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Unit-2
Sources of water
→ Water comes from the three main sources.
i. Rain water
ii. Underground water.
iii. Surface water
i.Rain water
The evaporated water from large water bodies like sea, Ocean, rivers etc. condensed at high altid altitude in the form of clouds and when it falls below the dew point. It starts falling in the form of rain, hails and other forms of water etc. During its fall high altitude to ground its absourbe oxygen, carbon dioxide and other gases along with dust, smokes, bactaria etc.
The rain can be collected in the following.
ways :-
-The roof of the houses [ Rain water harvesting System]
- From prepared catchment
1.The roof of the houses
Water is stored in small underground tonk or cistern for small individual supply.
2.Prepare catchment
The surface of catchment is made impervious by suitable lining materials and suitable slope is given
so that water is stored im in madrate size
reservior. This water is used for
community supply i.e for drinking purpose.
The quality of rain water on the open land is better than that falling on the city quality of rain water of the last season is usually good and can be used after little treatment.
ii.Underground water
The water which is found below the surface of the earth is known as underground water and the source
containing such water is known as underground courtes of water. The main sources of underground water is precipitation portion of precipitation
enter the surface of the earth. In entrance of rain water into the ground is known as precolation. The following are the main underground source of water:-
*Springs
*Wells
*Spring:
A springs is any natural situation where water flows from an aquifers earth surface. Ground water is stored in aquiters
which are underground recerviors. They
contains billions of gallons of water. Sometimes this water reappear at the ground surface in the form of spring. A spring is form when the pressure in aquifers causes the water to flow at the surface. Generally spring form under the following suitations:-
1)When the surface of the earth drops sharply below the normal water table.
2) When due to an impervious obstruction. the ground is collected in the form of reserviors and force the water to overflow. at the surface.
3) When the impervious stratum allows artesian water to flow in the form of spring.
*Well:
Wells are the vertical hole or shaft excavated in the Earth for bringing ground water to the surface wells are mainly divided into two types:
1.Open wells or dug wells
2. Bored or drilled or tube wells
Open wells:
These are sallow wells which are usually confined to coll ground, sand. graval to interupt water from top must water bearing stratum. the wells are suitable for small discharge about 20m³/hr. Open wells are mustly constructed in circular shape having diameter between I to 10m and depth may be upto 20m. The walls of these wells may be constructed with precast RCC or stone masonary.
Open wells are cheap in construction.
Bored well:
The discharge avilable from the odinary open well is very low. Due to their low discharge only useful for small locality area for private building etc. For obtaining discharge nowadays tube wells are commonly used. A tube well is long pipe sunk into the ground with the strainer which allows water to pass through but prevents sand comming along with water because of the strainer water can be taken out from aquifers at high velocity without danger of soil particals being carried away. These well receive their discharge from large number of danger of aquifers hence, their discharge capacity is much more than odinary open wells.
A tube well consists of long special pipe with strainer installed deep below the surface earth to tap water from various water layers.
-The depth of table from various water layers well may vary from 50 to 500m
-The maximum yeil of tube will be upto 200 liter per second.
-The yeil of average tube well is 50 liter per second.
-The discharge is more than one layer of water so maximum amount of water chould be produced in tube well.
-The quality of water from tube well is much better then open wellas they drew their supplies from deep.
iii. Surface sources
There are basically 5 surface sources of water. They are :-
1)streams
2)Lakes
3)Rivers
4)Pound
5)Impounded Reservoir
Impounded Reservoir:
It is found that their is great variation in the quantity of water in the river. In Monsoon and summer & season in some rivers the flow become very small and connot met the requriment of hot weather. In such cases it becomes essential to store water of monsoon to summer season. The water can be stored in the river by constructing a dam across the river at suitable location. The reservior thus formed is known as impounded reservior.
Sources selection of water
There are mainly two sources of water:- 1)Surface water
2)Ground water
Both the sources may be selected for the public water supply scheme. The selection. of particular sources depond upon permanency adcquancy and cast of the scheme. The selected cources should have the capability to fulfil water demand of targeted group through the year. In addition the sources should be located at such place from where water can be distrubuted to consumer easily at low cost.
Following are the main part points to be considered while selecting a source:-
-Quality of water
-Quantity of water
-Location of source
-cost
1)Quality of water:
Quality of water is the most important point to be considered while selecting sources. The quality of water in the source should be good chow that it can be treated easily at low. cost. It should not contain diseases i germs and pathogenic bacteria which may endanger the public health.
2)Quantity of water:
→ The selected sources of water should have sufficent quantity of water to meet the various demand of the city throughout the year. The selected source should be able to meet present as well as future demand of the city. The source of water chould able to met maximum demand in dry weather also.
3)Location of sources:
→The sources should be selected at such location which is free from polluation. If possible sources should be selected at high altitude so that water can be supplied to the consumer by gravity system avoiding the cost of pumping.
4)Cost
→The cost of water project should also be taken into account while selecting the sources of water. The cost of water supply scheme depend on supply on many factor such of system, distance between sources and supply area, method of distribuation, treatment of method etc.
Volumetric method of discharge measurement:-
→volumetric method of discharge measurement is the simplest way to estimate the flow by direction direct measurement of time to fill a container of known volume. The following procedure is formand followed to measure discharge from the source:-
1)Take a suitable size of container and determine its volume Let volume be V liter.
2)The flow from source is diverted into a channel or pipe which discharge into a container.
3)The time requried to fill the container is measured accurately with the help of stop watch Let time be T second.
4)Discharge is calculated as Q=V/T liter per second
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