The oceans hold about 97% of the world’s water. Water evaporated from the oceans may be carried as water vapour across land. As it rises above high ground, it condenses and falls to the ground as rain or snow. Rivers carry the water on the land’s surface back to the ocean and the cycle begins again. Much of the water evaporated from the oceans falls directly back into the oceans. This never-ending cycle of water moving between the ocean and atmosphere is called the water cycle.

Groundwater

Rivers carry much of the water that falls on land back to the oceans. Some rainwater seeps into the ground and flows very slowly through cracks or pores (tiny holes) in the rocks themselves. This is called groundwater.

Dew and frost

You can watch the water cycle happening in miniature whenever dew forms. At night, the land cools faster than the air. Any water vapour in the warmer air that touches the cooler land condenses. This covers everything with drops of water known as dew. As the air warms up in the sunshine in the morning, the dew evaporates.

If temperatures are below freezing, the water vapour turns into a layer of sparkling ice crystals called frost.