The chief sources of all water supplies are rainfall. This water after getting proper treatment we get from municipal corporation/water supply department i.e. public health engg. Department.
Other source of water is underground water. Water that has percolated into the ground is brought on the surface.
The upper surface of free water in the top soil is termed as ground water level/ table.
Form in which underground sources are found infiltration galleries. Infiltration wells are sunk in series on the bank of river. Other source is spring an outcrops of water. A ground well is defined as an artificial hole/pit made in the ground for the purpose of tapping of water. Following are types of wells-
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(a) Shallow wells.
(b) Deep wells
(c) Tube wells
(d) Artesian wells.
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Tube Wells –
Tube wells are of type-
(a) Strainer type
(b) Cavity type
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(c) Slotted type
(d) Perforated type.
Tube Wells:
Bores are made into the ground by hand & mechanically operated augers, percussion equipment or drilled by coring rigs.
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The most common bores are made by augers in which a pipe is inserted on a hand pump with a suction pipe is installed. Hand pumps are for local use and the wells are exposed to the same pollution risks as the dug wells.
A more scientific deep-bore hand pump called Mark IV, for drawing safe water from deeper strata, has been developed by Indian Scientists, and is now being extensively used in rural water supply schemes in India,.
Tubewells deeper than 30 m or so have a lesser chance of being polluted. The possibility of contamination in any Tubewell should never be discounted and water should be tested often to ensure safety.
Tube well is deep well having diameter 50 to 200 mm.
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A bore is drilled in the ground (Percussion core rotary drilling m/c.) For testing the yields of a well recuperation and constant pumping test is done, pipe for tube well is then inserted in the bore hole.
It consists, of strainer and blind sections. A strainer is a perforated pipe which is provided with an arrangement such as that only water will be admitted to inside of the pipe. Pumping is then started.
Maintenance of a Tube Well:
Use in the grounds and gardens, then it is essential to ensure that there is no possibility of the contamination of potable water supplies with these lower-quality supplies, The two systems must be physically isolated and outlet points with non-potable’ supplies must be clearly labeled as not suitable for drinking.
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(i) Cleaning of screen with hydro sulfuric acid. Hydrochloric acid.
(ii) Removal of lime particles – clogging of screen.
(iii) Replacement of parts. Failure of tube well is due to
(i) Corrosion
(ii) Incrustation – deposition of alkali salts on the inside walls of the tube well.
Types of Well Construction:
(a) Dug well – Shallow well
(b) Driven well – Deep well in unconsolidated solid
(c) Bored/Drilled well.
Sanitary Protection Of Well:
(a) Water tight connection of pump
(b) Covered top
(c) Casing depth 3m below the ground water table.
(d) Distance from the source of contamination, minimum 90 m
(e) No presence of trees
(f) Priming of pump by safe water
(g) Washing of cloth should be prohibited
Open Streams/Springs Etc:
(a) Whenever no other water source is available, it may be necessary to tap a local water-stream or river. However, the quantity, quality and dependability of the source have to be investigated. The methods of treatment e.g. filtration disinfection and storage must be decided on the basis of the results of these investigations.
(b) When the source of water is far away from its area of consumption a detailed survey of the area, route of pipe line has to be made for laying the water mains.
Rain Water Harvesting:
Conditions for Rain Water Harvesting
Many area endowed with a fair amount of natural precipitation do not have geographical or subsoil conditions to absorb and impound the rain water.
Rivers:
Rivers are commonly used as a source of water but normally require treatment before use particularly in downstream sections, rivers are often contaminated with waste materials from industry, agriculture and communities. Rivers are classified in terms of their quality:-
» Class 1a, Good Quality: water of high quality suitable for potable supply abstractions; game or other high-class fisheries; high amenity value.
» Class 2b, Fair Quality waters suitable for potable supply after advanced treatment supporting reasonably good coarse fisheries, moderate amenity value.
» Class 3, Poor Quality; waters which are polluted to an extent that fish are absent or only sporadically present; may be used for low-grade industrial abstraction purposes; considerable potential for further use if cleaned up.
» Class 4, Bad Quality; waters which are grossly polluted and likely to cause a nuisance.
Lakes (Natural and Artificial):
Where there is a shortage of underground water, lakes or artificial reservoirs may be used to provide water supplies but this water usually needs some form of treatment prior to use recently, there has been an increase in the occurrence of algae blooms caused by the growth of blue-green algae.
Some of these algae produce toxins which are poisonous to fish and mammals. The same classification scheme is used for rivers and lakes.
Oceans:
The oceans represent the most abundant source of water on the planet, but the cost of desalination is usually prohibitively high and therefore sea water is not often used as a source of water. Coastal waters are often contaminated with sewage and heavy metals.