Spatial Variability Of Groundwater Quality Research Articles

Cultivating sustainability: a multi-assessment of groundwater quality and irrigation suitability in the arid agricultural district of Dzira (Ksour Mountains, Algeria).

Groundwater serves a range of essential functions such as supplying drinking water, facilitating agricultural practices, and supporting industrial processes. This study examines with multiple methods the quality of groundwater in the agricultural region of Dzira, Algeria. By collecting 38 groundwater samples of different wells and boreholes, valuable awareness of the aptness of groundwater for irrigation in this arid landscape was gained. Most wells met Food and Agriculture Organization (FAO) criteria for the total dissolved solids (TDS) and the potential of hydrogen pH, but some areas had higher mineral content and electrical conductivity. Results show significant TDS variations, with 10.81% of wells exceeding limits and acceptable pH levels. Elevated EC values in 67.57% of wells show high salinity, affecting soil and plant growth. Major ions such as Mg2+ and SO4- exceeded FAO standards in 43.24% and 64.86% of wells, respectively, highlighting substantial mineral content in the groundwater. Suitability indices reveal that most wells pose low sodium hazards and are generally suitable for irrigation, though some areas face moderate to high restrictions. The irrigation water quality index (IWQI) ranged from 45.36 to 96.30, averaging 80.77, with 54.04% classified as "low restriction," suitable for sandy soils with good permeability but requiring caution on salt-sensitive soils. Hydrogeochemical analysis using principal component analysis (PCA) and hierarchical cluster analysis (HCA) identifies rapid evaporite dissolution from Triassic saline formations, with a correlation matrix showing associations between TDS and Ca2⁺, Mg2⁺, Na⁺, Cl⁻, and SO₄2⁻. This mineralization is likely from gypsum and halite. Zoning maps based on IWQI and other parameters depicted spatial variations in groundwater quality, guiding effective irrigation management strategies. Overall, the study underscores the importance of comprehensive water quality assessment for sustainable agriculture and emphasizes the need for targeted interventions to mitigate potential challenges associated with soil salinity and sodicity. Therefore, these findings can be useful to decision-makers and stakeholders in order to optimize water use and protect this vital resource.

Evaluating groundwater vulnerability and assessing its quality for sustainable management

Areas with a dry climate constitute about 15% of the Earth's surface, so groundwater can be considered a safe alternative available for people who are living in these areas. Groundwater has special advantages compared to surface water in terms of spatiotemporal presence, high stability, easy access, and often of high quality and capable of resisting pollution and could be the alternative to solve the problem of water shortage.The current study evaluated Irrigation Water Quality Indices (WQIs) as well as the predicting of GIS maps to evaluate groundwater resources for agricultural uses in Al-Najaf city. 24 samples were taken from the existing wells and examined for the characteristics relating the groundwater quality. Total hardness (TH), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Soluble Sodium Percentage (SSP), Magnesium Hazard (MH), Permeability Index (PI), and Kelley's Index (KI) were among the irrigation indices that were assessed and evaluated. The results showed that 95.8% of sites fall within the region of extremely high salinity danger /low sodium, and 4.2% of sites fall onto the medium sodium water class, Concerning SSP and RSC all samples are considered of good quality, 95.8% of samples are suitable for irrigation based on Kelly's Ratio index, while only 4.2% regarded unsuitable. The final WQIs values were exported to the ArcMap software to create the final study area's water quality indices maps. Conducting spatial variability of groundwater quality is essential for making reliable groundwater quality interpretations and for making accurate predictions of quality at any particular site, there must be a continuous salinity and contaminants concentrations checking up calculations in case there were a need for groundwater desalination process.

Anthropogenic Drivers of Spatial Trends in Groundwater Quality in the Upper Athi River Basin of Kenya, East Africa

