What happens to the rain after it hits the ground? Where does it go and where did it come from? Let’s start at the beginning!
Earth does not lose or gain any substantial amount of water. The water that we have, we got when the Earth was just being formed. This means that the water in your cup has been around for many hundreds of millions of years. It gets recycled through a process called the water cycle.
1. Evaporation
Have you ever left a glass of water out on the table for a few days before? If so, did you notice all of the water slowly disappear? This is caused by evaporation. The liquid water is turning into water vapour!
The evaporated water floats up into the atmosphere and combines with small pieces of dust. When the water and the dust collect, they form clouds in the sky.
Transpiration: Lakes, rivers, and open cups of water aren’t the only places that the clouds get water from. Water also comes from plants! The plants take water out of the ground through their roots and then they “sweat” through their leaves! Transpiration is the special name for evaporation off of plants.
2. Condensation
When the water is in the clouds it can’t stay in its gas form for too long. It is cold high up in the sky, so the water turns back into liquid or even ice. This process is called condensation.
3. Precipitation
Clouds can only hold so much water. When they get really full they release the water as precipitation.
Precipitation can be rain, snow, hail, sleet, or any other kind of water that falls from the sky. Most precipitation starts off as a solid and melts as it falls.
4. Ground Water and Runoff
But where does the water go when it hits the ground? That’s a harder question to answer.
When the rain hits cement, like when it lands on a road or a sidewalk, it may stay in one place and collect in a puddle. This is why we have storm drains on the side of the road for the water to go into. They give this pooling water a place to go so that our roads don’t get too flooded. These storm drains collect the water and then release it into streams, lakes, rivers, and oceans. We have to be very careful about what we put in these drains because the fish and other inhabitants of lakes, rivers, and oceans will be harmed if we put toxic things in them.
When the rain falls on grass, plants, or dirt it doesn’t usually form puddles. Why? We will call these places “green spaces”. Think of them as giant sponges, they soak up the water and slowly let it travel through the ground because soils have space in them for water to fill and flow through. In Waterloo, we actually get most of our drinking water from the ground! We have lots of wells that suck up water from under the ground.
Sometimes when it rains a lot, the ground cannot soak up all the water in time and it runs off the land and into streams, oceans, and lakes. This is called runoff.
When it snows the same thing happens, but there is a delay while the water stays in one spot until it melts and then continues through the water cycle.
5. Accumulation
Water sometimes collects and stays in one place for a really long time. This is called accumulation. Water in oceans and lakes sometimes spends thousands of years in one place until it is evaporated again.