Theoretically there are three types of groundwater, although you may not be able to access all.
- This constitutes the bulk of what you may exploit.
- It originates in the atmosphere, falls as precipitation and percolates through the soil to become groundwater.
- You may have noticed the fluctuation of the water level in wells. Yes, during the rainy season the level goes up while in the summers the level goes down.
- This is indicative of the fact that groundwater significantly depends upon water from the atmosphere.
- Another way in which the groundwater may be derived directly from atmospheric moisture is condensation of water vapour from air circulating through the pores and interstices.
- This is also known as condensational water and is the basic source of replenishment in the arid and semi-arid areas.
- During summers, the land is warmer than the air in the soil.
- This results in a difference of pressure between the water vapour in the atmosphere and the soil.
- The water vapour from the atmosphere penetrates into the rocks as the temperature of the water vapour drops in the cooler soil.
- A certain amount of water may accumulate this way.
- A third source is influent seepage from lakes, rivers, oceans and also man-made channels but the importance of this varies with the climate of the area concerned.
- In fact in humid regions, the groundwater contributes to stream flow by means of effluent seepage, and the gradient of this saturated groundwater more often than not slopes towards the surface water bodies and the oceans.
- This is the water that is entrapped in the interstices of sedimentary and volcanic rocks at the time of deposition.
- Connate water is highly mineralized and salty and does not mix readily with meteoric groundwater.
- Connate water is usually found deep down in the lower layers of the zone of saturation.
- Such water is considered to have been generated in the interior of the Earth.
- It has consequently travelled to the upper layers of the Earth’s surface for the first time; it is also known as magmatic water.