CLASSIFICATION OF SOURCES OF WATER SUPPLY
The various sources of water
available on earth can be classified into the following two categories
PRECIPITATION
Surface
sources such as
1.Lakes(natural)
2.Streams
and Rivers
3.Storage(impounded)reservoir
4.Oceangenerally
not used for water supplies at present
Sub
surface source ssuch as
1.Springs
2.Infiltration
galleries
3.Infiltration
wells
4.Wells&Tubewells(Borewells)
SURFACE
SOURCES are those
sources of water in which water flows over the surface of the earth and is thus directly available
for water supplies
NATURAL
PONDS AND LAKES:
The quantity of water available from pond or lake is however generally small though they are not considered as
principal sources of water supply. It depends on the catchment area of the Lake
Basin, annual rainfall and geological formations.
The quality
of water in lake is generally good and does not need much purification. Larger
and older lakes however provide comparatively pure water then smaller and new
lakes.
Self purification of water due to
sedimentation of suspended matter bleaching of colour, etc… makes the lake
water pure and better when compared to stream or river waters.
STREAMS
AND RIVERS: The
quantity or discharge of the streams is generally low, sometimes even go dry in summer season. Therefore they may be
considered as source of water supply only for small villages. The quality of
water in streams is normally good except the first runoff. But sometimes runoff
water while flowing over the ground is mixed with silt, clay, sand and other
mineral impurities. This can be removed in a sedimentation basin upto certain
extent.
(Rivers are formed when the
discharge of large number of springs and streams. Combine together. Rivers
(Perennial) are the most important sources of water for public w.s.s. Therefore
most of the cities are situated on the banks of the rivers the rivers may be
perennial or non-perennial (seasonal). Perennial rivers flow throughout the
year getting their waters during summer from snow and from rain in winter.
Perennial rivers may be considered as water supply sources directly where asnon
perennial rivers can be used as public water supplies by providing storage
barriers across these rivers.
IMPOUNDED
RESERVOIRS: During
summer the water which is flowing in the river may not be sufficient to feed the town and on the other hand during rainy
season it may be difficult to operate due to flood waters. Therefore hydraulic
structures are constructed across these river valleys forming impounded
reservoirs.
The
quality of water in these reservoirs is not much different from that of lake
water while top waters prove to develop algae, bottom layers of water may be
high in turbidity Co2, iron and manganese and on occasions H2S.
UNDER GROUND SOURCES (OR) SUB-SURFACE SOURCES
They are
nothing but sub-surface sources with regard to their quantity and quality
aspect rainwater percolating into the ground and escaping beyond the reach of
vegetation and either collecting in underground basins or flowing underground
in sub-surface streams constitutes a ground water source.
Generally ground water is clear and
colorless but is harder than the surface water of the region in which they
occur. In lime stone formation, ground water is very hard and dispositive
nature in pipe lines. In granite formations, they are soft. The water as it
seeps down comes in contact with organic and inorganic substances during its
passage through the ground and acquires chemical characteristics representative
of the starter it passes. Bacteria logically, ground water is much better than
surface water except where sub-surface pollution exists.
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