The diagram illustrates how the hydrologic cycle functions, beginning with the phenomenon of precipication and ending up with the cloud formation of the evaporated and transpired water bodies.
During the first stage of the water cycle, the water bodies concetrated in cloud formations are dropped into the surface of the Earth through rain and snow, depending on the temperature levels. At the second stage, rain and melted snow form water paths in the surface and subsurface of the earth. These water paths are directed towards the areas of lower amplitute of Earth based on mountain formations.
Once the water has accumulated in the lower amplitude regions, the phenomena of evaporation and transpiration complete the water circle. More specifically, during the warmer days of the year, Earth water bodies evaporate and tranform into cloud formations. However, evaporation can also be achieved through the green parts of plants and trees, where the water that is consumed by the plants evaporates and returns back to the original cloud formation.
To sum up, the presented graph depicts one the most important cycles for human life, the continuous and never-ending evaporation cycle, that make Earth conditions ideal for human life.