Sewer water shows drug spending in The Hague rose 21% in two years to €85 million

Over €85 million circulated in The Hague’s drug world last year, according to a bi-annual wastewater study commissioned by the municipality. That is an increase of 21% compared to the 2023 study, but according to the researchers, this is mainly due to more expensive cannabis, not increased use, Omroep West reported.

The study, conducted by the research institute KWR every two years, aims to gain insight into the local drug market. According to the researchers, wastewater “is a mirror of society,” so measuring the drug residues it contains is very effective to gain “insight into drug use in a specific area.”

The researchers took daily samples from the wastewater at the Houtrust treatment plant and the Leyweg pumping station during the first seven days of October 2025. According to the researchers, this covers nearly two-thirds of The Hague’s residents.

The results show that an estimated €235,000 exchanges hands on The Hague’s drug market per day, amounting to over €85 million per year. Cocaine and cannabis are by far the most used drugs in the city. The results are comparable to 2023, when the size of the drug market was €70 million per year. The increase is mainly due to cannabis becoming more expensive.

The results are also comparable to drug use studies in cities like Amsterdam, Rotterdam, Utrecht, and Eindhoven, with only “limited” differences. For example, cocaine, amphetamine, and ketamine use is roughly the same in The Hague as in Amsterdam, but Hague residents use less crystal meth than Amsterdammers.

According to Mayor Jan van Zanen of The Hague, the findings underscore the necessity of continuing to invest in tackling drugs. “The local drug market is an illegal market behind which serious forms of (undermining) crime lurk, and which puts further pressure on the livability and safety of neighborhoods and districts,” the mayor said in the letter he sent to the city council with the report.