Wednesday, October 7, 2009


Dr. Nitish Priyadarshi

Whether for irrigation, power generation, drinking, manufacturing, or recreation, water is one of our most critical resources. Visual Image interpretation can be used in a variety of ways to help monitor the quality, quantity, and geographic distribution of this resource and also deciphering ground water with help from aerial photograph.

Sediment pollution is often clearly depicted on aerial and space images. Materials that form films on the water surface, such as oil films, can also be detected through the use of aerial and satellite images. Normal colours or ultraviolet aerial photography is often employed for the detection of oil films on water.

Thick oil slicks have a distinct brown or black colour. Thinner oil sheens and oil rainbows have a characteristic silvery sheen or iridescent colour banding but do not have a distinct brown or black colour.

Jharkhand State now a days is affected with ground water scarcity forcing the people to depend on the surface water like lakes, rivers etc. which are polluted like Damodar river and Suwarnrekha river. Damodar river flowing through coal fields is affected with sediment pollution carrying coal mining wastes leading to lowering of water level from November to June.
In this paper, we are concerned principally with the use of visual image interpretation in water pollution detection, and deciphering of groundwater with special reference to Jharkhand State of India.


Water pollution is any physical or chemical change in water that can adversely affect organisms. It is a global problem, affecting both the industrialized and the developing nations. It is harmful to humans, animals, to desire able aquatic life or otherwise causes significant departures from the normal activities of various living communities in or near the bodies of the water.
All naturally occurring water contains some impurities. Water is considered polluted when the presence of impurities is sufficient to limit its use for a given domestic and /or industrial purpose. Not all pollutants are the result of human activity. Natural sources of pollution include such things as minerals leached from soil and decaying vegetation. When dealing with water pollution, it is appropriate to consider two types of sources: point and non point. Point sources are highly localized, such as industrial outfalls. Non-point sources, such as fertilizer and sediment runoff from agricultural fields, mining wastes, have large and dispersed source areas.

It is rarely possible to make a positive identification of the type and concentration of a pollutant by visual image interpretation alone ( Lillesand and Kiefer,2000). However, it is possible to use visual image interpretation to identify the point at which a discharge reaches a body of water and to determine the general dispersion characteristics of its plume. In some instances, such a s the case of sediment suspended in water, it is possible to make valid observations about sediment concentrations using quantitative radiometry coupled with the laboratory analysis of selective water samples. Sediment pollution is often clearly depicted on aerial and space images.

According to Verner (1977) the detection of pollutants in water is more complex because the light attenuation characteristics of water limit detection of below-surface pollutants to the visible and near-visible portions of the spectrum. Even for surface pollutants, detection is often difficult, because the characteristic scattering or reflection of sunlight by pollutants is a function of the state of surface roughness as well as the angle of incident and reflected sunlight. Also, many dissolved chemicals have no spectral signature detectable through remote analysis. On the other hand, there are classes of pollutants that may be detected when water surface conditions and sun angle permit. These are particulates, algae, petroleum products, and thermal anomalies.
Materials that form films on the water surface, such as oil films, can also be detected through the use of aerial and satellite images. Oil enters the world’s water bodies from a variety of sources including natural seeps, municipal and industrial waste discharges, urban runoff, and refinery and shipping losses and accidents. Thick oil slicks have a distinct brown and black colour. Thinner oil sheens and oil rainbows have a characteristic silvery sheen or iridescent colour banding but do not have a distinct brown and black colour (Lillesand and Kiefer,2000).

Direct human interventions over the years have lead to reduction in groundwater recharge. These include deforestation, destruction of local water systems (including traditional water systems, e.g. ponds, tanks, lakes, wetlands and so on). Deforestation also leads to change in river flow regime in the affected area that also affects the recharge in the given area.

There are larger and indirect human interventions that has also affected the groundwater recharge systems, including urbanization, concretization of more and more land, the those factors that lead to global warming also contribute in reduction in groundwater levels as evapo-transpiration needs are higher when temperatures go up, leading to more groundwater use.
Mining also leads to destruction of groundwater recharge systems in the mined areas. In fact mining areas (like Jharkhand) groundwater is many times unnecessarily pumped out to the near by rivers so that mining becomes possible.

A knowledge of groundwater location is important for both water supply and pollution control analysis. Groundwater is one of the most important source of water. Almost 85% of the rural water supply in India is dependent on groundwater (Ministry of rural Development, government of India). Remote sensing plays a vital role in delineating potential areas of groundwater occurrence for detailed exploration, thus reducing the cost and time involved in groundwater exploration. Potential groundwater areas cannot be seen on satellite images directly. The clue to the groundwater search is the fact that sub-surface geological elements forming aquifers have almost invariable surface expressions, which can be detected by remote sensing techniques (Joseph,2005). Satellite data provide information about geomorphic features, structures, land uses and rock types (in a few cases) indicating the presence of groundwater. Some selected landforms and structural features that are indicators for potential groundwater zones are valley fills, palaeochannels, alluvial fans, dykes, interdunal depression etc.

