Updated On 02/09/2017 | Originally Published On 12/14/2015
Long before we understood how to control and distribute water to support our lifestyles, the Earth had already devised its own sophisticated way to move water around the planet to support life. We call this natural phenomenon the water cycle. You might be surprised how efficiently it works and how effective this natural recycling process is.
A Circular System
The entire planet’s supply of water already exists — there’s currently no effective way to create new water. However, Earth is constantly recycling its supply of water, which we can (thankfully) reuse. This cycle changes water from one state (solid, liquid, or gas) to another, redistributing it all over the world along the way — so water from a lake in Ohio could turn into rainfall in Pennsylvania. How does this work?
Let’s start at ground level: Water evaporates from land, and from bodies of water as their surface temperatures increase. Water also evaporates through transpiration, a process through which a plant’s leaves “sweat” moisture. All of this water vapor then rises up into the atmosphere.
As altitude increases, air temperature decreases. Water vapor clings to dust and other particles in the air, and as the water vapor cools, it condenses into water droplets. Eventually, the water droplets become too heavy to remain airborne and they fall from the sky as precipitation, also known as rain and snow. Believe it or not, it only takes about ten days for evaporated water to return to the surface of the Earth, where it replenishes groundwater, lakes, rivers, and oceans.
Plants and animals (including us!) rely on this cycle to provide the water we all need for survival. For a very long time, this cycle has sustained life by redistributing water supplies around the globe. The process creates a certain kind of balance: Where there’s lots of water to evaporate, lots of water returns as precipitation; where there’s little to evaporate, little returns as precipitation. Unfortunately, this balance can result in extreme conditions — too much rainfall in one area contributes to flooding, while too little rainfall in another creates drought, and both conditions make land unworkable and unlivable.
The world as we know it wouldn’t exist if it weren’t for our ability to capture and redirect water. From drinking and farming to powering industrial processes, our ability to harness water makes modern life possible. Of course, the ways we tap into the water cycle — in particular, moving or removing sources of water, and changing the quality of the water we have — make a big impact on the lives of billions of people.
Moving and Removing Water: Dams, Irrigation, and Deforestation
Getting fresh water to where we live and where we grow our food requires channels that can move water from one location to another, and keep it there. Dams and irrigation are both tried-and-true methods for creating artificial supplies of water: Dams create reservoirs of stored water in places that need it, while irrigation disperses water to crops in place of rain. When we use too much water — for example, to grow more food in a specific area — we risk depleting one source of water (like a reservoir) and drying up surrounding land, while oversaturating another area (such as farmland) and making it prone to flooding.
As room is made for new housing or industry, as well as for more agriculture and livestock production, the result is often the uprooting of natural vegetation. While the drawbacks of deforestation are not limited to its negative impact on the water cycle, when large swaths of plant life are removed from our ecosystem the amount of water vapor that reaches the atmosphere through transpiration is reduced, limiting the potential for future rainfall in a given area.
Changing Water: Sewage and Pollution
For centuries, water has played the main role in laundering, bathing, and plumbing. Locating clean water used to be as simple as moving upstream from contaminated sites — but trash, toxic chemicals (like pesticides and fertilizers from industrial farming), and industrial waste (like discharge from power plants) have made their way into our water sources. This pollution can harm aquatic life and local ecology, and diminish the quality of our water supply. As plants can’t rely on a polluted water supply, they die out, taking a source of transpiration away. Furthermore, treating polluted water to make it drinkable requires more energy than treating non-polluted water. Contaminated water can sometimes even be untreatable.
Playing A Part
Since there is a fixed amount of water on this planet (and a relatively limited amount of fresh water, which is the only water we can really use) conserving resources is the best way we can allow the water cycle to continue in its natural process unimpeded. There’s a delicate balance between the ecosystem and the faucet, and helping to keep that balance going starts with small steps — taking shorter showers and turning off the faucet while you brush your teeth are great ways you can contribute to a healthy water supply for everyone. Additionally, try to choose food grown in its native area during its natural growing season; this usually requires less water than growing it somewhere else. Recycling helps conserve water too, as it often requires less water to make recycled products than to make products from scratch.
There are tons of ways to use water wisely and help the water cycle run smoothly. How do you conserve water? Share your tips and ideas in the comments below