Hydrogeochemical and GIS Analysis of Groundwater Quality for Drinking and Irrigation Purposes in Kuzhithuraiyar Sub-Basin, Kanniyakumari District

A hydrogeochemical analysis was conducted to fnd the suitability of the groundwater for drinking and irrigation purposes in the Kuzhithuraiyar sub-basin, Kanniyakumari district, Tamil Nadu, India. 48 groundwater samples were collected from the diferent locations of the study area during both the pre-and postmonsoon periods. Tis study assesses the groundwater quality for drinking and irrigation purposes based on the analytical results, water quality index, Wilcox plot, and irrigation parameters such as electrical conductance, Kelly’s ratio, sodium absorption ratio values, magnesium hazards, bicarbonate, and the residual sodium carbonate index. Te pH values ranged from 8.5 to 6.5, suggesting generally acceptable conditions. TDS concentrations range from 24 to 1277mg/L, whereas EC values range from 37.50 to 1996 μ S/cm. It is observed from the collected samples that the pre-monsoon water samples TDS’ values were exceeded the recommended TDS limits than postmonsoon samples. Water quality indices indicate that 50% of premonsoon samples and 48% of postmonsoon samples are suitable for drinking. In total, 10% of samples are admissible to a doubtful category before and after the monsoon, 6% are good to permissible during the monsoon, and 84% are good to permissible. Kelly’s ratio shows that 56% and 48% of samples collected during the post-and premonsoon are suitable for irrigation, respectively, whereas the remaining samples are not. Due to magnesium hazards, 40% and 44% of pre-and postmonsoon samples are not suitable for irrigation. Overall, the postmonsoon samples exceeded the permissible TDS limit (1000mg/L) by 10% and the premonsoon samples by 6. 13% of samples obtained after the monsoon and 19% collected before the monsoon have a potential salinity greater than three, indicating that these samples are unacceptable. Te sustaining water quality and mitigating possible hazards in the Kuzhithuraiyar sub-basin require continuous monitoring and focused measures.


Introduction
Groundwater is extensively used in dry and semiarid regions for industrial, agricultural, and residential uses [1][2][3].People's health and socioeconomic development are impacted by the water quality [4,5].97% of the earth's water is found in the oceans and it is too salty to drink, grow crops, or be used for most industrial purposes.Fresh water makes up 3% of the earth's water supply.Approximately 68 percent of fresh water on Earth is found in glaciers and icecaps, while just over 32 percent is found in groundwater [5,6].Te incorrect application of agricultural chemicals, rapid industrialization, poor waste management, and needless water extraction are just a few of the numerous causes of ion imbalance in the water quality [5].A solid understanding of hydrochemistry is necessary to assess the quality of groundwater used for irrigation and drinking [7][8][9].
When choosing a water quality ft for household use, the water quality index (WQI) is helpful.In India, weighted arithmetic and integrated WQIs are frequently used to evaluate surface and groundwater because they produce results with greater precision [10,11].Both natural and artifcial activities that cause a decline in the groundwater quality can further restrict the use of groundwater resources.Natural and human activities can decrease the groundwater quality, limiting its utility.Geological, weathering, and microbial processes can pollute groundwater with minerals and pollutants.Groundwater concentrations can rise as minerals such as arsenic or fuoride dissolve from geological formations, making it unsuitable for certain uses.Agriculture, industry, and improper waste management harming the groundwater quality.Chemicals and heavy metals from industrial processes can pollute groundwater.Nitrates and other agrochemicals from excessive fertilizer and pesticide usage can damage groundwater [12,13].A vast amount of groundwater (million cubic meters) is used in agriculture for plant growth and yield [12][13][14].Depleting the water table level due to excessive groundwater usage without adequate recharging is a signifcant threat to the sustainability of agriculture.Te type of aquifer utilized, its salinity, and its TDS all afect the quality of irrigation water [14][15][16][17].Both human health and agricultural productivity are negatively impacted by water quality [8,18].
Tere is a consistent fow of tourists into the Kanyakumari district, which could lead to overextraction of groundwater.As a result, certain coastal pockets may experience a drop in water levels [19][20][21].Wells drawing heavily from tertiary aquifers and coastal alluvium during summer may cause saline water intrusion into freshwater areas [22].Urbanization, industrialization, and agricultural activities in the Kanniyakumari district in Tamil Nadu, India, are some elements that infuence the water quality.Analyses and comparisons with standard permitted limits were conducted on the water quality indicators, including turbidity, total dissolved solids (TDS), electrical conductivity (EC), pH, hardness, nitrite, sulfate, phosphate, bacteriological examinations, and fecal coliform [23].
Te research gap in this context is the need for a more detailed investigation into the factors contributing to groundwater quality degradation in the Kanniyakumari district.Tere is an opportunity to delve deeper into the impact of tourism, urbanization, industrialization, and agricultural practices on the water quality.Additionally, further research could explore efective strategies for sustainable groundwater management, especially in the face of potential overextraction and saline water intrusion.Detailed studies on the specifc aquifers, their salinity, and the associated efects on the irrigation water quality may also provide valuable insights.Moreover, assessing the long-term consequences of groundwater depletion on agriculture and human health could require a more comprehensive investigation.
Te main objective of the present study is to examine the suitability of the groundwater for drinking and irrigation purposes.Chloroalkaline indices, hydrochemical facies, and statistical analysis-Pearson's correlation, salinity, and sodium hazards, total ionic concentration, permeability index, Wilcox's plot, Doneen's plot, USSL plot, and Piper trilinear plots and water quality index were used to assess the suitability of the groundwater.Te study's fndings can directly impact the health and well-being of the local population by identifying potential contaminants or hazards in the groundwater that could pose health risks upon consumption.Analyzing the suitability of groundwater for irrigation purposes helps ensure sustainable agricultural practices, which are crucial for the livelihoods of farmers and the local economy.So far, no detailed study using this comprehensive methodology has been found in this area.

