Hydrologic cycle describes the continuous movement of water on, above and below the surface of the Earth. In general, circulation and conservation of earth’s water as it circulates from the land to the sky and back again is called the ‘hydrological cycle’ or ‘water cycle’. It is essential for the maintenance of most life and ecosystems on the planet. The study of this movement of water between its various states, or within a given state, or simply quantifying the amounts in these states in a given region is termed as Hydrology with the circulation of water throughout the Earth through different pathways and at different rates as its central theme. Hydrology is the scientific study of water: its properties, its influences, and its distribution over and under the earth’s surface. The areas of research within hydrology concern the movement of water between its various states, or within a given state, or simply quantifying the amounts in these states in a given region. Parts of hydrology concern developing methods for directly measuring these flows or amounts of water, while others concern modelling these processes either for scientific knowledge or for making prediction in practical applications. Hydrological research can inform environmental engineering, policy and planning. The branches of Hydrology include: Hydrogeology, Chemical hydrology, Ecohydrology, Hydroinformatics, Isotope hydrology, Surface hydrology, Hydrometeorology, Drainage basin management and Water quality. Surface Hydrology or Surface-water hydrology is a branch of Hydrology. Understanding the hydrologic cycle therefore, is basic to understanding water supply and is a key to the proper management of water resources. The water cycle involves the exchange of energy, which leads to temperature changes.