Water is made up of two elements: hydrogen and oxygen. Each molecule contains 2 parts hydrogen to 1 part oxygen.
Most of the Earth’s water is found in the sea and the seas cover approximately 70% of the planet’s surface. The rest are in the polar caps, rivers, lakes, reservoirs, clouds, sea ice, and trapped underground in aquifers.
Sea water contains salt so it is not drinkable, but the other sources mentioned are mainly fresh and this is what humans need to drink.
Water is constantly moving in something called the water cycle. Basically, the water that is exposed to the sun evaporates and the steam created eventually forms a cloud. When the cloud can’t hold any more liquid, it rains and falls back to Earth, only to start the process all over again.
The balance of water on the planet remains fairly constant, but individual molecules move in and out of the atmosphere. Water moves from one reservoir to another and goes through different phases of solid, liquid, and gas.
There are a few processes involved in the water cycle: evaporation, condensation, precipitation, infiltration, underground runoff, and surface runoff.
The sun drives the water cycle with evaporation. Evaporation implies that water absorbs energy from the environment and subsequently cools the environment. Liquid water turns into gas and rises into the atmosphere.
When in the atmosphere, the particles collide and get bigger, forming clouds. This happens through the condensation process in which the gas turns into a liquid.
Precipitation is the scientific name for rain. It falls on land, sea and bodies of fresh water. It can also fall as snow or hail.
The water that falls on the ground seeps into the ground and reaches the groundwater supply, filling it. Water flows under the surface and finds its way into rivers and the sea. The water that moves underground is groundwater runoff.
Other water that falls on the land runs into rivers and streams – this is surface runoff.
Then it enters the rivers and seas and will be subject to evaporation again.
There is another way that water can enter the atmosphere and that is through perspiration from trees. Trees move groundwater from their roots to the pores in their leaves, where it evaporates; This process is called evapotranspiration. About 10% of the water in the atmosphere arrives in this way. Then it condenses into clouds and falls again due to precipitation.
Water comes from many places on Earth, but it is certain that it has been in more places than you think due to the water cycle.
The next time you have a glass of water, think about the incredible journey it has taken to get there.