Current World Environment

Introduction

In the environment, groundwater is a scarce resource that supports the water needs of over two-thirds of India’s population for domestic, agricultural, and industrial purposes.^1,2,5,18,30 With rapid industrial growth and increasing urban demands, the dependence on subsurface water has doubled in recent decades.^1,2 Compared to surface water, groundwater is more resilient to seasonal variability; however, once contaminated, it is extremely difficult to remediate due to its slow movement through subsurface formations. This makes groundwater contamination a silent and long-lasting environmental threat.^4,24

Recent assessments by the Central Ground Water Board5  highlight a growing concern: out of 6,584 assessment units across India, 1,034 have been classified as over-exploited, 253 as critical, and 96 as saline.³ In states like Tamil Nadu, particularly in districts like Tirupur that host dense clusters of textile and dyeing industries, industrial effluent discharge and overuse of fertilizers have been reported as major contributors to groundwater degradation.^6,7 Elevated concentrations of chloride nitrate^, sulfate, and heavy metals have been documented in aquifers near industrial zones, threatening both drinking water safety and irrigation viability.^6-9,15

Despite growing awareness, existing literature presents several research gaps. Most previous studies have either focused on isolated physicochemical analyses or provided single-season snapshots without integrating seasonal variations. Additionally, limited studies have applied comprehensive water quality assessment tools^10,11 such as the Water Quality Index (WQI), or used Multiple-variable statistical techniques like Principal Component Analysis (PCA) to identify and interpret pollution sources.^7,9

Furthermore, the use of Geographic Information Systems (GIS) for the spatial depiction of groundwater quality has not been widely adopted in localized studies of Tirupur district, despite its known industrial stress.^1,3,12

To bridge these gaps, the present study provides a comprehensive, seasonally stratified assessment of groundwater quality in selected industrial regions of Tirupur District. It evaluates samples from 10 locations during both summer and winter seasons, using WQI to determine suitability for human use, correlation matrices to understand inter-parameter relationships, and PCA to identify dominant pollution sources. The study also explores spatial patterns using GIS, offering actionable insights for sustainable groundwater management and pollution mitigation in rapidly industrializing environment

Study Area

The location of the samples was selected based on the industrial areas. Tirupur is one of the cities which is situated inside the state of Southern India known as Tamil Nadu which has          many industries around the Noyyal River.¹⁰ The samples were collected in residential areas near the industrial sectors .^16,26 Ten location was selected nearby the industrial areas and the samples were collected with the help of bottles and stored in a cool storage.

Materials and Methods

Groundwater recharging is a mainly as a result of rain water, infiltration in monsoon and non-monsoon periods, rainfall, seepage from wet cultivation, infiltration from tanks, check dams, canals and reservoirs.^14,22 Since there is a scarcity of water storage especially for the following raining seasons the water available in the wells of the banks is only available during the rainy seasons. In this study 20 physicochemical characteristics include color, appearance, odor, temperature, turbidity, electrical conductivity (EC), pH, alkalinity, hardness, and total dissolved oxygen (TDS), Dissolved oxygen (DO), manganese, calcium, magnesium, sodium, potassium, chloride, fluoride, sulfate, and phosphate were assessed from 10 location, which were assessed and compared with BIS 10500: 2012 for drinking purposes tabulated in Table 1, Table 3 and Table 5. Samples were collected in dry, clean plastic bottles and are stored in refrigerator and all the samples are examined with the help of manuals and the values are noted and analysed periodically.¹³ For both rainy and summer seasons the samples are collected and analysed manually using titration methods^.19,20

Methodology

The study commenced with the selection of suitable study areas based on factors such as population density, reliance on groundwater, agricultural activity, and potential contamination sources.^21,22 Ten borewell sampling points were then identified within the study region, ensuring appropriate spatial distribution and accessibility. Groundwater samples were collected during both summer and winter to take seasonal changes in water quality into consideration. The samples were obtained following standard procedures, stored in pre-cleaned polyethylene bottles, and transported under refrigeration for laboratory analysis.^6,7,8

Various physicochemical parameters were analysed using standard methods in the code book Indian Standards for Water Supply and Quality- IS 10500: 1991: Drinking water standards- IS 3025: Methods of sampling and testing for water and wastewater, covering parameters like pH, turbidity, and chemical contaminants.

