Hydro – logical Cycle: It is also called the Water Cycle. In this, the movement of water and its conversion into gaseous, liquid and solid states are included. Its main process is condensation through which the rainfall occurs. Storage and flow of underground water and, evaporation on earth and atmospheric humidity are included.
Thus, in the hydro – logical cycle, the regular cyclic system of water in the hydrosphere, atmosphere and lithosphere is included. The cyclic stages of water occurring in different forms are called the hydro – logical cycle.
There are mainly three stages of the hydro – logical cycle: Evaporation and transpiration, precipitation and air circulation. The hydro – logical cycle passes through these three stages. This cyclic system of water is presented by the of following fig:
Water bodies: Area of the entire earth is 50.995 million sq. km. in which the hydrosphere is extended on 36.106 million sq. km. area and the lithosphere on 14.889 million sq. km. Oceans which are the First Order Relief are vast reservoirs of water. As the study of air – mass has an important place in climatology, in the same way, water bodies have a special place in oceanography.
Under the water bodies of the world, in addition to the vast oceans (Pacific, Atlantic, Indian and Arctic oceans), refractory seas like Mediterranean Sea, Red Sea, bays located on the shores of continents and the seas and lakes located on the continents are included.