Satellites orbiting Earth tracking health of New Zealand lakes, potential threats to humans

Satellites orbiting high above Earth are being put to use tracking the health of some New Zealand's biggest lakes.  

A team at Waikato University is using the images from space to hunt out toxic algal bloom.

The scenic and secluded Lake Rotoehu is a fly-fishing haven, but images taken from space paint a very different picture.

"It's always green and sometimes it's a little more green than on other days," says Moritz Lehmann from the Xerra Earth Observation Institute.

Bright green swirls are algal blooms and the lake near Rotorua is one of the dirtiest.

"Some of the algal blooms that can happen here can actually be toxic and so have serious health implications for animals and humans," says Lehmann.

That's why a study between the University of Waikato and German researchers is so important. It is utilising satellites from the European Space Agency to help track the blooms and guide teams on the ground to hot spots. 

"It helps us to know where we're going and when to go to certain places," says Lehmann.

A 2019 report by the Government's environment commissioner found water quality data was lacking for most of our lakes. The satellite imagery can fill some of the gaps and is used in routine monitoring by the Bay of Plenty Regional Council.

"We can understand a lot more about the bloom than if we were just to come out and take discreet water quality samples every month," says Bay of Plenty Regional Council environmental scientist James Dare.

Summer poses two problems - it's peak algal bloom season and people flock to lakes. It's a toxic combination. 

"We want to make sure that our community is informed of the dangers when something like that is occurring," says Dare.

With satellites flying over New Zealand constantly, the methods used on Bay of Plenty lakes could assist scientists nationwide.

"We won't be able to replace all the environmental monitoring with satellites but it's another tool in our tool kit," says Lehmann.