




































 
 

 

70 
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Asian Review of Environmental and Earth Sciences 
Vol. 6, No. 1, 70-77, 2019 

ISSN(E) 2313-8173/ ISSN(P) 2518-0134 
DOI: 10.20448/journal.506.2019.61.70.77 

© 2019 by the authors; licensee Asian Online Journal Publishing Group 

   
 

 
 
 
Groundwater Quality Determination for Drinking Purpose by Using Water Quality 
Index Technique: A Case Study of Gadap Town, Karachi, Pakistan 

 
Asal Eghbal Bakhtiari1     

Adnan Khan2   

Zubaid Saeed3    

Ayesha Kanwal4   

  
( Corresponding Author) 

 
1,2,3,4Department of Geology, University of Karachi, Karachi, Pakistan. 

 

 
Abstract 

Present study is aimed at assessment of groundwater quality of Gadap Town for drinking purpose 
using water quality index (WQI) technique. Gadap is located in the outskirt of Karachi city and 
mainly influenced by the agriculture activities. Groundwater samples (n = 22) were collected 
mainly from boring wells and a few through tube wells from variable depths (100-600 feet). The 
analytical results of water reveal occurrence of very high TDS (range: 466-3810; mean: 1402) and 
hardness contents (range: 250-2800 mg/L). On the other hand, pH varies (range: 6.9-8.1; mean: 
7.5) within WHO guidelines (6.5-8.5) with a few samples showing turbidity. About one third of 
total collected samples (n = 8) were analyzed for qualitative determination of microbial 
contamination which are found positive, except one sample, indicating the sewage mixing. Major 
chemistry of groundwater is also found disturbed in terms of high content of Na (mean: 219 
mg/L), K (mean: 15 mg/L), Ca (mean: 144 mg/L) and Mg (mean: mg/L 137). Similarly, anions 
varied in the order of Cl > HCO3 > SO4 > NO3. Although some parameters show the bad quality 
of water but Water quality index (WQI) value (16.18) indicates that the groundwater quality is 
suitable for drinking purpose. It is inferred from the present study that water quality is partly 
polluted due to anthropogenic activities mainly by sewage infiltration. 

 
Keywords: Groundwater, Geochemistry, Drinking quality, WQI, Gadap Town, Karachi. 

 
Citation | Asal Eghbal Bakhtiari; Adnan Khan; Zubaid Saeed; 
Ayesha Kanwal (2019). Groundwater Quality Determination for 
Drinking Purpose by Using Water Quality Index Technique: A 
Case Study of Gadap Town, Karachi, Pakistan. Asian Review of 
Environmental and Earth Sciences, 6(1): 70-77. 
History:  
Received: 3 September 2019 
Revised: 7 October 2019 
Accepted: 13 November 2019 
Published: 30 December 2019 
Licensed: This work is licensed under a Creative Commons 

Attribution 3.0 License  
Publisher:  Asian Online Journal Publishing Group 
 

Acknowledgement: Authors are indebted to Department of Geology, 
University of Karachi for providing the analytical facilities. Dr. Ghulam 
Murtaza Arain, laboratory Incharge of Pakistan Council for Research in 
Water Resources (PCRWR) is also thanked for analyzing the samples to 
determine some parameters. 
Funding: This study received no specific financial support. 
Competing Interests: The authors declare that they have no conflict of 
interests. 
Transparency: The authors confirm that the manuscript is an honest, 
accurate, and transparent account of the study was reported; that no vital 
features of the study have been omitted; and that any discrepancies from the 
study as planned have been explained. 
Ethical: This study follows all ethical practices during writing.   

 

 

Contents 
1. Introduction ...................................................................................................................................................................................... 71 
2. Materials and Methods ................................................................................................................................................................... 71 
3. Results and Discussion ................................................................................................................................................................... 73 
4. Conclusion ......................................................................................................................................................................................... 77 
References .............................................................................................................................................................................................. 77 
 

 

 

 

 

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Contribution of this paper to the literature 
This paper will augment the worth of WQI technique being used for explaining the water quality 
objectively. It will also add the information about groundwater behavior occurring in the suburbs of the 
mega city. 