Rapid urbanization and population growth in the upper Athi River basin in Kenya have increased the strain on the sub catchments water supply and sanitation situation. Due to increasing demand, inadequate supply of drinking water and lack of sanitation facilities, people in the sub-catchment are increasingly reliant on groundwater as a primary or supplementary water source. However, the use of on-site wastewater systems and agricultural pollution, mainly from runoff containing fertilizers, pesticides, herbicides, and faeces, pose a threat to groundwater in the sub catchment. Subsequently, the current study was conducted in the Thiririka sub catchment, Kiambu County, Kenya, to determine the safety of groundwater sources and to examine the factors influencing groundwater quality in the catchment area. This study assessed the influence of anthropogenic activities on the physical, chemical, and bacteriological quality of groundwater in the Upper Athi River basin of Kenya between April and June 2022. Twenty variables were analyzed and compared with water quality standards to determine hydro chemical characteristics, evidence of contamination, and suitability of groundwater. Shallow wells (SW) had higher concentrations of major ions and key parameters than boreholes (BH), such as alkalinity (7%), turbidity (96%), nitrates (92%), sulfates (48%), phosphates (93%), chlorides (77%), potassium (84%), sodium (30%) and fecal coliforms (99%) significant at p < 0.01. Concentrations of eleven water quality variables however were comparable in both systems. Farming, animal husbandry, and pit latrines were negatively but significantly correlated with the water quality of SW explaining substantial amounts of variation (≤ 45%) in concentrations of water quality variables. Ionic and coliform levels increased with decreasing distance and vice versa. IDW interpolation maps were generated in ArcGIS software to determine the spatial variability of groundwater quality in the basin. Anthropogenic activities such as pit latrines and animal husbandry impaired the quality of groundwater which in most cases was not potable.

Spatial variation in groundwater quality and health risk assessment for fluoride and nitrate in Chhotanagpur Plateau, India.

The evaluation of groundwater quality is vital to assess the risk to human health. The present study assesses groundwater quality for drinking purposes and human health risks due to ingestion of fluoride and nitrate through drinking water in Chhotanagpur Plateau, India, using geoinformation techniques. For drinking water quality assessment, analyzed parameters were compared with World Health Organization (WHO) standards, and water quality index (WQI) was used. Results reveal that most of the samples come within the desired limit suggested by WHO. In a few samples, conductivity, hardness, chloride, sulfate, and calcium are higher than the desirable limit, whereas fluoride and nitrate are beyond the permissible limit in 70% and 27% of the samples, respectively. WQI highlights that poor to very poor water is present in 25% of the samples. Anthropogenic activities have played a critical role in deteriorating groundwater quality, resulting in harmful impacts on human health. To assess non-carcinogenic health risks, the hazard quotient (HQ) and total hazard index (THI) were computed. THI ranges from 0.01 to 7.46, 0.01 to 7.05, and 0.01 to 9.05 for males, females, and children, respectively. THI is greater than the allowable limit in 84%, 78%, and 89% of the samples for males, females, and children, respectively, indicating high risk to human health, particularly children. The study advocates properwater management strategies. Knowledge of spatial variation and anomalous concentration is vital for groundwater management as well as health risk assessment. The findings of this study will be helpful to government officials, policy planners, and local communities.

Evaluation of Seasonal a Spatial Variation of Groundwater Quality by Determining Factors Associated with Water Quality Using Multivariate Analytical Methods, Erbil Central Sub-Basin

The study area is located in the northern Iraqi province of Erbil, covering a total area of about 1400 Km2 (3.5% of Iraq). The Erbil basin is mostly covered by Quaternary sediments, with only a few outcrops of Miocene–Pliocene formations in the east and northeast of Sharabot-Dedawan highlands, Avanah Mountain in the west and southwest in narrow strips, and Damirdagh in the north. The lithology of sediments ranges from clay, silt, sand, and gravel (sandstone, clay stone, and conglomerate). Erbil Basin, also known as Dashty Hawler Basin, Erbil provinces is the largest groundwater reservoir, with a surface area of 3200 Km2 and a depth of approximately 800 meters. Erbil Basin, one of the Middle East's most important groundwater basins, is bounded on the north by the Greater Zab River and on the south by the Lesser Zab River. Thirty water samples (27 samples of groundwater wells, and 3 samples of wastewater channels) were collected during May (Water surplus period) and September (Water deficit period) 2020 in Erbil central sub-basin and analyzed. Physical analyses include temperature (T), pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD5), Chemical oxygen demand (COD), Dissolved oxygen (DO), Total Suspension sediments (TSS), whereas the geochemical analysis included concentration determination of the major, minor and trace elements. This article aims to evaluate the pollution in groundwater of the Erbil central sub-basin due to different kinds of wastewater, the samples of water in the study area were collected from different locations and sources, deep wells, and waste. all chemical, physical, and trace elements parameters are presented in this work, the pollution has been founded in the study area due to waste water by Kahrez (old groundwater distribution in Erbil basin), cesspools, and septic tanks.

