Possibility of Use of Surface Water Resource in an Arsenic Contaminated Region, Prubasthali I and II Block, Burdwan, West Bengal: A GIS Approach

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1 Possibility of Use of Surface Water Resource in an Arsenic Contaminated Region, Prubasthali I and II Block, Burdwan, West Bengal: A GIS Approach Biplab Biswas 1 1 Department of Geography, The University of Burdwan, Burdwan, India Abstract: Arsenic values in groundwater above the maximum permissible limit of 0.05 mg/l (Indian standards) have been reported from Bhagirathi-Hooghly flood plain regions of West Bengal. The present study at Purbasthali I and II block in Burdwan district, West Bengal, has emerged from the flood plain forming processes. Many flood plain features are mapped using satellite image. The tube wells are providing very crucial water for domestic and irrigation purposes. But unfortunately most of the tube wells are arsenic contaminated. It has been studied that the higher amount of arsenic content tube wells (>0.05mg/l) are located around the major flood plain features like ox-bow lakes. Arsenic of surface water is harmless and it can be suggested that the villagers can use surface water with proper treatment for their daily uses. More than half of the total population of the Blocks resides around the major lakes or ponds. If the remaining less than 50 per cent population are interested to walk for an average distance of 250 meters, will get a big pond or lake for the much needed arsenic free water. The villagers must be provided purified alternative safe drinking water from surface water bodies for their sustenance. Keywords: Arsenic, Ground Water, Surface water, Peoples Sufferings, Remote Sensing, GIS 1. Introduction Water is life. But it is often associated with various problems and issues. In some parts, the issue lies with the lack of adequate water whereas in some other parts, it suffers from poor water quality. Water pollution may be either natural or anthropogenic origin. The present study is concerned with the arsenic (atomic number 33) related problems in the lower Gangetic flood plain region of West Bengal. Groundwater is available here in shallow aquifers in adequate quantity. But arsenic is very much common occurrence in shallow water of the flood plains and it is available in various parts of the world also e.g. Argentina, Australia, Bangladesh, Canada, Chile, China, Finland, Hungary, Japan, Mexico, Southern Thailand, Taiwan, United Kingdom, USA, Vietnam and India (Acharyya, S. K. S. Lahiri, B.C. Raymahashay, A. Bhowmik 2000: ; ACIC 2000). Although West Bengal has achieved remarkable successes in development of ground water for providing drinking water to the rural population in the recent past, unfortunately, higher level Arsenic (As III) in groundwater causing major health hazard in this part of West Bengal. The occurrence of arsenic rich ground water in the Bengal Deltaic Region (BDR) was first discovered in West Bengal in 1978 (Bhattacharya, P. D. Chatterjee and G. Jacks 1997: 79-92). Thousands of people have already shown the symptoms of arsenic poisoning and several millions are at risk of arsenic contamination from drinking tube-well water. It is believed that mg arsenic can cause acute arsenic poisoning to human beings (Bhattacharya, P. G. Jacks, K. M. Ahmed, A. A. Khan, and J. Routh 2001: ). Visible symptoms of chronic arsenic poisoning ( arsenicosis ) become apparent after long-term exposure, some times 6-8 years or even longer. The Inorganic arsenic (As III) accumulates in skin, hair, nail, tongue, stomach, mouth, bone, and eye lenses. Common visible symptoms are skin disorders such as hyper-pigmentation or hyperkeratosis, and ultimately cancer. Arsenic is a natural constituents in earth s crust and is distributes in a variety of minerals, commonly as compounds of iron, copper, lead, silver and gold or as a sulphide minerals. Arsenic can enter the environment either through natural or anthropogenic activities. The bio-geochemical cycling of arsenic occurs through natural water with bedrocks, sediments and soils together with the local environment. The weathering of different geologic formations such as volcanic rocks, as well as mining waste consequently results in elevated levels of arsenic in surface and ground water, where it can be transported as suspended particles (Naidu, R 2000). Anthropogenic activities are equally important for the arsenic pollution and distribution. Arsenic based compounds have been used in pesticides, herbicides, insecticides and fungicides. Mining and related activities are other main sources of arsenic in the ground and surface water (Naidu, R 2000). The present study area is