Here is a compilation of essays on ‘Water’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Water’ especially written for school and college students.

Essay on Water

Essay Contents:

  1. Essay on the Introduction to Water
  2. Essay on the Types of Water
  3. Essay on the Water in the Universe
  4. Essay on the Water and Habitable Zone
  5. Essay on the Water Cycle
  6. Essay on the Effects of Water
  7. Essay on the Importance of Water
  8. Essay on the Bacteriological Analysis of Water
  9. Essay on the Diseases Transmitted by Water

Essay # 1. Introduction to Water:

Water in three states – liquid, solid (ice), and (invisible) vapor in air. Clouds are droplets of liquid, condensed from water vapour. Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapour or steam. Water covers, 71% of the Earth’s surface.

On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapour, clouds (formed of solid and liquid water particles suspended in air), and precipitation Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%.

A very small amount of the Earth’s water is contained within biological bodies and manufactured products. Other water is trapped in ice caps, glaciers, aquifers, or in lakes, sometimes providing fresh water for life on land.

Water moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt (1012kilograms) per year. Over land, evaporation and transpiration contribute another 71 Tt per year to the precipitation of 107 Tt per year over land.

Clean, fresh drinking water is essential to human and other life. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability a situation which has been called a water crisis by the United Nations.

Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70 per cent of freshwater is consumed by agriculture.

The most important use of water in agriculture is for an irrigation and irrigation is key component to produce enough food. Irrigation takes up to 90% of water withdrawn in some developing countries.

Essay # 2. Types of Water:

Water can appear in three states; it is one of the very few substances to be found naturally in all three states on earth. Water takes many different forms on Earth- water vapor and clouds in the sky; seawater and rarely icebergs in the ocean; glaciers and rivers in the mountains; and the liquid in aquifers in the ground.

Water can dissolve many different substances, giving it different tastes and odors. In fact, humans and other animals have developed senses which are, to a degree, able to evaluate the portability of water, avoiding water that is too salty or putrid.

Humans also tend to prefer cold water to lukewarm; cold water is likely to contain fewer microbes. The taste advertised in spring water or mineral water derives from the minerals dissolved in it, as pure H2O is tasteless. As such, purity in spring and mineral water refers to purity from toxins, pollutants, and microbes.

Essay # 3. Water in the Universe:

Much of the universe’s water may be produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.

Water has been detected in interstellar clouds within our galaxy, the Milky Way. It is believed that water exists in abundance in other galaxies too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems, such as ours.

Water vapour is present on:

i. Mercury – 3.4% in the atmosphere, and large amounts of water in Mercury’s exosphere.

ii. Venus – 0.002% in the atmosphere.

iii. Earth – trace in the atmosphere (varies with climate).

iv. Mars – 0.03% in the atmosphere.

v. Jupiter – 0.0004% in the atmosphere.

vi. Saturn – in ices only.

vii. Enceladus (moon of Saturn) – 91% in the atmosphere exo-planets known as HD 189733 b and HD 209458 b.

Liquid water is present on:

i. Earth – 71% of surface.

ii. Moon – small amounts of water have been found (in 2008) in the inside of volcanic pearls brought from Moon to Earth by the Apollo 15 crew in 1971. Strong evidence suggests that liquid water is present just under the surface of Saturn’s moon Enceladus. There is probably some liquid water on Europa.

Water ice is present on:

i. Earth – mainly on ice sheets

ii. Polar ice caps on Mars

iii. Titan

iv. Europa

v. Enceladus

Probability or possibility of distribution of water ice is at- lunar ice on the Moon, Ceres (dwarf planet), Tethys (moon). Ice is probably in internal structure of Uranus, Neptune, and Pluto and on comets.

Water covers 71% of the Earth’s surface; the oceans contain 97.2% of the Earth’s water. The Antarctic ice sheet, which contains 90% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the Earth’s albedo.

Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology.

The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth’s approximate water volume (the total water supply of the world) is 1,360,000,000 km3 (326 000 000 mi3).

Of this volume:

i. 1,320,000,000 km3 (316,900,000 mi3 or 97.2%) is in the oceans.

ii. 25,000,000 km3 (6,000,000 mi3 or 1.8%) is in glaciers, ice caps and ice sheets.

iii. 13,000,000 km3 (3,000,000 mi3 or 0.9%) is groundwater.

iv. 250,000 km3 (60,000 mi3 or 0.02%) is fresh water in lakes, inland seas, and rivers.

v. 13,000 km3 (3,100 mi3 or 0.001%) is atmospheric water vapour at any given time.

