The water cycle

Water is found in seas, rivers and streams, in the ground and in the air. Some areas have plenty of water, while others have very little. Wherever water is found, it is constantly moving. It always flows toward the lowest point and always finds its way to a sea. But how does it get from the sea to the land, up high mountains and across wide plains? Nature has created a wonderful cycle to make this happen.

It all begins above the sea. The sun warms the water. Evaporation starts at the surface. Fine water vapor forms.  The salt in seawater does not evaporate; it stays behind in the sea. The water vapor floats in the air. Since the air is also warmed by the sun’s rays, it rises and travels upwards. Warm air can hold a lot of water vapor.

At higher altitudes, however, the air cools. It can no longer hold as much water vapor, so the vapor becomes visible again. We say it “condenses.” Tiny droplets form and join together. Many fine water droplets become clouds. The wind pushes the clouds along, blowing them over the sea and across the land. Some look bright, while others are dark and almost a little threatening. The darker they look, the more water droplets they contain. Over land, clouds often bump into mountains. More and more clouds pile up, but they cannot get over the mountain.

Then it starts to rain or snow. In the clouds, tiny water droplets eventually turn into large raindrops or snowflakes that fall to the ground. Rain or snow also falls over land when the air cools. Sometimes snow lies on the ground for a long time, but eventually it melts. A small amount of the water that reaches the ground as rain or snow evaporates again right away. Some of it flows into drains or trickles and streams, which then form rivers and lakes. A third part seeps into the ground and becomes groundwater. Trees and other plants draw on this water to live. We get our drinking water from rivers, lakes and groundwater.

It’s a good thing that all the salt is left behind when water evaporates from the sea. Plants, animals and people can’t tolerate salt water. By the way, we sometimes call the water in the ground, rivers and lakes fresh water.

Groundwater reappears at the surface in springs. Streams flow from springs, take in water from other streams and smaller rivers, and eventually become broad, mighty rivers that flow towards the sea. Water evaporates along the way too, forming clouds from which rain or snow eventually falls. Most of the water, however, flows back into the sea. Rivers are said to “drain” the land. This means the seas never dry up, and living things on land are supplied with water. This wonderful water cycle is kept going above all by the sun. It warms water, which evaporates, rises, forms clouds, is carried inland by the wind, and falls from the sky as rain or snow. The water then flows back to the sea, and everything starts again.