The Water Quality Index (WQI), which assigns weights to each parameter according to their relative importance, was computed using the weighted arithmetic index approach. Statistical tools such as the Pearson correlation coefficient matrix were employed to identify relationships among water quality parameters, while.

Table 1: Sampling site details with latitude and longitude

Table 2: Classification of groundwater quality based on Water Quality Index (WQI) using the weighted arithmetic method.^1,4,7

Results

Physicochemical Characteristics

The statistical analysis of groundwater samples from Tirupur District revealed substantial variation in key physicochemical parameters across sites and seasons. Total Dissolved Solids (TDS) and Electrical Conductivity (EC) recorded mean values of 2058.4 mg/L and 2940.1 µmho/cm in summer, and 1794.6 mg/L and 2563.0 µmho/cm in the rainy season, respectively, both of which exceeded BIS permissible limits. Hardness, calcium, magnesium, sodium, and chloride concentrations also surpassed acceptable levels in several locations, indicating contamination from both geogenic and anthropogenic sources.^25,26 Fluoride levels reached as high as 3.6 mg/L, exceeding the 1.5 mg/L limit, raising potential health concerns.^27-29

Water Quality Index (WQI)

The WQI classification revealed that groundwater quality at many sites fell into “poor” or “unsuitable” categories. During summer, WQI values ranged from 7.14 (good) to 224 (unsuitable), while in the rainy season they ranged from 85 (very poor) to 481 (unsuitable). These values indicate that a considerable proportion of the study area is unsafe for direct human consumption without treatment.²⁷

Seasonal Variations

Seasonal variation was evident in the results. Higher concentrations of TDS, hardness, and chloride were observed in summer, likely due to evaporation and reduced dilution. In contrast, the rainy season showed improved quality at some sites due to dilution but deterioration at others due to surface runoff carrying pollutants into aquifers. Figures 1–13 illustrate these variations in key parameters such as TDS, hardness, EC, sodium, chloride, calcium, and fluoride.²³

Correlation Analysis

Pearson correlation analysis (Figures 14 and 15) highlighted strong positive relationships between TDS and EC, chloride and hardness, and calcium and total hardness. Negative correlations were observed between dissolved oxygen (DO) and TDS/EC, suggesting that increased salinity reduces oxygen availability. These interrelationships provide insights into common pollution sources and chemical interactions in groundwater.¹⁷

Principal Component Analysis (PCA)

The PCA results (Table 7; Figures 16–17) identified major pollution sources influencing groundwater chemistry. In summer, the first two components explained 64.84% of the total variance, while in the rainy season they explained 52.63%. Industrial effluents, agricultural runoff, and natural geogenic processes were identified as dominant contributors to groundwater contamination.

Table 3: Descriptive statistics of physicochemical parameters of groundwater samples (summer season) compared with BIS standards.

Descriptive Statistical of the groundwater quality and its coherence with BIS standard (SUMMER) are mentioned in table 3

The statistical summary of groundwater samples from Tirupur District reveals significant variation in key physicochemical parameters, many of which exceed BIS (10500–2012) permissible limits. Total Dissolved Solids (TDS) and Electrical Conductivity (EC) showed elevated mean values of 2058.4 mg/L and 2940.1 µmho/cm, respectively, suggesting high ionic concentrations and possible contamination from industrial discharges. Hardness, calcium, magnesium, and chloride also surpassed acceptable limits, indicating both geogenic and anthropogenic influences. Fluoride levels exceeded the BIS threshold and posed possible health hazards; they ranged up to 3.6 mg/L, with a mean value of 1.68 mg/L.

The high standard deviations in parameters such as TDS, hardness, and sulphate reflect strong spatial variability across the study sites. Parameters like phosphate, turbidity, and nitrate further point toward agricultural runoff and wastewater intrusion. While pH values were generally within the acceptable range, other indicators suggest deterioration of groundwater quality in the region. These findings emphasize the need for site-specific groundwater management strategies and regular monitoring to mitigate industrial and agricultural impacts.

