ASSESSMENT OF GROUND WATER VULNERABILITY USING GIS-A CASE STUDY ON THIRUVANNAMALAI DISTRICT,TAMILNADU,INDIA Praveen Kumar.G∗,Kaviarasan.M,G.Rashmi, P.Geetha Remote Sensing and Wireless Sensor Networks Division, Centre for Excellence in Computational Engineering and Networking, Amrita Vishwa Vidyapeetham University,Coimbatore-641112. praveen16003@gmail.com Commission VI, WG VI/4 KEY WORDS: Water Quality,Groundwater contamination,Physico-chemical parameter, GIS,Thiruvannamalai,WHO ABSTRACT: Water is indispensable for sustaining life on earth. Millions of people lack access to clean water owing to geographical and anthropogenic factors. Ground water contamination has always been a reason of concern and it is very expensive and difficult to clean up. In a country like India where the population density and land use is high, ground water is highly prone to contamination. The consequences of contamination manifests as poisoning and diseases such as hepatitis and cancer. Hence an assessment and subsequent action is needed.The present work is a survey of ground water samples in rural and urban location of Thiruvannamalai district in the state of Tamil Nadu, India. The physico-chemical parameters of water samples like pH, EC, Total Hardness, Ca, Mg, Na, K, sulphate,nitrate,Chloride are analyzed. A comparison of each parameter is performed with that of the standard permissible limit as recommended by World Health Organization (WHO). Our main objective is to determine the quality of ground water with the help of Geographical Information System (GIS) which gives the exact location of ground water contamination. 1. INTRODUCTION Water availability and its quality has a profound impact on the overall well being of people of a country and in its development. With the ever increasing demand for food production, industrial growth, population explosion a situation of unprecedented exploitation and contamination of both surface and ground water prevails. Ground Water has an important role in meeting the water requirements of agriculture, industrial and domestic sectors in India. About 85 percent of India’s rural domestic water requirements, 50 percent of its urban water requirements and more than 50 percent of its irrigation requirements are being met from ground water resources (Dynamic Ground Water Resources of India, 2011). The ground water recharge is the amount of water that will percolate down to the water table. It greatly depends on rainfall, nature of soil, rocks etc. It has been recognized that the quality of ground water is of nearly equal importance to quantity. As greater development and use of ground water continues, combined with the reuse of water, quality suffers unless consideration is given to protecting it (Adhikary et al., n.d.). The Remote Sensing Technology and Geographical Information System (GIS) has enabled data collection and subsequent assessment possible even in the most inaccessible areas thus helping in effective study of ground water. GIS helps in creating geographical databases and thematic models of ground water depth, quality etc . Ground water contains a wide variety of dissolved inorganic chemical constituents in various concentrations resulting from chemical and biochemical interactions between water and geological materials. Inorganic contaminants include salinity, chloride, flouride, nitrate, iron and arsenic are important in determining the suitability of ground water for drinking purposes (Ground Water Quality In Shallow Aquifers of India, 2010).Chemical composition of ground water is influenced not only by geographical factors like type of soil, rocks through which the water percolates but also by anthropogenic factors like use of chemical fertilizers, pesti∗ Corresponding author.praveen16003@gmail.com cides, uncontrolled disposal of industrial wastes etc. In this paper, the ground water samples of Thiruvannamalai district, Tamil Nadu is analysed. The ground water level in this district has come down owing to erratic precipitation. Ground water quality of this district is analyzed by studying the physico-chemical parameters present, against the WHO standards. A case study is carried on the spatial assessment of ground water vulnerability of Thiruvannamalai district using GIS. 1.1 Study Area Thiruvannamalai district of TamilNadu, India is well renowed for its cultural significance. It covers a distance of 6191km2 and lies between 11◦ 55′ and 13◦ 15′ North latitude and 78◦ 20′ to 79◦ 50′ East longitude. The district is bounded by Vellore district on the north and west, by Villupuram district on the south, by Dharmapuri district on southwest and by Kanchipuram district on the east. The district has a population of 2,464,875 as per the 2011 census. Nearly 41 percent of the area is used for agriculture and dug wells are the major source of irrigation. The rivers Palar, Cheyyar and Ponnaiyar drain this district on a seasonal basis and it also forms a portion of the basins of Palar and Ponnaiyar. It has a tropical climate and gets rainfall of 601.80mm from the North East monsoon and about 485.90mm from the South West monsoon. 