International Journal of Civil, Structural, Environmental and Infrastructure Engineering Research and Development (IJCSEIERD) ISSN 2249-6866 Vol. 3, Issue 2, Jun 2013, 135-144 © TJPRC Pvt. Ltd.

ASSESSMENT OF SPATIAL DISTRIBUTION OF GROUNDWATER QUALITY IN KONDAGATTU CATCHMENT OF GREATER MUNICIPAL CORPORATION, – A GIS BASED APPROACH

JANARDHANA SWAMY C1, VENKATESWARA RAO T2 & PRADEEP KUMAR G. N3 1Research Scholar, Department of Civil Engineering, College of Engineering, Sri Venkateswara University, Tirupati, , India 2Scholar, Department of Geo-Engineering, College of Engineering, Andhra University, Visakhapatnam, Andhra Pradesh, India 3Professor, Department of Civil Engineering, College of Engineering, Sri Venkateswara University, Tirupati, Andhra Pradesh, India

ABSTRACT

Qualitative analysis of groundwater is having equal importance on par with the quantitative assessment for best water management practice. Present study appraises the groundwater quality in Kondagattu Catchment of Greater Visakhapatnam Municipal Corporation. Groundwater Quality Index (GWQI), a congregate parameter representing the quality and suitability of groundwater is computed and coupled with GIS technology. Spatial analyst module in ArcGIS software has been used to generate the spatial distribution of water quality parameters. Based on the analysis, most of the area under study falls in good water zone. The results revealed that the spatial distribution maps generated for various physico•chemical parameters using GIS techniques could be useful for planners and decision makers for initiating groundwater quality development.

KEYWORDS: Spatial Distribution, Groundwater Quality Index (GWQI), Greater Visakhapatnam Municipal Corporation, Geographical Information System (GIS)

INTRODUCTION GENERAL Groundwater, of late has become an important source of water to reckon with to meet different needs of an individual and also society. Heavy and indiscriminate usage of this source obviously results in degradation of its quality. Ascertaining the quality is crucial before its use for various purposes such as drinking, agricultural, recreational and industrial use.

Water Quality Index (WQI) is an important parameter for ascertaining water quality and its suitability for use. It is one of the most comprehensive tools to yield information on the quality of water. It is simply an integration of data on complex quality parameters and generating a score that describes water quality status. It is also defined as a rating that provides the composite influence of quality parameters.

Brown et al. (1972) developed a water quality index paying great rigor in selecting parameters, developing a common scale, and assigning weights for which elaborate Delphic exercises were performed. This effort was supported by the National Sanitation Foundation (NSF) and that is why also referred as NSFWQI. This work seems to be the most comprehensive and has been discussed in various papers (Brown et al, 1972; Landwehr and Deininger, 1976). 136 Janardhana Swamy C, Venkateswara Rao T & Pradeep Kumar G. N

Swarna Latha et al. (2010) used raster interpolation technique in GIS is used to delineate the distribution of various water quality parameters. Along with raster interpolation technique, point layer data of sampling location were imported duly assigning unique codes and standard permissible and excessive values of various water quality parameters in the study area resulted in delineation of spatial distribution maps of water quality parameters and groundwater quality index (GWQI).

STUDY AREA

Greater Visakhapatnam Municipal Corporation (GVMC) is the second biggest city with rapid urbanization in the State of Andhra Pradesh. Visakhapatnam or Vizag is located midway between two metropolitan cities of India namely Kolkata and Chennai. The city consists of golden beaches, green fields, hills consisting of valleys with peaceful living conditions, great history and varied environment. The Greater Visakhapatnam, lies between 17º 32' N to 17º 51' N latitudes and 83º 05' E to 83º 24' E longitudes with semi arid maritime tropical climate situated in coastal Andhra Pradesh on the east coast of India.