 

1. Introduction 
Groundwater is one of the imperative natural resource to drive the life cycle. It is widely used for various 

purposes including industry, drinking, washing and irrigation. It can only be used if available in sufficient quantity 
with acceptable quality [1]. Hydrological cycle naturally works as a big pump which continuously transfers the 
water from oceans to land; mainly underground [2]. Modern agricultural practices, urbanization and 
industrialization have created the menace of water pollution [3]. These anthropogenic activities not only alter the 
physicochemical characters of water bodies but also contaminate the environment. Once the groundwater gets 
polluted it is difficult and costly to be cleaned up. Hence, to identify the potential toxicants and mechanism of 
release from their sources is important to prevent these water resources. Agricultural practices are common in 
areas where the fertile soil and water is available in copious amount. However, due to nutrient deficiency in 
agricultural soils, plenty of fertilizer or manure is used to get required crop yield. On the other hand, 
eutrophication, a result of high nutrient loads (mainly nitrogen and phosphorus), is considered to be the prevailing 
water quality problem for surface water [4]. Other pollutants originating in agricultural activities include 
sediments, oxygen-demanding substances and pesticides. Similarly, salinization is also reported as the most 
widespread groundwater quality problem and as having the greatest environmental and economic impacts [5]. 
This in turn leads to release various toxic elements into the water which ultimately contaminate the groundwater 
resources. This groundwater is also used by the dwellers of the agriculture-based community as main source of 
cooking, washing and drinking.  As a result, the health and life of such community gets threatened. It is therefore 
important to monitor and regulate the groundwater of such areas to prevent from any catastrophe. 

About 60% of urban population in Pakistan is using groundwater for drinking and domestic purpose without 
regulating the water as per World Health Organization (WHO) standards [1]. Karachi is the largest city of 
Pakistan which is blessed with several ephemeral streams and channels culminating at two main rivers namely 
Lyari and Malir which ultimately discharge to Arabian Sea. The land around these natural water courses is being 
used for agricultural activities since long. Some agricultural sites are still pristine however others are rapidly 
transforming into the urban centers. Gadap Town is the agricultural periphery of Karachi city which is the hub of 
vegetable supply to this mega city and adjoining areas. Some reports on the base line data have shown the 
occurrence of high nitrate in the groundwater of Gadap (e.g. Chughtai, et al. [6]). As a result, the health of people 
living in Gadap town is questioned. However, no detailed work has been carried out so far to address the 
groundwater quality and possible sources of contamination in this part of Karachi city. Therefore, present study is 
aimed at assessing the groundwater quality of Gadap town using a new approach i.e. water quality index (WQI). 
Other objective is to statistically trace out the factors responsible for influencing the chemistry of groundwater in 
study area.  
 

2. Materials and Methods 
2.1. Study Area 

Gadap town is subdivision of Malir district which situated in the northwestern part of Karachi city Figure 1. 
This town is also forming the provincial border between Sindh and Balochistan, while to the north and east 
are Jamshoro district and the Kirthar Mountains. Gadap town has 8 union councils with over 400 rural villages 
accommodating the population of about 289,564 (1998). Gadap basin is influenced by the ephemeral channels 
occurring in the outskirt of Karachi city and mainly influenced by the agriculture activities. Over the last decade 
the Gadap is transformed into semi-area urban.  
 

 
Figure-1. Location map of Gadap Town, Karachi, (after Mahboob, et al. [7]). 

Source:  This map has been taken from Mahboob, et al. [7] paper which is cited in the figure 
caption. 

https://en.wikipedia.org/wiki/Town
https://en.wikipedia.org/wiki/Karachi
https://en.wikipedia.org/wiki/Sindh
https://en.wikipedia.org/wiki/Balochistan_(Pakistan)
https://en.wikipedia.org/wiki/Jamshoro_District
https://en.wikipedia.org/wiki/Kirthar_Mountains


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2.2. Sample Collection 
Twenty-two groundwater samples were collected from boring wells at a depth range of 100-600ft. 