Groundwater and fresh water are useful or potentially useful to humans as water resources.

Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers.

The most important geological processes caused by water are – chemical weathering, water erosion, water sediment transport and sedimentation, mudflows, ice erosion and sedimentation by glacier.

Essay # 4. Water and Habitable Zone:

The existence of liquid water and to a lesser extent their gaseous and solid form, on Earth is vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the solar system; if it were slightly closer to or further from the Sun (about 5%, or about 8 million kilometres), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.

Earth’s mass allows gravity to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a greenhouse effect which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would cause temperature extremes preventing the accumulation of water except in polar ice caps (as on Mars).

It has been proposed that life itself may maintain the conditions that have allowed its continued existence. The surface temperature of Earth has been relatively constant through geologic time despite varying levels of incoming solar radiation (insolation), indicating that a dynamic process governs Earth’s temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis.

The state of water also depends on a planet’s gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity. There are various theories about origin of water on Earth.

Essay # 5. Water Cycle:

The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants.

Water moves perpetually through each of these regions in the water cycle consisting of following transfer processes:

i. Evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into air.

ii. Precipitation, from water vapor condensing from the air and falling to earth or ocean.

Most water vapour over the oceans returns to the oceans, but winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year. Precipitation, at a rate of 107 Tt per year over land, has several forms- most commonly rain, snow, and hail, with some contribution from fog and dew. Condensed water in the air may also refract sunlight to produce rainbows.

Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is hydrological transport model. Some of water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers.

A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation.

Fresh Water Storage:

Some runoff water is trapped for periods, for example in lakes. At high altitude, during winter, and in the far north and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. This water storage is important, since clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply.


Tides are the cyclic rising and falling of Earth’s ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides.

Essay # 6. Effects of Water:

i. Effects on Life:

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body’s solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism.

In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes).

Water is thus essential and central to these metabolic processes. Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, dust collection, etc.

Water is also central to photosynthesis and respiration. Photosynthetic cells use the sun’s energy to split off water’s hydrogen from oxygen. Hydrogen is combined with CO2 (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun’s energy and reform water and CO2 in the process (cellular respiration).

Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H+, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7.

Stomach acid (HCI) is useful to digestion. However, its corrosive effect on the esophagus during reflux can temporarily be neutralized by ingestion of a base such as aluminum hydroxide to produce the neutral molecules water and the salt aluminum chloride. Human biochemistry that involves enzymes usually performs optimally around a biologically neutral pH of 7.4.

For example a cell of Escherichia coli contains 70% of water, a human body 60-70%, plant body up to 90% and the body of an adult jellyfish is made up of 94-98% water.

ii. Effects on Human Civilization:

Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Large metropolises like Rotterdam, London, Montreal, Paris, New York City, Buenos Aires, Shanghai, Tokyo, Chicago, and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade.

Islands with safe water ports, like Singapore, have flourished for the same reason. In places such as North Africa and the Middle East, where water is scarcer, access to clean drinking water was and is a major factor in human development.

iii. Health and Pollution:

Water fit for human consumption is called drinking water or potable water. Water that is not potable can be made potable by filtration or distillation (heating it until it becomes water vapor, and then capturing the vapor without any of the impurities it leaves behind), or by other methods (chemical or heat treatment that kills bacteria). Sometimes the term safe water is applied to potable water of a lower quality threshold (i.e., it is used effectively for nutrition in humans that have weak access to water cleaning processes, and does more good than harm).

Water that is not fit for drinking but is not harmful for humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes called safe water, or “safe for bathing”. Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1-2 ppm of chlorine not yet reacted with impurities for bathing water).

This natural resource is becoming scarcer in certain places, and its availability is a major social and economic concern. Currently, about 1 billion people around the world routinely drink unhealthy water. Most countries accepted the goal of halving by 2015 the number of people worldwide who do not have access to safe water and sanitation during the 2003 G8 Evian summit.

Even if this difficult goal is met, it will still leave more than an estimated half a billion people without access to safe drinking water and over 1 billion without access to adequate sanitation. Poor water quality and bad sanitation are deadly; some 5 million deaths a year are caused by polluted drinking water.