Figure 1: Map Showing the Study Area The study area is located adjacent to the Meghadri Gadda watershed bounded between latitudes 17043'30" to 17049'00" and from longitudes 83011'45" to 83016'30". Kondagattu Catchment area is starting from Visakhapatnam Air Port and is ending at covering famous Hindu pilgrimage of Simhachalam Hills. The temperature exhibits extreme characteristics, decreases due to South West Monsoon and tumbles to a mean minimum of 18o C by December and then gradually increases to mean maximum temperature of 40o C by the end of May. The study area receives annual normal rainfall between 1028 to 1111 mm, the maximum received is from south-west monsoon season from August to October. The relative humidity averages 72% over the year with 64% of lowest average occurs in November and December and 77% of highest average occurs in April and May. The maximum altitude is 478 m., on top of Simhachalam Assessment of Spatial Distribution of Groundwater Quality in Kondagattu Catchment 137 of Greater Visakhapatnam Municipal Corporation, India – A GIS Based Approach hill and the minimum elevation is about 10 m. observed in the southern part of the study area at Kothapalem. The study area is as shown in figure 1.

MATERIALS AND METHODS Groundwater Sampling and Analysis Water samples were collected in November’ 2012 from 73 wells spread over 20 suburbs of the study area. Plastic containers were used for the collection of water samples and analyses were carried for water quality parameters viz. pH, Total Dissolved Solids (TDS), Alkalinity (Al), Chlorides (Cl), Fluorides (F), Nitrate (No3), Sulphate (So4), Calcium (Ca), Magnesium (Mg), Total Hardness (TH) and Electrical Conductivity (Ec) in the laboratory.

Global Positioning System (GPS) was used for locating sampling stations. As per APHA (1995) , methods adopted for estimating various groundwater parameters are detailed in Table 1.

Table 1: Methods Adopted for Estimating Different Physico-Chemical Parameters of Groundwater in the Study Area

Sl. No. Parameters Method 1 pH Digital pH meter 2 Total Dissolved Solids (TDS) Elico meter 3 Alkalinity (Al) Titrimetry 4 Chlorides (Cl) Titrimetry 5 Fluorides (F) Spectrophotometric method 6 Nitrate (No3) Spectrophotometric method 7 Sulphate (So4) Spectrophotometric method 8 Calcium (Ca) Titrimetry 9 Magnesium (Mg) ICP Mass Spectrometry 10 Total Hardness (TH) EDTA titration method 11 Electrical Conductivity (Ec) Elico meter

Water Quality Index (WQI)

Numerical representation of overall quality of water is Water Quality Index, which is proven to be a very useful tool in water quality management. Horton (1965) defined Water Quality Index as a reflection of composite influence of individual quality characteristics on the overall quality of water.

It is an effective tool to bring several water quality parameters onto a common scale and forming into a unique number with a chosen method of estimation. WQI value greatly varies with quality parameters selected.

In the present study, eleven physico-chemical parameters namely pH, Total Dissolved Solids (TDS), Alkalinity, Chloride, Fluoride, Nitrate, Sulphate, Calcium, Magnesium, Total Hardness and Electrical Conductivity were used to calculate WQI.

Estimation of Water Quality Index (WQI)

A widely used method of computing WQI, developed by Brown et al. (1972) and supported by the National Sanitation Foundation (NSF) is used in the present study to compute WQI.

Each of the 11 parameters has been assigned a weight (wi) based on its influence on health hazards. A maximum weight of 5 has been assigned to parameters like chloride, magnesium and electrical conductivity.

A minimum weight of 1 is given to calcium. Other parameters were assigned a weight between 1 and 5 as listed in Table 2. 138 Janardhana Swamy C, Venkateswara Rao T & Pradeep Kumar G. N

Relative weight (Wi) of each parameter is computed using Equation (1):

Wi = wi / ( ∑ wi ) (1)

where wi = weightage of individual parameter, ∑ wi = sum of all the weightages.

Then quality rating is computed using Equation (2)

qi= ( ci / si ) *100 (2)

where, qi = the quality rating, ci = concentration of each chemical parameter in each water sample in mg/l and si = allowable water quality standard for each chemical parameter in mg/l (Table. 2).