Study Area.
Te study area is located on the western side of Kanniyakumari district, Tamil Nadu, India (Figure 1).Te basin has a unique advantage in terms of rainfall during both the southwest and northeast monsoon seasons.Gathering secondary data sources involves creating thematic geology maps (source: Geological Survey of India Map) and soil (source: National Bureau of Soil Survey and Land Use Planning Map).Tese maps were then digitized using ArcGIS before that these data were properly georeferenced and projected.Te study area has a heterogeneous geology with igneous, sedimentary, and metamorphic rocks.Geomorphology includes alluvial plains, coastal plains, denudational hills, peneplains, and structural hills.Te study area can be divided into four signifcant landforms: hills, plains, valleys, and coastal belts.In a hilly region, gravelly soil is found, and the crops in this region include rubber, nutmeg, cloves, and pineapple, followed by plains and valleys where red loamy soil covers are found with the paddy, tapioca, banana, coconut, etc., crop pattern.In the coastal regions, sandy soil is found and cashew nuts, coconut, mango, and tamarind are the major crops.Permeable and fssured formations can be found beneath the study area.Worn, fssured, and fractured crystalline rocks coexist in the examined region with semiconsolidated and unconsolidated strata to produce the critical aquifer system.Tese rock types are made up of limestone and sand stone and play an important role in the groundwater occurrence in the present study area.Phreatic type of groundwater aquifers found in sand dunes near the point where the Kuzhithuraiyar river joins the Arabian Sea and in worn, broken, and fssured crystalline rocks [21].Te water table is worn and semirestricted to constrained conditions in these rock fracture and fssure zones at 8-18 m depths below the surface.Dunes have water levels of 4-8 m below the surface [24].

Sampling and Analysis.
Te water samples were collected during both the pre-and postmonsoon seasons in 2022.Te concentrations of the major anions and cations in the groundwater, along with the pH, EC, and TDS, were determined by standard procedures using 48 samples collected across the basin (Figure 1).An ion electrode was employed to measure the EC and pH.To obtain TDS, multiply EC by 0.64.Te titrimetric method was used to analyze anions such as Cl − , CO 3 − , and HCO 3 − , as well as cations such as Ca 2+ and Mg 2+ .We used a fame photometer to observe Na + and K + and a spectrophotometer to look at SO 4 − and NO 3 − .All physicochemical parameters were compared with WHO standards [25].Te following equation was used to determine the normalized charge balance index [26][27][28]: Applied and Environmental Soil Science where ΣT + Z is the total sum of cations in epm and ΣT - Z is the total sum of anions in epm.

