GROUND WATER QUALITY PROBLEM IN VARIED HYDROGEOLOGIC REGIONS OF WEST BENGAL – AN OVERVIEW

Ground water quality of the State of West Bengal is assessed for the last three decades by various institutions including State Water Investigation Directorate. The parameters determined include pH, specific conductance, dissolved major ions (pass through 0.45 mm pore size membrane filter) like Ca⁺⁺, Mg⁺⁺, Na⁺, HCO3^-, CO3^{- -}, Cl^-, SO4^{- -} . Minor ions like iron, arsenic and fluoride are also included to ascertain the quality of ground water for drinking purpose. Partial analysis of water quality parameter reveals that the quality of groundwater in the State can be grouped into three classes (i) low chloride and high bicarbonate type, (ii) chloride – bicarbonate type, (iii) sodium or magnesium – calcium – chloride type with variable bicarbonate. Since historical past the State of West Bengal is considered as one of richest states in respect of ground water storage . The quality problem in ground water, extracted from shallow depth aquifers (< 100 m. bgl.) has been high level of total iron content in major part of riverine plains. Besides, the coastal aquifers of prograding Ganga – Brahmaputra delta front are infested with both connate and cyclic salinity. These two problems are of perpetual nature. While the first problem i.e. high iron content is usually mitigated by individual capacity, the issue of development and management of the second one i.e. salinity in ground water is under concern of the Government. But after eighties the Government Departments and researchers dealing with ground water are challenged with new facets of problems due to toxicity in groundwater by contamination of arsenic and fluoride.  Out of 341 blocks of the State, ground water in almost all the Blocks are suitable for agriculture except 59 Blocks of coastal region. But for safe drinking water purposes the scenario is complex as a consequence of toxic ion contamination by mainly Arsenic and Fluoride. The problems of Arsenic toxicity in ground water have been detected, mostly in the top and middle aquifers, from 81 blocks of the State. Presence of fluoride in ground water has been detected in the hard rock (basalt and granite) terrain of Birbhum district in 4 blocks only.  Arsenic contamination has also been found in scattered locations of South Kolkata. In the State of West Bengal severe effects of Arsenic toxicity are found in 26 blocks and that for fluoride is 1. Causes of the high level of Arsenic and Fluoride contamination are thought to be geogenic. However, the detailed geochemistry of such occurrences is under study. The Chromium contamination (~3mg/lit) is detected at Raghabpur in Purulia –I block. The source of chromium contamination is under investigation. Groundwater in and around industrial areas of Howrah and Burdwan are prone to contamination by industrial effluents.

 The multidimensional facets of groundwater problems prevailing in the state made it open for SWID to extend its scope of work in all the major user sectors. Significant database in respect of groundwater quality is generated and periodical updating of the same is a continuous process for the SWID within its available resources. Investigations are in progress throughout the state for updating the arsenic and fluoride spread maps. Such a centrally assisted Project for study of arsenic spread was taken up under Rajib Gandhi National Drinking Water Mission in the year 2003. Central assistance may help to take up new projects with the said objective. The Ministry of Water Resources, GOI, has provided financial assistance to SWID to study dilution of Arsenic in ground water by artificial recharge. Another centrally funded R&D project of special nature has been completed in collaboration with B.C.K.V.V., Kalyani and NBSS & LUP, wherein the effect of use of arsenical water for irrigation on selected agro-produces has been studied in parts of North 24 Parganas. Central assistance is needed to continue the study in other areas as well. The mechanism of salinisation in parts of the coastal tracts by isotope techniques was studied jointly with BARC. The study may be continued if fund is made available. Detail research on tube wells sealing methodology is essential for development of groundwater in coastal saline region. Intensive study on aquifer geometry of coastal area may be envisaged by other methodologies like resitivity survey, tracer study, fresh-sea water interface geochemistry and exploratory drilling.

