Tuesday, August 25, 2009


Maps are defined as a two dimensional, geometrically accurate representation of a three dimensional space. It is graphic representation of a set of features whose relationships are shown by size, position and time. Map is a tool by which we can view, measure and understand our environment. Map is one of the easiest tools and probably the best tool for establishing any environmental dialogue. It has generally been observed that the basic knowledge about maps is rather low among the people of this country, even among the formally educated. Map learning can make people able to handle geo-environmental information of local, regional, national and global levels efficiently and more accurately. Science Communicators’ forum, a Kolkata based NGO is pursuing map literacy programme in West Bengal since 2004. The organisation had implemented map literacy programme in 40 rural schools of West Bengal where 3000 students were given training on understanding, using, updating and creating maps of their local area. The exercises had given them a better idea and understanding of their local environment. They learnt how to observe the changes that occurred in terms of demography, social pattern, natural resource, pollution and biodiversity. Environmental mapping programme can be a part of environmental education where the learners will learn to prepare local area thematic maps based on different environment related themes and develop local environmental database. In an advance stage of map learning other geo-informatics tools like GPS, remote sensing and GIS may be introduced. A systematic curriculum can be prepared

Monday, July 20, 2009

Does groundwater respond to solar eclipse?

In the year 1980, during the total solar eclipse I conducted some experiments in the unconfined aquifer of Jalpaiguri district of West Bengal, India. The study was conducted in open dug well of depth of about 10 metres. Depth to water level measurements started one our before the start of the eclipse and completed after one our after the end of the eclipse. Water level had actually risen by 15 to 16 centimeters during the peak of the eclipse. Though the total eclipse was not visible at Jalpaiguri the groundwater appeared to respond to this astronomical phenomenon.

In the year 1995 there was another total eclipse, which was visible from South 24 Parganas of West Bengal. I along with my colleagues of SWID selected one observation station at Falta where we desired to take water level measurements from very deep and moderately deep tube wells. We started taking measurements at 5 minutes interval from the wells using metallic tapes. We observed the rise of water level during the eclipse and found that the maximum water level rise was achieved at the time of totality. What was actually remarkable that the water level of deeper well rose by 34 cm whereas in the shallower well water level rose by 10 centimetres only.

This year on 22nd July the members of JCSES are going to conduct similar experiments in Jalpaiguri district. They will conduct water level measurements from dug wells for 24 hours starting from 21st July evening.

Friday, June 26, 2009


Pradip K Sengupta
Water footprint is a new concept in the field of water management. It is expected that if water consumption or need of a country is assessed on the basis of water footprint an efficient water management practice can be achieved. To allocate water in individual sectors and for finding political solutions of a water conflict water footprint and virtual water can contribute a lot. The concept of water footprint is introduced recently at the beginning of this century. The concept was originally launched by A.Y. Hoekstra in the year 2002. A document on water footprint has been released by the UNESCO-IHE in 2002. In that document an attempt was made to assess the water footprint of individual nations. But what is a water foot print? Water footprint is a consumption based indicator of water use. The water footprint of an individual, business or nation is defined as the total volume of freshwater that is used to produce the foods and services consumed by the individual, business or nation. A water footprint is generally expressed in terms of the volume of water use per year. The calculation of water footprint is based on the amount of agriculture product, meat, industrial product and raw water consumed by an individual, business or nation.
Each product, whether agricultural or industrial consume some amount of water in the production process. In agriculture water is consumed from soil, and lost through evapo-transpiration. Similarly when meat is produced water requirement is increased because water is consumed by the animal through fodder and direct utilization of water.
The water footprint of a country (NWFP) has two parts. One is the internal water footprint (IWFP) and another is the external water footprint (EWFP).
The internal water footprint of a nation is the volume of water used from domestic water resources to produce the goods and services consumed by the inhabitants of the country. The external water footprint of a country is the volume of water used in other countries to produce goods and services imported and consumed by the inhabitants of the country.

