Hydrology
![Water covers 70% of the Earth's surface.](/Images/godic/202501/19/Land_ocean_ice_cloud_10245343.jpg")
![Building a map of groundwater contours](/Images/godic/202501/19/Building_a_map_of_groundwater_countours5343.gif")
![](/Images/godic/202501/19/The_Earth_seen_from_Apollo_175343.jpg")
Hydrology is the scientific study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability. A practitioner of hydrology is a hydrologist, working within the fields of earth or environmental science, physical geography, geology or civil and environmental engineering.