When you were in school, you probably learned about the water cycle. Your teacher probably told you that it involved three different steps: Condensation, precipitation, and evaporation. While the life-giving fluid may have taken a brief detour through your home from a water company in MD, it mostly cycled through these three steps, or so your teacher may have told you.
The water cycle is actually a lot more complicated than that, and therefore a lot more interesting. There are many different courses water can take and transformations it can go through.
You know that solid water, or ice, can melt into a liquid; liquid water can evaporate into a vapor; and the vapor can condense back into liquid. There is also a way that solid water can transform directly into vapor. It is called sublimation, and it only occurs with water under certain circumstances. If sunlight hits ice or snowpack with enough energy to reach the heat of vaporization, sublimation can occur. Sublimation can also take place when a dry chinook wind hits a snowpack, causing it to evaporate.
Plants need water to grow, and they absorb groundwater through their roots in a process called plant uptake. Once a plant is done metabolizing, it releases byproducts including oxygen and water vapor. The process by which the gaseous water is released into the atmosphere is called transpiration. It comes from the Latin root word “spiro,” which means “to breathe.”
Infiltration and Percolation
For plants to be able to grow, there has to be water in the ground for them to draw from. Groundwater accounts for about one-third of all the freshwater on Earth, but it doesn’t just appear there. It starts on the surface as runoff from snow and rain flowing from higher elevations. Eventually, it is absorbed into the ground through the processes of infiltration and percolation.
The traditional three-step water cycle is a simplification of a complex concept. This makes it easier for students to grasp.