Springs - Subsurface Source of Water | Water Supply Engineering

Spring is a natural outflow of groundwater which is appeared at the ground surface in the form of a current or steam of flowing water. It is mainly seen in hilly areas.

As shown in the figure, it's a hilly mountainous region with a higher level of water table. If we dig at a particular point at this level, water splits out and is called springs. 

Fig.1. Springs-Subsurface Sources of Water

Springs can be classified into gravity and non-gravity springs. 

1. Gravity Springs

Gravity springs result from the water that flows under hydrostatic pressure. It can be classified into:

1. Depression springs
2. Contact or surface springs
3. Artesian springs

Depression Springs

Depression springs are formed when the water table intersects with the ground surface, due to which the water overflows. These type of springs varies based on the lowering and raising of the water table. 

In order to meet such fluctuations of springs, a trench is constructed near such a spring as shown in figure.2. 

Fig.2. Depression Springs

If the trench is constructed deeper, the saturated ground or water table will be above the elevation of the trench bottom. This helps to act continuous flow of water and compensate for fluctuations of the water table. The water collected in the storage act as a storage reservoir.

Contact Springs or Surface Springs

Surface springs or contact springs are formed when a permeable water-bearing formation that lies over an impermeable or less permeable formation, intersects the ground surface as shown in figure.3.

Fig.3. Surface Springs

This source of water is relatively small in amount and is likely to cease after a drought period. So, a cut-off wall or cutoff trench can be constructed to develop these springs.

Artesian Springs

Artesian springs result from the release of water under pressure from a confined aquifer either at an outcrop of the aquifer or through an opening in the confining bed as shown in figure-4. 

The amount of water that is available in an artesian spring is large when the catchment area is large.

Fig.4. Artesian Springs or Wells

As shown in the above figure, the well is dug into the confined aquifer - called the artesian aquifer, and we get water in the artesian well. 

2. Non-Gravity Springs

Non-gravity springs include volcanic springs and fissure springs. These are thermal springs that discharge water having higher temperatures in excess of the normal local groundwater. Also called as hot or warm springs. They are highly mineralized and have sulfur content.

Fig.5. Hot Springs

Water Supply Using Surface Spring

Springs can be considered as a source of water supply to meet the demand for small towns near hills or bases. Hot springs cannot be used to supply water for domestic purposes. 

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