Water Quality Index (WQI).
Te WQI is a quantitative measure used to evaluate the overall quality of groundwater.Tis report ofers a compilation of water quality criteria assessed in groundwater samples, which can aid in comprehending and conveying the overall condition or appropriateness of the water for diferent purposes, such as drinking, irrigation, industrial use, or preservation of the environment.Every parameter in the current study has a distinct weight based on how signifcant they are to groundwater quality for drinking purposes [29,30].A rank between 1 and 5 is assigned for all the hydrogeochemical parameters.pH and TDS are ranked highest because of their importance in water chemistry.Chloride is ranked lowest due to its low impact on the water quality.Te relative weight (W i ) is calculated using the following formula: Te quality rating scale (q i ) is determined using the following formula: where C i is the concentration of groundwater parameter and S i is the drinking water standard based on WHO [25].Te subindex (S i ) is calculated using the following formula: where W i is the relative weight and q i is the quality rating scale Te water quality index is calculated using the following formula: where WQI is the water quality index.

Hydrogeochemical
Parameters.Many hydrogeochemical characteristic changes will occur through the water's ionic interaction.Tese have been identifed through the parameters below.Applied and Environmental Soil Science 2.4.1.Chloroalkaline Indices.Te ion exchange process constantly alters the chemical composition of the groundwater.Ions undergo exchange as groundwater fows through geological strata [31].When water encounters minerals that contain ions such as calcium (Ca 2+ ), magnesium (Mg 2+ ), sodium (Na + ), and potassium (K + ), these ions can replace other ions that are already in the water.Calcium and magnesium ions can substitute sodium and potassium ions that are attached to minerals in the aquifer.Te ion exchange mechanism has a profound impact on the chemical composition of water.Chloroalkaline indices measure this process, which relies on stativity, groundwater fow, and other aquifer processes.It is possible to calculate the chloroalkaline indices (CAI-1) and (CAI-2) [32] by using the following formulas: Positive chloroalkaline indices 1 and 2 indicate a direct ion exchange process, while negative values indicate a reverse ion exchange process.

Groundwater Classifcation.
Groundwater hydrochemical facies are categorized according to their unique compositions and features.Tese classifcations help people understand the chemical composition of groundwater, identify its sources, and evaluate its possible uses and risks.Hydrochemical facies of groundwater can be determined using the following equations proposed by [33]: r1 greater than 1 is categorized as Na 2+ -SO 4 2+ type of water, and r1 less than 1 is categorized as Na 2+ -HCO 3 -type of water.Te meteoric genesis index indicates that deep meteoric percolation occurs when values are less than 1, while shallow meteoric percolation occurs when values exceed 1 [33].

Parameters Responsible for Irrigation Suitability.
Te quality of water and soil productivity is altered by the chemical ions such as K + , Na + , Mg 2+ , Ca 2+ , SO 4 2-, and HCO 3 - [14].Elevated concentrations of sodium in irrigation water, particularly when paired with bicarbonate, can lead to soil sodicity.Sodic soil is substantial in salt.When irrigation water contains high salt levels, especially when paired with bicarbonate, soil can become sodic.Tis causes excessive salt saturation in the soil, which can harm the plant development and structure.Sodic soils have low fertility, permeability, and drainage, which reduces agricultural production [34,35].Sodicity is crucial to the health of soil and agriculture; thus, readers must grasp it.SAR stands for the sodium adsorption ratio, which measures the proportion of sodium compared to other ions such as calcium and magnesium.Soil structure deterioration, less water infltration, and detrimental impacts on plant growth can occur due to increased soil dispersion and decreased water availability [36].Soil dispersion occurs when water or wind erosion breaks down aggregates of soil into smaller particles.Soil dispersion breaks down the soil structure, separating the particles and making them more prone to erosion and compaction [36].Furthermore, these ions enhance the soil structure and hinder the sodiuminduced soil dispersion.Ensuring sufcient calcium and magnesium in the soil facilitates optimal aeration, root development, and water penetration.Potassium is crucial for numerous physiological processes in plants [37].Optimal quantities of potassium in irrigation water can enhance the crop yield and quality.Potassium is a vital nutrient for plant growth as it is necessary for various physiological activities.Te presence of bicarbonate ions in the soil can lead to an elevation in alkalinity, which, in turn, can infuence the pH of the soil and potentially afect the availability of nutrients.