2. METHODOLOGY GIS is a powerful tool for the integration of the spatial data with the attribute data along the ground truth. Topomaps of Thiruvannamalai district were obtained from the Geological survey of India, Chennai. The maps are scanned and digitized followed by georeferencing of the map with digitization of boundaries using ARCGIS software. Then maps are traced out along the toposheets to create the spatial database of the taluks and blocks. Then the labelling is carried in blocks. Attribute database of the depth level Table 1: Physico-chemical parameters I Figure 1: Thiruvannamalai district view and physiochemical paramaters like pH, Electrical Conductivity, Nitrate, Chloride, fluoride etc of the ground water is being obtained from the Central Ground Water Board(CGWB), Chennai. With the available data the integration of the Spatial database and Attribute database is done. With these we arrive at the output of vulnerable zones of the entire district. Similarly the exploitation level of the blocks is also drafted. Location pH EC TH Ca Mg Na ANNAVADI ARNI CHETPET CHEYYAR MELMAKOOTROAD PACHEL POLUR THANDARAMPATTU THANIPADI THIRUVANNAMALAI VANDAVASI WALAJABAD 8.00 7.40 8.02 8.16 8.10 8.15 8.10 7.97 8.20 8.10 8.00 8.00 925 2070 1614 446 1639 1027 594 695 1440 1092 773 668 320 630 470 200 625 500 260 325 435 340 235 250 52 80 82 52 122 60 42 62 74 46 28 48 46 105 64 17 78 85 38 41 61 55 40 32 78 192 145 9 108 44 23 20 114 108 84 31 minerals from rocks and soil (Thompson et al., 2007). The permissible limit is 6.5 to 8.5. Thanipadi area considered shows the highest value for pH and Arani area shows minimum value for pH respectively. All areas have their pH values well within the specified limit. 3.2 EC Electrical conductivity of water is its ability to conduct electrical current due to the presence of dissolved materials. The more the dissolved material higher is the EC. The study areas have values from 446 S/cm to 2070 S/cm with Arani showing the highest value and Cheyyar area has a low value for EC. 3.3 TH Water hardness represents the total concentration of calcium and magnesium ions that is responsible for scaling of boilers. It does not pose any direct health risk. The permissible limit for hardness of water is given to be 100mg/L. In this district all the study areas exceed this limit with Melmakootroad showing the highest value of 625mg/L. 3.4 Calcium Calcium is from natural sources like granitic terrain which contains large concentration of these elements (Thangavelu, 2013). The permissible limit for calcium is 75mg/L. Melmakootroad shows a very high value of 122mg/L and the lowest value is found in Vandavasi(28mg/L). 3.5 Magnesium Figure 2: Flow chart of the methodology 3. RESULTS AND DISCUSSIONS The samples obtained are analyzed. Each physico-chemical parameter is taken and compared against the WHO standards and discussed as follows: 3.1 pH Water is classified as acidic or alkaline based on the pH value. pH is an important indicator of the ability of water to dissolve For individuals at the borderline of magnesium deficiency, waterborne magnesium can make an important contribution to the total daily intake. Magnesium content in water plays a critical role due to its higher bioavailability Rubenowitz et al. (1996). The desirable limit for magnesium is 30mg/L and it can extend upto 100 mg/L. This limit is exceeded in the study area of Arani showing 105mg/L. Cheyyar shows the minimum value for magnesium content of 17mg/L. 3.6 Sodium The permissable limit for sodium is 200mg/L above which the taste of water is affected. The maximum value is seen in Arani area with a sodium content of 192 mg/L. The minimum values of 9 mg/L is seen in the samples taken from Cheyyar area. Figure 3: topomap Figure 5: EC spatial distribution Figure 4: pH spatial