FUNDAMENTALS OF AQUIFER MAPPING

The water Resource Ministry of Government of India has released a notification and a fact sheet on National Aquifer Mapping Programme (NAQUIM). The Central Groundwater board and the State Groundwater Departments will act as the main functionaries in this programme. It is also decided by the government that national level aquifer mapping will progress substantially through the 11^th five year plan period. Considering the fact that those government departments alone cannot accomplish the job it has been decided that stake holders and NGOs would be involved in this endeavor.  This national level programme also has components like nation wise training and human resource development.

But, what is an aquifer map and what it is for?

The concept of aquifer mapping is not new. Many developed countries like Australia and USA have already completed aquifer maps in certain areas like Murray Darling Basin and Texas. They have already published some of the reports and maps. An aquifer map is not a single map, on the other hand it is a group of several maps that would describe the aquifer system and management criteria and options in an area.

In NAQIM programme of India it has been proposed that aquifer maps would include (1) Identification of Aquifer Management Units (AMU) (2) Evaluation of AMU, (3) Data preparation and generation of different categories (4) Prioritization of AMU, (5) Preparation of aquifer management plans and aqifer management and information system, (6)  Participatory groundwater management.

1.      IDENTIFICATION OF AQUIFER MANAGEMENT UNITS:

Aquifer management units are something different from a Hydrogeological unit. In a hydrogeological map generally geological units are described by its hydrogeological characteristics. But an AMU contains much more than that. It includes the 3 dimensional matrix of all information like extent of the aquifer, depth, thickness, geology, hydrology, land use on it, recharge and discharge related information and its political and social boundaries.

2.      EVALUATION OF OF AMU:

This is the most difficult task. Aquifer evaluations are conducted for various purposes including water supply development as well as groundwater contamination and remediation situations. They can range from fairly intense evaluations involving test drilling, geophysical investigations, installation of monitoring or observation wells, test pumping, physical and chemical water quality analyses, analytical and digital modeling to rapid evaluations based on existing data.

3.      DATA PREPARATION AND GENERATION OF DIFFERENT CATEGORIES:

The groundwater departments and states are generating groundwater data on regular basis. But those data are generally categorized on the basis of revenue boundaries and not on the basis of aquifer boundaries. So under NAQIM aguifer related data should be compiled and generated. A suggestive list of required data is given below.

   - Evaluation of existing data

   - Test drilling

   - Installation of monitoring or observations wells

   - Geoprobing and/or hydro probing

   - Geophysical investigations

   - Geophysical borehole logging

   - Groundwater gauging

   - Groundwater sampling and analyses

   - Test pumping

   - Slug testing

   - Analytical and digital groundwater modeling

   - Solute transport modeling

   - Groundwater monitoring

4.      PRIORITISATION OF AMU:

AMUs are basically aquifers subdivided into management units. These units are prioritized according to the demand and usage depending on the evaluated parameters of the aquifer. Before prioritization a management framework is required. The framework may include:

• Establish the baseline groundwater conditions and range of natural variability in the aquifer to facilitate enhanced knowledge and detection of change.

• Provide a consistent approach to understanding potential effects from all development activities on the surrounding environment.

• Facilitate projections of change based on future scenarios, such as expanding development or climate variability and change.

• Support and supplement the current pollution prevention and risk management principles as part of groundwater quality and quantity management.

 Prioritisation index:

Depending on the hydrogeology, quality of water and development status a prioritization index is to be developed by the groundwater authorities.

AMUs are initially ranked according to an index (equation 1) based on normalised current groundwater extraction, the fraction of groundwater allocation currently extracted , the fraction of sustainable yield currently extracted , a potential growth index and an index of the predicted future impact of groundwater extraction on surface water flow.

Apriority evaluation index has been attempted in Murray-Darling Basin Sustainable Yields Project (http://www.clw.csiro.au/publications/waterforahealthycountry/mdbsy/technical/Q-GMU-Prioritisation.pdf) Several other algorithms can be developed to prioritise aquifers in our country. In a GIS platform both raster and vector based analysis may lead to an efficient decision support system.