Table 2: The Weight, the Calculated Related Weight Values and Water Quality Standards as Per BIS & WHO

BIS & WHO Relative Weight Sl. No Chemical Parameters Standards Weight (wi) Max. Limit (Si) (Wi) 1 pH 8.50 2 0.0526 2 Total Dissolved solids (mg/l) 2000.00 3 0.0789 3 Alkalinity (mg/l) 600.00 4 0.1053 4 Chlorides (mg/l) 1000.00 5 0.1316 5 Flouride (mg/l) 1.50 2 0.0526 6 Nitrate (mg/l) 45.00 5 0.1316 7 Sulphate (mg/l) 400.00 4 0.1053 8 Calcium (mg/l) 200.00 1 0.0263 9 Magnesium (mg/l) 30.00 5 0.1316 10 Total Hardness (mg/l) 600.00 2 0.0526 11 Electrical conductivity (µS/cm) 3000.00 5 0.1316 ∑w 38 i

Weighted quality rating, Sii, is then determined for each parameter using Equation (3).

Sii = Wi * qi (3)

qi = rating based on concentration of ith parameter.

Groundwater Quality Index (WQI) is then arrived at using Equation (4):

n GWQI =  Sii (4) 1

n = number of parameters.

Computed WQI values are then classified into five categories as excellent, good, poor, very poor and unfit for drinking as shown in Table. 3.

Table 3: Classification of Groundwater Based on GWQI

GWQI Range Type of water < 50 Excellent water (EXW) 50-100 Good water (GOW) 100-200 Poor water (POW) 200-300 Very poor water (VPW) > 300 Unfit for drinking (UFD)

Assessment of Spatial Distribution of Groundwater Quality in Kondagattu Catchment 139 of Greater Visakhapatnam Municipal Corporation, India – A GIS Based Approach

Table 4: List of Groundwater Sampling Sites in the Study Area

Adavivaram Venkatapuram Simhapuri colony Hindusthan Polymers Pata Naidu thota Baji.Junction Simhachalam Rly station Simhachalam Pendurithi Yellapuvanipalem Palli Narayanapuram Vijanagaripalem Appannapalem Golla naryanapuram Pinapple Colony Vepgunta Kothapatnam Ramanna Cheruvu

GIS Application

Arc GIS software with raster interpolation technique of spatial analyst module is used for the present study to delineate the spatial distribution of various water quality parameters. The sampling locations were imported into GIS software through point layer.

Figure 2: Flow Diagram of Preparing GWQI Map in GIS A unique code for each sample point was assigned and the data base file contains values of all chemical parameters in separate columns along with a sample code for each sampling station. This geo•database was used to generate the spatial distribution maps of all the water quality parameters tested including water quality index (WQI).

RESULTS AND DISCUSSIONS Groundwater Quality Variation The results obtained from the physico•chemical analysis are presented in Table. 5. pH

The negative logarithm of hydrogen ion concentration of a solution is the pH represented in moles per litre. In the study area the pH is ranging from 7.12 to 7.62, which is within permissible limit.

Electrical Conductivity (EC) and Total Dissolved Solids (TDS)

The ability of electrical current that passed through the water is its electrical conductivity. Concentration of 140 Janardhana Swamy C, Venkateswara Rao T & Pradeep Kumar G. N ionized substances present due to dissolved inorganic substances in water decides the value of electrical conductivity. In the study area, electrical conductivity varies from 177 to 2260 µS/cm.

Electrical conductivity of water is considered to be an indication of the total dissolved salt content (Hem, 1985). Elico meter is used to determine the Total Dissolved Solids in a sample. The mean values of TDS are varied from 115.05 to 1469 mg/l. Groundwater from entire study area is suitable for drinking purpose from the point of view of EC and TDS.

Alkalinity

Carbondioxide, bicarbonate and carbonates in dissolved state produce alkalinity in water. Alkalinity of the study area is found to vary between 14 to 202 mg/l and is within permissible limit.

