Sources of water• The various sources of water available for potable water are classified as Surface and underground

• Surface water sources consists of; Rivers and Streams; Ponds and lakes, Reservoirs and oceans while,

Subsurface water sources are springs, infiltration wells, and tube wells.

• Surface sources of water supply: Surface sources of water are readily available for water supply. These

sources are (i) Natural ponds and Lakes; (ii) Streams and Rivers ; and (iii) Reservoirs.

Ponds and Lakes: A natural large sized depression formed within the surface of the earth, when gets filled

with water is pond or Lake. When the depression is small is pond, while large size is lake. The source of

water is the catchment area to which the streams or drains contribute. Sometimes the underground water

through springs enters into it. The quantity of water from such sources depends on catchment area,

rainfall and geological formation. Such source of water is useful for small community like villages or town.

The Quality of such source is generally good and does not need proper purification. Natural purification of

water due to sedimentation of suspended matter, removal of bacteria and bleaching of color further

purify water. The problem of algae, weed and vegetable growth take place, imparting bad smells, taste

and colors to their waters.

Streams and Rivers: small streams channels feed the water to lakes and rivers. Such source of water is

not reliable for water supply as of less quantity and sometimes dry. They are useful for small community.

Larger and perennial streams may however be used as a sources of water supply. Rivers are the important

source of water supply schemes. Perennial rivers can be used as sources of public supplies by providing

storage on the upstream of the intake works. On non perennial rivers dams has to be constructed.

• The water quality of rivers is not reliable as it contains large amount of silt, sand and other suspended

matters. The disposal of untreated sewage further contaminate water. The river water must therefore be

properly analyzed and well treated before supplying to the community.

• Reservoirs: A water supply scheme using river or stream water directly may not satisfy the consumer

demand during low flow, while a high flows it is difficult to withdraw water due to flood situation. A

barrier therefore be constructed across the river so as to form a pool of water on the upstream side of

the barrier. This pool is known as storage reservoir. The stored water can not be used only for water

supply but also for other purposes as well. The quality of such reservoirs is like a lake.

• Surface water supplies are classified as to whether they come from a lake, reservoir or river. Generally a

river has the lowest water quality and a reservoir the highest. River water is quality is largely influenced by

point source pollution like municipalities, industries and non point source pollution like agricultural

practices. During rains or period of runoff of turbidity increases, making water more polluted. Some of the

river water have color, taste and in odor producing compounds.

• Reservoir and lake sources have much less day to day variation than rivers. Also the quiescent conditions

will reduce both turbidity and color.

Sub surface or underground sources: The water which store in the ground water reservoir through

infiltration is under ground water. This water is generally uncontaminated but may contain aesthetically or

economically undesirable impurities. Such water are rich in dissolved salts, minerals and various gasses.

Ground water may be classified as

3

Ground water

Surface water

Shallow Well Deep well

Lake Reservoir River or stream

General characteristics of ground water and surface water

Ground water Surface waterConstant composition Varying compositionHigh mineralization Low mineralizationLittle turbidity High TurbidityBacterial safe Microorganisms presentNo dissolved oxygen Dissolved oxygenHigh hardness low hardness

(i) Shallow Well and (ii) Deep well

• Ground water is classified as deep or shallow wells. Deep wells usually have high concentration of iron,

calcium, magnesium, manganese, carbonate and other minerals. Shallow wells are recharged by a nearby

surface water sources. It may have qualities similar to the deep wells or of the characteristics of Surface

water. Strata of sub soil act as filter and remove the suspended impurities as water infiltrated into the soil.

• Selection of Source of Water:

When selecting a source of water supply the following points consideration is essential

Quantity: The quantity of water available at the source must be sufficient to meet the demands during the

entire design period of scheme.

Quality : The available water must not be toxic or other injurious to health. The impurity present in water

must be as less as possible and should be easily removable by treatment.

Distance of source supply: The source of water must be situated as near the city as possible. It reduce the

cost of pipe lines as well as other appurtenances as required for distribution of water for consumption.

Topography of the area: The area between the source and the city should not have more depressions and

elevation. In such uneven topographies, the cost for conveyance of water by pipes or constructing of

tunnels increase the cost of water supply schemes.

Elevation of source of supply: The source of water must be on high contour, so as to flow water by gravity.

When the water is available at low elevation than the city level, pumping has to be used, which involves

huge expenditure and possible breakdown.