5.      MANAGEMENT PLAN

This initiative will seek to protect the long term water supply capacity of the aquifer by controlling average annual aquifer use and balancing it with average annual recharge.

                                i.            Aquifer Protection Plan: This initiative will seek to assess the quality of the water in the aquifer and then to protect it by encouraging activities that enhance water quality and by discouraging activities that degrade it.  The key components are

                              ii.            Maintain Status Quo where water level is alarmingly depleted.

                            iii.            Reduce withdrawal of water: Water withdrawal may be reduced by introducing innovative farming, recycling of water and reducing consumption. The management plan will address aquifer specific recommendation.

                            iv.            Enhance Natural Recharge: To enhance natural recharge proper steps should be taken. This may include afforestation, gully plugging, construction of sub surface dykes etc. This initiative will seek to maximize aquifer recharge with good quality water by encouraging beneficial land and water management practices and by investigating the potential to use stream flow.

                              v.            Monitoring plan: This initiative will seek to maintain a current and comprehensive scientific database on the aquifer by collecting, compiling and evaluating data. The current aquifer monitoring activities could be reviewed to coordinate and redesign them, focusing on the comprehensive protection of the Aquifer.

                            vi.            Manage Pollution Risks: Activities carried out in pits and dumping areas within the primary recharge area present a variety of risks to aquifer water quality. The risks associated with these activities could be assessed and, where required, action taken to manage them as part of an aquifer protection plan. Other risks like geogenic contamination like As and Fl should be properly addressed in the management plan to reduce public health hazards.

                                      vii. Reduce Incoming Salt Water: The regional salt water flow to the aquifer could possibly be intercepted by installing a set of management structures or through innovative engineering activities.

6.      AQUIFER EDUCATION PLAN

The potential long term success of this management plan depends on the understanding and cooperation of a diverse group of people.  It is believed that a better informed group makes better decisions.  Only common understanding will engender the cooperation needed to formulate,  implement and maintain a successful long term stewardship plan for the Aquifer. Additional study is required to achieve a better understanding.  Extension education is required to make knowledge gained available to all area residents.

PRESENT GROUNDWATER SCENARIO OF WEST BENGAL

Introduction
Introduction
Groundwater is prime natural resources in the earth .Not only it supported almost all types of life form to evolve, but also helped in growth of human civilization. It quenches thirst and meets the household demands. Used in the fields for production of food grains .Lastly the industries catering to the various needs and luxuries of human being have started consuming voluminous quantity of Water .Groundwater is therefore a precious national asset and planning, development and Management of water resources need to be governed by national perspectives.
In the beginning, water from rainfall and snow and rivers were only source of water to mankind. As these surface water sources were dependent on rainfall, localized shortage was often witnessed. With primitive technologies men was not able to build sustainable water reservoir to see them through the drought period .But once man came to know of groundwater, his dependence on it increased with the advent of civilization. At present about two billion people in the world is dependent on groundwater. Fortunately, groundwater is a renewable resource that is recharged every year through rainfall. However, this recharging process is not entirely dependent on rainfall but on various other natural factors that differ from region to region and within space and time. Therefore, recharge of groundwater is never a constant factor .When the average quantity of draft exceeds recharge for repeated years we face the situation of over exploitation.
The manner and the scale in which the use of groundwater has accelerated, human being has become so much dependent on the assured source that no sign of the over increasing demand for groundwater stabilizing.
Beginning of 20th century witnessed demand for groundwater in industrial sector rising phenomenally at a faster rate than that in agriculture and domestic sector.
West Bengal is the only state in India that stretches from Mountain to the Sea and truly a “Asamudra himachalam” state as the meaning goes. West Bengal has a very good groundwater potential. The reason of such affluence is due to her geographical location, high rainfall and favorable geological setting .The state have land area of about 2.7% but have about 6% of total replenishible groundwater resources of India. Groundwater is the most exploited resource in west Bengal particularly in agriculture sector With the introduction of water intensive high yielding variety , the need for groundwater have skyrocketed. Quinquennial census of minor irrigation structures indicated a 64% growth in number of STWs over last 16 years,@4% annually.
Table Showing Number of Groundwater Structures from 1986 to 2001