characterized by shallow arsenic rich aquifers. Arsenic gets deposited together with the sediments, becoming fixed in the mineral constituents of the aquifer (Nickson, R 1997), (Oremland, R.S. J. F. Stolz, 2005: 45 49). It is a monotonous alluvial plain with relief in the range of 8 11 m. A.S.L. Various levees, active / abandoned channels, cut-off meander loops, ox-bow lakes, back swamps and inter-levee depressions / flood basins mostly aggraded are common. The active channels are Banka, Faria, Brahmani, Khari, Gurjani etc. traversing the Purbastali Block from west to east and meet the Bhagirathi Hoogly River in the east. The general slope is from north to south and southeast. The present landscape evolved from the shifting of channels, which align primarily north to south, with convexity towards the east. The present work attempts to map and identify the possibility of use of surface water from the numerous existing surface water bodies those are created by fluvial processes. The inorganic arsenic is oxidised and gets deposited in the bed of the surface water bodies. If the surface water is treated and supplied for the drinking and other domestic purpose, the arsenic poisoning can be reduces. 2. Arsenic Distribution in Purbasthali Block I & II 2.1. Spatial Distribution For the study of arsenic distribution in the Purbasthali I and II Blocks of Burdwan district of West Bengal, 40 villages were taken as sample. Average arsenic content in the shallow tube wells of each of the villages of have been calculated from data of the State Water Investigation Directorate, Burdwan. The frequency distribution and number arsenic contaminated villages are presented in Table: 1, Fig: 1. The Indian cut-off level of arsenic content in the drinking water is 0.05 mg/l. Out of 40 villages, 28 villages i.e. 70 per cent of the total villages have more than Indian standard of arsenic tolerance limit. The villages contain about 73 per cent of the total population of the regions. Or in other words 73 per cent of the total population (2001) is directly exposed to arsenic pollution. Eight of the sampled villages, i.e. 20 per cent of the villages have arsenic above 0.09 mg/l. They contain about 23 per cent of the total population. The population is the worst affected and live at the much higher level of danger than the normal. One of the 24

2 villages (J.L. No. 98) has arsenic as high as 0.30 mg/l. Name of the village is Mandra. It is located almost in the centre of the Purbasthali block. It has been learnt from the field visits, that this village is the worst sufferers from the arsenicosis. The villagers were the first to report the problems of arsenic pollution in the entire region. Table 1. FREQUENCY DISTRIBUTION OF ARSENIC VALUES IN PURBASTHALI ( ) Arsenic Content (mg/l) Frequency of Villages (in %) % of Population to Total < > meters to 30 meters, suddenly the average arsenic content decreased from 0.09 mg/l to 0.04mg/l, which was in safe limit as per Indian standard. Further depth of meter the average arsenic content decreased to 0.03mg/l. So, planners were of the belief if the depth of the tube wells can be increased, then international standard of drinking water may be available. But unfortunately, after that with increasing depth of tube wells, it was observed that the average arsenic content increased to 0.12 mg/l to 0.08mg/l at 110 meter depth of tube wells. Presently 15 per cent of the total villages are getting water from this depth. The numbers of deep tube wells are growing fast in the belief that it will reduce arsenic contamination. The Fig 2 explains the relationship between gradually increasing depth classes (independent variable) and two other dependent variables i.e. average arsenic concentration and number of contaminated villages. The bars representing average arsenic concentration distribution along with the distinct depth zones depicts an alternate oscillatory graph (rise and fall) of arsenic concentration; whereas, the frequency of contaminated villages are experiencing a gradual decreasing trend with the increasing depth of the tube wells. Maximum number of installed tube wells are belongs to shallow depth. The average arsenic concentrations are high at the lowest and highest depth tube wells. On the other hand highest numbers of contaminated villages are concentrated in the shallow depth i.e. below 50 meter. The linear regression established between tube well depth and average arsenic concentration shows a gentle positive trend i.e. level of arsenic concentration are gradually increasing with depth which is contradictory with the previous hypothesis that the shallow depth tube wells are more vulnerable to arsenic contamination, but in reality the data