Police will begin testing wastewater networks for several types of drugs across the country after a pilot programmes were conducted in Auckland, Christchurch and Whangarei.
Testing for methamphetamine, cocaine, heroin, MDMA and Fentanyl has been conducted at treatment sites in the three cities since 2016, police said, and they are now expanding the programme to include a total of 38 sites across 12 police districts.
Police Commissioner Mike Bush said testing like this gives good intelligence on the prevalence and usage of various drugs in different communities, which gives police guidance on where they should concentrate their efforts.
"Over the past 18 months, 1.5kg of methamphetamine was estimated to have been consumed on average each week across the three test sites," Mr Bush said.
"This translates to an estimated $2 million a week in social harm.
"Expanding the number of sample locations will help us identify differences in drug use between geographic regions and will act as an early warning system for emerging risks."
The testing will be carried out by the Institute of Environmental Science and Research and is expected to capture data from about 80 per cent of New Zealand's population.
Testing for cannabis will also be introduced in Northland and Auckland regions, and testing for ephedrine/pseudoephedrine will be introduced nationwide.
Police expect to begin the nationwide testing scheme by the end of October.