Introduction

Before discussing the life cycle of water it is important to have an understanding of what water is, the importance of water, and its origins.

What is Water?

Water also commonly known as H20 is an inorganic chemical compound made up of two hydrogen atoms and one oxygen atom, in its purest form it is a see-through, colourless, odourless and tasteless substance.

The Importance of Water

It plays a vital role in life as we know it, and is deemed one of the six essential nutrients in addition to protein, fat, carbohydrates, vitamins and minerals

All living organisms need water to survive, from Nanoarchaeum (the smallest entity universally recognised to be a living organism) to larger organisms such as humans or Giraffes.

The human body is made up of an estimated 60 % of water, with a person being capable of lasting around three days without it, whereas they could last on average 1 to 3 months without food.

https://www.medicalnewstoday.com/articles/how-long-can-you-go-without-food

Water has many important roles within the human body, it is involved in many different processes such as the transportation of nutrients, regulation of body temperature, assisting in the digestion process to the excretion of waste products from the body.

The scientific community deem the existence of life on other planets to be impossible without the presence of water. As a result, the search for extraterrestrial life on other planets by organizations such as NASA revolves around the search for water.

Facts About Water

 

Water is the most abundant substance on earth, covering an estimated 70% of the planet's surface, amounting to roughly 1.386 billion cubic kilometres (333 million cubic miles)

It surrounds us everywhere and is not always visible to the eye, the oceans contain an estimated 96% of all water on earth, ice caps, glaciers & permanent snow 1.74 %, groundwater 1.69%, with the remaining 0.03% existing in soil moisture, ground ice & permafrost, lakes, swamp water, rivers,  the atmosphere and even in animals and humans as biological water.

https://www.usgs.gov/special-topics/water-science-school/science/how-much-water-there-earth

The use of water in the context of our everyday lives can be categorised according to direct and indirect usage, with direct use instances being more obvious, including its utilization for drinking, cooking, cleaning etc whereas it also plays a critical role in many indirect ways and less obvious ways. The indirect use of water may not be at the forefront of one's mind, even though they far outweigh direct use instances as is used in the agriculture industry for the feeding of livestock and irrigation, as a cooling agent in industry or during the manufacturing process of wood and steel for example, or even in medical procedures.

There is such an abundance of water on earth, that it is easy to take its existence for granted, and forget the fact that as of the time of writing, it is the only known planet or moon to have liquid water on its surface on a consistent basis and in a stable manner.

The question arises, where does all this water in our aquifers, swamps, rivers, lakes, seas etc come from?

 

The Origins of Water on Earth

 

The water we use both directly or indirectly did not just come from the tap or from a local aquifer, lake, river or sea, its creation occurred in deep space, long before earth even existed.

The exact origins of how water ended up on planet earth, is a hotly debated topic amongst planetary scientists, astronomists, and astrobiologists. There are three different schools of thought, that the water on earth was present during its formation,  that it was deposited during collisions with ice-laden asteroids and comets or that it is a combination of the two.

As of this moment in time, there is no definitive conclusion to the question surrounding the origins of water on earth, however regardless there is no such confusion or debate over the life cycle water on this planet undertakes.

The Water Life Cycle on Earth

The Water on planet earth exists in three different states, as a gas (water vapour aka steam) as a liquid (water), or as a solid (ice), which are dependent on its temperature.

https://education.nationalgeographic.org/resource/hydrosphere

The term the water cycle is also known as the Hydrologic Cycle and is an umbrella term to describe the sum of all the processes involved in the continuous movement of water in its varying states between the earth and the atmosphere 

https://education.nationalgeographic.org/resource/hydrologic-cycle

The main processes involved in the water cycle are evaporation, condensation, and precipitation, with the others being evapotranspiration, radiative exchange, surface runoff, groundwater and stream flow, infiltration, percolation and soil moisture.

These processes describe the evaporation of water, its ascent into the atmosphere, how it gathers to form clouds, and returns to Earth in the form of rain, sleet or snow collecting in rivers, lakes and oceans, only for the process to start all over again in a never-ending cycle.