Table 5: Physico•Chemical Analysis of Groundwater Samples Collected in the Study Area

Station pH TDS Alkalinity Cl F No₃⁻ SO₄ Ca Mg TH Ec WQI Classification * 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 7.3 803.40 102.00 160.00 1.40 48.20 68.00 45.00 56.00 230.00 1236.00 65.02 GOW 2 7.42 664.95 126.00 80.00 1.20 32.80 42.00 34.00 46.00 190.00 1023.00 52.17 GOW 3 7.26 410.15 52.00 110.00 0.60 28.60 12.00 42.00 51.00 210.00 631.00 46.78 EXW 4 7.28 482.30 72.00 100.00 0.80 31.60 24.00 34.00 46.00 190.00 742.00 47.22 EXW 5 7.32 546.00 84.00 105.00 0.80 22.80 26.00 45.00 56.00 230.00 840.00 50.55 GOW 6 7.28 536.90 76.00 90.00 0.60 28.20 24.00 46.00 58.00 250.00 826.00 51.97 GOW 7 7.12 117.00 28.00 20.00 0.40 10.20 12.00 16.00 12.00 50.00 180.00 17.02 EXW 8 7.46 1107.60 148.00 160.00 1.60 44.60 84.00 50.00 68.00 280.00 1704.00 74.97 GOW 9 7.38 885.95 108.00 100.00 1.40 33.60 72.00 50.00 67.00 280.00 1363.00 66.41 GOW 10 7.42 1088.10 132.00 270.00 1.20 11.20 84.00 74.00 100.00 410.00 1674.00 80.22 GOW 11 7.56 1279.20 152.00 250.00 1.20 22.60 108.00 64.00 96.00 380.00 1968.00 84.26 GOW 12 7.36 900.25 132.00 180.00 1.40 31.60 72.00 50.00 66.00 270.00 1385.00 66.9 GOW 13 7.28 649.35 78.00 160.00 0.60 38.60 24.00 52.00 75.00 320.00 999.00 65.34 GOW 14 7.36 657.80 72.00 155.00 0.80 38.80 28.00 50.00 68.00 280.00 1012.00 62.73 GOW 15 7.48 1062.10 112.00 230.00 0.80 44.60 64.00 72.00 98.00 400.00 1634.00 85.97 GOW 16 7.56 1045.20 152.00 225.00 1.00 36.80 48.00 72.00 92.00 380.00 1608.00 81.65 GOW 17 7.38 954.20 128.00 200.00 1.00 34.80 46.00 52.00 73.00 310.00 1468.00 69.97 GOW 18 7.42 1082.90 112.00 85.00 1.00 36.40 68.00 42.00 48.00 210.00 1666.00 58.66 GOW 19 7.38 802.75 128.00 135.00 0.60 31.60 46.00 50.00 68.00 280.00 1235.00 62.68 GOW 20 7.28 475.80 96.00 80.00 0.40 24.60 234.00 32.00 43.00 180.00 732.00 47.94 EXW 21 7.46 1017.90 96.00 165.00 0.40 41.60 64.00 50.00 68.00 290.00 1566.00 67.64 GOW 22 7.36 803.40 116.00 155.00 1.00 28.20 52.00 46.00 58.00 240.00 1236.00 58.49 GOW 23 7.26 593.45 92.00 220.00 0.40 28.20 20.00 30.00 34.00 140.00 913.00 42.05 EXW 24 7.36 743.60 92.00 195.00 0.40 38.60 36.00 46.00 63.00 260.00 1144.00 60.84 GOW 25 7.36 671.45 52.00 245.00 0.40 28.20 24.00 48.00 63.00 280.00 1033.00 56.86 GOW 26 7.48 1170.65 104.00 220.00 0.40 42.80 84.00 56.00 85.00 350.00 1801.00 79.1 GOW 27 7.36 902.20 102.00 250.00 1.00 38.60 52.00 64.00 87.00 360.00 1388.00 77.61 GOW 28 7.42 920.40 124.00 140.00 0.80 44.20 48.00 52.00 65.00 270.00 1416.00 67.01 GOW 29 7.48 876.20 136.00 90.00 1.40 38.80 56.00 32.00 39.00 160.00 1348.00 54.23 GOW 30 7.46 1190.80 104.00 285.00 0.60 43.20 66.00 64.00 88.00 350.00 1832.00 81.91 GOW 31 7.36 977.60 168.00 165.00 1.50 36.80 52.00 52.00 68.00 280.00 1504.00 70.48 GOW 32 7.58 1289.60 164.00 250.00 1.50 34.20 96.00 56.00 78.00 320.00 1984.00 80.21 GOW 33 7.62 1352.00 202.00 275.00 1.60 41.60 102.00 80.00 102.00 420.00 2080.00 96.28 GOW 34 7.38 899.60 108.00 175.00 1.60 40.80 52.00 52.00 73.00 300.00 1384.00 72.63 GOW 35 7.46 1170.00 82.00 295.00 0.60 42.40 78.00 80.00 107.00 440.00 1760.00 90.68 GOW 36 7.56 1384.50 108.00 340.00 0.60 72.80 102.00 78.00 102.00 400.00 2130.00 101.2 POW 37 7.38 882.70 102.00 180.00 1.00 41.60 64.00 50.00 70.00 290.00 1358.00 69.44 GOW 38 7.24 449.80 102.00 75.00 1.20 28.60 18.00 34.00 44.00 180.00 692.00 46.44 EXW 39 7.36 863.20 128.00 150.00 0.20 68.60 52.00 34.00 44.00 180.00 1328.00 61.47 GOW 40 7.32 753.35 92.00 130.00 1.20 32.20 44.00 50.00 68.00 280.00 1159.00 63.63 GOW 41 7.48 1144.00 132.00 225.00 0.60 32.80 72.00 78.00 92.00 380.00 1760.00 80.45 GOW 42 7.26 450.45 84.00 75.00 1.40 28.60 24.00 30.00 34.00 140.00 693.00 42.2 EXW 43 7.28 486.85 104.00 75.00 1.50 22.80 16.00 27.00 36.00 150.00 749.00 42.35 EXW 44 7.38 915.20 104.00 175.00 1.20 42.80 56.00 48.00 63.00 260.00 1408.00 67.23 GOW 45 7.56 1181.70 182.00 180.00 1.50 42.20 96.00 52.00 78.00 320.00 1818.00 80.71 GOW 46 7.38 957.45 176.00 125.00 1.60 43.80 64.00 34.00 44.00 180.00 1473.00 60.98 GOW 47 7.56 1469.00 178.00 315.00 1.60 44.20 116.00 88.00 107.00 440.00 2260.00 101.2 POW 48 7.28 765.70 76.00 135.00 0.60 38.30 42.00 50.00 66.00 270.00 1178.00 62.2 GOW 49 7.52 1062.75 142.00 260.00 1.20 26.20 64.00 72.00 108.00 450.00 1635.00 87.75 GOW 50 7.16 137.15 28.00 20.00 0.20 38.80 8.00 8.00 14.00 60.00 211.00 25.69 EXW 51 7.28 573.30 62.00 100.00 0.80 42.50 32.00 48.00 64.00 260.00 882.00 60.11 GOW 52 7.36 611.00 82.00 95.00 0.80 38.70 36.00 52.00 68.00 280.00 940.00 61.81 GOW Assessment of Spatial Distribution of Groundwater Quality in Kondagattu Catchment 141 of Greater Visakhapatnam Municipal Corporation, India – A GIS Based Approach