In order to promote sustainable, fair and efficient use of water on a global scale seven global groups have launched the Water Footprint Network in October, 2008. Their aim is to work toward a common approach to water footprint measurement, accounting, and reporting. Partners of this group are the World Business Council for Sustainable Development, the University of Twente in the Netherlands, WWF, UNESCO-IHE Institute for Water Education, the Water Neutral Foundation, the International Finance Corporation (part of the World Bank Group); and the Netherlands Water Partnership.

India has the largest water footprint in the world (987 Gm3/yr) but it also has a very high national self-sufficiency ratio (98%), The total which implies that at present India is only little dependent on the import of virtual water from other countries to meet its national demands. Whereas Bangladesh has its renewable water resource to the tune of

The water required for production of a commodity, good or service is called virtual water. This means that the amount of water required for producing a unit amount of that product is the virtual water of that product. So when we consume anything we are actually consuming the virtual water for that product. The concept of virtual water was introduced by Professor John Allan of King’s College, London, in 1997 as an economic tool and an alternative means of measuring the global distribution of water through trade and was awarded the 2008 Stockholm Water Prize for it. In the past the in place of virtual water the term embedded water was in use. But virtual water has gained interest of the scientists and the term is now accepted as a term used for measuring the environmental cost in terms of water. In the same way trade of a commodity or service may be translated as the trade of virtual water.
The virtual water of an agricultural product in a country may be different from that of the same product produced in a different country. For example tomato produced in USA contains less virtual water than tomato produced in Israel. This happens due to the difference in climatic condition between those countries. It is becoming evident that some water scarce countries will likely import food that is water intensive to produce.
To determine the virtual water use we need data on crop water requirements over the growing season, evapotranspiration rates, the annual yield and the amount of water used in processing the crop.( Hans Schreier, Les Lavkulich and Sandra Brown May 2007) .The concept of Virtual Water should be an additional consideration in all water balance calculations.
The virtual water content of different food products in India. (afterVijay Kumar* and Sharad K. Jain2007)
Product Virtual water (cubic m/tonne)
Agricultural Product
Wheat 1654
Rice (paddy) 2850
Mustard oil 4643
Maize 1937
Banana 415
Orange 364
Sugarcane 159
Grapefruit 411
Lentils 6652
Apple 1812
Soybeans 4124
Pear 1287
Jute 2823
Cotton lint 18694
Potatoes 213
Tomato 302
Coffee (roasted) 14500
Tea (green) 1804
Sugar (refined) 1391
Groundnut oil 8875
Product Virtual water (cubic m/tonne)
Livestock and livestock products
Bovine meat 7386
Milk powder 6368
Swine 4119
Yogurt/milk product 1592
Sheep 3397
Buttermilk 2068
Goat 3018
Cheese 6793
Fowl/poultry 6024
Egg (birds) 7531
Leather (bovine) 17710

Virtual water trade is another concept that can be related to trade of commodities.
The virtual water consumption of a country can therefore be = domestic virtual water+ imported virtual water- exported virtual water.
If the virtual water import is higher than the export then the country is a water importer. Virtual water may become an additional consideration in deciding what to export/import. This concept can be useful in making agricultural choices within the country among various states. But this new concept has not yet been used in decision making processes in most areas. It may also be added that for evolving water management policies, the concept of virtual water has to be used along with other aspects such as hydrology, geology, agriculture, engineering, land use, culture etc. It is not advisable that all decisions on water allocation should be based solely on virtual water assessment. At the global level, virtual water trade has geo-political implications: it induces dependencies between countries. Therefore, it can be regarded either as a stimulant for co-operation and peace or a reason for potential conflict.

Chapagain, A. K. and Hoekstra, A. Y. (2003). Virtual water flows between nations in relation to trade in livestock and livestock products. Value of Water Research Report Series No. 13, UNESCO-IHE Institute for Water Education, Delft, The Netherlands.
Real and Virtual Water and Water Footprints:A Comparison between the Lower Fraser Valley and the Okanagan Basin Hans Schreier, Les Lavkulich and Sandra Brown, Final Report for the Walter and Duncan Gordon Foundation May 2007
Virtual water trade … iran http://news.moe.org.ir/vdce.z8xbjh8f7k1ij.html%2017th%20may%202009
Vijay Kumar* and Sharad K. Jain, CURRENT SCIENCE, VOL. 93, NO. 8, 25 OCTOBER 2007

