The quality of canals, ponds, rivers and other waterways in and around The Hague improved in several areas during 2025, according to a new report from the regional water authority. However, pollution remains a significant challenge, and environmental targets are still far from being met.
The report was published by the Hoogheemraadschap van Delfland, the regional water authority responsible for managing water levels, flood protection, wastewater treatment and water quality across The Hague, Delft, Westland and surrounding municipalities.
“Clean water is not something we can take for granted, but it is essential,” says Stijn van Boxmeer, the Delfland board member responsible for water quality. “Not only because of legislation, but because clean water is vital for people, nature and a healthy living environment.”
Water Quality in 2025
The waterways across the Delfland region continue to face increasing pressure from population growth and longer periods of dry weather. Pollutants from businesses, industrial areas, agriculture, horticulture and households still find their way into canals, ponds and rivers.
Despite these challenges, some improvements were recorded compared with 2024. Levels of nitrogen and phosphorus, two nutrients that can negatively affect water quality when present in excess, decreased in many monitored waterways. Nitrogen concentrations improved in seven of the eight waterways monitored under the European Water Framework Directive, while phosphorus levels improved in six of the eight.
The report also found fewer exceedances of environmental standards for pollutants such as PFAS, heavy metals and other substances of concern. However, these waterways still do not meet the required standards.
The ecological health of waterways showed mixed results. While some locations saw improvements in aquatic plants and wildlife, others declined. The use of pesticides remains a concern, although the number of exceedances is continuing to fall. Nine greenhouse horticulture areas recorded little or no toxicity in 2025, compared with only two areas in 2024.
A Shared Responsibility
According to Van Boxmeer, improving water quality is not something the water authority can achieve alone.
“As a water authority, we are doing everything we can to improve water quality. The necessary transition is a societal challenge that can only be solved together.”
Delfland expanded its monitoring efforts during 2025 by analysing data from all of its monitoring locations and by measuring water quality closer to pollution sources. Through initiatives such as the “Measuring at Ditch Level” pilot, the organisation worked directly with businesses and other organisations to identify where pollutants are entering waterways.
Municipalities have already invested in nature-friendly banks and waterways, while the greenhouse horticulture sector has also shown progress. However, many businesses still need to take further action.
The report also highlights the role of residents. Everyday activities, such as flushing unsuitable products down toilets or allowing pollutants to enter drains, can have a direct impact on local waterways.
Delfland says that raising awareness, monitoring pollution and enforcing regulations are all important, but lasting improvements will depend on businesses and residents reducing pollution at its source.
More Information
The full Water Quality Report and Progress Report for 2025 are available at www.hhdelfland.nl/waterkwaliteitsrapportage.
Source & Image: Hoogheemraadschap van Delfland