Table 5- Contd., 53 7.42 878.80 108.00 160.00 0.80 44.20 52.00 58.00 78.00 340.00 1352.00 73.07 GOW 54 7.34 729.30 102.00 200.00 0.60 29.20 32.00 52.00 72.00 300.00 1122.00 63.13 GOW 55 7.42 769.60 96.00 180.00 0.60 35.60 34.00 50.00 66.00 270.00 1184.00 62.26 GOW 56 7.22 245.05 44.00 40.00 1.00 22.20 16.00 24.00 21.00 120.00 377.00 29.39 EXW 57 7.26 454.35 72.00 60.00 0.60 28.60 24.00 48.00 62.00 240.00 699.00 52.42 GOW 58 7.48 1138.80 132.00 180.00 1.20 44.80 88.00 52.00 76.00 320.00 1752.00 77.96 GOW 59 7.38 972.40 122.00 150.00 1.20 36.80 64.00 50.00 75.00 330.00 1496.00 72.18 GOW 60 7.28 339.30 48.00 55.00 0.40 46.80 18.00 32.00 16.00 140.00 522.00 33.93 EXW 61 7.52 952.90 92.00 160.00 1.40 42.20 44.00 56.00 28.00 320.00 1466.00 52.8 GOW 62 7.48 720.20 88.00 125.00 0.80 32.60 32.00 46.00 22.00 230.00 1108.00 40.97 EXW 63 7.56 1199.90 128.00 265.00 1.00 43.60 72.00 88.00 46.00 480.00 1846.00 66.96 GOW 64 7.32 330.20 48.00 95.00 0.60 26.20 24.00 32.00 22.00 170.00 508.00 32.1 EXW 65 7.28 509.60 62.00 100.00 1.40 24.20 28.00 50.00 32.00 260.00 784.00 42.08 EXW 66 7.26 301.60 46.00 50.00 0.60 18.80 16.00 32.00 16.00 160.00 464.00 26.05 EXW 67 7.38 522.60 68.00 80.00 0.80 28.60 24.00 42.00 22.00 220.00 804.00 36.33 EXW 68 7.42 717.60 88.00 120.00 1.20 32.80 32.00 36.00 18.00 180.00 1104.00 39.97 EXW 69 7.46 736.45 86.00 130.00 1.20 28.60 36.00 42.00 20.00 200.00 1133.00 40.31 EXW 70 7.36 499.20 72.00 80.00 0.60 18.80 24.00 44.00 22.00 210.00 768.00 32.5 EXW 71 7.34 596.70 76.00 90.00 1.20 22.20 28.00 46.00 28.00 220.00 918.00 39.68 EXW 72 7.22 115.05 14.00 20.00 0.40 12.20 4.00 8.00 4.00 40.00 177.00 13.5 EXW 73 7.32 213.20 18.00 45.00 0.40 16.20 12.00 24.00 12.00 120.00 328.00 20.81 EXW Note: * Classification is as Per Table. 3.