Sodium Adsorption Ratio (SAR).
Te suitability of irrigation water and its possible efects on plant growth and soil structure were evaluated using the SAR of irrigation water.Te quantity of sodium in irrigation water is determined by comparing it with other positively charged ions, such as magnesium and calcium [38] developed the (10) of the SAR, Four classes can be classifed according to the sodium adsorption values.Tey are as follows: (1) Less than 10 indicates excellent.(2) 10 to 18 indicates good.(3) 18-26 indicates doubtful.(4) Greater than 26 indicates unsuitable.Te lower the value, the higher the infltration rate, whereas the higher the value, the lower the infltration rate.

Residual Sodium Carbonate (RSC).
RSC can be surpassed by Na + adsorption in soil, which aids in accumulating Ca 2+ and Mg 2+ caused by excessive CO 3 2-and HCO 3 in groundwater [14].RSC is calculated using the following equation coined by [39]: Tree classes are characterized based on the values of RSC, i.e., low or good (<1.25),medium or doubtful (1.25 to 2.5), and high or unsuitable (>2.5).
2.4.7.Kelly's Ratio.Kelly's ratio of less than 1 means the water is suitable for irrigation.At the same time, water is unsuitable for irrigation if it is greater than 1.Kelly's ratio was calculated using the following formula proposed by [43] and modifed by [44]: 2.4.8.Permeability Index (PI).Te interconnectivity of the grains, which is impacted by ongoing groundwater agriculture, is directly correlated with PI.Utilizing groundwater abundant in Mg 2+ , Ca 2+ , Na + , and HCO 3 -can Diminish Soil Permeability.It Was Calculated Using the following equation coined by [45]: Te values can be classed into three types: Class I good (>75%), Class II doubtful (25-75%), and Class III unsuitable (<25%).
2.4.9.Magnesium Hazard.In water, calcium and magnesium often remain in equilibrium.Te excess magnesium content in water harmfully afects the crop yield.Magnesium hazard for irrigation water has been calculated using the following equation developed by [46]: If the magnesium ratio exceeds 50, it is considered harmful and unsuitable for irrigation [47].
2.4.10.Potential Salinity.Salinization is the process of salt buildup in the soil, which can negatively impact soil fertility, plant growth, and agricultural output.Potential salinity can be calculated using the following formula proposed by [45]: Potential salinity less than 3 is defned as suitable and greater than 3 is defned as unsuitable for irrigation.
2.4.11.Total Dissolved Solids.TDS measures the number of dissolved solids in water.TDS in water originates from a diverse range of natural and human-related sources.
Weathering and disintegrating rocks and minerals with water fow through geological formations are examples of natural sources.Water interacts with rocks and soil, dissolving various minerals, including calcium, magnesium, sodium, potassium, bicarbonates, chlorides, sulfates, and other similar substances.Anthropogenic pollution arises from multiple causes, such as industrial discharges, agricultural runof, sewage efuents, and human activities introducing contaminants into waterways [48,49].TDS is classed into three types: suitable (<450 mg/L), doubtful (450 to 2000 mg/L), and unsuitable (>2000).

