Hydrological Cycle

The hydrological cycle is a global sun-driven process by which water is transported from the oceans to the atmosphere, from atmosphere to the land and then back to the sea.

Hydrological cycle extend from an average depth of about 1 km in the lithosphere to a height of about 15 km in the atmosphere.

The hydrological cycle has no beginning or end. It may be assumed to start from the oceans for our convenience.



Water in the oceans evaporate due to heat energy provided by solar radiation.

The water vapours move upward and form clouds. While much of the clouds condense and fall bacj to the oceans as rain, part of the clouds is driven to the land areas by wind. There they condense and precipitate on to the land mass as rain, snow, hail, sleet etc.

A part of the precipitation may evaporate back to the atmosphere even while falling.

Another part may be intercepted by vegetation, structures and other surface modifications.

A portion of the water that reaches the ground, enters the earth's surface through infiltration, enhances the moisture content of soil and reaches the ground water table.

Vegetation sends a portion of the water from under the ground surface back to the atmosphere through the process of transpiration.

Some infiltrated water may merge to surface eater bodies as interflow, other portions may become ground water flow.

Ground water may be discharged into streams or may emerge as springs and ultimately reaches to the oceans.