Chlorides (Cl)

It is a known fact that the sea water intrusion shows abnormal concentration of chloride. In potable water, the salt taste is produced by chloride concentrations. At concentrations above 250 mg/l, water acquires salty taste which is objectionable to human consumption. Bureau of Indian Standards prescribes 250 mg/l as desirable limit and 1000 mg/l permissible limit as in the absence of alternate source. In the study area, Chloride concentration ranges between 20 to 340 mg/l. Except at 11 locations all the other samples are found to have chlorides within desirable limits. However, in all these 11 locations, the concentration is within permissible limits.

Fluorides (F)

Fluoride is essential for human beings as a trace element. Higher concentration of this element causes toxic effects. Concentration of fluoride between 0.6 to 1.0 mg/l in potable water protects tooth decay and enhances bone development. Bureau of Indian Standards has suggests permissible limit of fluoride in drinking water at 1.0 mg/l and tolerance range is upto 1.5 mg/l. Water having fluoride concentration above 1.5 mg/l leads to fluorosis, dental mottling and bone diseases. In the study area, fluoride concentration ranges between 0.2 and 1.6 mg/l indicating slight fluoride contamination in 9 locations.

Nitrates (NO3)

If concentration of nitrates increases beyond the permissible level water becomes poisonous. It has also been known to cause infant cyanosis (blue-baby) in children under the age of six months. As per BIS, the permissible limit of Nitrates is ≤ 45 mg/l. A glance at the values of Nitrate as listed in table 5, indicates that 4 samples are found exceed the permissible limit with a variation of values between 10.20 to 72.80 mg/l.

Sulphates (SO4)

Sulphates in a water sample as prescribed in BIS, should be from 250 to 1000 mg/l. In the present study the concentrations is varying from 4 to 234 mg/l and are found to be within the desirable limits.

Calcium (Ca) and Magnesium (Mg)

Calcium can be observed in most of the geological material aquifers. Calcium occurs in water mainly due to the 142 Janardhana Swamy C, Venkateswara Rao T & Pradeep Kumar G. N presence of limestone, gypsum, dolomite and gypsiferrous minerals. Calcium is a major constituent of most igneous, metamorphic and sedimentary rocks. Excessive calcium in drinking water is linked to the formations of concretions in the body and may cause gastro intestinal diseases and stone formations. Bureau of Indian Standards prescribes limits for calcium as 75 mg/l as desirable limit and 200 mg/l permissible limit. Calcium concentration in the study area ranging between 8 to 88 mg/l and is within the permissible limits.