Groundwater was electrically pumped for 2-3 minutes to get true samples. Location of the wells was marked with 
the help of Global Positioning System (GPS) on the Google earth image and transformed on the map prepared by 
using GIS Technique Figure 2. Groundwater samples were collected in plastic bottles of 1.5-liter capacity for 
physico-chemical analysis. Bottles were properly washed and rinsed thoroughly with distilled water and then with 
groundwater at sampling site. To determine nitrate concentration groundwater samples were collected in bottles of 
100 ml capacity and one ml boric acid solution was injected through sterile syringe in each water sample to cease 
any further reaction. 
 

 
Figure-2. Sample location map of study area. 

      

2.3. Groundwater Analysis 
All the physico-chemical tests were carried out in the laboratory of Geology Department, University of 

Karachi. The pH and TDS/EC of collected groundwater samples (n=22) were measured with the glass electrode 
pH meter (ADWA AD 111) and EC meter (ADWA AD 330) respectively. Concentration of sodium and potassium 
was determined by using flame photometer (Model No. JENWAY PFP7). Sulphate content was tested by 
gravimetric method, while bicarbonate and chloride were estimated by Argenometric titration method. The 
method used for the analysis of calcium and total hardness was EDTA Titration Standard Method (1992). 
Magnesium was estimated as the difference between hardness and calcium with the help of formula. Groundwater 
samples preserved in the boric acid were analyzed to determine the nitrate concentration by Cadmium Reduction 
method (HACH-8171) on Spectrophotometer. 
 

2.4. Water Quality Index (WQI) 
Groundwater quality index of Gadap town was determined by using weighted arithmetic index method as 

proposed by Brown, et al. [8] to evaluate the water quality status of study area. Physicochemical parameters 
including pH, TDS, major cations (Na, K, Ca, Mg) and anions (HCO3, Cl, SO4, NO3) were used to calculate WQI of 
groundwater in Gadap town. WQI is calculated by using following formula. 

WQI=∑QnWn/ ∑Wn 
Where, 
Qn is the quality rating of nth water quality parameter. 
Wn is the unit weight of nth water quality parameter.  
The quality rating Qn is calculated using the equation .  

Qn=100*[(Vn – Vi) / (Vs- Vi)] 
Where,  
Vn is the actual amount of nth parameter present.  
Vi is the ideal value of the parameter, Vi = 0, except for pH (Vi = 7). 
Vs is the standard permissible value for the nth water quality parameter.  
Unit weight (Wn) is calculated using the formula. 

Wn= k / Vn, 
Where, k is the constant of proportionality and it is calculated using the equation  

K= 1 / ∑Vs= 1, 2, …, n 



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3. Results and Discussion  
3.1. Physical Parameters 

The characteristics of collected groundwater samples (n = 22) have been summarized in Table 1. Although a 
few samples are slightly saline and some show yellow color but others are safe in terms of color, taste and odor 
Table 1. The groundwater pH is slightly alkaline (mean: 7.5) with subtle variation in range (6.9-8.1) which is 
within the permissible range of WHO (6.5-8.5) for drinking. The groundwater temperature is low (mean: 28 °C) 
which fluctuates between 25 to 32˚C suggesting that it’s meteoric origin which has been hosted in the aquifers 
through surface water infiltration [9-17]. Only 5 samples (10, 13, 18, 21 and 22) are found turbid Table 1 which 
are also sewage impacted as indicated by occurrence of pathogenic bacteria Table 1. 

Turbidity in water is function of suspended load including organic particles, bacterio-plankton units, colloids, 
air bubbles and other non-uniformities in the water samples [18, 19]. In study area, people use to drain sewage 
into open pits or channels because they live in semi urban set up where lined sanitation is not yet available. As a 
result, organic matter and solutes are likely to infiltrate through sediments up to aquifers depths, causing high 
turbidity [20, 21]. Sewage contamination is reported even at the depth of 500 feet in groundwater of study area. 