Name of Structure 1986-87 1994-95 2000-2001
Dug Well 63387 55983 39377
Shallow Tubewell 368316 504638 603667
Deep Tubewell 3122 4039 5139

Hydrogeological Condition
Geologically West Bengal can be divided into two broad units (A) Consolidated or semi consolidated formation occurring in the northern most and western part of West Bengal and (B) Unconsolidated formation in the rest of West Bengal.
(A) Consolidated/ semi consolidated formations:
These formations cover the western and the northern part of the state. These are comprised of Archaean crystalline rocks and Gondwana group of rocks including Rajmahal traps covering part of Purulia, Bankura Paschim Medinipur, Birbhum and Burdwan.. Archaean metamorphics, Siwalik and Gondwana covers part of Darjeeling and Jalpaiguri District. In the western part and in some part of Darjeeling district , these hard and semi consolidated rocks are overlain by weathered residuum and laterite capping.
(B) Unconsolidated formations:
These formations belonging to the Tertiary and Quaternary age and covering rest of West Bengal. These formations may be subdivided into (a) Secondary laterite (b) Older alluvium and (c) Recent alluvium.

Secondary laterite occurs at the marginal area between the Consolidated/ semi-consolidated rock and older alluvium mainly in the districts of Bankura, Paschim Medinipur, Burdwan and Birbhum. Older alluvium occurs mainly in the elevated terraces fringing the lateritic margin of the Chhotonagpur plateau in Bankura, Pascim Medinipur, Burdwan, Birbhum, Hoogli and Murshidabad district and in the Barind region of North Bengal. Recent sediments occupy the river courses and flood plains.


Depletion of groundwater
In spite of having high groundwater reserve, exploitation of the resources in West Bengal shot up to such level that 80’s decade first witnessed the sign of depletion of groundwater level in some blocks of Murshidabad, Burdwan, Medinipur, Hoogly where pre-monsoon water level dropped below the centrifugal pumping limit and hand tubewells went dry. Introduction of Submersible motor driven pump though came as a blessing to the cultivators, for it can draw water from far deeper depth – caused further lowering of groundwater level.
Depth to water level data analyzed by the State Water Investigation Directorate, Govt. of W. Bengal, indicated significant average annual fall in pre monsoon depth to water level during the period 1995 to 2004 to the tune of 16 to 70 centimeters in some blocks of Murshidabad, Burdwan, Purba Medinipur and Hoogly districts. In some parts of Hooghly, Burdwan and Murshidabad districts, significant fall was noticed in both pre and post monsoon period.

Case 1 No change


Case 2- Post monsoon no change but pre monsoon falling trend


Case 3 both pre & post monsoon show falling trend


Case 4: Pre monsoon rising trend, post monsoon falling.


