Jobghost.blogspot.com
provides the study materials for most important topics in Civil engineering for
the candidates who are going to appear for the GATE-2016 examination. Here the
“ENVIRONMENTAL ENGINEERING-Sources of water” topics are explained. And also the
GATE-2016 practice sets, Example problems, previous year Question papers are
available in jobghost.blogspot.com.
1. Source of water:
Water is the important
factor for human beings to survive. So the water should be supplied to the
people. The study of these collection and supplying system is called water
supply engineering. Before going to this we need to know the various sources of
water.
There are two types of
water available in the world.
i. Surface water
ii. Sub-Surface water
Surface water is openly
available over the surface area. We can collect it easily without much trouble.
But Sub-Surface water is available in underground. So it should be collected by
using pumping mechanism. The surface water get polluted by dust and wastes
dumped over it. And the ground water get polluted due to minerals present in
the underground also the dumping underground wastes.
Let us see the Sources
of Surface water…
Surface water- Sources:
Water is openly
available in the ground surface
a) Lakes and ponds:
The lake water is
available over large area and contains plenty of algae, weed and other
vegetable growth imparting bad smell, taste and colour to the water. Lakes and
ponds are natural water sources.
b) Streams and rivers:
Stream water is very
pure when it comes from the mountains. But when it reaches the plain surface it
quality deteriorates considerably. It takes lot of suspended impurities such as
clay, silt, etc., while flowing. Stream is a small channel and river is a big
channel.
c) Storage reservoir:
Storage reservoirs are
used to store the water over the large area for the large cities. This plays a
major role for the water demand. It is an artificial water source.
Reservoir Yield => It is the amount of water
which can be supplied from a reservoir in a specified interval o0f time. And it
is depends upon the inflow of reservoir.
Safe reservoir Yield => It is the maximum quantity of water
which can be taken from the reservoir during critical time period or Dry
period.
Secondary Yield => It is the quantity of water
available in excess of safe yield during the period of high flows.
d) Oceans:
As we know that, ocean
is the largest water source contains salinity .The removal of salt from sea
water is called “Desalination”.
Sub-Surface
water-Sources:
a) Infiltration galleries:
Infiltration galleries
are artificial source of water. Infiltration galleries build along the length
of river over the bank. It is usually rectangle in cross section and held in
horizontal position. The infiltration gallery constructed on the river bed with
permeable wall. So that water can enter into the gallery. It usually located
near perennial recharge source to meet the demand.
So the infiltration
galleries are tunnels constructed along the bed of the river to yield the
seeping water. The yield of water can be calculated by following formula.
K------> Co-Efficient of
permeability
L ------> Length Of Gallery
H ------> Height of Water table
Above Bed
h -------> Depth of water in
gallery
R ------> Radius of influence
a) Infiltration wells:
These are shallow wells
constructed in series along the banks of the river to collect water seeping
through the banks of the river. It actually closed at top and opened at the
bottom. The water seeping through the bed collected in the wells. And these
water is pumped to treatment plant for the further process.
b) Springs:
The groundwater present
in the hilly region may come to the surface due to the pressure. This forced
water is called as streams. This can supply a small quantity of water for the small
towns near the hilly region.
c) Wells and tube wells:
Wells are usually
located in the surface constructed by digging the ground. These wells are not
very deep and yield the water available near the well.
Shallow Open wells are
the wells which rest in a top water bearing strata and draw their supplies from
surrounding materials.
Deep open wells are rest
on impervious strata and collects water from the bore holes made on the
impervious layer. It mainly collects water from below impervious strata.
Tube wells are long deep
well connecting two or more impervious layer and yields more ground water from
below layer.
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