Tuesday, September 1, 2009

Effect of Urbanization on Ground water in Ranchi city, India.

Ranchi people needs 33858160 liters of water per day.
Dr. Nitish Priyadarshi

Ranchi the capital city of Jharkhand state of India is located at 23.350 N and 85.330 E. The total area covered by Ranchi-Municipal area is about 141 square kilometers and the average elevation of the city is 645 m above Mean Sea Level (MSL). As of 2001 India census Ranchi had a population of 846,454.

Water supply, in adequate quantity and at desirable quality, is essential for any sustainable urbanization. Water supply in Ranchi dates back to more than 50 years ago.

There are three main dams ( Hatia, Rukka, and Kanke dam) from where the water is supplied to the city. Surface water is always vulnerable to pollution. People of Ranchi are dependent more on purer source like groundwater. Of the total consumption more than 60% comes from groundwater storage. Due to increasing population more pressure has developed on groundwater from the aquifer beneath the city.

The process of urbanization and industrialization from last 20 years has caused changes in the water table as a result of decreased recharge and increased withdrawal. Many of the small ponds which were main source of water in the surrounding areas are now filled for different construction purpose affecting the water table. Lots of DEEP- BORING in the Ranchi city has also forced the water table to move down as well as Ranchi plateau

Large scale abstractions always bring changes in the natural system of the aquifer and also in the environment. Over exploitation of groundwater beneath some large cities of the world has resulted in serious environmental hazards like groundwater quality deterioration.

The International Conference on Water and Environment, Dublin, 1992 enunciated two crucially important guideline principles, namely, that all human beings have a basic right to access to clean water and sanitation at an affordable price, and that water has an economic value in all its competing uses and should be recognized as economic good.

Groundwater in Ranchi city:

Groundwater in Ranchi city is mainly stored here in secondary porosity features or void spaces developed as result of weathering, fracturing, jointing, shearing or faulting phenomena. The gneisses and granitic rocks with associated schists and quartzites constitute the main consolidated rock terrain of Ranchi district.

Major portion of Ranchi city which is part of the Chotanagpur Plateau occupied by hard rock which are devoid of primary porosity and occurrence and movement of groundwater is controlled by the joints, fractures and fissures present in them.

During the long span of geological history these rocks have been deformed and tectonised in many ways including deep erosion.

In Ranchi city water table in the consolidated formations is now at its lowest from April to June. Water table is at its highest peak during August, gradually stabilizing in the month of November.

Sources of groundwater recharge in Ranchi city and the other parts of Jharkhand State is the vertical percolation of rain water. Although city experiences about 1000 to 1200 mm rainfall annually, the rate of vertical percolation is hindered by the presence of highly weathered and metamorphosed rocks. The Ranchi plateau gradually slopes down towards south east into the hilly and undulating region of Singhbhum. Due to this uneven topography the rain water are lost through surface runoff resulting in less water percolation below the surface. The thin soil layer of Ranchi plateau which is becoming more thin due to weathering is gradually loosing its water retaining capacity, Moreover, present land development practices in the recharge area and natural canals or rivulets in and around the city is also reducing the natural recharge significantly. More than 40% of the rain water is lost in the form of surface runoff. The rate of decline ranges between 1m/year to 5m/year at different observation locations within the city.
The daily physiological consumption of drinking water for human varies from 1- 4 L per capita per day, depending upon the climate ( high in the summer), the kind of work a person does (a manual worker working in open sun would need to drink more water, than a person working in an air-conditioned office), and social habits. If we calculate total consumption of water it increases up to 40 L per capita per day especially in the country like India . Seeing the population of Ranchi, i.e. 846454 we can easily calculate average consumption of water in Ranchi city for domestic purpose per day. It is 33858160 L per day and it is increasing many fold every year. If we add the water being used in construction of houses, malls, buildings the figure will be more. As Ranchi is becoming one of the important business center in Eastern India there is a rampant increase in construction and expansion of city. Due to inadequate water supply from the dams, dependency on ground water is increasing. Over pressed zones are Upper Bazar, Main Road, Ratu Road, Chutia, Hindhpirhi, Circular Road, Burdwan Compound, Lalpur and Harmu Road.

