Source: https://www.eea.europa.eu/publications/92-9167-001-4/page003.html
The water quality variables can be grouped into the following broad categories:
- Basic variables (eg. water temperature, pH, conductivity, dissolved oxygen, and discharge) used for a general characterization of water quality.
- Suspended particulate matter (eg. suspended solids, turbidity and organic matter (TOC, BOD and COD)).
- Organic pollution indicators (eg. dissolved oxygen, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), ammonium).
- Indicators of eutrophication: nutrients (eg. nitrogen and phosphorus), and various biological effect variables (eg. chlorophyll a, Secchi disc transparency, phytoplankton, zoobenthos).
- Indicators of acidification (eg. pH, alkalinity, conductivity, sulphate, nitrate, aluminium, phytoplankton and diatom sampling)
- Specific major ions (eg. chloride, sulphate, sodium, potassium, calcium and magnesium) as essential factors in determining the suitability of water for most uses (eg. public water supply, livestock watering and crop irrigation)
- Metals (eg. cadmium, mercury, copper and zinc)
- Organic micropollutants such as pesticides and the numerous chemical substances used in industrial processes (eg. PCB, HCH, PAH).
- Indicators of radioactivity (eg. total alpha and beta activity, 137Cs, 90Sr)
- Microbiological indicator organism (eg. total coliforms, faecal coliforms and faecal streptococci bacteria)
- Biological indicators of the environmental state of the ecosystem (eg. phytoplankton, zooplankton, zoobenthos, fish, macrophytes and birds and animals related to surface waters).