Table 4: Water Quality Index (WQI) values and classification of groundwater samples (summer season) in Tirupur District.

Table 5: Descriptive statistics of physicochemical parameters of groundwater samples (rainy season) compared with BIS standards.

Table 6: Water Quality Index (WQI) values and classification of groundwater samples (rainy season) in Tirupur District.

The groundwater quality data from the industrial areas of Tirupur District show considerable variation in key physicochemical parameters when compared with BIS (10500:2012) standards. Total Dissolved Solids (TDS) and Electrical Conductivity (EC) recorded mean values of 1794.6 mg/L and 2563.0 µmho/cm, respectively, far exceeding their respective limits (500 mg/L and 1400 µmho/cm), indicating high salinity and ionic load likely influenced by industrial discharges. Parameters such as hardness (mean: 537.0 mg/L), calcium (198.5 mg/L), magnesium (79.7 mg/L), sodium (187.1 mg/L), and chloride (223.3 mg/L) also surpassed acceptable levels, reflecting both geogenic influence and anthropogenic contamination. Fluoride (mean: 1.3 mg/L) and sulphate (mean: 215.5 mg/L) approached or slightly exceeded safe limits, raising health concerns in some locations.²⁹

High standard deviations, particularly in TDS, hardness, and sulphate, suggest significant spatial variability across the sampling sites. The pH values ranged from 7.4 to 9.4, with some samples exceeding the upper BIS threshold of 8.5, indicating possible alkaline conditions. Elevated turbidity, phosphate, and dissolved oxygen (DO) levels may be attributed to organic waste and agricultural runoff. These findings reflect the degraded groundwater condition in the industrial belt of Tirupur and underscore the urgent need for periodic monitoring, localized treatment interventions, and stricter regulation of industrial effluent disposal.

Figure 1: Seasonal variation of Water Quality Index (WQI) values in groundwater samples across Tirupur District (summer vs rainy seasons). Click here to view Figure

The Water Quality Index (WQI) analysis across 10 groundwater locations in Tirupur reveals clear seasonal variation between summer and rainy seasons. During summer, the WQI values ranged from 95 to 251, with most locations (Loc 4, 6, 7, 9, and 10) indicating moderate to high levels of contamination. This suggests reduced dilution capacity and potential concentration of pollutants during dry months due to lower recharge and higher water usage.

In contrast, rainy season WQI values ranged from 94 to a peak of 682 at Loc 6, showing a more extreme spatial variation. While some locations showed improvement due to rainwater dilution (e.g., Loc 1–4), others (notably Loc 6 and 7) exhibited worsening quality, likely from surface runoff carrying industrial and agricultural pollutants into shallow aquifers. The very high WQI in Loc 6 during the rainy season strongly suggests that surface-to-groundwater interaction and contamination are significant during monsoon months in industrial zones.

These seasonal disparities underscore the importance of dynamic water management strategies, tailored to both climatic conditions and land use patterns, especially in industrialized zones like Tirupur.

Figure 2: Total Dissolved Solids (TDS) concentrations in groundwater samples during summer and rainy seasons compared with BIS permissible limits. Click here to view Figure

In most locations, the TDS levels during the summer season are notably higher than in the rainy season, with some values such as sample point 4 showing a drastic spike well above 3000 mg/L. This exceeds the permissible limit, indicating poor water quality, especially during drier periods. The elevated TDS levels in summer could be due to evaporation, increased mineral runoff, or reduced dilution in the water sources. In the context of current global environmental concerns, such as climate change and water scarcity, this suggests that water quality is likely to worsen in drier, hotter seasons, which are becoming more frequent and intense due to global warming.

Figure 3: Seasonal variation in groundwater hardness levels at study locations relative to BIS standards. Click here to view Figure

Sample points such as 2, 4, and 5 show hardness levels exceeding permissible limits in summer. which, because of increased rates of evaporation and mineral leaching,  can be more  common during the dry season. The rainy season brings down these concentrations through dilution. This trend reflects broader environmental issues such as increased mineral pollution due to urban runoff and declining groundwater quality, which are exacerbated by human activities and climate variability. The presence of high hardness levels in drinking water can pose health risks and also damage infrastructure through scaling in pipes and appliances.

