Threshold values should reflect, where appropriate, the quality level that reflects the significance of an adverse effect for a criterion and should be set in relation to a reference condition. Threshold values should be consistent with Union legislation and set at appropriate geographic scales to reflect the different biotic and abiotic characteristics of the regions, subregions and subdivisions. This means that even if the process to establish threshold values takes place at Union level, this may result in the setting of different threshold values, which are specific to a region, subregion or subdivision. Threshold values should also be set on the basis of the precautionary principle, reflecting the potential risks to the marine environment.

Source: EURO-Lex

Producing a clear picture of the state of aquatic biodiversity inter alia through a regular assessment of the ecological status of waters (every 6 years). Characterisation of aquatic ecosystems will provide detailed information to be used as the reference condition for assessing changes to the ecological status of waters, inter alia species composition and abundance, spatial and temporal variations, specific indicator organisms and indicator functions. A better understanding will be provided on hydrological and ecological interaction between wetlands, the riveraine zone and the aquatic ecosystem in a river basin.

Source: EURO-Lex

Article 4(1)(c) of Decision (EU) 2017/848 provides that threshold values shall, where appropriate, distinguish the quality level that reflects the significance of an adverse effect for a criterion and be set in relation to a reference condition. In this regard, Recital 13 of the Decision inter alia states: ‘Threshold values should reflect, where appropriate, the quality level that reflects the significance of an adverse effect for a criterion and should be set in relation to a reference condition.’ It is to be noted that the term ‘adverse effect’ is used in Commission Decision (EU) 2017/848 independently of the reference to ‘significantly adversely affects’ in the definition of ‘water damage

Source: EURO-Lex

(performance indicator) Performance indicators compare actual conditions with a specific set of reference conditions. They measure the 'distance(s)' between the current environmental situation and the desired situation (target): 'distance to target' assessment.

Source: EEA Glossary