Groundwater is the water present below earth’s surface and is a vast resource of water. Almost 22 percent of water is below the surface land in the form of groundwater. Groundwater is important as it is used for water supply in rural and urban area. It is also often used for municipal, industrial and agricultural use by building and operating extraction wells.


The groundwater is more convenient and less exposed to pollution. So, it is commonly used as water supplies for public.

Groundwater makes up about twenty percent of fresh water supply of the entire world’s water, including oceans and permanent ice.

Groundwater Pollution:

Generally, groundwater is good for drinking. Groundwater that is polluted is less visible and difficult to clean up than lakes and rivers. Most often groundwater pollution results from disposal of wastes improperly including household and industrial chemicals, wastewater from mines, leaking underground oil storage, oil field brine pits, garbage landfills and sewage systems.

Prevention of groundwater pollution can be done through storing rainwater, watertight materials, and collecting leachate with drains.

What is Porosity and Permeability?

Porosity: It is a measure of the void spaces (pores) that exist between particles of clay, grains of sand, or pieces of gravel, in the layer. It is usually expressed as a fraction of the volume of void space divided by the total volume, and written as a percentage between 0–100%.

Permeability: It refers to the ability of water to move between these pore spaces.

Porosity and Permeability Ranges for Sediment:

Sediment Type Porosity Permeability
Uniform size sand or gravel 25-50% High
Mixed size sand and gravel 20-35% Medium
Glacial Till 10-20% Medium
Silt 35-50% Low
Clay 33-60% Low


Groundwater Recharge:

Groundwater recharge is also known as deep percolation or deep drainage. It undergoes hydrologic process, which moves surface water to groundwater. It is a primary method where water enters an aquifer. The recharge occurs at plant roots and is often known as a flux to the water table surface.

Types of groundwater recharge:

Water Cycle: Naturally, through the water cycle.

Anthropogenic Processes: Anthropogenic process is also called as artificial groundwater recharge, where rainwater and reclaimed water is routed to the subsurface.

Practise This Question

A cubical block of side 'a' is moving with a velocity 'v' on a smooth horizontal plane as shown in the figure. It hits a ridge at point O. The angular speed of the block after it hits O is: