Hydrology is the scientific study of the movement, distribution and management of water on Earth and other planets, including the water cycle, water resources and environmental watershed sustainability. Hydrology (IHP) The Intergovernmental Hydrological Programme (IHP) is the only intergovernmental programme of the United Nations system devoted to water research and management, and related education and capacity development. The IHP started out in 1975 as an internationally coordinated hydrological research programme.