In this article we will discuss about the hydrological cycle with the help of a suitable diagram.
Entire moving water of the universe whether in an atmosphere or on the earths surface or below the surface is constantly changing its state and passing from one state to the other. As a whole it forms an endless chain of various processes and is known as a Hydrological cycle.
Sun’s heat energy is responsible for the entire process. In short, the hydrological cycle represents circulation of water from the oceans to the land via atmosphere and back to the oceans by overland and terrain routes.
It may be properly considered as consisting of two main divisions, they are:
(i) Atmospheric division, and
(ii) Surface division.
Each division consists of three main phases, namely:
(a) Transportation of water in some form,
(b) Temporary storage, and
(c) Change of state.
The atmospheric division comprises:
(a) Vapour flow
(b) Vapour storage in the atmosphere, and
(c) Change from vapour to water.
It may be rainfall or change may be in some other form for example, snowfall, frost, dew etc.
The surface division comprises:
(a) Surface runoff, infiltration or ground-water flow
(b) Surface, ground-water, soil moisture storage, and
(c) Change from water to vapour or evaporation due to heat.
The hydrological cycle can be best exemplified pictorially as shown in Fig. 4.1.
From the above discussion it is clear that the rain in hot regions and snow in cold regions are the primary sources of water. Subsequently they give rise to other sources of water, for example, rivers, streams, tanks, wells etc.