do not support it. So, we can say that tube wells of any depth contain arsenic at the much higher level than the safe level (WHO standard). TABLE 2. FREQUENCY DISTRIBUTION OF ARSENIC CONTAMINATED TUBE WELLS OF DIFFERENT DEPTHS (M) AT PURBASTHALI ( ) Fig 1. Distribution of Arsenic in Purbasthali I and II Block 14 villages of the study area i.e. 35 per cent villages are having average arsenic content ranging from 0.05 to 0.07 mg/l. There are 7 villages i.e per cent of the study villages, where the arsenic content is less than 0.03 mg/l. These villages contain about 16 per cent of the total population. As per the Indian standard of the safe level we can say that only 16 per cent of the total population presently are in safe condition from the potential threat of arsenic poisoning. WHO specified safe level of arsenic in water is below 0.01mg/l. If we consider the international level, the whole sampled villages have more arsenic content than the specified level in the domestic tube wells. So the entire population is living on the danger level of arsenic poisoning Vertical Distribution The depth of the tube wells of the region varies from 10 meter to 110 meter (Table 2 and Fig 2). It is surprising to observe that arsenic is available, well above the danger level, in every range of depths. Shallow tube wells were the extensive establishment for supplying drinking water in the region. Depth of shallow tube wells ranges from meters and the average arsenic content at this depth is 0.09 mg/l. Presently per cent villages are still dependent on the shallow tube wells for domestic water. Finding the water of this depth unsafe, people started for higher depth of tube wells. Initially, when the average depth of the tube wells increased from Average Depth Average (m) of Tube Arsenic Wells Content (mg/l) Frequency Villages of % of Tube wells Source: SWID, Burdwan and Author s Calculation Fig 2. Arsenic Content in Different Depths (m) Tube Wells 25

3 3. Availability and Distribution of Surface Water Bodies The study area, Purbasthali I and II Block are part of the Bhagirathi-Hoogly River flood plain. It is a strip of relative smooth land area bordering a stream and overflowing at times of high water. From the satellite image (Fig 3) of the study area it is clearly evident that the river Bhagirathi-Hoogly has developed lot of floodplain features in this particular reach. Major flood plain features were identified using the topographical sheets (73 A/ 2, 3, 6 and 7), surveyed in The map has further been updated using the satellite imagery of IRS_1C_LISS_III, Visual image classification of the image is done. The major flood plain features that are found within the study region are discussed below. Fig 3. Satellite Image of Purbasthali I and II Block 3.1 The River Channel The river Bhaghirathi formed the north and eastern border of the block and flowing from the north to south direction. There are some other rivers which are flowing from western part to meet Bhaghirathi in the east. Other active channels are Banka, Faria, Brahmani, Khari, Gurjani etc. The rivers pass through 52 villages, i.e. 27 per cent of the total villages of the Blocks. Total population living in these villages is i.e. about 21 per cent of total population of the Blocks. Almost all the rivers of the region are sinuous to meandering. The sinuosity index ranges from 1.30 to 1.95 (Table 3). It can be interpreted the river is travelling with more distance than the air distance. It signify that the region have enough flowing surface water resources. All of the rivers are perennial and navigable through out the year. TABLE 3. CHANNEL PATTERN OF MAJOR RIVERS OF PURBASTHALI (2000) Name of the Rivers flowing through the Blocks Total Length (km) Sinuosity Index (Leopold, et. al. 1957) Category Bhagirathi-Hoogly Meandering Banka Sinuous Brahmani Sinuous Khari Sinuous 3.2 Ox-bow Lakes; Meander Scrolls and Sloughs The ox-bow lake, meander scrolls and sloughs represent the cut-off portion of meanders, depressions and rises on the convex sides are meander scrolls and areas of dead water formed both in meander-scroll depressions are identified as surface water bodies. From the 1974 s topographical sheet and by updating the map using 2000 s satellite imagery (IRS-1C), many more ox-bow lakes, sloughs, marshy lands, bills, ponds or tanks are identified and mapped. (Fig 4). In general about 5 per cent area to total area of the Block is covered by the standing surface water bodies. The table no. 4 shows that there is one village (J.L. No. 142) where the surface water bodies cover 89 per cent of its total area. About 17 % of its total villages have no such important standing water as lakes or ponds. But they are having