Magnesium occurs in water mainly due to the presence of olivine, biotite, augite, hornblende and talc minerals. As per BIS, permissible limit of magnesium is 30 mg/l. Magnesium is present in water because it is washed from rocks and subsequently ends up in water. Large dose of magnesium causes muscle slackening, nerve problems, depressions and personality changes vomiting and diarrhea.

The subsurface of the study area consists of Khondalite rocks (which are light coloured, metamorphosed rocks, on weathering they show brown colour due to leaching and are jointed). Magnesiohornblende present in Khondolite rocks in the study area are the main source for Magnesium contamination. Magnesium concentration in the groundwater in the study area is found to range between 4 mg/l to 108 mg/l and representing 79% of the area is effected with Magnesium contamination which needs immediate attention.

Total Hardness (TH)

Total hardness is a measure of the capacity of water to the concentration of calcium and magnesium in water and is usually expressed as the equivalent of CaCO3 concentration. In the present study, the total hardness of the samples is found to vary from 40 to 480 mg/l. Bureau of Indian Standards (BIS, 2003) prescribes limits for TH as 300 mg/l as desirable limit and 600 mg/l permissible limit as in the absence of alternate source.

Groundwater Quality Index (GWQI)

Groundwater Quality Index (GWQI), computed using Equation (4), which is a reflection of composite influence of individual quality characteristics on the overall quality of water, is found to vary from 13.50 to 101.21 for the study area. However, from the Table 3, it is obvious that, if the GWQI value is less than 50, the groundwater is categorized as excellent, for GWQI within 50 to 100, it is considered as good quality water, for GWQI between 100 and 200 , the groundwater is classified as poor , for GWQI between 200 and 300 , it is placed in the category of very poor and finally for GWQI exceeding 300, it regarded as UFD.

From the results of experimental investigation on groundwater quality in Kondagattu catchment spread over 73 wells, it may be observed that groundwater from 22 wells falls under EXCELLENT, that from 49 wells is found to be GOOD in quality and groundwater from 2 wells is of poor quality. That is, 30% of study area has excellent quality water, 67% good quality water and 3% suffer from poor quality water.

GIS Application

ArcGIS software has been used to prepare spatial distribution map of each water quality parameter using interpolation options. These maps have been used as thematic maps for preparing GWQI map of the study area. GWQI map was developed from the thematic maps of water quality parameters using overlay and index method. The GWQI map shows the demarcation of sites having suitable groundwater quality for drinking purposes.

The present study strongly advocates the use of geostatistical techniques for water quality assessment and investigating spatial variation of water quality as an effort towards a more effective groundwater quality management. Assessment of Spatial Distribution of Groundwater Quality in Kondagattu Catchment 143 of Greater Visakhapatnam Municipal Corporation, India – A GIS Based Approach

The spatial distribution maps, as shown in Figure 3, of the study area make sense to a layman about the status of the water quality in a location. Further, the maps help to create awareness among the local residents regarding the importance of protecting the quality of water in their area. These maps also help the government organizations to assess the impact of local contamination and adopt the suitable and economic type of treatment and also for proper management of groundwater resources.

Figure 3: Spatial Distribution Map of Groundwater Quality Parameters CONCLUSIONS

The study has demonstrated the utility of GIS technology combined with laboratory analysis in evaluation and mapping of groundwater quality in urban region. About 3% of the study area comes under moderately polluted category as revealed by the WQI studies. The spatial distribution maps generated for various physico•chemical parameters using GIS 144 Janardhana Swamy C, Venkateswara Rao T & Pradeep Kumar G. N techniques could be useful for planners and decision makers for initiating groundwater quality development in the area. The study illustrates the use of geostatistical techniques for water quality assessment and investigating spatial variations of water quality as an effort towards a more effective groundwater quality management.

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