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 (Ref. Wikipedia).

There are two broad sub-disciplines within the science of hydrology. The ground-water hydrology focuses on the distribution and movement of water beneath the earth’s surface. The surface-water hydrology focuses on water on and above the surface of the earth. The science is trying to answer the question about the amount and/or flow rate of water that will be found at given location and at given time in rivers and streams.

Hydrology work provides a better understanding of the processes involved in the hydrologic cycle, and insight for water resources development, policy and planning. Practical hydrology has been traditionally occupied with floods, droughts and assessment of water resources. Recently hydrology is focusing increasingly on the problems caused by pollution of surface water and groundwater, and general issues such as the effects of climate change and land use change.

The assessment of the water resources of Liberia and the efficient design of hydropower projects requires reliable hydrological records. In recent years, Liberian Hydrological Service together with the NVE Project re-established a network of hydrometric stations on main Liberian rivers and started collection of hydrological data.