Drought science a combined effort

HBRC Kathleen Kozyniak is the BHRC's principal climate scientist. Photo / Paul Taylor

Given that the region has experienced particularly dry conditions over the past few months it may seem fair to assume Hawke's Bay is on the brink of drought, however the science says otherwise.

The National Institute of Water and Atmospheric Research (NIWA) is just one of several organisations that collate data which helps the Ministry of Primary Industries (MPI) assess dry areas.

While the Ministry of Primary Industries doesn't necessarily declare droughts, it works with local stakeholders when there is a natural disaster (storm, flood, drought, earthquake) to classify the 'adverse event' in terms of how it will impact the area.

NIWA climate scientist Nava Fedaeff said rainfall in Hawke's Bay this summer has been well below normal.

"During December much of the weather got low rainfall amounts, about half of the normal amount," she said.

Ms Fedaeff said so far in January the Hawke's Bay Airport received just 7 per cent of the usual amount of rainfall (5mm), Wairoa received just 4 per cent (4mm) and Mahia received 22 per cent (13mm).

"It is really dry and I guess the other piece to the story is it's looking like it's going to stay that way for the next few weeks," she said.

While a drought, alternatively referred to as an adverse event, has not been announced, Hawke's Bay Regional Council climate scientist Dr Kozyniak said measures have been put in place to monitor the region's stress levels.

Regional climate briefings have been held for the public every six weeks to outline the previous month's conditions and effectively keep a finger on the "pulse" of the region in terms of stress, Dr Kozyniak said.

"We get together with MPI to discuss the stage and if people are experiencing stress we might create a regional drought committee," she said.

Dr Kozyniak said at this stage conditions are not much worse that other years, however the low rainfall over the past three months with the additional drying effect of windy conditions has left the region with low soil moisture.

NIWA's Soil Moisture Deficit graphic refers to the amount of water plants need while the Soil Moisture Anomaly graphic refers to the difference between the average rainfall and the current rainfall.

"It's unusual but at the same time, going forward with climate change, time spent in drought in the eastern part of the North Island is projected to double or triple by 2040," Ms Fedaeff said.

"This could become the new normal for Hawke's Bay," she said.

While much of the region has experienced negligible rain this summer, Ms Kozyniak said there had been a helpful amount of rainfall in the Ruahine Ranges which has helped boost headwaters.

Dr Kozyniak said the last time the Bay experienced a drought was 2012/2013, where dry conditions were well spread over the country and Hawke's Bay had an anticyclone sitting over the region for a period.