5.Hydrological Cycle

Solar energy evaporates the water from oceans, rivers, and lakes into the atmosphere where it forms the clouds. The wind transports these clouds to various parts of the earth. The vapours in the clouds condense and precipitate in the form of dew, rain, snow or hail on the earth. A large part of the precipitation takes place over the oceans i.e. (75%), while the remaining precipitates on the land masses i.e.(25%).

Of the water falling on the land surfaces, some of it is evaporated again and some is returned by surface that run off to drains, streams, rivers, and lakes reaching finally to the oceans. The remaining is filtered into the soil, and percolates deep into the ground water level from where a part of it may seep into streams, lakes, or directly to the oceans. Some water on the land is absorbed by the plants and consumed by the animals. This water, however, is released again into the atmosphere by respiration and evapotranspiration.

5.a Human Interference with Hydrological Cycle

Man influences the hydrological cycle in many ways. Main are:

1. Gov. is/ People are increasing the mass deforestation, and making surfaces pucca. This is resulting into reduction of ground water.

2. Gov. is/ People are now trying for the change in course of our flowing waters and diverting them to the areas of need, which may cause enormous ecological problems. The creation of dams for storage of flowing water is also of ecological concern. This increases the natural evaporation of water by increasing the surface area of water. Dams can induce earthquake as has been reported in many parts of the world.

3. Due to global warming glaciers are melting and there is less precipitation in the form of snow.

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