Both in 2009 and in 2015, only 0.4 percent of Dutch surface waters complied with the standards for good ecological status according to the Water Framework Directive. The low score is mainly due to poor biological quality as well as to excessive concentrations of substances including nutrients, heavy metals and other persistent pollutants. The percentage of surface water bodies with a good biological status increased from 3 percent in 2009 to nearly 5 percent in 2015.
Distribution of more than 700 surface water bodies over the classes for ecological status assessment according to the Water Framework Directive. The ecological status is determined on the basis of the components biological status (4 sub-tests), physico-chemical quality, and standards for other relevant pollutants. The biological status is usually decisive for the score on ecological status. The total proportion of waters with good biological status consists of the sum of the categories Ecology good and Biology good.
The ecological status is a measure for the health of surface water. The availability of healthy fresh water resources is a key factor for green growth. Healthy water bodies can contribute in general to human well-being and the economy through their different uses such as for bathing, fishing, recreational shipping, water for irrigation, for the preparation of potable water and for use in industrial processes.
The ecological status of Dutch surface water is moderate to poor due to several reasons, including excessive levels of persistent substances (often caused by historical emissions), eutrophication caused by nitrogen and phosphorus resulting in excessive algae growth, and emissions of pesticides. Another contributing factor is the interference in the physical properties of water bodies. Examples are the channelling of streams, monitoring of predetermined water levels and paving of soft banks. As a result, natural habitats disappear or cannot develop and the natural dynamics are limited. The many pumping stations and weirs also cause fragmentation of the water systems, which means that fish can hardly migrate. In recent years, many measures have been taken to lower the negative impact of these causes, for instance by reducing pollutant discharges, building fish passages near weirs, the restoration of the natural course of brooks as well as the construction of nature-friendly banks. The effects of these measures, however, are not yet visible in the 2015 compliance check, but must lead to improvement in the long term (Environmental Data Compendium, 2018 and 2018). The next formal compliance check will be done for the year 2021.