New tool for measuring drought

Developed by NIWA with the support of the Ministry for Primary Industries, the New Zealand Drought Index uses the best scientific information available to determine the status of drought across the country. It is a tool to acknowledge the onset, duration and intensity of drought conditions.

Minister for Primary Industries Nathan Guy says until now there hasn’t been one definitive definition of a drought.

“Applying the latest scientific knowledge and technology like this index does, helps us to know exactly what is happening and can better inform producers, agri-businesses, councils and the Government to make the right decisions at the right time.”

The New Zealand Drought Index (NZDI) combines four commonly-used drought indicators: the standardised precipitation index (SPI); soil moisture deficit (SMD); soil moisture deficit anomaly (SMDA); and potential evapotranspiration deficit (PED) to show levels of dryness and when that turns into drought conditions.

A map of New Zealand and time series plots for each region are updated daily and freely available on the New Zealand Drought Monitor webpage.

“Droughts are not uncommon in parts of New Zealand, but when they extend for many months or affect wide regions they can have a major impact on rural communities,” says Guy.

“It doesn’t all finish the first time it rains either, because the on-farm effects of drought often linger due to the impact on forage quality, animal health, breeding stock numbers and farm cash-flow.

“This is another good example of smart agriculture, using technology to help farmers make early decisions.”

MPI works with local stakeholders to monitor adverse weather events such as storms, floods and droughts. The focus is on the impact of the event on the rural community, and how well they can cope and manage their primary industry businesses under the circumstances.

“When a region has been in drought for a period of time, the Drought Index will be one extremely useful factor to confirm the duration, scale and intensity of the dryness. It will be one of the important factors used in deciding when a medium or large scale adverse event should be classified, which defines when the impact of the event requires additional recovery measures for the affected communities,” says Guy.

The index is available at http://www.niwa.co.nz/drought-index