Groundwater Quality
In addition to the phenomenon of lowering of water level, deterioration in Chemical quality of groundwater was noticed in some parts of the state that took place in the form of Arsenic and Fluoride contamination. On the basis of preliminary survey 81 blocks in the state have been identified where Arsenic was found in groundwater above permissible limit. Similarly, presence of Fluoride beyond permissible limit in groundwater was detected in 49 blocks of the State.
It was observed that the entire younger and recent alluvium formation east of Bhagirathi River is arsenic bearing and reason for such occurrence is solely Geogenic. Arsenic held by the solid phases within the sediments, especially iron oxides, organic matter and sulphides might constitute the primary arsenic sources in groundwater under condition condusive to arsenic release from solid phases.
Occurrence of Fluoride, in groundwater is generally recorded from hard rock areas. The subsurface water may be contaminated with dissolved substance due to disintegration and dissolution of bed rock that rendered water unfit for drinking due to presence of certain toxic constituents. Fluoride is one such chronic toxic substance, that have affected large number of people causing Skeletal or Dental fluorosis. Fluorite (CaF2), Cryolite (Na Al F6) is the rock forming minerals which contribute Fluoride to the groundwater. Wastewater containing Fluoride originating from various industries viz phosphate fertilizer, ceramic industry brick kiln and pharmaceutical industries may find its way to the groundwater and elevate the Fluoride level.

Assessment of Groundwater Resources
Apprehending phenomenal increase in extraction of Groundwater, Government of India considered that quantitative assessment of these resources is necessary for planning and sustainable development. Accordingly , Ministry of water Resources formed Groundwater Estimation Committee , which came out with a methodology based on reasonably valid scientific principles and reliable data .The first assessment of the resources was carried out in 1984. Meanwhile, Central Groundwater Board and different State Water investigation Organizations carried out further detailed studies and generated additional database which along with the ever-rising Groundwater utilization through the country, indicated need for modifying the methodology for more precise assessment. Another Estimation Committee was set up in 1995 came out with modified methodology in 1997 known as GEC ’97 methodology. Assessment of Groundwater resources of all the States were carried out jointly by the Central Groundwater Board and the respective State groundwater Organizations with block as unit and 2004 as base year.
The assessment revealed that the national average for stage of groundwater development is 58% whereas the same for the State of West Bengal is 42%.The assessed blocks were categorized, on the basis of stage of development and long term significant decline of groundwater level, as ‘Safe’, ‘Semi-Critical’, ‘Critical’ and ‘Over exploited’ .In the national scenario, 4078 blocks are Safe out of total 5723 blocks.
In West Bengal assessment was carried out in 269 blocks out of total 341 blocks leaving aside 13 hilly blocks in the north and 59 Saline blocks of coastal region. As per the assessment carried out by application of GEC’97 methodology, 231 blocks have been found to be Safe .28 blocks were assessed to be Semi-Critical and 10 blocks as Critical. However State committee on groundwater assessment is reviewing assessment and categorization of this 10block.
Based on the assessment carried out the net groundwater availability in West Bengal was calculated to be 27.46 BCM, whereas existing groundwater draft in all sectors –irrigation , domestic and industrial , is 11.65 BCM, leaving 15.81 BCM of dynamic resources reserve for further use.
Planned approach for Groundwater development
The groundwater scenario at national level and that of West Bengal reveal that exploitation of groundwater in the state has not yet reached alarming critical stage .The national water policy 2002 states that exploitation of groundwater should be limited to the extent of annual recharge. Although the average stage of groundwater development is 42% in the state , adverse effects like water level depletion and chemical degradation have been noticed in some areas in scattered manner. Government is concerned about incidents of suffering of the local population in such areas due to shortage of water in peak summer and from diseases due to consumption of arsenic and fluoride contaminated water.
It was apprehended that if indiscriminate use of water go on unabated, adverse effects of degrading hydrogeological regime of the state, will amplify and will engulf the whole state in such a manner that the whole agriculture and industrial development process will suffer a set back. The Government had determined view not to allow such situation and decided to promulgate suitable Act to control and regulate the use of groundwater in the State.

Groundwater Act
West Bengal Groundwater Resources (Management , Control & Regulation ) Act 2005 was promulgated with effect from 15th September ‘2005.This act stipulates obtaining mandatory permit for installation of groundwater extraction structures operated by engine or motor driven pump .This act also , stipulate registration of all such structures existed before the act came into force.
Apart from West Bengal, other states viz. Himachal Pradesh, Kerala, Goa and Tamil Nadu have already passed suitable acts for control and regulation of groundwater .Andra Pradesh had enacted Water , land and tree act in 2002. Maharashtra enacted groundwater (regulation for drinking water sources) Act in 1993 for limited purpose of regulating public drinking water. For the remaining states either the groundwater bill is under drafting or draft bill is under consideration of the respective government.