Monday, February 2, 2009

Governing Body of JCSES

President: Asitava Datta
Secretary: Sibabrata Basu Roy
Treasurer: Ruma Bhattacharya
Vice President: Amitabha Sengupta

Saturday, January 17, 2009

Science Fair at New Barrackpore

A Science fair was held at New Barrackpore ( North 24 Parganas, West Bengal, India) from 20th to 26th December 2008. Jadavpur Centre for Study of Earth Science organised one stall at the exhibition. The main exhibits of the stall were rocks, fossils, minerals and a set of posters on Earth Science. About 10,000 Students teachers and common people visited the stall with great enthuciasm.

Thursday, January 15, 2009

Hydrogeology of Kolkata

Pradip K Sengupta


Kolkata is one of the most populated metropolitan cities of India. For the last 300 years this city has experienced a huge population growth. Due to huge development and increase in population demand of water for domestic purpose mainly has increased by many folds. Domestic water supply is done mainly from the Hoogli River through the Tala pumping stations and the Garden Reach pumping stations. In spite of this surface water sources a huge amount of water is drawn from the groundwater aquifers below Kolkata. This exploitation is so huge that permanent depletion of water level has occurred in the groundwater of Kolkata. The state government and the Central Groundwater board conduct regular monitoring of water level and water quality of Kolkata. The studies have revealed that water quality in Kolkata has deteriorated and arsenic contamination in ground water has been observed in some parts of Kolkata. Study of arsenic contamination in groundwater in Kolkata was conducted in 2001 by the author. 119 tube wells were studied and arsenic was found in 26 samples.


The Objective of the study was to establish the geomorphology of Kolkata with the help of secondary parameters and to find out if there is any scope for correlating geomorphology with chemical quality of groundwater with special emphasis on arsenic concentration.


In the study area, fluvial processes have resulted in the formation of extensive Holocene flood plains with a dominance of coarser grained sediments, representing the overlapping of a number of sub- deltas). Avulsion of the major streams in the area, which are tributaries or distributaries of the River Ganges, within a time scale of 100 years, has resulted in a thick layer of tens of meters of Recent overbank silts and clays incised by channel sands The coastal region of the south Bengal has a mixture of fine- grained sand and mud deposits with peat layers, which have resulted from eustatic influence. Deposition of the lowest parts of the Bengal Alluvium began at the onset of the Pleistocene glacial maximum, with sea level (i.e., regional base level) at least 100 m below present MSL. Thus, the rivers draining the plain during that time must have scoured through the earlier plains. Around 11,000 to 10,000 years before present (BP), deposition of lower delta mud over low-stand oxidized sand units started, suggesting sea level rise to about 45 m below present MSL. The present GBM delta began to prograde into the Bay of Bengal at this time. From ∼10,000 to ∼7,000 years BP, rapid marine transgression occurred resulting in the deposition of fine sediments. Since ∼7,000 years BP to the present, the general trend of the eustatic sea-level curve shows continuing sea-level rise, although with a decreased gradient. (Mukherjee et al, 2007)

Geologically and geomorphologically Kolkata belongs to the lower deltaic plain of the Ganga-Padma river system.. The surface material is clay and clay loam. This clay extends up to a depth of 10 to 25 m bgl in most of the area. Below this clay bed a fine sand bed is found which extends up to a depth of 30-to 35-metre bgl. Below this level another clay, dark brown to grayish brown in colour occur up to a depth of 60 to 100-metre bgl. From this depth another sand zone occur which comprises of fine, medium and coarse sand and extends up to a depth of 120 to 180 metre bgl. Below this sand zone gravel bed occurs. Tertiary black and sticky clay occurs at the bottom of the sand and gravel zone.