perennial rivers. River Bhagirathi is one of them. As the rivers are meandering or sinuous, so they travel at lest 1.5 times than the air distance of the village. About 6 per cent of the total villages do not have significantly large water bodies. Among these villages, some of them are uninhabited village and less than 4 per cent of the total population are living. The absence of large significant water bodies may not have any important negative implication to the livelihood to the local people. About 15 per cent of the total villages have >10 per cent of their total area under surface water bodies. They contain about 17 per cent of total population of the Blocks. All most all the water bodies are permanent and have water through out the year. Many of the ponds are even connected by some narrow links with the main rivers. So, availability of surface water is not a problem in the region. TABLE: 4. AREA UNDER SURFACE WATER BODIES (2000) % of Area under Water Body % to Total Village >

4 Fig 4. Distribution of Flood Plain Features (2000) The distributions of surface water bodies have been quantified. The whole region has been divided into one sq. km. grids and counted the number of surface water bodies within each sq. km. Isolines of 5, 10 and 15 has been drawn on the and a frequency map of surface water bodies per one sq. km has been drawn (Fig 5, Table: 5). The lowest isoline zone of 0 5 numbers of ponds/sq. km, covers about 73 % area of the blocks. The zone is distributed through out the block. TABLE 5. ISOLINES ZONES OF FREQUENCY OF SURFACE WATER BODIES PER SQ. KM. (2000) Isoline Zones of Surface Water Body Area Covered (Hec.) % of Area > Isolines zones of 10 and above are concentrated in the west-central part and it is running through the central part of the Blocks. In the south-western part of the Blocks another zone is there where many ponds are concentrated. This region is covering about 30 per cent area of the Blocks. People do use the water of the ponds mainly for bathing, washing and irrigation too. Some of the water bodies are used for jute retting also. Water bodies are important aspect to the livelihood of the villagers. Fig 5. Surface Water Frequency Map (2000) 4. Association between Arsenic Distribution and Surface Water Bodies as Geomorphic Features In the West Bengal part of the Bengal Delta, the Holocene sequence is classified into the Older Alluvium Plain (OAP), overlain by the Young Delta Plain (YDP). Both are incised by the present channel and delta plain of the Bhagirathi River (Sengupta, S. P. K. Mukherjee, T. Pal, S. Shome, 2004: ). The present landscape evolved from the shifting of channels, which align primarily north to south, with convexity towards the east. Fluvial depositional processes produced different landforms here. It has been established that arsenic comes to this delta as a natural contaminant carried in by the sediments of the Himalayan Rivers. The element is deposited together with the sediments, becoming fixed in the mineral constituents of the aquifer (Nickson, R 1997). Arsenic distribution in the aquifer sediments is a product of the same process that created the fluvial landscape. In other word, where there are more geomorphic features, more concentration of Arsenic in ground water may be available there. The surface water bodies of the region are developed due to geomorphic processes. An attempt has been made to correlate the presence of surface water bodies and the arsenic content in ground water of the region. The Fig 4 shows the distribution of the flood plain features in the Purbasthali block. There are numerous ponds or tanks, distributed through out the block. The location, shape, size, association and pattern of distribution and the field visits, clearly indicate that most of the tanks / ponds are geomorphic in origin. For the present discussion, those features have been taken into consideration. The Fig 6 clearly shows that the flood plain features and the surveyed villages have very close association. From the map it can be interpreted that the villages where there is arsenic some flood plain features are present in those villages. The table 6 shows the percentage distribution of the area coverage by the flood plain features to the total area of the villages and also the average arsenic content (mg/l) in the shallow tube wells. It has been observed that 15 villages or per cent of the sampled villages have less than one percent flood plain features to their total area. Average arsenic content in the shallow ground water of those villages is 0.06mg/l. 27

