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.
The wastewater is also tested for MDMA, also known as ecstasy and "the party drug". That amount has increased since early 2019, with the highest of 86g consumed during a week in July 2020.
Cocaine is also tested for, but none at all was found in Whanganui's wastewater in the second half of 2020.
Those three drugs were chosen for testing because they caused the most harm, were readily available and were easy to test for, a police spokesperson said.
Methamphetamine was a big concern to police. Current pricing is at $500 per gram.
"Criminals who peddle illicit drugs to members of our community often accumulate significant assets, and in doing so cause incredible harm.
"Methamphetamine destroys the lives of users, as well as harming the friends, family and community around them."
Addiction can also fuel crime - most often burglaries and shoplifting.
Police want to hear about illegal drug use. Phone 105, or talk anonymously to Crimestoppers on 0800 555 111.
People who want help with addictions can contact the Alcohol and Drug Helpline, 0800 787 797, or free text 8681.