Water quality surface water WFD, 2024

Methods for assessing water quality according to the WFD

According to the Water Framework Directive (WFD) all EU-surface water bodies must achieve good status by 2027. The WFD includes a method to evaluate the quality of surface water. This assessment takes into account, amongst others, the presence of plants and animals (biology), nutrient concentrations (nitrogen and phosphorus), and concentrations of toxic substances such as pesticides, metals, and industrial chemicals.

In the WFD-reporting to the EU, these so-called quality elements are combined to assess a water body as follows:

1 Chemical status
This is determined by the concentrations of toxic substances that pose a problem throughout the European Union, known as priority substances. 

2 Ecological status
This is determined by the biological quality, physico-chemical quality, and the concentrations of toxic substances that are specifically problematic in the Netherlands (so-called specific pollutants). Physico-chemical quality is assessed based on nutrient concentrations (nitrogen and phosphorus) and several physical characteristics such as water clarity and temperature. 

According to the WFD, water bodies only achieve a good status when all quality elements achieve a good score (the one-out/all-out principle). The objectives must be met by 2027, except where achieving them is not possible due to natural conditions. In such cases, the necessary measures must at least have been implemented to make it possible to achieve the objectives in the longer term.

Ecological water quality

In 2024, only one of the 741 Dutch water bodies met the requirements of the WFD. This is because, in virtually no water body, all 77 specific pollutants (including metals, pesticides, and industrial chemicals) comply with the environmental quality standards. As a result, the highest achievable overall ecological rating is fair.

In addition, the biological quality was insufficient in 85 percent of the water bodies because it was classified as fair, poor or bad. The physico-chemical quality met the required standards in only 50 percent of the water bodies. Nutrients, particularly nitrogen and phosphorus, are the main factors contributing to a fair physico-chemical status in many water bodies.

Chemical water quality

The chemical status is based on 45 so-called priority substances, for which standards have been established at the European level. These include industrial chemicals, pesticides, biocides, and inorganic compounds, including metals. The objectives for priority substances generally had to be achieved by 2015, except for substances that were added to the priority substances list at a later date. For those substances, the final deadline is 2027.

At present, the chemical status is considered satisfactory in only about 1 percent of the assessed water bodies. Over the years, the assessment of chemical status has become less favourable. This is partly because a larger number of substances are now being assessed and partly because some standards have been tightened because of new scientific insights.

Significant effort needed to achieve the targets

Between 2015 and 2021, the number of water bodies with a good biological status increased. However, since 2021, biological quality has shown no further improvement. During the same period, the share of water bodies with a good physico-chemical status continued to increase, rising from 40 percent in 2021 to approximately 50 percent in 2024.

Because no improvement occurred in relation to specific pollutants, the number of water bodies with a good ecological status remained virtually zero. This means that a substantial effort is still required to meet the requirements of the Water Framework Directive (WFD) by 2027.

To address this challenge, the Dutch government launched the WFD Impulse Programme in 2023. The primary focus of this programme is to ensure that provinces, water authorities, municipalities, and the national government implement the measures agreed upon in the river basin management plans. In addition, a number of supplementary actions have been identified to help bring the WFD objectives closer to being achieved.

According to the interim evaluation of the WFD carried out in 2024, it is unlikely that the objectives will be met by 2027. One of the key obstacles is that other stakeholders, including the agricultural and industrial sectors, have not yet been sufficiently engaged in the implementation process.

Trend

The status of Dutch water bodies is reported under the Water Framework Directive (WFD) every six years (each planning cycle), and at the same time the objectives for the subsequent planning cycle are established. When assessing water quality, water authorities use the assessment methods and standards applicable to each quality element at that particular time. These assessment methods and standards (for achieving good status) are revised for each planning cycle. As a result, it is difficult to make direct comparisons between years based on the official WFD assessments.

Such comparisons are possible, however, when the original data are evaluated against a uniform set of standards. This approach shows that the biological quality of water, particularly with regard to macrophytes and aquatic plants, has improved slightly over the past 30 years, although it remains at a relatively low level.

Main causes

The main causes of the fair to poor quality of Dutch surface waters are:

• Pollution by chemical substances such as pesticides, pharmaceutical residues, and industrial chemicals. Persistent substances that were discharged in the past also continue to play a role. Exposure to chemical substances can lead to declines in algae, insect populations, aquatic plants, and fish stocks. In cases of long-term exposure, recovery is almost impossible without remediation measures.
• Nutrient enrichment (eutrophication) caused by nitrogen and phosphorus. These nutrients promote excessive algal growth in standing waters. As a result, aquatic plants receive insufficient light for growth, which in turn creates difficulties for certain fish species that depend on these plants. 
• Unnatural watercourse design and modification. Many streams and rivers have been straightened over the past century and have steep, engineered banks with few natural habitats for plants and animals. Only a small proportion of streams still meander naturally. Similarly, most lakes and canals have hardened shorelines, limiting the development of riparian ecosystems. Water levels are typically regulated at fixed levels, restricting natural hydrological dynamics.
• Habitat fragmentation caused by pumping stations and weirs. These structures significantly hinder fish migration. Fish passages are being constructed to improve connectivity and facilitate migration. 
• The introduction of invasive species, which negatively affects aquatic biodiversity. Examples include the Red Swamp Crayfish, which consumes aquatic plants, and New Zealand Pygmyweed, which outcompetes native aquatic vegetation by forming dense floating mats that block sunlight from reaching submerged plants. 
• Climate change, which can have numerous direct and indirect impacts. Examples include increased concentrations of nutrients and chemical substances in surface waters, as well as oxygen shortages for aquatic organisms because higher water temperatures reduce the solubility of oxygen. Climate change can also cause rapid shifts in species distributions and population dynamics, potentially occurring faster than ecosystems can adapt.