Conclusion
Crisis of Water is probably the worst curse any civilization would like to face. It will be tragic for the next generation facing this crisis due to lack of foresight in part of the present generation. The groundwater resources, although renewable, are limited and vulnerable. Crisis of water may not be only quantitative; quality degradation may also add a different dimension to the problem.

West Bengal, which is considered to have tremendous groundwater potentialities, is no exception. Crunch is already felt in drinking water sector in rural west Bengal during Boro cultivation season precipitating a situation of artificial draught in almost every year. Unpredictable monsoons, destruction of green coverage, siltation of rivers, uncontrolled urbanization have compounded this problem. Area under arsenic and fluoride are increasing day by day. Failures in part of the authority to implement the Groundwater Act and lack of awareness in part of the users have failed to check unrestricted growth of tubewells in the state. Stages of groundwater development with 2004 as base year that show a meager 42% stages of groundwater development in the state as against a national average of 58% , needs to be upgraded .The 4th Minor Irrigation Census is presently underway and results might reflect a higher Stages of groundwater development for this state. The act for controlling extraction of groundwater is probably not adequate in itself for total management of groundwater resources unless people is made to aware about the adverse situation which may arise from unplanned and indiscriminate use of groundwater. The other strategies involve co-ordinate approach to conservation, augmentation and conjunctive use of groundwater, wherever possible. This can be successfully achieved through rain water harvesting and artificial recharge that make it possible to:
1. Restore supply in aquifer, depleted due to overexploitation.
2. Improve chemical quality
3. Prevent salinity ingress.
4. Increase hydrostatic pressure against land subsidence

To implement rain water harvesting and artificial recharge to be implemented , it is necessary to adopt policy decisions like mandatory installation of roof top rain water harvesting and artificial recharge structures in urban areas and restoration of all derelict tanks in the villages , building check dams etc in high slope areas.
Groundwater is not an isolated resource. It is a phenomenon within the hydrological cycle. So depending on the hydrogeological condition, water level condition and stage of development proper measure for augmentation of groundwater should be taken.

BOTTLED RAINWATER: A GREENER ALTERNATIVE

Recently rainwater has come in competition with purified bottled water. An article published in the water efficiency journal states that there will be an international water testing competition in the historic spa town of Berkeley Springs, West Virginia where bottled rainwater from Richard's Rainwater, Oregon Rain, Texas Rain and Tasmanian Rain will enter along with about one hundred bottled waters from around the globe. Already available at health food stores and premier grocers, bottled rainwater is becoming recognized and accepted by consumers as a new "greener" alternative to traditional bottled waters. Bottled rain will soon be found in retail outlets nationwide. This year six of the entries will be bottled rainwater sponsored by the 501(c)(3) nonprofit American Rainwater Catchment Systems Association (ARCSA - www.arcsa.org).

Rainwater, in India had been traditionally accepted as an alternative source of pure water, even suitable for drinking. Recently in a seminar of rainwater harvesting held in Kolkata members of Jadavpur Centre for Study of Earth Science presented a paper on the rainwater quality of different parts of the West Bengal. It is revealed that rainwater is purest in the Darjeeling, Japaiguri, Coochbehar and Purulia district in terms of tested parameters like pH and TDS. The rainwater samples had been collected by school students of the district and had been tested in their school laboratories.

The news of the West Virginia contest may inspire small scale local entrepreneurs in West Bengal to come forward in rainwater bottling business which may be more environment-friendly and cheaper alternative to bottled purified water manufactured from groundwater resource. Area specific technology may be developed for harnessing rainwater economically.