distribution Figure 6: TH spatial distribution Figure 7: Ca spatial distribution Figure 9: Na spatial distribution Figure 8: Mg spatial distribution Figure 10: K spatial distribution Figure 11: Cl spatial distribution Figure 13: NO3 spatial distribution Figure 12: SO4 spatial distribution Figure 14: F spatial distribution 3.7 Potassium 4. CONCLUSION Potassium is mostly present in water due to potassium permanganate usage for water treatment. The study areas show values ranging between 5mg/L to 38mg/L which are well within the permissable limits. Arni and Pachel show the lowest and highest value respectively. Table 2: physico-chemical parameters II Location K Cl SO4 NO3 F ANNAVADI ARNI CHETPET CHEYYAR MELMAKOOTROAD PACHEL POLUR THANDARAMPATTU THANIPADI THIRUVANNAMALAI VANDAVASI WALAJABAD 8 5 31 20 11 31 16 20 23 7 10 8 74 284 305 35 333 156 67 103 142 199 113 71 72 48 288 34 240 202 86 96 206 91 53 24 10 12 28 1 29 11 3 5 24 5 3 1 1.14 0.74 0.82 0.93 1.46 0.88 0.88 0.91 0.82 0.72 1.27 0.78 This study demonstrates the efficiency of GIS in assessing the ground water vulnerability in Thiruvannamalai area . A few areas have high values of Total Hardness, chloride, nitrate content that exceed the standards specified by WHO. In these areas water treatment like softening is essential to ensure the safety of drinking water. This comprehensive study shows that regular monitoring of ground water samples is also essential. The analysis made on the ground water quality can be used as a reference for further study and investigations in this district. The spatial maps give a clear visualization of the ground water scenario. The future work is to apply prediction modelling for the ground water study. References Adhikary, S. K., Ahmed, C. A. and Saha, G. C., n.d. Mapping of shallow groundwater quality using gis: A study from a small catchment in northwestern region of bangladesh. Dynamic Ground Water Resources of India, 2011. Ground Water Quality In Shallow Aquifers of India, 2010. Guidelines for Drinking water quality., 2003. World Health Organization. 3.8 Chloride Chloride in drinking-water originates from natural sources and industrial effluents, urban runoff containing de- icing salt and saline intrusion. The main source of human exposure to chloride is the addition of salt to food and the intake from this source is usually greatly in excess of that from drinking-water (Guidelines for Drinking water quality., 2003). The areas of Chetpet, Melmakootroad and Arani exceed the permissible limit of 250mg/L as specified by WHO with Melmakootroad showing the maximum value. When chloride exceeds the permissable limit it impacts the water taste. 3.9 Sulphates Sulphates seep into ground water through effluents from industries like tanning, paper mills or through usage of chemical fertilizers in agriculture. The permissable limit as given by WHO is 150 mg/L to 400mg/L. Dehydration results when sulphates are in excess. The values for the study areas ranges between 24mg/L to 288 mg/L with Chetpet and Walajabad areas showing the highest and lowest limit respectively. For all areas analyzed sulphates content is within the specified limit. 3.10 Nitrates Nitrates occur due to usage of fertilizers and an excess of this compund though not directly toxic, affects the infants resulting in matheomoglobinemia(blue baby syndrome). The WHO recommended limit is 45mg/L with no relaxation. The study areas of Pachal, Thanipadi, Arani show high value with the latter having the highest value of 148mg/L. 3.11 Fluoride Fluoride content in excess can have an adverse effect on the teeth enamel and skeletal tissues of the human body. The permissible limit is upto 1.5 mg/L. In the study Melmakootroad area shows a high value with it approaching 1.46 mg/L. It must be noted that when fluoride tends to exceed this limit dental and skeletal fluorois occurs. Rubenowitz, E., Axelsson, G. and Rylander, R., 1996. Magnesium in drinking water and death from acute myocardial infarction. American journal of epidemiology 143(5), pp. 456–462. Thangavelu, A., 2013. Mapping the groundwater quality in coimbatore city, india based on physico-chemical parameters. IOSR Journal Of Environmental Science, Toxicology And Food Technology 3, pp. 32–40. Thompson, T., Fawell, J., Kunikane, S., Jackson, D., Appleyard, S., Callan, P., Bartram, J., Kingston, P. et al., 2007. Chemical safety of drinking-water: assessing priorities for risk management. World Health Organization.