Following a drop through The Water Cycle


Water Cycle

By: USGS



Ocean

You may be familiar with how water is always cycling around, through, and above the Earth, continually changing from liquid water to water vapor to ice. One way to envision the water cycle is to follow a drop of water around as it moves on its way. I could really begin this story anywhere along the cycle, but I think the ocean is the best place to start, since that is where most of Earth’s water is.


If the drop wanted to stay in the ocean then it shouldn’t have been sunbathing on the surface of the sea. The heat from the sun found the drop, warmed it, and evaporated it into water vapor. It rose (as tiny “dropettes”) into the air and continued rising until strong winds aloft grabbed it and took it hundreds of miles until it was over land. There, warm updrafts coming from the heated land surface took the dropettes (now water vapor) up even higher, where the air is quite cold.


Evaporation

When the tiny dropettes cooled down enough it turned back into liquid water.   This process is called condensation.  The water drop condensed on a tiny particle in the air like salt, smoke or dust.


condensation


cloud

When the water drop forms around the particles it forms a cloud.


After a while, the water drop combines with other tiny drops and they get really big.  These large drops are too heavy for the particles hold and they fall back to Earth as precipitaion. 


The rain drop could land in many different places.  It might land on a leaf on its way back to Earth.  If it does it would evaporate and start its journey back to the clouds. 


Rain on a Leaf

If the drop misses the leaf it could land in dry land and seep through the soil.  It could also land in a pond, stream, lake, river, or puddle and stay as surface water.


Surface water


Irrigation system

A lot of surface water is used for irrigation.  Even more is used by power-production facilities to cool their electrical equipment. From there it might go into the cooling tower to be evaporated. Talk about a quick trip back into the atmosphere as water vapor—this is it. But maybe a town pumped the drop out of the river and into a water tank. From here the drop could go on to help wash your dishes, fight a fire, water the tomatoes, or (shudder) flush your toilet.



Back home to the Ocean

If the surface water is not used for any of these purposes, then it will make its way back home to the ocean to start the process all over again.