5 The second category of the flood plain distribution is 1.00 to 3.00 per cent area coverage by the food plain features to the total area of the villages. There are 10 villages, i.e per cent of the total surveyed villages are falling in this category. The average arsenic content of the villages is mg/l. It is less than the Indian standard of arsenic tolerance but much higher than the WHO (0.01 mg/l) standard. The villages having flood plain features coverage 7.00 to per cent to their total geographical area have average arsenic content as high as mg/l. The villages where the flood plain features coverage is > per cent to their total area have average arsenic content mg/l. From the table 6 and the Fig 6, it is clearly visible that with the increasing flood plain / geomorphic features coverage, the arsenic content in the shallow water is increasing. Fig 6. Distribution of Arsenic in Relation to Flood Plain Features TABLE 6. FREQUENCY DISTRIBUTION OF ARSENIC CONTAMINATED VILLAGE IN PURBASTHALI (2001) % of Flood Plain Features To Total Area Frequency of Villages % Frequency of Villages Average As Content (mg/l) < > SOURCE: SWID, BURDWAN AND AUTHOR S CALCULATION Further, some statistical test for the relationship between the average arsenic content of the villages and their average flood plain features. The Product Moment Correlation Coefficient (r) test between these two variable is The value signifies that there is very strong positive relationship between the presence of flood plain features and availability of arsenic content of the tube wells of any depth. t test of the r is significant at 99% confidence limit or 1% level of significance. From the above discussion it can be concluded that the arsenic content in the ground water has very much close relationship with the flood plain / geomorphic features. 5. Possibility of Use of Surface Water Resource: GIS Approach From the above discussion we have learnt that the entire region and specially Purbasthali I and II blocks are worst sufferers from Arsenicosis. There are various existing methods of filtering the arsenic from the ground water. At the same time it has already being proved that the filters are being disposed without much care and the possibility of contamination increases several folds. Almost every village have some areas under surface water bodies / Geomorphic features. More the presence of geomorphic features, more the probability of having arsenic contamination in their tube wells water. No tube well is out of arsenic contamination in the region. According to the international standard of 0.01mg/l, no village of the region is out of danger level of arsenic poisoning. Arsenic (As V) in the surface water bodies is not harmful to human health. There should be earnest effort to make the surface water available for domestic and drinking water in the arsenic affected regions. TABLE 7. SURFACE WATER BODIES, WATER HOLDING CAPACITY AND DEMAND (2001) Buffer Distance from Water Bodies (m) % of No. of Settlement to Total Population (%) in the Villages % Surface Water Bodies Water holding Capacity Gallon (00000) Water Demand Gallon (00000) Difference between Water Available & Demand (00000) > SOURCE: AUTHOR S CALCULATION Geographic Information System (GIS) has been used to identify the proximity of surface water bodies to the villages. Buffers have been created along the large water surface water bodies. Buffers of 50, 100, 200 and 500 meter are created and the percentage of villages covering by the buffers are analyzed (Table: 7). The buffer analysis suggested that one of the important locational characteristics the settlements of Purbasthali I & II Blocks are mainly water front location. About 62 per cent of total settlements are located at the water front. In another word, the surface water is available with no distance from the villages. These villages contain about 53 per cent of the total population of the Blocks. These 62 per cent villages contain about 60 per cent of the total available surface water bodies of the region. The depth of the surface water bodies varies spatially and as well as temporally. During the field visit it has been learnt that even in the driest months, the most of the surface water bodies contain more than 2 meter of depth. Considering the average annual depth of 2 meter, the surface water bodies of this particular category can hold about Gallon of water. While the annual water demand for the villagers (40 Litters/Day) will be Gallon. So, after meeting the domestic demand there will be about Gallon of excess water in the region, which can be used for other purpose. Fig 7. Surface Water bodies (1) and the after 100 meter Buffer (2) of a portion of the Block From the table: 7 it is seen that about 72 per cent villages are located with in 500 meter of distance from a large surface water bodies. And the water holding capacity of the water bodies available in the region will always exceed the requirement of water for domestic purposes. If few people willing to travel on an average 250 meter, will get a large surface water bodies for 28

