Once a month, the Delfland Water Board carries out a helicopter inspection flight in the areas containing greenhouses. Robbert Ballings, project leader of Risicogestuurde aanpak glastuinbouw , is then usually on board the helicopter himself. He explains how the inspection flights help Delfland to spot illegal discharges and tackle offenders. 'We want to improve our water quality, so we don't turn a blind eye to anything.'
Robbert works at Delfland for the Supervision and Enforcement Department. 'No later than 1 January 2027, our surface waters have to meet the requirements of the European Water Framework Directive,' he says. 'So they have to be clean and healthy, but that is quite a challenge. Especially in the greenhouse horticultural area with some 1,500 greenhouse farms. Leaked and discharged crop protection agents and all kinds of nutrients still have a negative impact on the water quality here.' Delfland still regularly detects substantial norm violations of both permitted and banned crop protection products.
From area-based to risk-based
To improve water quality in the greenhouse area, Delfland took an area-oriented approach for a long time. Robbert: 'In doing so, we extensively monitored and informed greenhouse horticulture companies about the situation and that paid off. The number of deliberate discharges has decreased and the water quality is better than ten years ago. Yet we are not there yet, so we want to reduce conscious and unconscious pollutants even further. To get a picture of where something is going on, we sample 30 locations every month for crop protection agents and nutrients. We then refine our monitoring network in the polders with more toxic pressure, for instance, by measuring more for nitrate and eDNA. It is a risk-driven approach, with inspection flights also helping to find 'hotspots'.
Hotspots and hot spots
Delfland has long been using inspection flights to record the progress of major projects affecting water management. 'Think of the construction of tunnels and highways,' says Robbert. 'What many people don't know is that we also use them to survey for discharges. Because we fly low, we can see a lot in a short time. Think of discolored water, drains running from silos into ditches, and other indications of illegal situations. Sometimes we even get into the act. Like the other day when an entrepreneur discharged dirty water into the ditch via a submersible pump. We take photos of every violation. We then draw up an official report against the entrepreneur, often with an administrative penalty. We really can no longer accept this kind of abuse.'
Together for clean water
Despite the incidents, Robbert is positive about the water quality in the greenhouse area. 'Sometimes it still seems like a game of cat and mouse, but our relationship with greenhouse growers has greatly improved. Moreover, we are actually working more and more with the entrepreneurs on solutions that identify discharges and leaks early. We also work with water coaches from Glastuinbouw Nederland. They help entrepreneurs reduce their emissions. Good water quality is a joint challenge and we are happy to take it up.'
And the norm violations and illegal substances found by Delfland? They will be even sharper on those in 2025. 'The license to operate of the entire sector is under pressure because of entrepreneurs who use banned substances or leak or discharge polluted water from the greenhouse.'
Source: Delfland Water Board