Whanganui is one of 46 places in New Zealand where wastewater is routinely tested to find out how much of three drugs people are taking.
Wastewater is sampled across one week every two months. Figures released by police show 200g to 500g of methamphetamine were consumed in Whanganui in each of those months during 2019 and 2020.
The highest amount was 508g, worth $254,000, during a week in May last year. A police spokesperson was unable to say how this amount compared with that of similar centres.
The water is analysed by the Institute of Environmental Science and Research (ESR).
Police use the results to calculate how much money is being spent and how well their drug seizure and prevention strategies are working.