Generally, the sewage contamination occurs at very shallow depth but the presence of sewage at such depths 
seems to be the function of sediments having good transmissivity and infiltration which is characteristic of alluvial 
sediments comprising silty-clay to silty-sand. It is consistent with the fact that subsurface rocks in the study area 
are dominated by silty sand belonging to Nari Formation. These fine clastics have least tendency to hold/adsorb 
the organic matter on their surface as compared to clays therefore the occurrence of such organic material is 
plausible in the study area. Total dissolved solids (TDS) and total hardness (TH) of collected samples are found to 
be highly variable (466-3810 mg/L and 250 to 2800 mg/L respectively) in the groundwater of Gadap town. TDS 
content occur three times higher than the permissible limit of WHO (500 mg/L) for drinking water in most of the 
groundwater samples of study area Table 1. This wide variation in TDS content may attribute to geochemical 
process and anthropogenic activities [22] in the study area. As discussed earlier, the Gadap basin is an agricultural 
land where organic matter in the surface soil is ubiquitous. This organic matter is prime driver of generating the 
organic acids which is significantly leaching the ions from soil and sediments resulting in increased specific 
conductance or salinity of water [23]. On the other hand, semi-arid climate has also concentrated the salts in the 
groundwater due to intense evaporation [24, 25].  Likewise, sewage infiltration to the aquifer depth is also 
augmenting the salt contribution in the groundwater of Gadap basin. 

 

3.2. Chemical Parameters 
Sodium (Na) and potassium (K) are found to be highly variable in the study area ranging between 52.43-620 

mg/L and 3.73-105 mg/L respectively. Na with a mean of 219.9 mg/L is found to be the dominant cation among 
the solutes but only in few samples exceed the permissible limit of WHO (200 mg/L) set for drinking water Table 
2. Likewise, distribution pattern of calcium (Ca) is highly variable (range: 12 - 520 mg/L) in the collected samples 
Table 3. Similarly, the mean concentration of Mg (137.83 mg/L) in the groundwater of Gadap town is double the 
WHO permissible limit (50 mg/L) which spans between 12.5 to 388 mg/L Table 3. This suggests the role of 
multiple sources for contributing this element into the aquifer of study area. 

On the other hand, K content is marginally high (mean: 15.9 mg/L) in some of the samples (n=6) violating the 
desired limit (12 mg/L) of WHO Table 2. Chloride (Cl) and Bicarbonate (HCO3) are dominant anions followed by 
sulphate (SO4) and nitrate (NO3). Chloride shows elevated concentration (Mean: 597.31 mg/L) in almost all of the 
collected groundwater samples which is almost double the permissible limit of WHO (250 mg/L) for dirking water. 
However, SO4 concentration is found to be within the permissible limit set for drinking water by WHO (250 
mg/L) in all of the samples except 5 Table 2. 

 

3.3. Ionic Interrelationship  
Statistical analysis of the collected groundwater samples shows the strong positive correlation of hardness with 

all physical and chemical parameters except HCO3, NO3 and F and the same pattern is expressed by TDS Table 4. 
Strong positive correlation of TDS with Mg (0.6) and SO4 (0.8) indicates the influence of Clay minerals through 
water rock interaction.  Elevated concentration of salts (Na, K, Mg, Cl, SO4) coupled with bacterial occurrence also 
suggests mixing of sewage with groundwater [26]. On the other hand, very high hardness (mean = 776.7 mg/L) 
of these collected samples indicate dissolution of limestone and Mg release from clays. 

 

3.4. Hydrofacies Analysis 
Hydrofacies reflect the effect of chemical processes occurring between minerals within the lithological 

framework and the groundwater [27]. For this purpose, the Piper diagram is used to show the relative 
concentration of the major cations and anions [27, 28].  The results of groundwater analysis indicate that 
dominant hydrofacies occurring in the aquifers of Gadap town is Mg-Cl (50%).  

 
 
 
 

 



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Table-1. Physical parameter of collected samples from GADAP town. 