The ocean covers an estimated 71 percent of the earth's surface and contains an estimated 97% of all the water on it with 78% of global precipitation occurring over it, as a result, it is the source of 86% of global evaporation

https://science.nasa.gov/earth-science/oceanography/ocean-earth-system/ocean-water-cycle

 

Evaporation

 

Water is comprised of molecules consisting of two hydrogen atoms and one oxygen atom which is why it is referred to as H20. These atoms share electrons with one another, which is referred to as a covalent bond.

In liquid water, these covalent bonds are constantly being formed and broken by the energy of motion aka kinetic energy.

As the sun heats the earth, it causes the temperatures of the earth's water in our lakes, rivers, oceans etc to rise, which increases the kinetic energy of the water molecules. As the temperature increases so too do the movement of the water molecules, moving faster and faster until they reach a point where they are moving fast enough to cause the hydrogen bonds to break completely, allowing water molecules to separate and escape into the air in a state known as gas (water vapour aka gas) in a process known as evaporation.

https://www.usgs.gov/special-topics/water-science-school/science/evaporation-and-water-cycle

Evaporation of water occurs at any temperature above freezing point as the collision between air molecules and water molecules generates energy aka heat. The higher the temperature, the greater the rate of evaporation with evaporation occurring faster at higher temperatures, for example, water evaporates faster at 90 degrees Celsius (194 degrees Fahrenheit) versus 30 degrees Celsius (86 degrees Fahrenheit).

 

Transpiration

 

Plants absorb liquid water from the soil for use in all manner of processes vital to survival, such as the transportation of mineral ions, cooling, regulation of turgor pressure, photosynthesis etc. 

The vast majority of water absorbed by plants, estimated to be as much as 97-99% is released back into the atmosphere through microscopic pores on their leaves known as stomata, in the form of vapour in a process known as transpiration.

https://www.sciencedirect.com/topics/chemical-engineering/transpiration

During periods of growth, a plant's leaf will transpire many times more water than its own weight. A large oak tree can transpire around 151,000 litres (40,000 gallons) of water per year.

Transpiration amounts to an estimated 10 percent of the earth's atmospheric moisture.

https://tree-nation.com/projects/inside-tree-nation/article/14793-what-is-evapotranspiration

The term evapotranspiration is used to describe the combined processes involved in evaporation and transpiration.

 

Condensation

 

Condensation is the opposite of evaporation, it is a term used to describe the process involved in water vapour being returned to its liquid state when exposed to cold temperatures.

Condensation occurs when warm air encounters a colder surface, cooling rapidly as a result, water vapour condenses, forming liquid droplets on the cold surface in the process.

In a process which takes 9 - 10 days on average, condensation also occurs when vapour rises higher into the Earth's atmosphere, the vapour cools due to the lowering temperatures. Once cold enough, it condenses after encountering cloud condensation nuclei such as dust, ice and salt, returning to its liquid state in the form of water droplets. These water droplets combine to form clouds.

https://education.nationalgeographic.org/resource/hydrologic-cycle

 

Precipitation

As more and more water droplets combine with one another, they become too heavy to remain suspended in the cloud and fall to Earth in the form of rain, sleet or snow in a process known as precipitation. Once on Earth, these water droplets end up in our soil, plants, trees, aquifers, lakes, rivers, and oceans and the hydrological cycle starts over. This is a never-ending process.

https://www.noaa.gov/education/resource-collections/freshwater/water-cycle

An estimated 505,000 cubic kilometres (121,000 cubic miles) of water falls each year in the form of precipitation.

https://en.wikipedia.org/wiki/Earth_rainfall_climatology

 

Conclusion

 

Although we may not know the true origins of water on earth, there is no such mystery surrounding its life cycle or to the important role, it plays in our everyday lives.

Throughout its lifecycle on Earth water comes into contact with many contaminants, naturally occurring and man-made, both organic and inorganic.

Ensuring that our water is free from contaminants is extremely important as water is a vital resource and pollution can have serious consequences for our health and well-being including acute and chronic illnesses.

The use of an at-home water filtration system is a simple way in which we can protect ourselves and our families and ensure that our water is free from harmful contaminants. 

Your Health Is Your Wealth

 

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