The World Health Organization estimates that safe water could prevent 1.4 million child deaths from diarrhea each year. Water, however, is not a finite resource, but rather re-circulated as potable water in precipitation in quantities many degrees of magnitude higher than human consumption.

Therefore, it is the relatively small quantity of water in reserve in the earth (about 1% of our drinking water supply, which is replenished in aquifers around every 1 to 10 years), that is a non­renewable resource, and it is, rather, the distribution of potable and irrigation water which is scarce, rather than the actual amount of it that exists on the earth. Water-poor countries use importation of goods as the primary method of importing water (to leave enough for local human consumption), since the manufacturing process uses around 10 to 100 times products’ masses in water.

In the developing world, 90% of all wastewater still goes untreated into local rivers and streams. Some 50 countries, with roughly a third of the world’s population, also suffer from medium or high water stress, and 17 of these extract more water annually than is recharged through their natural water cycles The strain not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources.

Essay # 7. Importance of Water

i. As a Dissolving Agent or Solvent:

Dissolving (or suspending) is used to wash everyday items such as the human body, clothes, floors, cars, food, and pets. Also, human wastes are carried by water in the sewage system. Its use as a cleaning solvent consumes most of water in industrialized countries. Water can facilitate the chemical processing of wastewater. An aqueous environment can be favourable to the breakdown of pollutants, due to the ability to gain an homogenous solution that is pumpable and flexible to treat.

Aerobic treatment can be used by applying oxygen or air to a solution reduces the reactivity of substances within it. Water also facilitates biological processing of waste that have been dissolved within it. Microorganisms that live within water can access dissolved wastes and can feed upon them breaking them down into less polluting substances.

Reed beds and anaerobic digesters are both examples of biological systems that are particularly suited to the treatment of effluents. Typically from both chemical and biological treatment of wastes, there is often a solid residue or cake that is left over from the treatment process. Depending upon its constituent parts, this ‘cake’ may be dried and spread on land as a fertilizer if it has beneficial properties, or alternatively disposed of in landfill or incinerated.

Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization. A disadvantage is that water and steam are somewhat corrosive.

In almost all electric power plants, water is the coolant, which vaporizes and drives steam turbines to drive generators. In the nuclear industry, water can also be used as a neutron moderator. In a pressurized water reactor, water is both a coolant and a moderator. This provides a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down.

ii. Extinguishing Fires:

Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. However, water cannot be used to fight fires of electric equipment, because impure water is electrically conductive, or of oils and organic solvents, because they float on water and the explosive boiling of water tends to spread the burning liquid.

Use of water in firefighting should also take into account the hazards of a steam explosion, which may occur when water is used on very hot fires in confined spaces, and of a hydrogen explosion, when substances which react with water, such as certain metals or hot graphite, decompose the water, producing hydrogen gas.

The power of such explosions was seen in the Chernobyl disaster, although the water involved did not come from fire-fighting at that time but the reactor’s own water cooling system. A steam explosion occurred when the extreme over-heating of the core caused water to flash into steam. A hydrogen explosion may have occurred as a result of reaction between steam and hot zirconium.

iii. Chemical Uses:

Organic reactions are usually quenched with water or a water solution of a suitable acid, base or buffer. Water is generally effective in removing inorganic salts. In inorganic reactions, water is a common solvent. In organic reactions, it is usually not used as a reaction solvent, because it does not dissolve the reactants well and is amphoteric (acidic and basic) and nucleophilic.

Nevertheless, these properties are sometimes desirable. Also, acceleration of Diels-Alder reactions by water has been observed. Supercritical water has recently been a topic of research. Oxygen-saturated supercritical water combusts organic pollutants efficiently.

iv. Recreation:

Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, waterskiing, boating, and diving. In addition, some sports, like ice hockey and ice skating, are played on ice. Lakesides, beaches and waterparks are popular places for people to go to relax and enjoy recreation. Many find the sound of flowing water to be calming, too. Some keep fish and other life in aquariums or ponds for show, fun, and companionship.

Humans also use water for snow sports i.e. skiing or snowboarding, which requires the water to be frozen. People may also use water for play fighting such as with snowballs, water guns or water balloons. They may also make fountains and use water in their public or private decorations.

Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products. Solutes such as salts and sugars found in water affect the physical properties of water.

