteristics of Canterbury droughts at weather stations with at least one hundred years of rainfall data highlighted the extreme 1897/98 drought, which affected much of the region.

Using a storyline approach, a worst-case drought scenario was developed. The 1897/98 drought was compared with more recent known high impact droughts in 1988/89, 1997/98, and 2000/01 using rainfall and, where available, soil moisture data from two stations situated in the intensive dairying area of the Canterbury Plains. Each drought exhibited unique characteristics: the 1988/89 event had the driest March–November period on record, while the 2000/01 drought experienced the driest December–May. However, the most severe 15-month rainfall deficits occurred during the 1897/98 drought, marking it as an unprecedented event in Canterbury’s climate history. The findings highlight an increased risk of severe and prolonged droughts in Canterbury under climate change.

Understanding historical drought spatiotemporal patterns and constructing a worst-case scenario provide valuable insights for assessing future drought risk, supporting the development of targeted mitigation and adaptation strategies in a changing climate.