These results highlight the significance of routine evaluations of water quality and incorporating all of environmental monitoring into infrastructure design and public health.

Figure 4: Electrical conductivity (EC) of groundwater samples across summer and rainy seasons in Tirupur District industrial zones. Click here to view Figure

The spike in EC during summer suggests higher concentrations of these ions, likely due to increased evaporation, limited dilution, and possible leaching of contaminants from dry soils and industrial runoff. In contrast, the rainy season shows a noticeable reduction in EC, likely due to dilution by rainfall. In the context of global environmental challenges, especially those related to climate change and urbanization, such trends indicate rising pollution and salinization of water sources. The increased ion concentration in dry seasons could threaten both agriculture (through soil salinity) and drinking water quality, making it essential to monitor EC as a key indicator of environmental and water system health.

Figure 5: Magnesium concentration in groundwater samples across summer and rainy seasons. Click here to view Figure

The magnesium concentration graph reveals elevated levels in the summer season compared to the rainy season at most sampling sites. In some locations, the values either approach or exceed the permissible limit, such as at sample point 1 and 7. Magnesium is a common mineral found in groundwater, and elevated levels often arise from weathering of rocks or anthropogenic sources such as fertilizer runoff and industrial waste. Higher levels during summer suggest intensified leaching and reduced dilution, while rainy season values are generally lower due to the dilution effect.

Figure 6: Chloride levels in groundwater samples compared with BIS permissible limits during both seasons. Click here to view Figure

Particularly at locations like 4 and 5, the chloride levels exceed the permissible limit of 250 mg/L, reaching values above 600 mg/L. This seasonal spike is often attributed to factors such as increased evaporation, which concentrates salts, and possibly anthropogenic influences like sewage discharge or industrial effluents that become more prominent in the absence of rainfall dilution. The reduction in chloride levels during the rainy season is likely due to the diluting effect of rainwater. High chloride concentrations can make water unpalatable and corrosive, and pose health risks in vulnerable populations. It also contributes to the salinization of agricultural soils, which is a growing global threat to food security.

Figure 7: Sodium concentrations in groundwater samples (summer and rainy seasons) relative to standard limits. Click here to view Figure

The sodium content chart shows that in both summer and rainy seasons, values across many sites remain close to or above the permissible limit, with minimal seasonal variation compared to other parameters. Notably, points 3 and 5 exhibit significant spikes, with summer values nearing or exceeding 300 mg/L. Sodium in drinking water is often introduced through natural mineral deposits, industrial pollution, or excessive use of road salts and fertilizers. The relatively consistent sodium levels across seasons may suggest persistent anthropogenic sources that are less affected by dilution from rainfall.

Figure 8: Potassium concentration trends in groundwater samples during summer and rainy seasons. Click here to view Figure

The potassium concentration graph reveals moderate levels across all locations, with a clear seasonal variation where summer values are generally higher than those in the rainy season. At sites such as 4, 5, and 7, the potassium content reaches or slightly exceeds 30 mg/L, though it mostly remains within the permissible limits. Potassium, being a naturally occurring element in soils and fertilizers, often seeps into water systems due to agricultural runoff, especially during dry seasons when evapotranspiration increases the concentration of dissolved substances. In the rainy season, dilution from precipitation reduces its presence in water bodies. Globally, potassium is less frequently monitored in water quality programs, yet its increase is an indicator of agricultural intensification and unsustainable land use.

Figure 9: Calcium levels in groundwater samples compared with permissible limits across study sites. Click here to view Figure

The calcium chart exhibits notable variability among sampling points, with summer concentrations generally higher than rainy season values, particularly at points 1, 2, 5, and 6. Elevated calcium levels can be attributed to natural rock weathering, especially in calcareous regions, as well as industrial effluents and leaching from construction materials. Seasonal concentration changes are primarily due to evaporation during the summer, which concentrates minerals in the water.

