Hydrology is the study of movement, distribution, and quality of water throughout the Earth. A person who studies hydrology is called a hydrologist. The central theme of hydrology is how the water circulates. This is called the water cycle. The most vivid illustration of it is the water evaporation from the ocean with the formation of clouds. These clouds drift over the land and produce rain. Related pages Civil engineering Climatology Hydraulics Hydrography Notes