Hydrogeochemical assessment of groundwater quality for drinking and irrigation applying groundwater quality index (GWQI) and irrigation water quality index (IWQI)

In recent times, the contamination of groundwater in the extended part of Chota Nagpur Plateau becomes a big concern. The demand of high-quality drinking and irrigation water has been significantly augmented. Consequently, productivity and fertility of soils are being reduced in the recent years due to use of low quality irrigation water. Thus, it is crucial to know the groundwater quality for the appropriate planning and management of groundwater resources to determine its use for drinking and irrigation purposes. Therefore, the principal objectives of this study are (i) to evaluate the magnitude and spatial variations of groundwater quality using the Groundwater Quality Index (GWQI) for drinking and (ii) to examine the irrigation suitability of groundwater using irrigation water quality index (IWQI). Sodium absorption ratio (SAR), Soluble sodium percentage (SSP), Magnesium hazard (MH), Kelly's index (KI), Permeability Index (PI) have been applied for suitability of irrigation water. Result showed that in 2021, GWQI values vary from 51.75 to 171.18 and seven blocks of the Purulia district among twenty blocks have poor drinking water quality while in 2022 it ranges from 70.27 to 178.45 and eight blocks stand poor water quality. In terms of irrigation water quality, Purulia II and Hura blocks come under the ‘doubtful’ or ‘poor ‘categories in pre and post-monsoon seasons for both the years. Hydro-chemical facies through Piper, USSL and Durov's diagram showed medium to high salinity and low to medium sodium hazards in this region. Feldspar and biotite minerals of granite and gneiss accelerate the bicarbonate and chloride ions in groundwater. Non point sources are also responsible for water quality deterioration in this agricultural dominated region. These research findings will help to policy makers and administrators for the management of groundwater resources and agricultural sustainability particularly in the dryland region.

Hydro-Chemical Facies Water Sources. The Region Rabat-Sale-Zemmour-Zaer of Morocco

A sampling network of fifty-one (51) samples of water sources has been chosen as a geographic and habitat significant enough to afford to acquire representative data on the spatial variability of groundwater quality of the Rabat-Salé-Zemmour-Zaer. This network consists of three groups of water areas and covers almost the entire study site. With the help of the method of Piper diagram, the waters of different origins are easily differentiated.

Geospatial Analysis of Spatial Variability of Groundwater Quality Using Ordinary Kriging: A Case Study of Dungarpur Tehsil, Rajasthan, India

Groundwater is one the major sources of natural water being exploited excessively for various uses in India.
 Thus, it is very essential to monitor the spatial and temporal variability of groundwater quality. Geo-Statistical Interpolation using GIS has been considered as the best and most advanced method for the interpolation and prediction studies of groundwater pollution and quality, and is adopted universally. In this paper, ordinary Kriging with logarithmic data transformation has been used to interpolate and predict the spatial variation of groundwater quality parameters - EC, TDS, pH, Na+, Ca2+, Bi-Carbonate, Fluoride, Chloride, Sulphate and Nitrate using data pertaining to 48 well locations in the Dungarpur tehsil. Data was transformed and normalized using Logarithmic Transformation Method and Semivariograms were drawn and analyzed for selecting the suitable model. The best Semivariogram model was obtained based upon cross validation and on the lesser RMSE criterion and Coefficient of Determination. The results show that the best semivariogram model based on RMSE varied for each water quality parameter. For log transformed data Exponential model was found suitable for EC, TDS, Na+, TH etc.; Spherical model for Ca2+ ; Chloride Gaussian Model for Chloride. For original or raw for non-transformed data Exponential Model was found suitable for Fluoride, Sulphate and Nitrate; and Gaussian Model for pH and Bi-Carbonates.

Spatial variation in groundwater quality with respect to surface water seepages in Kadhan area District Badin (Indus Delta), Sindh, Pakistan

Spatial variation in groundwater quality with respect to surface water seepages in Kadhan area District Badin (Indus Delta), Sindh, Pakistan

Estimating suitability of groundwater for drinking and irrigation, in Odisha (India) by statistical and WQI methods.