Figure 10: Fluoride concentrations in groundwater samples (summer vs rainy seasons) with comparison to BIS standards. Click here to view Figure

The fluoride concentrations show significant fluctuations across the different locations, with several summer values—particularly at location 2 exceeding the permissible limit of 1.5 mg/L, reaching nearly 3.5 mg/L. In general, fluoride levels are higher in the summer compared to the rainy season, likely due to reduced water volume and increased leaching from fluoride-bearing minerals under high temperatures. The data suggests the need for localized water treatment strategies such as activated alumina filtration, and underscores the importance of integrating geogenic contamination monitoring into public health frameworks in an era of increasing water scarcity and climate stress.

Figure 11: Sulphate levels in groundwater samples across summer and rainy seasons compared with permissible limits. Click here to view Figure

The sulphates graph illustrates that levels across most sites remain within permissible limits, though peaks are observed at sites 3 and 4, especially during the rainy season. The increase during rainfall can be attributed to runoff from agricultural fields and industrial areas, which introduces sulphate-rich fertilizers and byproducts into water bodies. Elevated sulphate levels are not typically toxic when combined with chloride and other salts.

Figure 12: Phosphate concentrations in groundwater samples during summer and rainy seasons indicating agricultural influence. Click here to view Figure

The phosphate levels in the chart remain mostly within permissible limits (typically set at 0.1 mg/L for surface water), with noticeable spikes at locations 2, 4, and especially 5 during the rainy season. This trend suggests strong influence from agricultural runoff during monsoon periods, where phosphate-rich fertilizers are washed into local water bodies. This nutrient enrichment leads to algal blooms, oxygen depletion, and the collapse of aquatic ecosystems. The significant increase in phosphate concentrations during rainy seasons across multiple sites highlights a broader issue: poor land use management and unregulated agricultural practices.

Figure 13: Turbidity of groundwater samples compared with WHO permissible limits across summer and rainy seasons. Click here to view Figure

Turbidity levels show consistent exceedance of the permissible limit (5 NTU for drinking water by WHO standards) at most sites, especially in the summer season at location 2, which spikes above 20 NTU. This poses serious risks to water safety, especially in areas lacking advanced filtration. Turbid water not only interferes with disinfection processes but is also a visual indicator of deteriorating water quality.

Pearson Coefficent Matrix

Figure 14: Pearson correlation coefficient matrix for groundwater quality parameters (summer season). Click here to view Figure

Figure 15: Pearson correlation coefficient matrix for groundwater quality parameters (rainy season). Click here to view Figure

Hence, the influence derived from the parameters of water quality correlation studies is critical in the study of groundwater.

In Figure 14 calcium and pH(0.70), Alkalinity and     potassium, chloride and alkalinity (0.9), chloride and Total Hardness (0.8), Fluoride and pH( 0.9), Phosphate and pH(0.9), Phosphate and Total Hardness (0.9), Calcium and Turbidity (0.8) shows strong positive relationship towards the samples

In Figure 15 Total Hardness and TDS (0.80), Total Hardness and EC (0.80), Magnesium and Alkalinity (0.7), Magnesium and Total Hardness (0.7), Potassium and Alkalinity (0.8), Phosphate and Sodium (0.9) shows strong positive relationship towards the samples.

The Pearson correlation matrix of rainy groundwater samples reveals significant relationships among various physicochemical parameters. Electrical Conductivity (EC) shows a very strong positive correlation with Total Dissolved Solids (TDS) (r = 1.0), Chloride (Cl^-) (r = 0.9), and Calcium (Ca²⁺) (r = 0.8), suggesting that EC is primarily influenced by the presence of dissolved salts. Similarly, Total Hardness (TH) is positively correlated with Calcium (r = 1.0) and Magnesium (Mg²⁺) (r = 0.5), indicating that hardness is largely controlled by these cations.

pH exhibits a moderate negative correlation with parameters like Aluminium (Al) (r = –0.6) and Turbidity (r = –0.1), suggesting that acidic conditions may increase metal solubility. Notably, Sodium (Na⁺) and Potassium (K⁺) show moderate correlations with each other and with Chloride and EC, pointing to possible anthropogenic or industrial influences. Dissolved Oxygen (DO) is negatively correlated with TDS, EC, and Cl^-, which may imply that higher salinity reduces oxygen availability.