S. No Locality Depth (ft.) Color Taste Odor Turbidity pH TDS mg/L EC µs/cm Temp. ˚C Hardness mg/L Mico. (-ve/+ve) 

1 Chanesar Goth 360 Color less Normal Odorless #NT 7.3 1170 150.4 28 500 +ve 
2 Khameso Goth 350 Color less Normal Odorless NT 7.8 533 682.9 26.7 250 +ve 
3 SorafaqirSorab Goth 300 Color less Normal Odorless NT 7.4 920 1176 31.6 270 +ve 
4 BadamBagh 500 Color less Normal Odorless NT 7.6 1240 1562 27.1 780 +ve 
5 Gabol Stop 400 Color less Saline Odorless NT 7.6 1050 1382 28.5 560 -ve 
6 Manzor Baloch Hotel 600 Color less Saline Odorless NT 7.8 836 1073 25.1 450 TNP 
7 Lucky Farm House 350 Color less Normal Odorless NT 8 1370 1709 28.9 700 TNP 

8 Bhitai Farm House 330 Yellow Saline Odorless NT 7.1 2110 2707 27.9 1300 TNP 
9 Bhitai Farm House 100 Color less Normal Odorless NT 7.3 690 880.6 27.5 480 TNP 
10 Bhitai Farm House 320 Color less Saline Odorless Turbid 7.2 1630 2093 27.9 1030 TNP 
11 Haji KhudaBaksh F.H. 220 Color less Normal Odorless NT 7.4 466 595 26.4 350 TNP 
12 Haji KhudaBaksh F. H. 400 Color less Normal Odorless NT 7.6 532 681 30.2 500 TNP 
13 Dattari Farm House 500 Color less Normal Odorless Turbid 7.6 970 1240 28.3 480 TNP 
14 Sarim Farm House 340 Color less Saline Odorless NT 7.5 740 947.8 28.1 450 TNP 
15 Radho Goth 400 Color less Normal Odorless NT 7.2 3390 4780 29.4 2800 TNP 
16 RadhoJokhio Goth 220 Color less Saline Odorless NT 7.3 3810 5280 28.4 2350 TNP 
17 Goth Rado 200 Color less Normal Odorless NT 7.3 771 1083 30.1 700 TNP 

18 M.Ishaq Baloch Bohlari 150 Yellow Normal Odorless Turbid 7 2870 4040 30 2250 TNP 
19 M.Ishaq Baloch Bohlari 120 Color less Saline Odorless NT 7.3 950 1484 30.1 890 TNP 
20 Gajan Village 250 Color less Normal Odorless NT 8.1 790 1090 28 *TNP +ve 
21 Radho Goth 170 Yellow Saline Odorless Turbid 7.6 3210 4429 29 TNP +ve 
22 Haji Arzi Village 200 Color less Saline Odorless Turbid 8 800 1104 28 TNP +ve 

Note: #NT = Non turbid. 
*TNP = Test not performed. 



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Table-2. Chemical characteristics of collected groundwater samples. 

        Note: *BDL=Below Deduction Level. 
 

Table-3. The statistical descriptive of the collected samples in the groundwater of the Gadap town. 

Parameters  Min. Max. Mean SD 

Depth    ( ft) 100 600 308.2 130.4 
pH 6.95 8.1 7.47 0.31 
TDS    (mg/L) 466 3810 1402 1008 
EC       (µm/L) 150.4 5280 1826 1466 

Temp    (◦C) 31.6 31.6 28.42 1.46 

Ca       (mg/L) 520 520 144.63 150.48 
Mg      (mg/L) 388 388 137.83 102.25 
Na       (mg/L) 52.43 620 219.19 128.08 
K         (mg/L) 3.73 105 15.96 21.39 

Cl        (mg/L) 141.84 1524.78 597.31 488.45 
HCO3  (mg/L) 230 1000 390.6 206.1 
SO4      (mg/L) 25 490 138.22 108.51 
NO3      (mg/L) 0.67 2.71 1.15 0.55 

                             
Table-4. Correlation matrix of the collected samples in the study area. 

