Drought research looks at impacts

These are a hydrological drought and a meteorological drought.

Hoa Pham, the council’s resource scientist - surface water, with the support of her manager, natural resources science manager Jean-Charles Perquin, has recently written an article on the issue for the New Zealand Hydrological Society. This will be presented at the society’s upcoming conference in Rotorua this week. 

Pham says with Northland experiencing several droughts in recent years, their research is expected to provide valuable and useful information.

She noted that over the period studied for the presentation (July 2018 - June 2019) the amount of water in some Northland streams had reduced “dramatically”.

Pham says in very broad terms, the simplest explanation of meteorological drought is what most people understand a drought to be – a lack of rain over a reasonably long time making things very noticeably dry.

“It’s pretty easy to measure low rainfall and how long this has been going on.” 

But hydrological drought is arguably more complex and is what happens to the region’s actual hydrological processes -- its rivers, lakes, reservoirs and groundwater -- especially over the longer-term.

In some cases, the impacts of meteorological drought are still effectively impacting on local stream flows, which can remain lower than usual, more than a year after the rain comes again and a drought appears to be well and truly over.

The duo are now investigating the relationship between the two types of drought, including the historical impacts (including severity) of meteorological droughts, their influence on stream flows and how these can be used to model current and future impacts.

Another dry summer?

The Northland Regional Council (NRC) is already keeping a close eye on the water situation in Northland with the region inching ever closer to another potentially dry summer.

Figures released by the NRC in October showed the Mid North and Far North areas had typically received 33 - 40% less rain than usual over the past 12 months.

The problem had been made worse by consecutive dry periods leading up to winter this year.

In the first six months of this year, Kerikeri and Whangarei were the driest they’d been in more than 80 years (since 1935 and 1937 respectively). The situation hasn’t really improved since then, with lower than average rainfall through winter.

Water restrictions are already in place in some areas.