Hoa Phamand her manager Jean-Charles Perquin will present on their research into the differences between, and local implications of, meteorological and hydrological drought in Northland at a New Zealand Hydrological Society conference in Rotorua. Photo / NRC
When is a drought not a drought? When it's a hydrological drought instead of a meteorological drought, according to a Northland Regional Council scientist and her manager.
Resource scientist (surface water) Hoa Pham has been investigating the differences between, and local implications of, the two drought types in Northland, and
with the support of her manager, Jean-Charles Perquin, has written an article on the issue for the New Zealand Hydrological Society, which she will present to the society's upcoming conference in Rotorua this week.
In very broad terms, Ms Pham said, the simplest explanation of meteorological drought was what most people understood a drought to be — a lack of rain over a reasonably long time that made things very noticeably dry.
"It's pretty easy to measure low rainfall and for how long this has been going on," she said, but hydrological drought, which was more complex, was what happened 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 would be displayed by stream flows, which could remain lower than usual more than a year after rain returned.
