Rights: The University of Waikato Published 15 April 2009 Download

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.


There are a variety of different concerns about leaving… about water deteriorating. And it’s what we term as scientists ‘ecosystem services’. Nature provides incredibly important functions in purifying water, and purifying the air, and enabling us to breath and obviously… and to be able to drink the water. When we deteriorate those ecosystems services, then we can bring about a whole range of different things, and that might necessitate much, much higher levels of water treatment, which can be very costly. It might mean that we need to put in some very expensive management options to control water quality in lakes. And those types of predictions are really concerning, because they indicate that our land use is intensifying around New Zealand, and many of the things that we hold dear, in fact the quality of our lakes and our clear blue waters, are going to change in the future. So when we collect the data, one of the things that we do is we use the data that is collected to develop computer models that will help us to predict lake water quality into the future. And so the idea of being able to predict that lake water quality is to be able to play all sorts of games on the computer, to say, “What if we did this? Would it improve water quality or would it make it worse?” And some of the things are really extreme. We might say, “What would happen if we suddenly changed land use so that we multiplied nutrients going into the lake by 10 times? How would the lake respond?” Those are the sorts of games that it enables you to play. And many of them aren't real, but some of them are, and some of them are being used by regional councils or district councils to be able to better understand the way in which a lake might respond.

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