WATER TEMPERATURE FACT SHEET
Why Water Temperature is Important
Water temperature is critical because it is an important quality in environmental parameters. It is important to measure water temperature. By doing so, we can see the characteristics of the water such as the chemical, biological, and physical properties of the water, as well as the possible health effects. Water temperature is an important factor in determining whether a body of water is acceptable for human consumption and use.
- The temperature in water governs the kinds and types of aquatic life that live in it.
- It regulates the maximum dissolved oxygen concentration of the water.
- Temperature influences the rate of chemical and biological reactions.
- It affects the dissolved oxygen level in water, photosynthesis of aquatic plants, metabolic rates of aquatic organisms, and the sensitivity of these organisms to pollution, parasites, and disease.
In the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document -Temperature it is stated that “temperature is currently defined by the ‘International Practical Temperature Scale of 1968, amended edition 1975’ in terms of the electrical resistance of a standard platinum-resistance thermometer at three calibration points. (The triple point of water, the boiling point of water at one standard atmosphere, and the freezing point of zinc).”
The aesthetic objective for water temperature in the Guidelines for Canadian Drinking Water Quality is 15°C. This is because most consumers complain about tap water at 19°C or higher. The intensity of taste is greatest for water at room temperature and is significantly reduced by chilling or heating the water. Increasing the temperature will also increase the vapour pressure of trace volatiles in drinking water and, therefore, could lead to increased odour. It is also possible that micro fungi can grow inside the internal plumbing systems of buildings, leading to complaints of musty, earthy, or mouldy tastes and odours if the temperature rises above approximately 16°C. It is advisable to keep the growth of such organisms to a minimum by using cold water because certain organic growths have been shown to protect bacteria from the effects of chlorination.
In the Water Quality Guidelines, it states, “the temperature dependence of most chemical reactions stems from the activation energy associated with them. The rates of chemical reactions decrease with decreasing temperature. The relative concentrations of reactants and products in chemical equilibria can also change with temperature... Temperature can, therefore, affect every aspect of the treatment and the delivery of potable water.”
In the Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Temperature it is stated that “Measurement for water treatment purposes may be made with any good-grade mercury-filled Celsius thermometer. As a minimum requirement, the thermometer should have a scale marked for every 0.1°C and should be checked against a thermometer certified by the U.S. National Bureau of Standards.”
It is not economically feasible to alter the temperature of the water at the drinking water treatment plant. Therefore, the temperature is largely determined by the selection of the raw water source and the depth of the intake. In Canada, surface water temperature shows a wide seasonal variation in most localities (2ºC – 25ºC). Algal growth in surface water normally becomes noticeable only at temperatures above 15 ºC. Groundwater has a more constant seasonal temperature. The temperature of deep wells varies only by 2ºC - 3ºC. Larger variations occur in shallow ground water.
How Water Temperature Affects Water Treatment
When chemical treatment is involved, generally the rates of chemical reactions decrease with decreasing temperature because the temperature dependence of most chemical reactions stems from the activation energy associated with them. In addition, the relative concentrations of reactants and products in chemical equilibria can also change with temperature. Therefore, temperature can affect every aspect of the treatment and the delivery of potable water.
The efficiency of one of the key water treatment steps, coagulation, is greatly dependent on temperature. Also, the optimum pH for the coagulation process decreases as temperature increases. Furthermore, as temperature decreases, the viscosity of water increases, and the rate of sedimentation decreases. As a longer settling time is not available in a plant with a fixed flow rate and basin capacity, the efficiency of colour and turbidity removal by coagulation and sedimentation may be less in winter than in summer. Due to the stratification of warmer water over cooler water in the treatment basin, very small increases in the temperature (<1ºC) of the raw water source have been reported to decrease the efficiency of the flocculation-sedimentation process. However, appropriate plant and process design can defeat this problem.
Temperature affects the power of disinfection, how disinfection slows the growth and impedes the survival of microorganisms. When water has a pH value higher than 8.5, higher temperatures multiply the bactericidal effectiveness of chlorine, as well as its effectiveness in killing some viruses. Some studies have found that the rate of formation of chloroform in raw water treated with a chlorine dose of 10 mg/L multiplied at higher temperatures.
It has also been found that water temperature is perhaps the single most important factor influencing seasonal variation in trihalomethane concentrations.
