Do you know that Temperature of Water plays a significant role in Water Quality?

Yes it is one of the 6 factors. But do you know it is so important parameter that it affects almost all other parameters of water quality? Check out this guide on temperature of water and its effects on our health.

What is Water Temperature?

Water temperature is a physical property of water. It helps distinguish the presence or absence of heat in water. This explains how hot or cold the water is. For an X amount of water :

Temperature = Average Thermal Energy = Kinetic Energy of Vibrating molecule

The more energy we supply to the water molecules in form of heat, more rapidly will be the motion of the vibrating molecules of water.

Mode of heat transfer


In this mode, transfer of heat takes place physically from one molecule to another. This happens when water molecules on receiving the heat starts to vibrate rapidly. This cause multiple collisions among the water molecules. This physical collision transfers the energy among the molecules and thus heat transfer takes place.


As we know, heat transfers from a hot medium to a cold medium. When a molecule receives heat it starts to vibrate rapidly. As we know cold water/air is heavier than hot water/air. Hence molecules with increased kinetic energy starts to rise up in the medium. Cold water molecules rushes down the medium to take the place left behind by the hot water molecule. Hence heat transfer takes place by molecules physically carrying the heat and traversing the medium.


When water receives energy in form of heat its molecules starts to vibrate rapidly. This sets the atoms and molecules in the medium into random motion. This results into emission of charged photons and electrons. These photons are also called 'energy packets' and transfer the energy in form of electromagnetic waves. Since heat transfer in the medium takes place through electromagnetic waves, radiation mode is independent of the medium. Radiation mode is the only mode of heat transfer that can take place even in vacuum.

Factors affecting the boiling and freezing points of water


The boiling point of water increases with the increase in pressure. This correlation stands true only up to a critical point, where the gas and liquid property of water becomes identical.

The freezing point of water rises slightly with increase in pressure. 


Do you know water has one of rare quality where its solid form ice is less dense than its liquid form?

Yes water at 4°C temperature is more dense than water at 0°C. In fact the density of water is maximum at 4°C .

Density of water increases with decrease in temperature until the temperature falls to 4°C.

From 4°C to 0°C density of water decreases with decrease in temperature. This is the reason why a iceberg floats in water.

Effects of temperature on the properties of water

Solubility of solids and water temperature

Temperature Change






Solubility of gases and water temperature

Temperature Change






Viscosity and temperature of water

Viscosity of a liquid is its ability to resist the flow among its different layers. This happens because of friction to movement among different layers of the liquid. Each layer above has a lesser viscosity than the layer below. Hence the top most layer has least viscosity and flow easily while the bottom most layer has the most viscosity and makes little to no movement in respect to layers above it.

Increasing the temperature of water by heating increases their kinetic energy. Due to this kinetic energy the molecules starts to vibrate. This vibration increases with the increase in kinetic energy. When this energy supplied exceeds the force of attraction between the nucleus (protons) and the electrons, these electrons break away from their orbits leaving the molecule. The movement of the electrons in the medium increases. This make the water more fluid and free to flow thus decreasing the friction and hence viscosity.

The energy the electrons needed to break their bonds is known as threshold energy of the molecule.

Conductivity and temperature of water

Conductivity in water depends upon the movement of ions also known as ionic mobility. Ionic mobility in water increases with increase in water temperature. Upon supply of thermal energy, the kinetic energy of the molecules of water increases thus increasing their ionic mobility and hence conductance.

Why analyze Temperature for Water Quality?

Temperature is an essential parameter for all biological growth and activities in an aquatic ecosystem. Both the chemical and biological reactions in water are dependent on its temperature. The aquatic organisms are so susceptible to change in temperature that even a few degree increase/decrease can wipe out a number of the species to extinction.

Temperature is a one of the 6 parameters of water quality that affects almost all the other water parameters.

Water pH and temperature

The pH of water decreases with increase in temperature. This does not mean that water becomes more acidic at higher temperature. It is because any change in temperature shifts the entire pH range to a totally new different value.

As we know, water splits into

H2O = [H+] + [OH-]

H+ or Hydrogen ions decreases with increase in temperature
OH- or Hydroxyl ions decreases with increase in temperature

Whenever there is a change in equilibrium the entire reaction shifts left or right to counter the change and maintain equilibrium so that at any time pH = pOH

Water Temperature

Neutral pH Value







Hence temperature do alter the pH of water without making it more acidic or basic.

Salinity and water temperature

Water Salinity increases with the increase in temperature. This is because salts and minerals dissolve better in hot water than cold water.

The increase in salinity also increases the conductivity of the medium. This happens for the availability of salt ions increases which are good carriers of charge. Hence the conductivity of the medium increases. That's why electric current is better conducted through salt water rather than pure water medium.

Dissolved Oxygen and temperature of water

As we know solubility of gases in water is inversely proportional to temperature. Hence hot water tends to have less amount of dissolved oxygen than that be cold water.