From a general hydrogeologic point of view, these sediments have been categorized as aquifer (sand and gravel) and aquitard (clay). The position of the sandy clay is ambiguous: it can act as either less permeable aquifer or higher-permeability aquitard. Its exact category will vary from locality to locality based on the sand/clay ratio and permeability. Although the less permeable sediments like clay transmit some groundwater, they separate the overlying aquifer(s) from lower aquifer(s) by hydraulic conductivity (K) contrast. In the study area, the extent, thickness and K of these clay or aquitard layers are very important as they govern the three-dimensional flow of groundwater at the regional scale. In this report, the names of the sediment types and hydrogeologic categories will be used interchangeably for the description of both hydrostratigraphy and groundwater flow (Mukherjee & Alan E. Fryar & Paul D. Howell 2007)

The uppermost surface of Kolkata is clay of thickness between 5 and 40 metres. The upper clay contains at places lenses of fine sand and peat, which often act as perched aquifers. But these aquifers yield little water. Water content in this clay is great and a small amount of water may trickle down to the underlying sand zone when the piezometric level of the aquifer is sufficiently low.
The first or uppermost aquifer is about 10 to 20 metre thick on an average. The material is essentially fine sand. Most houses in Bansdroni and Garia area lift water from this zone.

The second aquifer occurs between the depth of 65 metre and 120 metre and this aquifer is about 30 to 50 metre thick. This is the most potential and most exploited aquifer of Kolkata. The present study is confined to 1st and 2nd aquifer only.
In general, the upper aquifer material comprises sub-rounded to sub-angular fine to medium sand with occasional clay lenses. Its heavy mineral assemblage (opaques, altered biotite, garnet, tourmaline, kyanite, zircon) indicates a mixed metamorphic-cum-igneous provenance. The intermediate aquifer constituted of sub-angular to sub-rounded medium sand, sandy clay and clay with fine sands and its heavy mineral assemblage (biotite, garnet, kyanite, opaques) indicates a dominantly metamorphic origin.
While the lower aquifer is constituted of sub-rounded to rounded fine to coarse sand with occasional clay bodies, and its heavy mineral assemblage (opaques, altered biotite tourmaline, rutile etc.) indicates an igneous provenance (Steering Committee Arsenic Investigation Project, PHE Dept, Government of West Bengal, 1991). The intermediate aquifer usually shows arsenic contamination. At the greater depth, aquifer arsenic may not be present at the beginning but may become contaminated in the course of time. This is what had been observed during our study.


It is very difficult to identify the different geomorphological units in Kolkata due to the urbanization and absence of exposure of surface materials in many areas. Satellite data do not reveal the detail geomorphic features apart from the pattern of settlements. Study of old maps (1817) published by the NATMO reveals that the settlement of Kolkata at that time was along the Hoogly River extending upto 2to 3 km towards the east. As old settlements generally develop on the levee of a river-side it is assumed that the Hoogly river levee extends from the hoogly river bank to the east.

Land level data generated from reduced level survey of the monitoring wells have been used to generate a contour map of Kolkata with 0.2 meter interval. This map reveals the surface features of Kolkata. From the contour map and traverse survey along Adiganga the reconstruction geomorphology of Kolkata is attempted. These maps show high land near the Hoogly River and also along the channel of Adiganga. The surface is gently sloping towards the east and south east and formed low lying areas in the east which transgresses into the saline lakes or east Kolkata wetlands.
Another attempt was made to determine the depositional features using spatial distribution pattern mapping of the thickness of surface clay of Kolkata. The map is given in figure.5.This map shows that along the Hoogly River the thickness of clay is maximum whereas along Adiganga channel the thickness is moderate. In the eastern part and in the south western part the thickness is minimum.

During this study ttempt has made to understand whether there is any relation between geomorphology or the sedimentation pattern and the chemical quality of groundwater. The groundwater chloride concentration and isoconductivity map of Kolkata is given in Figure 5 and Figure 6. These maps show some distinctive patterns compatible with both surface contour and clay thickness. Along the Adiganga channel both specific conductivity and chloride concentration is low. On the other hand both chloride concentration and specific conductivity is high near the Hoogly river and also at the eastern low lands.

Using these maps the geomorphology of Kolkata is reconstructed.

Geomorphologically Kolkata may be divided into four major features.