Parameters pH Hardness TDS Ca Mg Na K Cl HCO3 SO4 NO3 Fe 

pH 1            
Hardness -0.57 1           

TDS -0.42 0.95 1          
Ca -0.40 0.93 0.86 1         
Mg -0.45 0.95 0.96 0.81 1        
Na -0.28 0.80 0.89 0.69 0.80 1       
K 0.16 0.92 0.53 0.50 0.48 0.39 1      
Cl -0.40 0.91 0.96 0.80 0.94 0.84 0.52 1     

HCO3 0.34 -0.12 -0.09 -0.10 -0.14 0.13 0.25 -0.07 1    
SO4 -0.14 0.79 0.83 0.66 0.78 0.74 0.81 0.84 0.08 1   
NO3 -0.03 -0.53 -0.41 -0.10 -0.36 -0.40 -0.45 -0.31 -0.19 -0.35 1  
Fe -0.15 -0.53 -0.04 -0.30 0.04 -0.10 -0.20 0.11 -0.08 0.16 0.27 1 

        
Na-Cl (22.7%), with lesser abundance (9.10% each) of Ca-HCO3, Ca-Cl and Na-HCO3 Figure 3. The occurrence 

of Mg-Cl facies in the groundwater of study area is due to their high solubility in natural water. The dominance of 
these two ions clearly indicates the influence of ion exchange and clay mineral alteration or dissolution of dolomite 
[29-31]. Since the study area is an agricultural land where large amount of clay is present in the soil, the 
dominance of Mg-Cl is legitimate. On the other hand, subsurface rocks are dominated by silty clay with 
subordinate limestone. These rocks are also assumed to release their sorbed and structural Mg content into the 
aquifer system within circum-neutral pH conditions. Generally, bicarbonate species dominates in the meteoric 
groundwater but the occurrence of excessive chloride ion, the bicarbonate is replaced with latter one.  

This chloride may originate from various sources including halite and related minerals in evaporate deposits, 
concentration by evaporation and solution of dry fallout from atmosphere in arid regions. The excessive amount of 
this ion in the groundwater is due to its conservative nature which makes it free from ion exchange, adsorption and 
biological activities. On the other hand, anions of strong acids (SO4 + Cl) dominate over weak acids (HCO3 + CO3) 
which indicate anthropogenic influence in the groundwater system [32]. It is evident by the fact that intense 

S. No. 
 

Ca 
mg/L 

Mg 
mg/L 

Na 
mg/L 

K 
mg/L 

Cl 
mg/L 

HCO3 
mg/L 

SO4 
mg/L 

NO3 
mg/L 

Fe 
mg/L 

1 40 97.2 319.9 6.89 514 1000 106 1.17 0.05 

2 120 12.15 106.8 7.1 163.12 350 42 0.95 0.04 

3 12 41.31 182.4 7.69 297.86 400 54 0.76 BDL 

4 84 138.51 182.4 7.69 670.19 250 84 0.81 0.02 

5 56 102.06 201.1 7.14 370.56 240 112 0.82 BDL 
6 80 60.75 163.1 8.67 372.33 250 82 0.91 0.11 

7 72 126.36 244.7 8.19 659.56 340 152 1.64 BDL 

8 168 213.84 276.6 10.32 1219.82 340 260 1.45 0.34 

9 60 80.19 108.7 5.61 241.12 300 77 2.71 BDL 
10 80 201.7 197.9 9.91 886.5 310 162 0.70 0.58 

11 20 72.9 52.43 3.73 156.02 230 25 1.59 0.03 

12 36 99.63 70.5 4.45 187.93 260 67 1.03 BDL 

13 24 102.06 193.6 7.38 429.06 320 90 0.89 0.43 
14 40 85.05 158.1 5.53 219.85 380 86 0.64 BDL 

15 480 388 386 20 1524.78 340 178.86 0.04 0.024 

16 360 352.35 620 25 1489.32 260 341.46 0.03 0.022 

17 172 65.61 120 11 141.84 300 80.13 0.03 0.01 

18 520 230.85 362 19 1276.84 305 211.38 0.02 0.08 

19 180 106.92 130 11 177.3 330 65.04 0.02 0.07 

20 84 72 165 28 369 850 143 0.01 BDL 

21 378 312 340 105 1504 490 490 0.02 BDL 

22 116 71 241 32 270 750 132 0.01 BDL 



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agricultural activity is common in Gadap town since long and the unlined sanitation is also adding up the ions in 
the groundwater system of study area. 
 