The boiling and freezing points of water is affected by solutes. One mole of sucrose (sugar) raises the boiling point of water by 0.52 °C, and one mole of salt raises the boiling point by 1.04 °C while lowering the freezing point of water in a similar way Solutes in water also affect water activity which affects many chemical reactions and the growth of microbes in food Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water Solutes in water lower water activity.

This is important to know because most bacterial growth ceases at low levels of water activity. Not only does microbial growth affect the safety of food but also the preservation and shelf life of food. Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation.

Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grain of hardness Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains. The hardness of water may be altered or treated by using a chemical ion exchange system.

The hardness of water also affects its pH balance which plays a critical role in food processing. For example, hard water prevents successful production of clear beverages. Water hardness also affects sanitation; with increasing hardness, there is a loss of effectiveness for its use as a sanitizer. Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or its gaseous state, steam, while cooking water is used for dish-washing too.

Essay # 8. Bacteriological Analysis of Water:

Many methods are available for the detection of bacterial contamination of water, and various ones are selected according to the resources of the testing laboratory. Since it is impossible to test for all pathogenic microorganisms, water quality bacteriologists have adopted the practice of testing for certain indicator bacteria normally found in the human intestinal tract. If these bacteria are present, fecal contamination has probably taken place.

Among the most frequently used indicator organisms are the coliform bacteria. Coliform bacteria are normally found in the intestinal tracts of humans and many warm-blooded animals. They are able to survive for extensive periods of time in the environment, and they are relatively easy to cultivate in the laboratory. Escherichia coli is the most important indicator organism within the group.

The membrane filter technique is a popular laboratory test in water microbiology because it is straightforward and can be used in the field. A technician holds a specially designed collecting bottle against the current and takes a 100-ml sample.

The water is then passed through a membrane filter, and the filter pad is transferred to a plate of bacteriological medium. Bacteria trapped in the filter will form colonies, and by counting the colonies, the technician may determine the original number of bacteria in the sample.

Another method for testing water is the standard plate count technique (SPC). Samples of water are diluted in sterile buffer solution and carefully measured amounts are pipetted into Petri dishes. Agar medium is added, and the plates are set aside at incubation temperatures. A count of the colonies multiplied by the reciprocal of the dilution (the dilution factor) yields the total number of bacteria per ml of the original sample.

A third test is a statistical evaluation called the most probable number (MPN). In this procedure, a technician inoculates water in 10-ml, 1-ml, and 0.1-ml amounts into lactose broth tubes. The tubes are incubated and coliform organisms are identified by their production of gas from lactose. Referring to an MPN table, a statistical range of the number of coliform bacteria is determined by observing how many broth tubes showed gas.

Essay # 9. Diseases Transmitted by Water:

Water may be the vehicle for transfer of a broad variety of microbial diseases, including bacterial diseases such as typhoid fever, cholera, and shigellosis. Waterborne epidemics of these diseases, however, are rare due to continual surveillance. Many waterborne illnesses are due to less familiar bacteria such as species of Yersinia and Campylobacter, and toxin-producing strains of Escherichia coli.

An emerging pathogen associated with contaminated water is Vibrio vulnificus, a Gram-negative bacterium that can cause serious illness in persons with preexisting liver disease or compromised immune systems. In the ten-year period preceding 1993, 125 persons became infected with V. vulnificus and 44 died. Raw oyster consumption was implicated in the majority of deaths.

Viral diseases transmitted by water include hepatitis A, gastroenteritis due to Coxsackie or Norwalk virus, and in rare instances, polio. These diseases are generally related to fecal contamination of water. Many protozoa form cysts that survive for long periods in water.

For this reason water may be a vehicle for the transfer of Entamoeba histolytica and Giardia lamblia. A notable outbreak of Cryptosporidium infection occurred in 1993 when the municipal water supply of Milwaukee, Wisconsin, became contaminated.

Two dinoflagellates bear mention because of their involvement in human poisonings. The first, Gonyaulax catanella, produces a toxin that may cause muscular paralysis and death from asphyxiation. The toxin is ingested from shellfish that feed on the dinoflagellate. The second dinoflagellate is Gambierdiscus toxicus.

This marine microorganism is consumed by small fish that concentrate the toxin and pass it to larger fish such as sea bass and red snapper. Human consumption of the fish leads to neurological and muscular intoxication and a condition called ciguatera fish poisoning (from cigua for poisonous snail, originally thought to be the cause).