Case study of Jharkhand State:

Jharkhand meaning “forest tract” is the ancient name given, as a whole, to the forested upland geographically known as the Chotanagpur plateau forming the north-eastern portion of the peninsular plateau of India. It is a region of great unevenness consisting of a succession of plateaus, hills and valleys drained by several large rivers such as the Damodar, Subernarekha, Barakar etc.

On the basis of physiographic consideration, this plateau can be further sub-divided into the Ranchi and Hazaribag plateau.

The Chotanagpur plateau as a whole represents a denuded old land surface constituted of granitic rocks with associated metamorphic and basic igneous rocks as also two linear stretches of Gondwana rocks having coal basins running east-west in Hazaribag, Palamau and Dhanbad districts and north-south in Santhal Parganas districts, demarcated by faults on either sides.
The plateau has a number of drainages flowing almost in all directions. The northerly flowing rivers are the Son, North Koel, Punpun, Phalgu etc. Amongst the easterly flowing rivers, the Ajoy, Barakar, Damodar and Subernarekha are by far the most important ones. The southerly flowing rivers are the Sankh, south Koel etc. ( Central Ground Water Board Report 1976-1985).
A major part of the Jharkhand State are covered by yellow to reddish and medium light coloured catenary soils (Mahadevan, 2002). In the Netharhat Plateau of Palamau districts and the Rajmahal Plateau, soils derived from basaltic flows are black and heavy and develop wide cracks when dry and swell when wet.

Deciphering surface water pollution from Aerial photographs:-

Large scale mining operations and rapid urbanisation has adversely affected the surface water quality in Jharkhand State. Liquid effluents from coal handling plants, colliery workshops, and mine sites and suspended solids from coal washeries and mine wastes have caused serious water pollution in the region, adversely affecting fish and aquatic life. Damodar and Subernarekha valley are the cradle of industrialization in Chotanagpur plateau region. Damodar is the most polluted amongst Indian rivers. About 130 million litre of industrial effluents and 65 million litre of untreated domestic water finds way to Damodar drainage system every day.
The release of different toxic metals like arsenic, mercury, chromium, nickel etc. from the coals and mine spoil heaps in Damodar and its tributaries have caused severe damage to water quality ( Priyadarshi 2004 ,Priyadarshi 1999).

Sediment pollution is a tedious problem in major rivers of the Jharkhand. Sediments make the rivers, streams, channels and reservoirs to overflow. They also change the flow rates and depth of water systems( Sharma and Kaur, 1994). Sediment pollution is clearly depicted in Damodar river in above figures. In both figures silt laden Damodar river is seen passing through Coal fields of Jharkhand State. It has not only narrowed the river bed and flow but also posing threat to the existence of the river. Source of the sediments in this river are soils and remains of coal mine wastes deposited along the river sides which are washed away from the land by rain waters and surface runoff. These sediments may be the carrier of different trace elements like arsenic (already present), lead, nickel, chromium etc. as the coals of these areas contain above mention elements (Priyadarshi,2004; Geological Survey of India,1982). It may affect fish population by blanketing fish nests and food supplies. It may also reduce the sunlight available to green aquatic plants.

In above figures the water bodies are seen in dark black tone irrespective of the turbidity levels of the water. In both figures above image shows water bodies in different shades ranging from dark black to different hues of blue which represent various levels of turbidity, bottom reflection and depth of the water body.

Pond in above figure is situated near by Patratu Thermal Power Station 45 km north of Ranchi city (smoke coming out from the chimney is seen). Fly ash coming out from this thermal power station finally settles down in the surrounding areas including the pond. So special care should be taken to monitor the water quality of this pond.

Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia and severe reductions in water quality, fish, and other animal populations may occur.

Eutrophication is frequently a result of nutrient pollution, such as the release of sewage effluent, urban stormwater run-off, and run-off carrying excess fertilizers into natural waters.
Phosphorus is often regarded as the main culprit in cases of eutrophication in lakes subjected to point source pollution from sewage. The concentration of algae and the trophic state of lakes correspond well to phosphorus levels in water.
Ranchi Lake

Most of the lakes and ponds of the Jharkhand Sate are affected with Eutrophication as shown in above pictures of Google Earth.