Correlation Matrix. A correlation matrix, specifcally
Pearson's correlation matrix, examines the interrelationship among various variables inside a dataset.Using this tool, you can efectively ascertain the magnitude and orientation of linear correlations or interdependencies among variables.Pearson's correlation coefcient, represented as "r," allows for quantifying the intensity and orientation of the linear association between two continuous variables.Te variable "r" can take on values from −1 to +1 [50].A correlation coefcient +1 indicates a fawless linear link, implying that if one variable increases, the other similarly increases in direct proportion.A correlation coefcient −1 implies a strong negative linear relationship, where one variable consistently increases, while the other consistently declines in proportion [50].In general, a correlation coefcient near zero suggests the absence of a linear association between the variables.When analyzing water quality, variables such as pH, EC, and TDS and major cations (such as calcium, magnesium, sodium, and potassium) and anions (such as chloride, sulfate, and bicarbonate) can be examined using a correlation matrix with Pearson's correlation coefcient.

Results and Discussion
3.1.Drinking Water Quality Analysis.Te results show that the Kuzhithuraiyar sub-basin has pH values ranging from 6.5 to 8.5.Te range of EC is 37.50 μS/cm to 1996 μS/cm.TDS concentrations range from 24 to 1277 mg/L.Te current cation and anion trends are as follows: Cl − > HCO 3 − > SO 4 2− > NO 3 − > CO 3 − and Na + > Ca 2+ > Mg 2+ > K + .Kodumkulam and Villusari have 317 mg/L and 3 mg/L of sodium levels, respectively.Te calcium concentration ranges from 2 mg/L at Kodayar to 92 mg/L at Edavar.Magnesium concentrations at Edavar and Kodayar range from 58.32 mg/L to 1.22 mg/L.At Viricode, potassium levels are 37 mg/L, and at Churur, they are 1 mg/L.Edavar's chloride value ranges from 624 mg/L to 4 mg/ L. Bicarbonate values range from 366 mg/L at Kodumkulam to 4.97 mg/L at Vilamalai, averaging 90.96 mg/L.Te concentration range of sulfate is 77 mg/L at Edavar and 1 mg/L at Karod.At Vavarai, nitrate concentrations are 18 mg/L, and at Netta, they are 0.05 mg/L.At Manalodai, the range of carbonate is 0 to 4.33 mg/L.Te ionic concentration is closer to the coastline tract in the southwestern section than in other places.Tis leads to an interaction between salinity and ions.Te drinking water standards are compared with the WHO standards [25].Te spatial distribution map of major ions is shown in Figures 2(a)-2(j).Applied and Environmental Soil Science Te pH ranges between 6.5 and 8.5 in all samples collected before and after the monsoon.Te average EC limit was exceeded by 29% of samples in the postmonsoon period and 46% in the premonsoon period.Te salinity index of the groundwater samples was computed using electrical conductivity measurements.High-salinity (class 3) water is the perfect irrigation solution for crops that can withstand medium and high salt levels.Low-to moderate-salinity (classes 1 and 2) water does not cause signifcant harm to soil or crops [51].Te salinity index shows that 8% of samples are highly saline, and 92% are low to moderately saline.Te TDS value indicates that 10% and 15% of samples during the post-and premonsoon periods, respectively, exceed the limit.Drinking water with a TDS of 1000 mg/L is permissible [8,51].Samples taken before or after the monsoon had a 6% higher calcium content than samples taken during the monsoon.Samples taken before and after the monsoon showed 2% and 10%, respectively, more magnesium than the regulatory limit.Sodium concentrations before and after the monsoon are 8% greater than the allowed limit.Potassium contents increased by 23% and 14% in the postmonsoon and premonsoon seasons, respectively.Te chloride concentration was higher in 10% of the premonsoon samples and 8% of the postmonsoon samples.All samples had carbonate, bicarbonate, nitrate, and fuoride concentrations within permissible limits (Table 1). 2  and 3 show the calculation and results of the water quality index.According to the WQI value, water is categorized as follows: 0-25 is excellent, 25-50 is good, 50-75 is moderate, 75-100 is poor, and more than 100 is very poor for household use and drinking.Te water quality index during premonsoon is 50% and 48% during postmonsoon.Te water quality index results show that all the samples are good for drinking during both monsoons.

