The Water Cycle, Nature's Endless Journey of Every Drop

Every drop of water that falls as rain or flows in a river is part of a journey that never truly ends. The water we drink today has been traveling across our planet for an almost unimaginable length of time. This endless movement, which quietly shapes the world around us, is known to scientists as the water cycle.

What the water cycle is

The water cycle is the continuous movement of water on, above and below the surface of our planet. Water is always on the move, rising into the sky, drifting with the clouds and falling back down to the ground again. This steady circulation has been repeating itself for countless ages, long before any people walked the Earth.

What makes this process so remarkable is that the total amount of water on our planet stays almost the same. The very same water simply changes its form and its location again and again over time. It may be a drop in the ocean one day and a snowflake on a distant mountain peak the next season.

Evaporation and the power of the Sun

The great journey of water begins with the warm and gentle energy that pours down from the Sun. As sunlight heats the surface of oceans, lakes and rivers, tiny amounts of water slowly turn into an invisible vapor. This vapor then rises quietly into the air, carrying water upward without us ever noticing it happen.

Plants also play their own quiet part in sending water back up into the sky above us. Through their leaves, they release water vapor into the air in a gentle process of their own. Together with the vast oceans, these green helpers lift enormous quantities of water into the atmosphere each and every day.

Clouds and condensation

As the warm vapor rises higher and higher, it gradually reaches the cooler layers of the air far above. There the vapor begins to cool down and slowly turns back into tiny droplets of liquid water. Countless numbers of these minute droplets gather closely together to form the clouds we see drifting across the sky.

These clouds can take on an endless variety of beautiful shapes, sizes and shades of color. Some float lightly and gently, while others grow dark and heavy as they fill with ever more moisture. When a cloud finally holds more water than it can carry, the next stage of the journey is ready to begin.

Precipitation returns the water

When the droplets in a cloud grow large and heavy enough, they begin to fall gently back toward the ground. We know this familiar part of the cycle very well, for it reaches us as rain, snow, hail or sleet. This falling water is what scientists call precipitation, and it brings moisture back to the thirsty land.

Precipitation is a vital moment in the whole journey, as it returns fresh water to the surface of the Earth. It fills the lakes, soaks the soil and feeds the plants and animals that depend on it to survive. Without this regular and life giving return of water, the land would quickly become dry and barren.

Rivers, runoff and groundwater

Once water reaches the ground, it begins yet another fascinating stage of its long and winding journey. Some of it flows across the surface as runoff, gathering into trickles, streams and finally into mighty rivers. These rivers then carry the water steadily onward, winding their way slowly back toward the distant sea.

Not all of the water stays above the ground, however, for a good deal of it soaks down into the soil. There it slowly seeps deeper and deeper until it is stored as groundwater, hidden quietly beneath our feet. This underground water is a precious reserve that feeds wells, springs and rivers during the drier times of year.

A never ending journey

Eventually, much of the water that travels across the land finds its way back into the vast oceans. The oceans hold by far the greatest share of all the water found anywhere on our entire planet. From their wide surfaces, the warm Sun once again lifts water into the air, and the whole journey quietly begins anew.

In this way the water cycle turns on and on, without ever truly reaching a beginning or an end. It connects the oceans, the sky, the mountains and the rivers into one great and beautifully balanced system. The next time you watch the rain fall, you can picture the wonderful and endless journey that every drop is making.