Wastewater testing in Whangarei started in August and data was collected from the wastewater facilities for one week every month.
"The results indicate a high incidence of methamphetamine in the Whangarei wastewater," said Superintendent Russell Le Prou.
He said the wastewater results will provide an ongoing baseline of data to inform and measure both treatment and enforcement.
For example, he said, wastewater could be tested after a major police seizure of meth and a lower level would show the operation was successful.
"If no impact is seen it may indicate that further investigation is needed into methamphetamine supply."
Drugs are processed by the body into other compounds which make their way into the wastewater system.
Rataora is a screening and referral to treatment that givesan indication of the number of people using methamphetamine.
The trial was implemented within the Whangarei Hospital Emergency Department and the NZ Police Whangarei Custody suite, 24/7 over a one week period.
In the Emergency Department 350 patients were screened for substance use and 70 were referred to specialist services such as mental health and addiction, smoking cessation, the Alcohol Drug Helpline and Depression Line. A further 12 people were referred to their GP and another six people were given a brief intervention by a psychologist or at ED.
Four methamphetamine users were identified during the week of screening. If the screening was done for an entire year, about 200 methamphetamine users would be identified.