Drought and rainfall

This section describes changes in drought and rainfall conditions in New Zealand over time, and who might be most at risk of health impacts.

Climate models predict more droughts for parts of New Zealand

Drought frequency and intensity is projected to increase across most of New Zealand as a result of climate change. Regions that are particularly at risk are in the northern and eastern North Island and the eastern South Island [1].

Eastern New Zealand is drier

Areas with more frequent dry periods are more likely to experience droughts, now and in the future.

Eastern regions in both the North and South Island had more dry periods in 2015-2017 than the rest of the country (Movie 1).

Movie 1: Number of days with soil moisture deficit, 2000-2017 (three-year moving average), by Territorial Authority (TA)

Movie 1: Number of days with soil moisture deficit, 2000-2017 (three-year moving average), by Territorial Authority (TA)

Note: For more information on Soil Moisture Deficit and its calculation, please download the metadata sheet and the factsheet.

More time spent in drought conditions will affect our health

Drought can affect health in several ways [2][3][4]:

  • drinking water: Severe drought can reduce the quality and amount of drinking water available
  • gastrointestinal infections: Rates of gastrointestinal infections (such as cryptosporidiosis and giardiasis) are affected by rainfall patterns. Drought conditions might lead to a greater concentration of harmful organisms in groundwater and surface water sources
  • reduced food availability: Drought can reduce crop production, and diminish food supply from fresh water sources
  • mental health: Drought can have a significant effect on mental health, particularly for those in rural areas who rely on rainwater for their livelihoods.

Effects on vulnerable populations

Populations that are more vulnerable to the health effects of drought are:

Combining soil moisture deficit (Movie 1) and population data (see Population Vulnerability domain for more information) suggests, that the east coast of the North Island (i.e. Gisborne and Hawke’s Bay), are likely to be regions where people will be particularly affected by the health effects of drought.

Gisborne is a rural area with a substantial Māori population and significant socio-economic deprivation, plus a high percentage of the population is under 5 years old. Similarly, Hawke’s Bay is a rural area with a sizeable Māori population, high numbers of older people over 85 years old and children under 5 years old, and pockets of socioeconomic deprivation.

Information about the data

Specific change over time corresponding with climate change cannot be shown as the common baseline period in climate change science is 1960-1990, for which comparable data is not available.

Number of days with soil moisture deficit

Source: CliFlo. NIWA's National Climate Database

Definition: Climate station data of the number of days in soil moisture deficit from around New Zealand was sourced from NIWA. One climate station was used per Territorial Authority (TA), except for Auckland City TA for which data from three weather stations were averaged. The number of days in soil moisture deficit per year for each TA has been averaged over the three-year time period.


  1. Ministry for the Environment. 2016. Climate change projections for New Zealand: Atmospheric projections based on simulations undertaken for the IPCC 5th Assessment. Wellington: Ministry for the Environment.
  2. McMichael AJ. 2013. Globalization, Climate Change, and Human Health. New England Journal of Medicine 368(14): 1335-1343. DOI: 10.1056/NEJMra1109341 (accessed 4 December 2018).
  3. Britton E, Hales S, Venugopal K, et al. 2010. Positive association between ambient temperature and salmonellosis notifications in New Zealand. Australian and New Zealand Journal of Public Health 34(2): 126-9. DOI: 10.1111/j.1753-6405.2010.00495.x (accessed 4 December 2018).
  4. Lal A, Baker MG, Hales S, et al. 2013. Potential effects of global environmental changes on cryptosporidiosis and giardiasis transmission. Trends in Parasitology 29(2): 89-90. DOI: 10.1016/j.pt.2012.10.005 (accessed 4 December 2018).

Interested in more information?

Carolin Haenfling

Phone +64 4 979 3119 (ext 63119)
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