Water quality in Rotorua lakes
David Hamilton was the former Environment Bay of Plenty Chair in Lakes Management and Restoration at the University of Waikato. In his role, David studied 12 lakes in the Rotorua region to better understand how land use affects water quality and what might be done to preserve or restore water quality in the lakes.
Modelling water quality
There are many natural ways in which water is purified. Unfortunately, in some ecosystems, humans have had drastic impacts on these natural processes and now there are problems with water quality. David Hamilton explains that we have to consider careful water management and, at times, expensive treatment options in an effort to boost natural processes.
David Hamilton of Waikato University looks at the water quality in lakes and often uses models to calculate what might happen in the future. With existing data, he tries to predict what the effect might be when certain environmental variables are changed. If some of the modelled changes show good results, they can indicate how to improve water quality.
Nature of science
Scientists sometimes work with hypothetical examples to ask “What if?” questions. Using models allows them to experiment without having an impact on the natural environment.
David explains that the lakes in this region are highly interesting and very important. Not only are they extremely beautiful and we enjoy them for recreational purposes, they act as freshwater storage and are important for plants and animals living in and around them. They also provide a recreational resource for the people of Rotorua, other New Zealanders and overseas tourists. The Rotorua lakes are mostly volcanic lakes, which means that they were formed directly or indirectly through volcanic activity. This also explains why some of them are affected by geothermal activity, with geothermally heated springs that directly feed into some of the lakes.
Lake Rotorua water quality
In this video, David Hamilton explains what time and space means for the water cycle by taking a closer look at Lake Rotorua.
Lake Rotorua’s water quality is the result of what happened to the water that infiltrated the land around the lake – the catchment area – a long time ago.
Point of interest
Think about the factors we need to consider in lake restoration projects.
Nature of Science
Scientists sometimes work with hypothetical examples, to ask ‘what if’ questions. Using models allows them to experiment without having an impact on the natural environment.
What’s happening to the lakes?
Over many decades, human activities – like settlements with septic tanks and farming – have taken a heavy toll. Wastewater from septic tanks and run-off from farming has added a heavy load of nutrients and bacteria to some of the lakes. This has resulted in a deterioration of lake water quality, which sometimes shows up as short-term events like algal blooms when nutrient pressure is particularly high.
Lake Rotorua monitoring buoy
Scientists use monitoring buoys to collect data that they can use to determine the water quality and any changes to Lake Rotorua.
David Hamilton’s work involved intensive studies of these lakes. Some lakes had data collected in real time, at intervals of 15 minutes, on factors like water and air temperature, pH levels, concentrations of dissolved oxygen in the water and light penetration. A further activity was to produce computer models to help inform and predict ongoing management of the lakes with the ultimate goal of increasing biodiversity and reducing human impacts on the lakes.
Buoy design
These buoys measure water temperature, dissolved oxygen levels and pH, to monitor the lake quality and provide up-to-date data for the scientists to use.
Monitoring continues for seven of the Rotorua Te Arawa Lakes. Solar-powered buoys measure water quality variables from the water's surface to near the lakebed. Access up-to-date data on the Bay of Plenty Regional Council's environmental data portal.
Nature of science
Social and cultural elements play a part in the direction and funding of science research. The Rotorua lakes are culturally significant to local iwi and are highly regarded as recreational resources.
Activity idea
In Ground water contamination, students build an aquifer model to look at point source and non-point source pollution.
Useful links
Visit Rotorua Te Arawa Lakes Programme to see what is being done to preserve and protect the Rotorua Lakes for present and future generations.
This LakePedia blog looks at water quality changes in Rotorua Lakes over a 20 year period: 2000–2020.
See the information that David Hamilton and his research group collected on the Lake Ecosystem Restoration New Zealand website, there is lots of information including data on the Rotorua lakes.
