Dr Moritz Lehmann is a freshwater scientist specialising in lake water quality and remote sensing. He uses data1 from Earth observation satellites to gain more information about cyanobacteria2 blooms in New Zealand lakes.
Moritz references the Eye on Lakes project, a multi-year MBIE Smart Ideas -funded project run from the University of Waikato.
Questions for discussion:
- What are the advantages of using Earth observation satellites to monitor lakes?
- What is a disadvantage of using satellites to monitor lakes?
- What do you think Moritz means when he refers to manually checking a lake?
Transcript
Dr Moritz Lehmann
Aquatic remote sensing scientist
Senior Scientist, Xerra Earth Observation Institute
Adjunct Senior Research Fellow, University of Waikato
Eye on Lakes project is specifically looking for algal blooms3 or cyanobacteria blooms in lakes. Cyanobacteria are tiny microscopic bacterial cells that photosynthesise4, and under the right conditions5, they can proliferate and they can completely smother a lake.
There is evidence6 that these blooms are increasing. And it’s important to know the scale of this problem so that we can study the lakes and find the reasons why this happened, and mitigate7 the expansion of the cyanobacteria.
We like to identify a bloom, not when it’s already there and established, but on the way of happening, of ramping up. So we like to see the first signs, the first greening essentially of the lake that might lead to a severe bloom.
The objective of the Eye on Lakes project is to develop models to allow us to look at an image and say, “OK, so here we have a cyanobacterial bloom” or “Here’s a bloom in development.” The advantages of using this Earth observation remote sensing system is that we get this data coming in all the time from the same places in New Zealand. And so this allows us to create a monitoring system that, cloud cover permitting, looks at the planet every 5 days to get the cyanobacteria and the algal8 concentration in those lakes.
You have to build some kind of software, some kind of automated system to do this. It’s very well possible for anybody now to download a satellite9 image and do those calculations as well. But to do this over and over and over again would take too much time, and computers are really good at that. So we would like to implement these calculations in the software system that then monitors and tells the authorities and the citizens whether a lake is safe to swim in or whether a lake needs manual checking.
Acknowledgements
Dr Moritz Lehmann, Xerra Earth Observation Institute and University of Waikato Te Whare Wānanga o Waikato
Algae10 images, timelapse of Sentinel-2 imagery showing changing water colour, Lake Waikare, The colour of 1,486 New Zealand Lakes: Clean, green and pristine? Poster, Landsat satellite overpass of North Island, toxic11 algae indication sign, Dr Moritz Lehmann and Xerra Earth Observation Institute
Sentinel-2 global coverage animation, European Space Agency (ESA)