Water supply for Rural Area• More than 60% of Population living in rural area where a high percentage of population having no access

to piped potable water. It is not feasible to cover all villages with potable water supplies because of;

• Scattered and inaccessible nature of villages;

• Non availability of nearby water sources;

• Non availability of adequate funds to take up those projects which may serve few people, and hence may

not become financially viable.

On the basis of these constraints, it is difficult to supply piped potable water to the villages through a full

fledged conventional water treatment plant, and hence special simple methods are adopted to treat the

available water supplies in rural areas.

Most of our villages depend upon the ground water supplies to be extracted through wells and tube wells.

In hilly areas natural springs also available. The nature of treatment depend upon the quality of water

source available. The river and stream water containing low concentration of dissolved salts, high organic

and inorganic pollutants, and turbidity. Such water is generally not fit for drinking purposes without

proper treatment. The Lakes water are comparatively clean in those areas where industrial and urban

sewage are not discharges directly into it. Some times the growth of algae affect the quality of water and

make it unfit for drinking purposes. Springs are natural sources of ground water and is normally clean

water which can be used for drinking purposes. Proper protection of the site of spring from defecation

and drainage is important to avoid its contamination. Such sources of water can be used for community

without pumping at minimum cost and maintenance.

Rain Water Harvesting• Rain water harvesting is the collection of rainwater from the roofs and paved courtyards of houses either in

storage tanks or in the ground water reservoir. The collected water serves as a proper source of drinking water

in rural areas or in such areas where high rainfall occurs. This technique can also be used in urban areas where

more rainfall occurs, and other sources of water is scare, while the ground water levels have gone down. In its

simplest form the roof water is taking down through a pipe from the roof outlet to the ground floor, which can

be connected to a water tank. The rainwater before collection should be passed through a porous media like

sand or charcoal filter for removal of suspended particles and microorganisms that gained due to runoff. The

sand or sand and charcoal layers are usually followed by gravel layers. In this way two to three layers of sand

and gravel are arranged. Similarly, these filters must be cleaned periodically to prevent clogging of its pores. The

roof must also be as cleaned as possible at the time of rain fall. The sand filters must be periodically cleaned to

prevent clogging of its pores.

• Rain water collection for Direct Use. The rainwater for direct use can be collected from the roof into a storage

tank of plastic. RCC or masonry. The tank can be placed either above or below the ground depending on the

availability of space. The filter must be cleaned and disinfectant regularly. Where sufficient space is available,

the water can be stored in an open excavated pond, which acts as a settling pond for impurity. Similarly, if the

direct use of harvested water is not possible then such water can be used to recharge the ground water. For

such activity either the rain water is directing to infiltrate into the ground to improve the water table or through

a recharge pit or well, depending upon the available opportunities.

• Selection of suitable source of water for Rural Areas: When more than one possible source of water is

available, the choice should be made in order of the following priorities

(i) reliability of the source

(ii) Purity of the water available in the source; and

(iii) The ease with which the water from the source can be supplied to the consumers.

If water supply is planned from an unexploited source, laboratory tests are essential to know the level of

impurity and the need of treatment. Multiple samples taken over a period of time will provide more

information than a single sample. Samples should be analyzed soon after collection as some biological and

chemical changes occurs with time. The parameters to be tested for a given water source is depend on the

type of water source. Like for surface water and shallow wells BOD, Chlorine demand and ammonia test is

required. For deep wells the hardness, pH value, dissolved metals like lead, iron, fluoride, arsenic and

nitrates tests are required.

• Water Treatment Methods For Rural Supplies OR Appropriate technology for water supply. The water

treatment for rural area and small community depends on the quality of raw water, and the availability of

allocated funds to meet the cost of treatment as well as the operation and maintenance. The allocated

funds for rural areas are usually scare and not sufficient to meet the cost of conventional treatment plant.

Majority of water supply in rural areas are from wells and tube wells the quality of which is acceptable. In

some area just chlorination has to be done to eliminate bacterial contamination if present in water supply.

When tube well are used for water supply, then some chemical tests like nitrates, fluoride iron,

manganese tests are required.

• Excess nitrates are usually found as the end product of biodegradation of Human and Animal excreta. If

concentration of nitrates are high, then alternate source may be considered. If alternate source is not

available then even high concentration of Nitrates containing water be used.

• Excessive Fluoride in drinking water caused fluorosis