Ionic Suitableness for Irrigation Evaluation.
Te Indian coast can be classifed into two categories based on the geomorphic setup: (a) east coast and (b) west coast.Te vast coastal plains and sedimentary deposits along the east coast have given way to creating clearly defned deltaic plains at the river mouths [52].Te west coast is mostly rocky, with tidal creeks, and exposed rock [53].Te Kuzhithuraiyar, or Tamirabarani, is confuences on the west coast near Tengapattanam.Te ionic interactions in the samples are identifed through the chloroalkaline indices and meteoric genesis index.It shows that more than 50% of samples show reverse ion exchange processes and deep meteoric percolation, while 50% show the direct ion exchange and shallow meteoric percolation.Te irrigation suitability of the water samples is calculated using standard formulas, and their results are given in Table 3.
All samples are excellent and safe, according to the residual sodium concentration (RSC) and sodium absorption ratio (SAR).Figure 3 plots the SAR and EC measurements acquired from the USSL.It is possible to decrease the permeability and structure of the soil by increasing the amount of salt in the soil [54].Groundwater in the C4-S2, C4-S3, C4-S4, and C4-S1 categories cannot be used for irrigation in most soil types except those with high permeability [55].On the other hand, C3-S1 water can only be used for irrigation in semitolerant crops [56].Te USSL diagram indicates that the three samples taken before the monsoon and the four samples taken after the monsoon belong to the C3-S2 category, which denotes moderate salinity and mild alkali threats.Te research area has low to medium alkalinity and low to high salinity.
Premonsoon samples with cation and sodium concentrations show that 21% of them are good and 2% and 6% are excellent, 44% of premonsoon and 48% of postmonsoon samples are acceptable, and 33% of premonsoon and 23% of postmonsoon samples are doubtful.Te soil infltration rate and Na% are antagonistic [14].Tis antagonistic relationship is often observed in soils with high levels of sodium.High sodium levels can lead to the dispersion of soil particles, causing the formation of a compacted soil structure with reduced pore spaces.Tis compacted structure hinders water movement through the soil, resulting in a lower infltration rate.Sodium ions can harm soil structure, infuencing its permeability and reducing its ability to absorb and transmit water [57,58].Te Wilcox diagram shows the salt and electrical conductance proportion before and after the monsoon (Figure 4).10% of pre-and postmonsoon samples are classifed as dubious, 6% as good to permissible, and 84% as permitted.
According to Kelly's ratio, 56% and 48% of samples during the post-and premonsoon periods are suitable for irrigation, and the remaining samples are unsuitable for irrigation.In this study, magnesium hazard shows that 40% and 44% of samples during pre-and postmonsoon are unsuitable for irrigation.Potential salinity of 13% of samples during postmonsoon and 19% of samples during premonsoon is greater than 3, indicating unsuitability for irrigation.4 and 5, was employed to analyze the interrelationships among the physicochemical parameters.In pre-and postmonsoon, pH shows a positive correlation with bicarbonate (HCO 3 -) at a signifcant level (p < 0.01), indicating that as the pH levels increase, the concentration of bicarbonate in the water also tends to increase [56,57].EC, TDS, and most major ions, calcium, magnesium, sodium, potassium, chloride, and sulfate exhibit strong positive correlations among themselves (p < 0.01).Tis indicates a signifcant relationship, suggesting that these parameters increase or decrease in the groundwater samples.Chloride correlates positively with the concentrations EC, TDS, and most major ions, highlighting a consistent relationship among these parameters.Te relationship between carbonate and other parameters appears weak or negligible as low or insignifcant correlation coefcients indicate.Nitrate and fuoride seem to have very weak or little correlations with diferent parameters based on the provided correlation matrix [56,57].

