Sources of Water

◇The various sources of water available on the earth can be classified into following two categories:

a).Source surfaces 

1).Pond and Lakes 

2).Streams and Rivers 

3).Storage Reservoir 

4).Ocean (generally not used for water supply at present) 

b).Sub surface sources or Underground sources 

1).Spring 

2).Infiltration galleries 

3).Infiltration wells 

4).Wells and Tubewells 

◇Surface sources 

~Surface sources are those sources of water in which the water flow over the surface of the earth, and is thus directly available for water supplies.

◇Pond and Lakes 

~A natural large size depression formed within the surface of earth, when gets filled up with water is known as pond or lake. 

~The difference between a pond and a lake is only that of size. If the size of depression is comparatively small, it may be termed as pond and when the size larger it may be termed as a lake.

~The quality of water in a lake is generally good and does not need much purification.Self purification of water due to sedimentation of suspended matter ,bleaching of colour, removal of bacteria etc make the lake's water pure and better. 

~The quantity of water available from lake is generally small.Due to the smaller quantity of water available from them, lakes are usually not considered as principal source of water supplies.

◇Streams and River 

~Small steam channel feed their water to the lake or river. Small stream are generally not suitable for water supply scheme because the quantity of water available in them is generally very small and they may even sometimes go dry.

~River are the most important sources of water for public water supply schemes. River may be perennial or non perennial. 

~Perennial river are those in which water is available throughout the years.  Such river are generally fed by rains during rainy season and by snow during summer season. 

~Non perennial river can be used as sources of public supply by providing storage on the upstream of the intake works. The construction of dam is generally adopted on highly non perennial river. 

~The quality of water obtained from river is generally not reliable, as it contains large amount of still, stand and lots of suspended matters.

◇Storage Reservoirs 

~The pool or artificial lake formed on the upstream side of the dam is known as storage reservoirs.The quality of this reservoir water is not much different from that of a natural lake. The water store in the Reservoir can be easily not only for water supply but also for other purposes purposes.

◇Sub surface sources or Underground sources 

~The water which gets stored in the groundwater reservoir through infiltration is known as underground water. This water is generally pure, because it undergoes natural filtration during the prelocation through the soil pores. They are generally rich in dissolved salt, mineral gases etc.

◇Springs

~The natural outflow of groundwater at the earth's surface is said to form a spring. A previous layers sandwiched between two impervious layers,  give rise to a natural spring.A spring indicate the outcropping of the water table.

~The spring are generally capable of supplying very small amount of waters and are, therefore generally not regarded as a source of water supplies.

~Certain spring, sometime discharge hot water due to presence of sulphur in them.

◇Infiltration Galleries 

~Infiltration gallery are the horizontal or nearly horizontal tunnel constructed at shallow depth (3 to 5 meters) along the banks of river through the water bearing Strata. They are sometimes called horizontal wells.

~An infiltration Gallery is generally constructed of the masonry wall with roof slab, and extract water from the aquifer by various porous lateral drain pipes located at suitable intervals along the length the galleries. These pipes are generally covered with gravel, so as to prevent the entry of the fine sand particles into the pipes. These galleries are generally laid at a slope, and the water collected in them is taken to a sump well, from where it is pumped,treated and distributed to the consumers. It is quite useful when the water is available in sufficient quantity just below the ground level or so.

~Flow pattern and discharge in an Infiltration gallery 

◇Infiltration Wells 

~Infiltration wells are the shallow well constructed in series along the banks of river,  in order to collect the river water seeping through their bottoms. 

~These wells are generally constructed of brick masonry with open joints.They are generally covered at the top and kept open at the bottom. For inspection purpose, manholes are provided in the top slab cover.

◇Wells

~A water well is hole usually vertical, excavated through the earth strata for lifting groundwater to the surface.

~Type of Wells 

1).Open wells 

2).Tube Wells 

◇Open wells 

~Smaller amount of groundwater has been utilised for the ancient time by open wells. Open wells are generally open machinery was having comparatively bigger diameter,and a suitable for low discharge of the order of 18 cubic metre per hour.

~The yeild of an open wale is limited because such well can be excavated only to a limited depth, where the ground water storage is also limited. In such a well, that the water can be withdrawn only at critical velocity for the soil. Higher the velocities can't be permitted as that may lead to disturbance of soil grains, and the consequent subsidence of well lining in the hollow so formed.  

~Depending upon the availability, Types of open wells

a).Shallow open wells:It is the one which rests in a previous strata and draw its supplies from surrounding materials. 

b).Deep open wells:It is the one which rest on an previous motor layers and draw its supply from the previous formation lying below the motor layer,  through a bore hole made into mota layer (layer of clay,Cemented stand,kankar, which are often found lying a few metre below the water table in subsoil.  

◇Tubewells 

~Tube Wells is a long pipe or tube is bored or drilled deep into the ground, intercepting one or more water bearing Strata.

~In the tubewells, larger discharge can be obtained by getting a large velocity as well as large cross-sectional area of the water bearing Strata.

~Depending upon the entry of water through a cavity or a screen, Type of tubewells:

a).Cavity Type tubewell:It draws water from the bottom of well, and not from the side as is done by screen well. It is very economical, as it requires only plain well pipe, which is lowered into the bore, made through the ground strata upto the required depth as to tap the reqisite aquifer. 

b).Screen type tubewells:They are mostly widely adopted and have been extensively constructed in our country particularly for irrigation for purpose. It is subdivided into two types:

1).Strainer tubewells:It uses assembled strainer lengths, which are lowered into the bore hole and located opposite the water bearing formation, whereas plan pipe length are located opposite the non water bearing formation.

2).Slotted pipe gravel pack Tubewells:It uses a slotted pipe without being covered by any wire mesh. Such slotted pipe length are located opposite the water bearing formation as is done with the strainer in the strainer tubewells.