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Heating up what lies beneath

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Tracing of contamination in our drinking water supplies may be as easy as using hot water – according to an ESR scientist studying the Canterbury aquifers.

Groundwater scientist Theo Sarris has used heat to better understand the structures and contamination pathways in the aquifer, in an effort to better predict where a particular pathogen has entered the water supply.

Water supply contamination like that which hit Havelock North two years ago poses challenges for scientists trying to pinpoint the source.   

“If we can characterise the aquifers and understand their complex structures, we can model where contaminants may be coming from and how they travel through the subsurface,” says Dr Sarris.

Scientists traditionally use chemical tracers, which are both expensive and potentially harmful for the environment if applied at high concentrations.  The advantage of a heated water tracer is that it is a lot cheaper and only requires temperature “loggers” rather than the analysis required to measure dye concentrations.

In an experiment, carried out on a small section of the Canterbury aquifer at Burnham, ESR scientists injected water at 37 degrees (about 25 degrees above the normal groundwater temperature) over a 15-day period.

Analysis of the experimental data gathered over 78 days, was run on ESR’s high performance modelling server over a period of several months. The results, which have been published in the prestigious Journal of Hydrology, show that heat offers useful and practical information about the structure of an aquifer and how groundwater and contaminants move through them, especially in fast moving aquifers like those under Canterbury.

Dr Sarris says using heat is definitely another useful and environmentally friendly tool that helps scientists better understand the groundwater resources and how to manage them sustainably. 

“We are always trying to get a better idea of the structure of the groundwater aquifer.  Experiments like these help but there is still a lot we need to know.”