Discussion
. In this study, pH, EC, TDS, and major cations (e.g., sodium, calcium, magnesium, and potassium) and anions (e.g., chloride, sulfate, bicarbonate, and nitrate) were found to be highly variable.Te pH value ranges between 8.5 and 6.5, consistently within an acceptable range, indicating that the water is generally suitable for household and drinking use.According to the spatial distribution map, ionic concentrations vary with proximity to the coastline, which impacts interactions between salinity and ions.Tese variations illustrate the region's diverse geologic settings and anthropogenic infuences, which may afect water quality [59,60].In both premonsoon and postmonsoon periods, a proportion of samples exceed the recommended TDS   Applied and Environmental Soil Science limits.Although most samples are within permissible limits, high TDS in some samples during both seasons raises concerns regarding its impact on water suitability for drinking and agriculture.Comparing the pre-and postmonsoon value ranges, the postmonsoon values are comparatively low due to the infuence of precipitation, which dilutes the salinity in the water.As a result of the analysis of cation and anion concentrations, it is apparent that their levels vary across diferent locations within the sub-basin.Elevated concentrations may negatively impact soil quality and crop growth in areas where sodium, calcium, magnesium, and potassium concentrations exceed the acceptable limits.Te high sodium concentration in water afects the taste of drinking water.Excess sodium is toxic to some sensitive crops.Due to excess sodium in water, the soil acts as plastic in nature, afecting the soil's permeability.Te mineral content of the surface soils and sediments determines where the F in groundwater comes from.Seawater intrusion is responsible for the concentration of chloride and sulfate in groundwater, whereas fertilizers and pesticides used in agricultural practices are responsible for the nitrate concentration.
During pre-and postmonsoon seasons, the WQI assessments indicate that the water quality is generally good for drinking.Te results suggest that, despite some outliers in individual parameters, the water meets acceptable standards for household consumption.Correlation analyses using Pearson's correlation coefcient revealed signifcant relationships between water quality parameters.A positive correlation between pH and carbonate indicates that both

Conclusion
Diferent irrigation and drinking suitability metrics were used in the current study in the Kuzhithuraiyar sub-basin, leading to various interpretations.IDW spatial distribution analysis was performed using ArcGIS 10.8 software, which gave more ideas about the distribution of diferent ions in the study area.WQI shows good drinking water quality before and after monsoon season.EC and TDS readings indicate that most samples are drinkable.Te samples close to the coast are highly salinized.Tis implies that crops with a medium to high tolerance to salt can only be cultivated adjacent to the shore.Te SAR and RSC predict the sodium hazard, indicating a high infltration rate in the research area.Te USSL plot clearly shows that any soil can be used for irrigation with just a very minimal risk of exchangeable salt [61].
Five samples are shown on the Wilcox diagram to fall into the permitted to doubtful category pre-and postmonsoon.Seawater incursion from the Arabian Sea is reduced compared to the west coast of Tamil Nadu due to the structural features of the region having a signifcant role in controlling the seawater intrusion along the west coast.Te geology of Kodumkulam and Chankurutti is a hard rock terrain of Garnet Biotite Sillimanite Graphite Gneiss.Vavarai, Edavar, and Vaikalur are sedimentary terrains very close to the sea of sand, silt, clay partings, sandstone with clay intercalations, and clayey sand.
Artifcial recharge structures such as percolation ponds, check dams, and subsurface dykes in the coastal regions can be introduced.Te high salinity of Vaikalur, Chankurutti, Vavarai, and Edavar villages was due to anthropogenic activities and the tsunami in 2004.Previous studies have shown that the salinity level has decreased comparatively due to the frequent rainfall in the study area.Even though Kodumkulam village is 13 km away from the seashore, the water is saline in this region due to anthropogenic activities such as habitat encroachment, contamination of surface water bodies, and poor maintenance of surface water bodies.In the village of Kodumkulam, it is remarkable that no steps have been taken to ensure excellent water sanitation.Te surface water body, particularly a pond called Kodumkulam, which served as the village's primary water source, has now been converted into a domestic sewage collection pond.It needs to be adequately sanitized to raise the quality of the village's groundwater; otherwise, the health of the residents and habitats will be seriously jeopardized.So, the participation of every individual is required to improve the quality of the village.Applied and Environmental Soil Science

Table 1 :
pH, EC, TDS, and cation and anion concentration of groundwater samples of Kuzhithuraiyar sub-basin.

Table 2 :
Relative weight of the parameter.

Table 3 :
Water quality index and irrigation suitability of the water samples of Kuzhithuraiyar sub-basin.