Deciphering groundwater in Jharkhand:
State is occupied by hard rocks belonging mostly to Archaeans and Palaeo-Mesozoics (including Gondwanas), and these hard rocks bear groundwater only in their weathered top portion which rarely exceeds 10 metres. Joints and cracks in hard rocks also contain groundwater (Geological Survey of India, 1974).

The indiscriminate withdrawal of water from groundwater aquifers of limited potential to meet the growing demand has put acute pressure on the ground water aquifers in the Jharkhand including Ranchi city. Erratic and poor rainfall coupled with negligible attempts to recharge or replenish the groundwater aquifer has created an alarming situation. In many aquifers, either the water level has gone down or the aquifers have completely dried up. Even the surface water reservoirs has dried up due to lack of proper maintanence.

Identifying new groundwater sites, optimal water management through harvesting the available rainfall and recharging the underground aquifer appear to be the only solution to the above problems. During water harvesting, water can be stored in surface reservoirs or in underground aquifers. Location of potential sites and zones for this purpose is of utmost significance. Sometimes indicators for suitable sites for water harvesting can be identified directly on the satellite data.

Surface water forms a part of the hydrosphere which is linked without discontinuity to the groundwater and on this basis it is viewed as a direct hydrogeological index. Rivers, rivulets, lakes and temporary streams belong to this category. These are the features which are associated with recharge zones and it can be easily applied in Jharkhand State where there are rivulets, lakes, rivers and dams in sufficient amount.

The photographic image of rivulets is analogous to that of rivers and differs only in being of smaller size. The rivulets show the presence of outlets of groundwater upstream (Nefedov and Popova,1972; ).

So the rivulets shown in above figure may be taken into consideration for tapping and recharging groundwater.

Groundwater is also linked with lake water, which is direct positive indicator (Nefedov and Popova,1972). In aerial photographs, fresh water lakes are deciphered from the uniform tone of the reflecting water surface. Photos of the lakes shown in this article may be taken into consideration for deciphering groundwater.

Most of the abundant open coal mines serves as the good reservoir. In above figure small water reservoir is seen in abundant coal mines of North Karanpura Coalfield of Jharkhand. These reservoir can serve as a good recharge area for depleting groundwater. Water can be trapped in these abundant mines.

To facilitate recharge if a check dam is constructed across a rivulet on different intervals or stream flowing or at the meeting point of two rivers (as shown in above figure) will allow sufficient water to percolate to cause effective recharge to the groundwater aquifer.

Geological structures like synclinal folds, faults, unconformities, tilted strata and dykes help to locate possible aquifers (Pandey,2001). Some times they provide good opportunities for groundwater occurrence when the remaining lithological conditions are satisfied.

Sediment pollution is clearly depicted in the Damodar river flowing through the coalfield area. The aerial photographs helped us to identify potential areas of groundwater where detailed geophysical surveys can be carried to confirm availability of water. It has also helped in concentrating the field in selected areas where greater potential of groundwater may exist. It has also helped us to identify the sites where the check dams can be built to recharge the groundwater.

· Central Ground Water Board Ministry of Water Resources, Government of India (1976-1985). Monitoring of ground water from hydrogeological and chemical data of national hydrograph network stations in Bihar. Series “D”, No.8 Calcutta.
· Geological Survey of India (1974). Geology and mineral resources of states of India, part V-Bihar, No.30.
· Geological Survey of India Bulletins (1982). Trace elements studies in the major tertiary and gondwana coalfields of India, no.49 pp.66.
· Joseph, G. (2005). Fundamentals of Remote Sensing (2nd ed.). University Press, Hyderabad.
· Lillesand,T.M. and Kiefer, R.W. (2000). Remote Sensing and Image Interpretation. John Wiley and Sons, Inc. New York.
· Nefedov, K.E. and Popova, T.A. (1972). Deciphering of Groundwater from Aerial photographs. Amerind Publishing Co. Pvt. Ltd. New Delhi.
· Pandey, S.N. (2001). Principles and applications of photogeology. New Age International Publishers.
· Priyadarshi, N. (1999). Trace metal concentration in Damodar river of Bachra area of North Karanpura Bihar. In book “Environmental crisis and protective measures with special reference to the Chotanagpur region of Bihar”, edited by Sahay,U. and Bhagat, L.N. Jawaharlal Nehru College, Chakradharpur, Jharkhand, pp.49-55.
· Priyadarshi, N. (2004). Distribution of arsenic in Permian coals of North Karanpura coalfield, Jharkhand. Jr. Geol. Soc. India, vol.63, pp. 533-536.
· Sharma,B.K. and Kaur, H. (1994). Water pollution. Goel publishing house, Meerut.
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