There are many criteria to check the health of a water body. Physical, chemical and biological examination may be performed. www.jneenvironmental.ca lists the 8 major categories on which wastewater quality depends.
Aquatic animals cannot survive outside a certain temperature range. Elevated temperatures may cause microorganisms to grow faster which leads to reduced oxygen levels in the water. Temperature can be checked using thermometer.
Presence of solid wastes in water is a major indicator of unacceptable quality. Solids may be dissolved, suspended or settled. Various tests exist to determine quantity of each type. Turbidity and salinity can also provide indicators.
Dissolved Hydrogen is present in water. In the presence of mild amount of salt or acid, Hydrogen forms Hydronium ions (H3O+) and Hydroxyl ions (OH–). Presence of Hydrogen ions determine the pH factor of water.
Dissolved oxygen is a major indicator of the state of water. It gives a clear indicator of amount of organic and biological matters present. BOD (Biological Oxygen Demand) is used to test the presence of microorganisms, while COD (Chemical Oxygen Demand) gives an idea of the presence of oxidizable chemicals.
Nitrogen content is an estimation of algal bloom since elevated levels of nitrogen may increase organism content. Nitrogen is usually present in water as dissolved ammonia and other nitrates. They can be measured by Kjeldahl Test.
Phosphorous can easily contaminate water sources. US Environmental Protection Agency recommends phosphate levels of less than 0.1mg/L for streams not discharging into reservoirs, 0.05mg/L for streams discharging into reservoirs and .025mg/L for reservoirs.
Chlorine is largely used to clean and bleach water reserves. Chlorine residue (such as hypochlorite ions) can be measured to determine level of disinfection in water.
8. Biological Characteristics
Bioassay can test water bodies and compare survival of aquatic species in water from different sources in order to determine their health. Approximate biological population in water can also be a test measure. Test specific to identifying pathogens must be employed in risk areas.