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Differentiate between gravitational water and capillary water

Last updated date: 17th Jul 2024
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Hint: Capillary action is a process whereby the surface tension of water allows the molecules to actually climb up a thin tube almost as if they are resisting the forces of gravity. This helps in uptake of water in plants as well.

Complete answer:
Water that enters the soil is found in different forms that may or may not be available to plants.

Gravitational waterCapillary water
The water is directly pulled down by the force of gravity.The water which is attached between the spaces to the minute particles of soil.
It does not stick to soil particles, but moves freely in between the spaces till it reaches the water table above the bedrock.It forms a good layer around the soil particles, and it is essentially what remains behind after gravitational water has been pulled down through the soil.
It is generally not available to plants for use, unless pumped up by various methods of irrigation or digging of wells.This has a positive water potential and is freely available to plants.
It may also flow down along the water table if there is a slope and run-off into water bodies.

Besides these two, hygroscopic water is present in the soil. Hygroscopic water is bound very tightly to soil particles with a negative water potential, and is not available at all to the plants for use.

Note: Hygroscopic water is not available to plants, and has the other peculiarity that even after all the gravitational water and capillary water has drained out of the soil, hygroscopic water remains bound tightly to the soil particles.