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Thursday, April 23, 2015

Sources of Water-Water supply Engineering

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.
Infiltration gallery yield water environmental engineering
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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