1. Hoogly levee deposit: Extends upto 2-3 km from the Hoogli river bank
2. Adiganga levee deposit: Extends from north to south covering a large area from Khidirpur, Alipur, Tollygunge, Bansdroni, Naktal and Garia
3. Adiganga channel deposit : Covers a small srip along the river in Naktala and Garia
4. East Kolkata Marshland deposit: Covers a large area in the eastern part starting from, Ultadanga, Park Circus, Santoshpur and Garia in the east and extends towards the east


Due to heavy exploitation of groundwater a major change has been occurred in the water level condition of Kolkata. Investigations conducted in Kolkata for the last 20 years reflect alarming depletion of piezometric level. At present the piezometric level is 14 to 16 metres below ground level in the Alipur, Babughat, Ballygunge, Kalighat, Park circus area whereas in the Bansdroni and surrounding areas this level is 9 to 11 metre deep. At Garia and surrounding areas the piezometric level is between 8 and 10 metre below ground level. In the north at Baguihati, Sinthi, and Beleghata area water level in pre monsoon period is 12 to 14 metre below ground level, whereas in dumdum and surrounding area this level is from 10 to 12 metre BGL. Piezometric level is at a depth of 6 to 10 metre below sea level on an average. During the post monsoon period piezometric level rises to the tune of 1 to 1.5 metre in Alipur and about 2 metres in Bansdroni and Garia and in north Kolkata and Dumdum.

Groundwater movement in areas of flat topography in the Bengal basin may be mostly vertical and lateral flow may be limited to local scale. Sikdar et al. (2001) reported the presence of north–south regional flow near Calcutta in the 1950s, but flow had dramatically changed by the 1980s. Harvey (2002) argued against the persistence of any regional flow system in view of the extensive irrigation pumping currently practiced in the Bengal basin. Surface water–groundwater interaction generally occurs within local flow systems. The River Bhagirathi-Hoogly is a losing stream along most of its length and recharges the shallow aquifers. Deeper groundwater generally has insignificant interaction with the surface water bodies, and the deeper aquifers have restricted recharge (Mukherjee et al. 2007). The premonsoon water table contour map of Kolkata shows concentric flow and the contour pattern has no similarity with the topography or the chemical quality of groundwater.

Arsenic contamination in the Bengal Delta is confined to the Holocene Younger Delta Plain and the alluvium that was deposited around 10,000–7,000 years bp, under combined influence of the Holocene sea-level rise and rapid erosion in the Himalaya. Further, contaminated areas are often located close to distribution of abandoned or existing channels, swamps, which are areas of surface water and biomass accumulation. Extensive extraction of groundwater mainly from shallow aquifers cause recharge from nearby surface water bodies. Infiltration of recharge water enriched in dissolved organic matter derived either from recently accumulated biomass and/or from sediment organic matter enhanced reductive dissolution of hydrated iron oxide that are present mainly as sediment grain coatings in the aquifers enhancing release of adsorbed arsenic to groundwater. ( Mukherjee et al 2007)
Study for arsenic contamination in Kolkata was conducted by the author in 2001. 119 water samples were collected from different locations.

Monday, January 12, 2009

Welcome to JCSES

The year 2008 has been declared by the United Nation as the International Year of Planet Earth. The International Year of Planet Earth (2007 - 2009) aims to contribute to the improvement of everyday life, especially in the less developed countries, by promoting the societal potential of the world’s Earth scientists, as expressed in the Year’s subtitle Earth sciences for Society. Earth scientists all over the world, a professional community that is ready and willing to contribute to a safer, healthier and wealthier society if called upon by politicians and decision makers. To accomplish the goal of the year and to contribute the knowledge of earth science for the benefit of the society Jadavpur Centre for Study of Earth Science is founded. It is a professionally managed organisation of the Earth Scientists of high repute. Through this organisation professional guidance by Earth scientists is available in many aspects of everyday life including, for example, identification of the best areas for sustainable settlement and related infrastructure, sites to avoid for waste disposal, the location of new underground fresh water resources, sustainable mining of natural resources, and where certain toxic agents implicated in Earth related diseases may be located One of our major goals is to empower people through knowledge of earth science to improve their livelihood.