These correlations are critical for identifying pollution sources and understanding chemical interactions within groundwater systems in industrial areas during the rainy season.

Notably, the strong positive correlation between TDS and EC indicates that TDS is a major contributor to electrical conductivity. The relationships between pH and parameters like Fluoride and Phosphate suggest potential influences of agricultural or industrial activities on water quality. Furthermore, the correlations between hardness and ions like Chloride and Phosphate highlight the importance of considering multiple parameters in water quality management. These findings have implications for developing effective water treatment strategies and managing water resources sustainably during the rainy season.

Figure 16: Principal Component Analysis (PCA) of groundwater parameters for the summer season. Click here to view Figure

Figure 17: Principal Component Analysis (PCA) of groundwater parameters for the Rainy season. Click here to view Figure

Table 7: Rotated component matrix from Principal Component Analysis (PCA) of groundwater chemical parameters for summer and rainy seasons

The study's findings highlight the critical need for dynamic water management strategies in Tirupur district, where seasonal variations significantly impact groundwater quality. The elevated Water Quality Index (WQI) values during both summer and rainy seasons indicate contamination from various sources, including industrial effluents and agricultural runoff. By addressing these research directions and implementing effective water management strategies, the study can contribute to improving water quality, protecting public health, and promoting sustainable development in Tirupur district. In this present study the majority of groundwater is unsafe for drinking, according to the results of all indexing techniques, and those locations that are unsafe for drinking require treatment before consumption.

The comparison of correlation matrices between summer and rainy seasons can provide valuable insights into seasonal variations in water quality dynamics. By analyzing these correlations, policymakers and water managers can identify key parameters to monitor and create focused interventions to safeguard public health and enhance water quality. Ultimately, this knowledge can contribute to more effective and sustainable water resource management practices. From the analysed values according to BIS 10500: 2019 standards, physicochemical parameters such as pH, alkalinity, magnesium, fluoride are within the permissible limits. The majority of groundwater is unsafe for drinking, according to the results of all indexing techniques, and those locations that are unsafe for drinking require treatment before consumption.

Due to the rapid increase in population and industrial activities major problems occurs hardly following to that the industries can take reducing measures by use of water purifiers, distillation, flocculation, neutralize process, softening, reverse osmosis process, filtration, cation exchange, boiling process can be done. Principal’s component-I has explained 43.76 and 64.84 percentage of variance in pre and post monsoon season whereas principal component-II has explained 29.72 and 52.63 percentage of variance respectively. The loading relationship between the variables was displayed graphically in principle components I and II.

Conclusion

The present study demonstrated that Principal Component Analysis (PCA) effectively identified the major hydrogeochemical processes influencing groundwater quality. Two principal components were extracted, explaining the variance in pre- and post-monsoon seasons, with significant loadings observed for parameters such as Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^-, SO₄²^-, NO₃^-, and F^-. Seasonal variations revealed higher ionic concentrations during the summer due to reduced dilution and increased evaporation. Elevated levels of TDS, hardness, fluoride, chloride, and turbidity indicate risks to water safety and infrastructure, largely driven by agricultural runoff and industrial effluents. These findings emphasize the need for regular groundwater monitoring, effective treatment technologies, stricter regulation of effluent discharge, and sustainable land-use practices to safeguard water resources and ensure long-term public health protection.

Acknowledgement

I would like to express gratitude to all the staff of Department Environmental Engineering., Government college of technology, Coimbatore, for their help and encouragement.

Funding Sources

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Conflicts of Interest

The authors do not have any conflict of interest.

Data Availability Statement

The manuscript incorporates all datasets produced or examined throughout this research study.

Ethics Statement

This research did not involve human participants, animal subjects, or any material that requires ethical approval.

Informed Consent Statement

This study did not involve human participants, and therefore, informed consent was not required.

Permission to reproduce material from other Sources

Not Applicable

Author Contributions

Kavinaya Ravi: Data Collection, Analysis, Writing – Review & Editing.

Ravathi Mohanadhas Chandrika: Visualization, Supervision, Project Administration.

