What is a Hydrologic Cycle?

The Earth as we know it is made up of primarily water, considered the most precious of our natural resources. Snow storms, rain showers and thunderstorms play just a small part of what is know as the hydrologic cycle, or water cycle. The hydrologic cycle is made up of water in all three of its forms: solid, liquid and gas. The hydrosphere is the area which contains all the water in the atmosphere. Every cycle occurs in five different stages.

The hydrologic cycle starts in the evaporation stage. All water on the ground — including lakes, rivers and oceans — is at the mercy of the sun. Sunlight aids in the process to raise the water temperature and eventually change it from a liquid to a gas. As a gas, the water vapor rises into the atmosphere and starts to condense. During the condensation stage, the water vapor condenses on particles in the atmosphere and forms clouds. A smaller version of this process is dew on the grass in the morning.

From condensation to precipitation, the water can come in a variety of forms. Even though this is known as the precipitation stage, hail is one of the forms which can fall. The other likely scenarios are snowfall and rain showers. Once clouds form, upper atmosphere winds spreads the clouds across the entire globe until the clouds cannot hold all the moisture. Weather systems over lakes in the winter can actually stall out and lead to a longer more intense system as it sits over a larger body of water which speeds up the hydrologic cycle.

The infiltration and runoff stages are the final two parts of the hydrologic cycle. Both stages occur simultaneously. When the snow and rain hit the ground, it begins to seep into the ground during the infiltration process. During a flood, the ground has already absorbed the amount of water it can hold and begins to accumulate on the ground. The runoff stage goes from the ground, either above or below ground and flows into rivers and streams. The streams and rivers flow back into lakes and oceans which lead back to the start of the process, evaporation.