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The 5 different forms of water are as follows:
Liquid to Gas: By evaporation
Gas to liquid: By condensation
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Solid to gas: By melting and evaporation
Gas to solid: By sublimation when gas becomes cool.
1. Sub-cycles of Hydrological Cycle:
Water cycle always remains moving. Sun’s heat is available for its smooth movement and the above described water cycle is rarely visible because of its of complicated nature.
The Hydrological cycle is completed by combination of water sub-cycles. They are as follow:
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(1) Micro Sub-cycle:
Micro sub-cycle completes in a short period which can again be divided into two parts:
(i) Sub-Micro Cycle:
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While it is raining, evaporation of drops of water is taking place simultaneously. After evaporation, the same water again enters the atmosphere after condensation due to temperature and falls on ground through rain and completes the micro sub-cycle.
(ii) Micro Cycle:
After evaporation of water from oceans, it moves as vapour and after condensation through friction, it again reaches the oceans. Thus water of oceans to atmosphere and from atmosphere again to oceans completes the micro-cycle. 
Macro Sub-cycle:
This cycle takes comparatively more time as compared to the micro-sub-cycle. It is also divided in two parts:
(i) Long Macro Sub-cycle:
When water falls on the surface of ground at the time of rain, some part of water (out of flow water) evaporates and reaches the atmosphere and after friction falls on the surface of the earth and completes the long macro sub-circle.
(ii) Very Long Minor Macro Sub-cycle:
After rainfall, some part of the flowing water oscillates on earth, which is absorbed by roots of plants. Through transpiration and evaporation, this water again reaches the atmosphere and again comes to earth in the form of rainfall. Thus, this macro sub-cycle takes a very long time to complete. An ideal water cycle is found on oceans. On the ground level, from rivers, lakes and other minor water storage places, before water reaches the oceans, some part of the water evaporates and water cycles get completed.
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2. Inland Stage of Hydrological Cycle:
Inland stage of hydrological cycle starts right from the seepage of rain water inside the surface of the ground. It is known that about 25 to 50 per cent of average rainfall flows away on the surface of the ground. A large portion of surface water evaporates and the remaining part goes underground.
Inland water changes its flow according to flow routes as per geological structure of the relevant area. Some rocks are aquifers, others are aquiclude. Flow of water inside the ground is affected by structure and composition of the soil. Thus, even inside the earth, the process of hydrological cycle is performed.
3. Interruptions in Hydrological Cycle:
It is not necessary that all the ideal conditions of water cycle may be completed in the same sequence, because many factors affect this geographical process:
(i) Change in Atmospheric Composition:
As economic activities of the people are increasing, at the same time technology is developing. Man has artificially changed the atmospheric composition and thereby affected the water cycle. Climatic improvement programme, deterioration of ozone layer due to internal vibrations, change in vapour content in atmosphere etc. have affected possibilities of climatic system changes. As a result of such change, there can be change in movement of evaporation from ground as well as oceans and its direct effect is on quantity of rainfall.
(ii) Due to Increasing Industrialization:
Quantity of air particles is changing because granules emitted by industries work as humidity centers for formation of drops of rain. Thus, solid particles in atmosphere, effect of pollution and formation of clouds affect the quantity and image of rainfall.
(iii) Process of Cloud Formation also affect the hydrological cycle.
(iv) Man has affected water cycle by disturbing the ecological balance of nature through deforestation.
(v) Urbanization has also affected environment, for example air pollution, deforestation for urban expansion etc., also disturb the hydrological cycle.
(vi) Hydrological cycle is also affected by internal movement of water. Deforestation reduces it, whereas irrigation, tree plantation, dam construction and construction of water reservoirs increase it and evaporation also increases. Man affects the water cycle by impacting on surface flow of water in many ways.
(vii) Different types of pollution created on surface of the earth also hinder the movement of water cycle. Due to the economic race, man has done mining by unscientific methods, and thereby disturbed the balance of nature and the functioning of the hydro- logical cycle.
4. Importance of Hydrological Cycle in Nature:
Hydrological cycle is important on the earth for various organic activities because hydrological balance would be disturbed without water communication and any type of life would become impossible. Evaporation of water and its storage in atmosphere is a very important process.
Seasonal variations depend on it. Performance of rainfall on the earth is completed only by the hydrological cycle. Biogeochemical cycle is completed on the earth with water cycle. Among different biogeochemical cycles on the earth, vegetation is an effective medium for movement of sediments and chemical substances. Thus, biogeochemical cycles on the earth are possible only through movement of water.
5. Balance in Hydrological Cycle:
In nature, universal hydrological cycle is a closed ecological system because hydrological cycle on the earth does not exchange energy in the universe, it only gets energy. On the earth, it does not get humidity from outside, and the companion water in hydrological cycle is stable. It does not increase or decrease. There is only seasonal variation but on the world level there is no change in its quantity.
Total evaporation from oceans is 86 per cent and 14 per cent from ground level whereas, rainfall is 79 per cent on oceans and 21 per cent on the ground level. This additional 7 per cent moisture moves from seas towards the ground through clouds and again transfer of water from ground towards seas through rivers and groundwater maintains the balance.
In water balancing, water moves from one place to another. For example, evaporation from oceans is more than rainfall over oceans, but on ground level (except arid and desert areas) this situation is reverse. On the whole, universal evaporation balances rainfall. If evaporation is lesser, there would be increase or decrease in quantum of humidity in atmosphere from time to time. Flow of rivers on the earth balances the evaporation and rainfall.
On this basis, normal equation of water balancing is as under:
Precipitation/Rainfall = Evaporation +/-Flow
Water and ground both combined make the balance on universal level though its local form may differ, which is mainly affected by variations in climate (Legates and Mather, 1992). For example, in dry and hot Australia, rainfall is lesser than evaporation, whereas in tropical South American areas, in spite of more evaporation, there is high flow because rainfall is sufficient (Park, 1997).
Oceans play an important role in universal hydrological cycle because they contain maximum portion of water in them. Maximum rainfall occurs in the Pacific Ocean. Thus, it is clear that in the hydrological cycle in nature, existing water only moves in different forms and in different places. Its actual quantity remains stable. It is called universal water balance and the hydrological cycle is important for balancing quantity of water sphere.