References

1. Krishnakumar S, Logeshkumaran A, Magesh NS, Godson PS, Chandrasekar N. Hydro-geochemistry and application of water quality index (WQI) for groundwater quality assessment, Anna Nagar, part of Chennai City, Tamil Nadu, India. Appl Water Sci. 2015;5(4):335-343. doi:10.1007/s13201-014-0196-4
   CrossRef
2. Sajil Kumar PJ, Kuriachan L. Chemometric appraisal of groundwater quality for domestic, irrigation and industrial purposes in Lower Bhavani River basin, Tamil Nadu, India. Chem Ecol. 2020;36(7):637-658. doi:10.1080/03067319.2020.1770241
   CrossRef
3. Sudhakar V, Chidambaram S. Spatial distribution of groundwater quality assessment using Water Quality Index and GIS techniques in Thanjavur Taluk, Thanjavur District, Tamil Nadu, India. J Geol Soc India. 2016;88(3):295-302. doi:10.1007/s12594-016-0446-4
4. Kumar S, Loganathan K, Nithya A, et al. Water Quality Index of River Bhavani at Erode Region, Tamil Nadu, India. Natl Environ Pollut Technol. 2006;5(2):241-244.
5. Parameswari K, Prasanna MV, Annadurai R, et al. Water Quality Index of River Noyyal at Tirupur, Tamil Nadu, India. Natl Environ Pollut Technol. 2007;6(4):597-600.
6. Sajil Kumar PJ, James EJ. Water quality assessment in terms of Water Quality Index (WQI) using GIS in Lower Bhavani River Basin, Tamil Nadu, India. Int J Res Rev. 2018;5(7):40-48.
7. Umadevi P, Pradeep T, Sampathkumar V, et al. Groundwater quality assessment in a north-east region of Erode District, Tamil Nadu. Mater Today Proc. 2021;46:3922-3929.Doi:10.1016/j.matpr.2021.01.785
   CrossRef
8. Kannan R, Joseph S, Vijayaraghavan K. Groundwater quality assessment using water quality index (WQI) and GIS in parts of Coimbatore district, Tamil Nadu, India. Appl Water Sci. 2021;11:107. doi:10.1007/s13201-021-01376-7
   CrossRef
9. Saravanan K, Elangovan K, Ramkumar T. Groundwater quality assessment for drinking and irrigation uses in parts of Erode District, Tamil Nadu, India. Environ Monit Assess. 2013;185(1):387-404. doi:10.1007/s10661-012-2559-6
10. Prasanna MV, Chidambaram S, Nagarajan R, Elango L. Groundwater quality assessment and water quality index in a hard rock terrain of Gadilam River Basin, Tamil Nadu, South India. Arab J Geosci. 2012;5(2):285-294. doi:10.1007/s12517-010-0190-6
    CrossRef
11. Anbazhagan S, Archana T. Hydrochemical characterization and groundwater quality assessment in parts of Salem District, Tamil Nadu. Appl Water Sci. 2016;6(2):141-150. doi:10.1007/s13201-014-0202-0
12. Sreedevi PD, Ahmed S, Made B, Ledoux E. A study on the groundwater quality of Araniar River Basin, Tamil Nadu, India. Environ Geol. 2005;47:1099-1110. doi:10.1007/s00254-005-1231-3
    CrossRef
13. Kaviarasan T, Chandrasekar N, Rajamanickam GV. Assessment of groundwater quality for drinking purpose using WQI in parts of Kanyakumari District, Tamil Nadu. Indian J Geo-Mar Sci. 2015;44(12):1890-1896.
14. Magesh NS, Chandrasekar N, Elango L. Spatial variability of groundwater quality in the coastal aquifers of Tuticorin, Tamil Nadu, India—geostatistical and WQI approaches. Environ Sci Pollut Res. 2017;24(33):25729-25747. doi:10.1007/s11356-017-0218-4
15. Senthilkumar M, Elango L. Groundwater quality and its suitability for drinking and irrigation in parts of Palar River Basin, Tamil Nadu, India. J Earth Syst Sci. 2013;122(3):729-742. doi:10.1007/s12040-013-0308-6
    CrossRef