 
Figure-3. Piper diagram of groundwater samples from GADAP town. 

 

3.5. WQI for Drinking Water in GADAP 
The WQI considers eleven weighted parameters including pH, TDS, Hardness, Na, K, Ca, Mg, HCO3, Cl, SO4 

and NO3 to characterize water quality which has been summarized in Table 6. Weighted arithmetic index method 
of WQI has been used to assess the quality of groundwater in Gadap town. It is a simple method that aims at 
giving a single value to water quality by translating the list of parameters and their relative concentrations present 
in a sample into a single value. This single value in turn provides an extensive interpretation of the quality of water 
and its suitability for various purposes like drinking, irrigation, industrial etc. [33].  

First step for calculating WQI of groundwater is to estimate the quality rating of each parameter using the 

formula: Qn=100*[(Vn – Vi) / (Vs‐ Vi)]. If quality rating Qn = 0 means complete absence of pollutants, while Qn 
ranging between 0 - 100 indicates that the pollutants are within the prescribed standard and in case of Qn >100 
implies that, the pollutants are above the standards [34]. 

 
Table-5. Water quality index (WQI) of all collected water samples. 

Parameters Observed value (Vn) WHO Limits (Vs) Ideal value (Vi) Vn-Vi Vs-Vi Qn Wn=k/Vn Qn*Wn 

pH 7.5 8.5 7 0.5 1.5 33.33 0.38 12.88 
TDS 1402.1 500 0 1402.1 500 280.42 0.00 0.58 

Hardness 927.5 500 0 927.5 500 185.5 0.00 0.58 
Na 219.1 200 0 219.1 200 109.55 0.01 1.45 
K 15.9 12 0 15.9 12 132.5 0.18 24.16 
Ca 144.6 75 0 144.6 75 192.8 0.02 3.86 
Mg 137.8 150 0 137.8 150 91.86 0.02 1.93 
Cl 597.3 250 0 597.3 250 238.92 0.00 1.16 

HCO3 390.6 300 0 390.6 300 130.2 0.00 0.96 
SO4 138.2 250 0 138.2 250 55.28 0.02 1.16 
NO3 0.7 10 0 0.7 10 7.0 4.14 29 

WQI = 16.18 

 
In collected samples, Qn of TDS (280.42), hardness (185.5), Ca (192.8), Na (109.55), K (132.5), HCO3 (130.2) 

and Cl (238.92) are above 100 which indicates that these are the main components responsible for deteriorating the 
water quality Table 5. Moreover, chloride and bicarbonate of Ca, Na and K are mainly responsible for elevated 
hardness and very high TDS content in the groundwater of study area. However, the overall result determined by 
operation on concerned quality parameters the WQI value of 16.18 which according to Brown, et al. [8] is still of 
pristine in nature Table 6. 
 

Table-6. WQI range, status and possible usage of the water sample (Brown et al. 1972). 
WQI  Water quality status (WQS)  Possible usage  

0–25  Excellent  Drinking, irrigation and industrial  
26–50  Good  Drinking, irrigation and industrial  
51–75  Poor  Irrigation and industrial  
76–100  Very poor  Irrigation  
Above 100  Unsuitable for drinking and fish culture  Proper treatment required before use  

          Source: Brown, et al. [8]. 

 



Asian Review of Environmental and Earth Sciences, 2019, 6(1): 70-77 

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4. Conclusion 
Present study revealed that generally the groundwater quality of Gadap town is good for drinking purpose as 

indicated by water quality index of study area (16.18). However, some parameters are exceeding the permissible 
limit of WHO in a few wells. Water chemistry is being altered due to the interaction with clays in subsurface 
environment and anthropogenic activities (agriculture and sewage mixing). More focused study is needed to clearly 
understand the sources and mechanism responsible for elevating the concentrations of solutes in the groundwater 
of Gadap Town. 
 

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