Without corrosion inhibitors, the corrosion rate greatly increased when the water temperature was higher. The use of sodium hydroxide to increase the pH reduced this increase by half. However, at temperatures below 10ºC, water containing sodium hydroxide showed a higher corrosion rate than the untreated water.
As we have learned, bacterial activity is significantly decreased at low temperatures. Despite this fact, biological water treatment can still be used to effectively treat cold source water. Biological water treatment, as part of the Integrated Biological and Reverse Osmosis Membrane (IBROM) treatment process, has effectively treated cold groundwater in Saskatchewan. When the IBROM treatment process is used, the resultant drinking water not only meets the Guidelines for Canadian Drinking Water Quality but also all regulations and standards in the world.
Climate Change Effects on Water Temperature
The water cycle plays an important role in how much water there is for use and how much water is available for refilling lakes and rivers and other bodies of surface water that most communities use. The temperature of the water increases the rate of evaporation of the water into the atmosphere and increases the atmosphere’s capacity to hold water. Climate change can cause increased evaporation that can dry out some areas and fall as excess precipitation in other areas.
Climate change is having diverse effects across the globe, but one effect that is related to water is that winters in some locations are becoming warmer and shorter. In addition, the Arctic and other areas which are usually cold are warming and this is resulting in more warming (and, thus, melting) of ice sheets and ice caps. Warmer winter temperatures cause more precipitation to fall as rain rather than snow. This can alter the timing of streamflow in rivers that have their sources in mountainous areas.
As temperatures rise, people and animals need more water to maintain their health. Producing energy at power plants, raising livestock, and growing food crops require lots of water as well. The amount of water available for these activities may be reduced as the Earth warms.
The quality of the water could suffer in areas experiencing increased rainfall. For example, in the Northeast and Midwest, increases in heavy precipitation events could cause problems for the water infrastructure, as sewer systems and water treatment plants are overwhelmed by the increased volume of water. Heavy downpours could increase the amount of runoff into rivers and lakes, washing sediment, nutrients, pollutants, trash, animal waste, and other materials into water supplies, making them unusable, unsafe, or in need of water treatment.
Freshwater resources along coasts face risks from sea level rise. As the sea rises, saltwater moves into freshwater areas. In addition, as more freshwater is removed from rivers for human use, saltwater will move further upstream. Drought can cause coastal water resources to become more saline. Water infrastructure in coastal cities including sewer systems and wastewater treatment facilities face risks from rising sea levels and the damaging impacts of storm surges.
The impacts of climate change on water availability and water quality will affect many sectors including:
- Energy production
- Human health
- Agriculture and ecosystems
To learn more about how temperature affects water quality you can read the research conducted at Yellow Quill First Nation. The community was under a boil water advisory for nine years. Read Integrated Biological Filtration and Reverse Osmosis treatment of cold poor quality groundwater on the North American Prairies.
Reusable pH meters and reusable TDS meters which are available in Safe Drinking Water Foundation (SDWF)’s Operation Water Pollution (OWP) kits also measure the temperature of water. You can learn more about SDWF’s OWP program at https://www.safewater.org/operation-water-pollution
You can request sponsored SDWF kits, including OWP kits at https://www.safewater.org/sponsored-kit-request-form
If you would like to be guaranteed to receive an OWP kit and receive it right away, please purchase an OWP kit at https://www.safewater.org/order-kits
Would you like to help more schools receive Operation Water Pollution kits so students can test water samples for pH, TDS, and temperature, and they can learn about water pollution, including what causes it, how it can be prevented, how it is cleaned up, and what they can do about the problem?
Government of Canada. (2009, Feb. 6). Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Temperature. Retrieved from
Health Canada. (May 1979, Reprinted 1995). Temperature. Retrieved from https://www.canada.ca/content/dam/canada/health-canada/migration/healthy-canadians/publications/healthy-living-vie-saine/water-temperature-eau/alt/water-temperature-eau-eng.pdf
Oram, B. (2014). Stream Water Quality – Importance of Temperature. Retrieved from https://www.water-research.net/index.php/stream-water-quality-importance-of-temperature
United States Environmental Protection Agency. (2017, Jan. 19). Climate Impacts on Water Resources. Retrieved from https://19january2017snapshot.epa.gov/climate-impacts/climate-impacts-water-resources_.html
United States Environmental Protection Agency. (n.d.) Conventional Treatment. Retrieved from
Wheeling Jesuit University/NASA-supported Classroom of the Future. (2004, Nov. 10). Water Quality Assessment: Chemical. Retrieved from