Hardness in water and temperature

Higher the temperature, better a solvent water becomes. As minerals and impurities tends to dissolve better in hot water. That's why minerals like calcium and magnesium dissolve better in hot water than cold water.

Boiling on the other hand makes water soft by precipitating out the calcium and magnesium minerals from water.

Turbidity and water temperature

Warm water dissolves more minerals and hence carry more sediments than cold water. Increase in water temperature favors the water to be more turbid.




Is one of the important sources of energy responsible for change in temperature of water on a daily basis. Albedo is the measure of the proportion of incident light that is reflected by the medium instead of being absorbed. Albedo is an important metric to understand how responsive a medium is towards sunlight. Water has a relatively low albedo which means it reflects less light than it absorbs. Hence water can readily rise in temperature on being exposed to sunlight.

Land Temperature

Due to the different albedo of land(soil) and sea(water), a difference in temperature is observed. Low pressure develops in a region with high temperature and vice versa. Wind flows from a region of high pressure towards low pressure. This establishes a conduction cycle and transfer of heat thus causing variation in water (ocean) temperature.

Water Turbidity

The sediment suspended in water absorbs more sunlight than water does by trapping the heat. This in general raises the water temperature. Hence temperature of water rises with rise in turbidity.


Thermal or nuclear power plant discharge

Water is often used to cool off the core reactors in thermal power generation plants. In nuclear power plants, heavy water is used as absorbent. They are used to controls the chain reaction by absorbing the excessive neutrons emitted during the process.

All this use of water makes it very hot. This hot water if released untreated could wreak havoc onto the aquatic organisms residing in it. Thermal Pollution is a result of such careless faulty human activity.

Concrete Impervious Surface Constructions

Impervious surfaces are artificial surfaces such as pavements, sidewalk . They are constructed with materials such as concrete, asphalt or brick. These materials are used for being water resistant. But they allow very little to no transmission of heat. Due to this they rise in temperature for lack of heat dissipation. The runoffs from these surfaces get quite hot in summers. When they are blown away by wind into a water body they tends to increase its temperature.

Industrial Discharges

As we know water is an universal solvent. With easy availability it makes it a very essential commodity to almost all industrial use. It could be used for a variety of purposes ranging from washing salt from leather in tanneries to cooling up the energy power plants.


Cutting down trees in the name of rapid development releases huge amount of carbon trapped in the tree. This carbon released in form of Carbon Dioxide and Methane on a massive scale acts as greenhouse gases. These greenhouse gases raises the temperature of the entire planet by absorbing the heat. Water temperature in ocean and rivers also gets affected due to this rise in global warming. 

Urban Water Temperature Standards

Water temperature is an aesthetic quality of water. Variation in it can be easily detected and treated to be used as per individual needs. Since it poses no serious health concerns there are no government guidelines regulating it.

As per many surveys, there has been a general consensus among many organizations that water is best suited to drink at room temperature.

Artificially decreasing the temperature to drink cold water may quench the thirst better than hot water or water at room temperature. But this may cause health concerns as in common cold.

Common cold often happens when there is significant difference between the temperature of drinking water and body temperature.

Hot water is not reported to pose any such health concerns and many individuals believe it to even result in weight loss. 




Water temperature is a physical property of water. But change in water temperature is not possible by optical detection.

Touch and feel is a more appropriate way to determine the temperature of water.


There is no specific odor associated with change in temperature.


Water Thermometer is used to measure the exact temperature of various water samples.


Check out the water temperature thermometer in the market.

Urban Water Temperature Treatment

Temperature can be varied from hot to cold using many appliance such as :

Water Cooler

Water Heater




Aquatic plants

The photosynthesis rate of aquatic plants eg. algae varies with change in water temperature. Warm temperature is usually favorable to most of the aquatic plants.

Aquatic Animals

The metabolism rate changes with change in temperature of the water they live in. As seen in most of the studies on fishes, their metabolism rate increase with the increase in temperature. This happens only up to a certain tolerable temperature level beyond which they perish.


Compound toxicity level

As we know high temperature in water increases the solubility of various compounds including the toxic ones. Heavy metals like cadmium ,lead, zinc and ammonia can be non toxic at low temperature. But their toxicity increases with increase in water temperature. E.g. At high temperature free ammonia reacts with water to form toxic ionized ammonia.

Hence level of toxicity of compounds may increase with rise in temperature.


Temperature and Treatment of water

During chemical treatment, the rate and the success of the treatment depends upon the temperature of the water being treated. The rate of chemical reactions increases with the rise in temperature. This is because both the water molecules and the impurity molecules need some optimum threshold energy to overcome their bond of attraction and react with the chemicals added for treatment.

Coagulation, a key process of water treatment also gets affected by change in temperature. This happens because coagulation is dependent on the pH of the water. The pH of water decreases with rise in temperature.