Describe the various sources of water.
Enlist and differentiate different surface and ground water sources.
👉 The various sources of water available on the earth can be classified no the following two categories
(i) Surface sources (ii) Sub-surface sources or underground sources.
(1) Surface Sources They are generally divided in four categories ~
(a) Ponds and Lakes
(b) Streams and rivers
(c) Storage reservoirs
(a) Ponds and Lakes
A natural large sized depression formed within the surface of the earth, when gets filled up with water, is known as a pond or lake. The difference between a pond and a lake is only that of size. If the size of the depression is comparatively small, it may be termed as a pond, and when the size is larger, it may be termed as a lake.
The quality of water in a lake is generally good and does not need much purification. Larger and older lakes, however, provide comparatively purer Water than smaller and newer lakes. Self-purification of water due to Sedimentation of suspended matter, removal of bacteria, bleaching of colour, etc. makes the lake’s water purer and better. On the other hand, in still waters of lakes and ponds, the algae, weed and vegetable growth take place freely, imparting bad smells, tastes and colours to their waters.
The quantity of water in a lake is generally small. It relies on the catchment area of the lake basin, annual rainfall, and geological formations. Lakes are usually not considered as principal sources of water supplies because of smaller quantity of water available from them. They are, therefore useful for only small towns and hilly areas.
(1) Streams and Rivers –
Small stream channels feed thei waters to the lakes or rivers. Small streams are not suitable for water supp] schemes, because the quantity of water may not be sufficient. Larger an perennial streams may be used as sources of water, by providing storag. reservoirs, barrages, etc. across them.
Rivers are the most important sources of water for public water supp schemes. Rivers may be perennial or non-perennial. Perennial rivers are them in which the water is available throughout the year. Such rivers are generall fed by rains during rainy season and by snow during summer season. Perennial rivers can be used as sources of public supplies directly, whereas the nonperennial rivers can be used as sources of public supplies by providing storag on the upstream of the intake works.
The quality of water obtained from rivers is generally not reliable, because it contains large amounts of silt, sand and a lot of suspended matter. The rive waters must be properly analysed and well treated before supplying to the public.
(c) Storage Reservoirs –
A barrier in the form of a dam may sometimes be constructed across the river, so as to form a pool of water on the upstream side of the barrier. This pool or artificial lake formed on the upstream side of the dam is called storage reservoir. The quality of this reservoir water is not much different from that of a natural lake. The water stored in the reservoir cannot be easily used for water supplies but can be used for other purposes such as hydro-electric power generation, irrigation, fishery, etc.
(d) Oceans –
Generally not used for water supplies at presents_
(ii) Sub-surface Sources or Underground Sources –
The underground water is generally available in the following forms –
(a) Infiltration galleries
(b) Infiltration wells
(a) Infiltration Galleries
These are the horizontal or nearly horizontal tunnels constructed at shallow depth (3 to 5 m) along to banks or the river, They are sometimes known as horizontal wells.
An infiltration gallery is generally constructed of masonry well; With roof slab and extracts water from the aquifer by number of porous drain pipes placed at suitable intervals in the gallery. These pipes are generally covered with gravel, so as to prevent the entry of the fine sand particles into the pipes .
These galleries or tunnels 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. These infiltration galleries are quite useful when water is available in sufficient quantity just below the ground level or so.
The infiltration galleries may have width of about 1 m, depth of about 2 m and length varying from 10 m to as long as lOO m depending on the extent of the water field. Seldomely they are deeper than 6 m below the ground level. The quality of water is good and it requires no treatment. The quantity of water from this source is suitable for small water supply scheme.
(b) Infiltration Wells
These are the shallow wells constructed m series along the banks of a river, in order to collect the river water seeping with their bottom. These wells are generally made up of brick masonry with open joins, The water percolates through these joints and gets collected in the wells. The top of the well is covered with KCC. slab having manhole for inspection,
The various infiltration wells are connected by porous pipes to a sump well, called “jack well”. The water reaching the jack well from the different infiltration wells is lifted, treated and distributed to the consumers. The quality of water is good and it requires no treatment. The quantity of water from this source is suitable for small water supply schemes.
The natural outflow of ground water at the earth’s surface is said to form a spring. A pervious layer sandwiched between two impervious layers, gives rise to natural spring-A spring shows the outcropping of the water table. The springs are generally capable of supplying very small amounts of waters, aird are, therefore, generally not used as sources of water supplies. However, good developed springs may sometimes be used as water sources for small towns, especially in hilly areas. Certain Springs, sometimes discharge hot water due to the presence of sulphur in them. These hot springs usually emit sulphur mixed water, and hence cannot be used for water supplies,
though sometimes useful for taking dips for, the cure of certain skin ailments.
The water well is a hole generally vertical, excavated in the earth for bringing ground water to the surface. The wells may be of two types ~
(1) Open wells (2) Tube wells.