6 arsenic free water. Fig 7 shows portion of the Blocks with available surface water bodies (1) and after the same region with 100 meter Buffer of the water bodies (2). The buffer study suggests that if the area of the surface water bodies are increased by 100 metre, the entire settlement areas will be covered by them. To put it another way, it can be interpreted that if the people are willing to travel about 100 meter from their settlement, most of them will find a significantly large surface water bodies. There are some villages where major water bodies are available beyond 500 meter. They contain about 28 per cent of total population. Though the distance is not very far, but planning should be made to bring surface water more closely to them. 6. Conclusion The present study looked at the nature and extent of the arsenic pollution in Purbastali block of Burdwan district of West Bengal. Attempt has also been made to study the relationship with the flood plain or geomorphic features with the arsenic contamination and possibility of use the surface water for drinking and domestic use in the region. If the model works, it can easily be copied to another region. In the Purbastali I and II block area arsenic contamination in groundwater is largely being determined by the availability of flood plain or geomorphic features. Arsenic content in the aquifers show very high positive correlation with the availability of flood plain / geomorphic features and presence of arsenic in the tube wells. It can be concluded that prevalent geomorphic processes resulting the origin of the different geomorphic features leaving arsenic in the aquifers. The tube wells in the aquifers of the active geomorphic units have more arsenic contamination. Almost all the villages contain surface water bodies and in some cases the proportion of surface water bodies is 89 per cent to its total area. It has been established that every tube well is having high arsenic content. With the initial development of low value of arsenic in the deeper tube wells, planners went for even deeper depth of tube wells, but the arsenic content in the deep tube wells are also high and beyond tolerance. Total population of the Blocks is Supply of arsenic free water to the population is a challenging task for the planners. Planners should avoid the proximity of the surface water bodies or geomorphic features of active geomorphic units for the setting up shallow tube-wells. But there is almost no area which is free from having such features. The arsenic of the surface water bodies is harmless to human health. There are sufficiently huge concentration of surface water bodies and can hold considerably high amount of water which exceeds the demand of water. Planners must develop some plans and method to make to surface water potable. At the same time people, who are living in those active areas, should be careful about using shallow tube well water for drinking and other domestic uses. Immediate action should be taken for providing arsenic free drinking water Bhattacharya, P. G. Jacks, K. M. Ahmed, A. A. Khan, and J. Routh, Arsenic in Ground water of the Bengal Delta Plain Aquifers in Bangladesh, Bull. Env. Contamination and Toxicology, 69(4) pp Naidu, R Arsenic contamination of rural ground water supplies in Bangladesh, India and Australia: Implication for soil quality, animal and human health, Abstract from 31st International Geological Congress, Rio de Janeiro, Brazil. Nickson, R Origin and Distribution of Arsenic in Groundwater, Central Bangladesh. M.Sc. Thesis Report, University College London. Oremland, R.S. J. F. Stolz, Arsenic, microbes and contaminated aquifers, Trends Microbial, 13, pp Sengupta, S. P. K. Mukherjee, T. Pal, S. Shome, Nature and origin of arsenic carriers in shallow aquifer sediments of Bengal Delta, India, Environ Geol, 45, pp References Acharyya, S. K. S. Lahiri, B.C. Raymahashay, A. Bhowmik, Arsenic toxicity of groundwater in parts of the Bengal basin in India and Bangladesh: the role of quaternary stratigraphy and Holocene sea-level fluctuation, Environ Geol, 39, pp ACIC (West Bengal and Bangladesh), Aug, Arsenic sections of Draft Development Strategy of the National Water Management plan Bangladesh, URL http./bicn.com/acic. Bhattacharya, P. D. Chatterjee and G. Jacks, Occurrence of arsenic contaminated groundwater in alluvial aquifer from delta plains, Eastern India. Option for safe drinking water supply, Int. J. Water Resource Development, 13(1), pp. 29