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Overall status is the water body level water framework directive classification derived from combining both Chemical Status and Ecological Status/Potential using the one-out-all-out methodology. This means a water body can only be reported at Good Status Overall if it is assessed at Good Status (or Potential) for both Ecological and Chemical Status. Both natural and artificial or heavily modified water bodies are assessed for Overall Status on a High, Good, Moderate, Poor or Bad basis.

Ecological status is an assessment of the quality of the structure and functioning of surface water ecosystems. It shows the influence of pressures (e.g. pollution and habitat degradation) on the identified quality elements. Ecological status is determined for each of the surface water bodies based on biological quality elements and supported by physico-chemical and hydromorphological quality elements.

Good chemical status means that no concentrations of priority substances exceed the relevant EQS established in the Environmental Quality Standards Directive 2008/105/EC (as amended by the Priority Substances Directive 2013/39/EU). EQS aim to protect the most sensitive species from direct toxicity, including predators and humans via secondary poisoning. A smaller group of priority hazardous substances were identified in the Priority Substances Directive as uPBT (ubiquitous (present, appearing or found everywhere), persistent, bioaccumulative and toxic). The uPBTs are mercury, brominated diphenyl ethers (pBDE), tributyltin and certain polyaromatic hydrocarbons (PAHs).