Long term large-scale abstraction of ground water have deleterious effects on water quality, resources and ecology over a wide area.

Water quality deterioration due to overexploitation can take place in a number of ways. Depression in ground water level may result in reversal in flow directions and restrict ground water circulation. Restricted ground water circulation favours mineralization and thus increases the total dissolved solids (TDS) in the ground water. The results of ground water analysis indicate that fluoride is distributed heterogeneously in ground water of the city. Fluoride in high concentration is found in ground water of southern, western and southwestern zones of the Ranchi city. The water is found to be slightly acidic in nature and high in iron concentration in most of the zones.

Potential sources of contamination:
From experiences of other major cities of the world and observation made in Ranchi city, the possible sources of contaminants can be categorized as follows.

Municipal wastes:
Ranchi city is growing faster and without any proper municipal waste dumping policy, municipal waste can be seen dumped here and there in the city. Most of the by lanes in the city are chocked with municipal solid wastes. This municipal waste poses a serious threat to ground water quality. Leachate from a landfill can pollute ground water if water moves through the fill material. Possible sources of water include precipitation, surface water infiltration, percolating water from adjacent land, and ground water in contact with the fill. The problem of pollution from landfills is greatest where high rainfall and shallow water tables occur. Municipal waste, also called urban solid waste, is a waste type that includes predominantly household waste (domestic waste) with sometimes the addition of commercial wastes collected by a municipality within a given area. They are in either solid or semisolid form and generally exclude industrial hazardous wastes.

Municipal waste of Ranchi city is composed mainly of:

1.Biodegradable waste: food and kitchen waste, green waste, paper (can also be recycled).
2.Recyclable material: paper, glass, bottles, cans, metals, certain plastics, etc.
3.Inert waste: construction and demolition waste, dirt, rocks, debris.
4.Composite wastes: waste clothing, waste plastics.
5.Domestic hazardous waste (also called "household hazardous waste") & toxic waste: medication, paints, chemicals, light bulbs, fluorescent tubes, spray cans, batteries.

Municipal wastes produce toxic and carcinogenic chlorinated hydrocarbon solvents (CHSs) which have been found to contaminate ground water in many urban areas of the world. The CHSs are the components of the leachate produced at the disposal sites. Alongside with CHSs, leachate also contains higher amount of other dissolved solids which can also be potential source of ground water pollution. The concentration of CHSs in potable water is very hazardous, even at very low concentrations. Important pollutants frequently found in leachate include BOD, COD, iron, manganese, chloride, nitrate, hardness, and trace elements. Hardness, alkalinity, and total dissolved solids are often increased, while generation of gases, such as methane, carbon dioxide, ammonia, and hydrogen sulfide, are further by-products of landfills.

Polluted surface water:
Ranchi city is bounded by several small rivulets like Harmu river, Jumar river, Potpoto river, etc. These rivers are becoming sites for indiscriminate disposal of municipal, household and industrial wastes which may contaminate the city groundwater. This is particularly true for the Harmu river as the flow of the river is chocked with different household and municipal wastes. This river may pose major threat to the ground water quality.

Liquid waste:
Due to lack of proper drainage system most of the house hold liquid waste are sent in the disposal wells underground. Such disposal wells or soak pit tanks have been criticized from a health standpoint because of the potential for pollutants to be released directly into an aquifer. The problem is most critical where disposal wells are near pumping wells. Leakage from these wells can introduce high concentration of BOD, COD, nitrate, organic chemicals, and possibly bacteria into ground water.

Protection of ground water:

It is evident from the foregoing discussion that the aquifer beneath the city is getting overexploited and as consequence ground water resources are being depleted. Quality deterioration, an associated phenomena, of overexploitation, may be encountered. This quality deterioration will be relatively high in the overexploited and thickly populated areas. Once pollution has occurred, the water has to be treated at the point of abstraction. The cleanup of an aquifer is a very difficult task. It follows that every effort should be made to prevent the contamination of the ground water in the first instance. Rain water harvesting, harvesting of surface runoff and ground water recharge should be done in community level.
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