16. Ravikumar P, Somashekar RK, Angami M. Hydrochemistry and evaluation of groundwater suitability for irrigation and drinking purposes in parts of Erode district, Tamil Nadu, India. Environ Monit Assess. 2011;176(1-4):183-207. doi:10.1007/s10661-010-1579-0
    CrossRef
17. Thivya C, Chidambaram S, Prasanna MV, et al. Evaluation of groundwater quality in the coastal aquifers of Cuddalore District, Tamil Nadu, India: WQI and multivariate approaches. Appl Water Sci. 2015;5(2):161-172. doi:10.1007/s13201-014-0177-x
18. Sarala Thambavani D, Pushpa R. Assessment of groundwater quality for drinking purpose in and around Tiruchirappalli District, Tamil Nadu, India using WQI. Appl Water Sci. 2012;2(3):193-203. doi:10.1007/s13201-012-0039-7
19. Vijayakumar N, Elango L. Seasonal variation and WQI of groundwater in Minjur–Attipattu, north of Chennai, Tamil Nadu. Environ Monit Assess. 2010;165(1-4):603-613. doi:10.1007/s10661-009-0977-7
    CrossRef
20. Sajil Kumar PJ. Hydrogeochemical characterization and water quality assessment of groundwater in and around Bhavani Taluk, Erode District, Tamil Nadu. Environ Dev Sustain. 2013;15(3):735-746. doi:10.1007/s10668-012-9413-3
21. Balaji E, Nagarajan M, Mohan A, Periyannan G. Groundwater quality assessment using water quality indices in parts of Vellore District, Tamil Nadu, India. Groundw Sustain Dev. 2019;9:100224. doi:10.1016/j.gsd.2019.100224
    CrossRef
22. Sarvajith K, Dhivya S, Elango L. Groundwater quality mapping and WQI assessment in parts of Kancheepuram District, Tamil Nadu. Sustain Water Resour Manag. 2018;4:113-123. doi:10.1007/s40899-017-0121-7
23. Jayaprakash M, Srinivasalu S, Jonathan MP, et al. Assessment of groundwater quality in and around Chennai City, Tamil Nadu, India. Environ Geol. 2008;54(6):1237-1248. doi:10.1007/s00254-007-0891-1
24. Subramani T, Elango L, Damodarasamy SR. Groundwater quality and its suitability for drinking and agricultural use in Chithar River Basin, Tamil Nadu, India. Environ Geol. 2005;47(8):1099-1110. doi:10.1007/s00254-005-1233-1
    CrossRef
25. Sajil Kumar PJ, Elango L. Groundwater quality in Lower Bhavani Basin, Tamil Nadu: WQI, suitability for irrigation and industry. Int J Environ Sci Technol. 2019;16(11):6961-6974. doi:10.1007/s13762-018-2121-6
26. Dhanasekarapandian M, Chidambaram S, Thivya C, et al. WQI and hydrochemical evolution of groundwater in parts of Coimbatore–Tiruppur industrial corridor, Tamil Nadu, India. Environ Sci Pollut Res. 2021;28(15):18857-18876. doi:10.1007/s11356-020-11759-0
27. Shankar K, Elango L. Assessment of groundwater quality and WQI in parts of Nagapattinam District, Tamil Nadu. Appl Water Sci. 2019;9:213. doi:10.1007/s13201-019-1087-9
28. Vasanthavigar M, Srinivasamoorthy K, Vijayaraghavan K, et al. Application of WQI and geostatistics for groundwater quality assessment in Thirumanimuttar sub-basin, Tamil Nadu, India. Environ Monit Assess. 2010;171(1-4):595-609. doi:10.1007/s10661-009-1302-1
    CrossRef
29. Kumaresan M, Riyazuddin P. Hydrogeochemical studies of groundwater in the Palar River Basin region, southern India: implications for water quality management. Environ Monit Assess. 2006;123(1-3):299-312. doi:10.1007/s10661-006-9192-2
30. Prabhu A, Elango L, Srinivasan K. Groundwater quality for drinking and irrigation in and around Salem District, Tamil Nadu, India—WQI approach. Arab J Geosci. 2012;5(6):1423-1434. doi:10.1007/s12517-010-0282-3