General and specific water quality standards were formulated on a national scale in The Netherlands in the eighties of this century. A general environmental quality was defined as the minimum acceptable water quality level for all inland waters. For this quality level, standards for total phosphorus and total nitrogen were derived from measurements in shallow lakes sensitive to eutrophication for this quality level. No standards were developed for specific environmental quality.
In this study we tested whether single nutrient standards are sufficient to guarantee the minimum quality level in streams and ditches. We also investigated whether specific environmental quality requires specific standards. We, therefore, analyzed data collected by regional waterboards in The Netherlands.
The results show that nutrient standards for the general quality are not sufficient to guarantee the minimum quality for all water types. They do not provide appropriate protection for aquatic life. More specific standards should be set to protect and preserve the full biodiversity of ditches and streams.
Setting a single standard for general environmental quality and one for specific environmental quality for all types of water is not defendable. Different types of water have different aquatic communities and different nutrient levels. It is therefore recommended that water type dependent standards should be developed. In this study, standards for both general and specific environmental quality in respect to nutrients are proposed for six stream types and for six ditch types.