Twelve major hydro-geochemical parameters derived from about 1134 water samples were studied to understand spatial variation of groundwater quality in the coastal state of Odisha. Multivariate statistical analysis techniques, i.e., cluster analysis and principal component analysis (PCA), and varimax rotation were used to classify various types of groundwater, and plausible sources that control the quality of water in the region. The concentration of major ions varies in the order of Na+ > Ca2+ > Mg2+ > K+ and HCO3- > Cl- > SO42- > F-. Out of the three clusters identified, the 2nd cluster is having more mineralization and relatively poor quality of groundwater as compared to the first and the third cluster. Furthermore, estimates of the Water Quality Index (WQI) indicate that the groundwater in the area can be classified from excellent to medium quality. Furthermore, the sodium absorption ratio (SAR) and Kelly's ratio (KR) suggest that about 70% of groundwatersamples are of low to medium salinity, whereas about 30% show higher salinity. The Wilcox diagram reveals that almost 90% of the groundwater is suitable for irrigation. The mining activity appears less likely to be affecting the quality of subsurface water. Water-rock interactions and evaporation-crystallization may be the two dominant factors that appear to control the groundwater away from the coastal areas. Results of this study may be useful to identify the suitable sites for groundwater extraction for drinking and irrigation purposes, besides being useful to the policy-makers in formulating effective plans for preventing further contamination of groundwater aquifers.

Spatiotemporal Variation in Groundwater Quality and Source Apportionment along the Ye River of North China Using the PMF Model.

Groundwater quality deterioration has attracted widespread concern in China. In this research, the water quality index (WQI) and a positive matrix factorization (PMF) model were used to assess groundwater quality and identify pollution sources in the Ye River area of northern China. Research found that TH, SO42−, and NO3− were the main groundwater pollution factors in the Ye River area, since their exceeding standard rates were 78.13, 34.38, and 59.38%, respectively. The main groundwater hydrochemical type has changed from HCO3-Ca(Mg) to HCO3·SO4-Ca(Mg). These data indicated that the groundwater quality was affected by anthropogenic activities. Spatial variation in groundwater quality was mainly influenced by land use, whereas temporal variation was mainly controlled by rainfall. The WQI indicated that the groundwater quality was better in the flood season than in the dry season due to the diluting effect of rainfall runoff. Notably, farmland groundwater quality was relatively poor as it was affected by various pollution sources. Based on the PMF model, the main groundwater pollution sources were domestic sewage (52.4%), industrial wastewater (24.1%), and enhanced water–rock interaction induced by intensely exploited groundwater (23.6%) in the dry season, while in the flood season they were domestic sewage and water–rock interaction (49.6%), agriculture nonpoint pollution (26.1%), and industrial wastewater and urban nonpoint pollution (23.9%). In addition, the mean contribution of domestic sewage and industrial sewage to sampling sites in the dry season (1489 and 322.5 mg/L, respectively) were higher than that in the flood season (1158 and 273.6 mg/L, respectively). To sum up, the point sources (domestic sewage and industrial wastewater) remain the most important groundwater pollution sources in this region. Therefore, the local government should enhance the sewage treatment infrastructure and exert management of fertilization strategies to increase the fertilizer utilization rate and prevent further groundwater quality deterioration.

Application of geostatistical models to identify spatial distribution of groundwater quality parameters.

Groundwater quality management is a priority in arid and semi-arid zones where water is scarce. Leachate from open dumping of municipal solid wastes may threaten groundwater quality. This research aimed at assessing groundwater quality of the aquifer of Shur river basin in Tehran province, Iran. The pollution potential of leachate from a landfill, located at the center of the basin, was estimated to assess its impact on the aquifer. Samples from 38 wells and 2 leachate ponds around the landfill were analyzed for their physico-chemical parameters and heavy metals. Leachate Pollution Index (LPI) and Water Quality Index (WQI) were calculated and multivariate statistical techniques were employed through geostatistical models to predict the spatial variability of groundwater quality and assess its contamination sources. The groundwater quality map was developed by GIS Interface. LPI indicated that leachate from the closed cell (LPI = 36) was more contaminating than that of the active site (LPI = 25). Kriging and cokriging geostatistical interpolation methods were applied to groundwater quality parameters. The best interpolation model was then identified through cross-validation with RMSE and GSD criteria. Cokriging yielded more accurate results than kriging. Spatial distribution maps showed high groundwater contamination and degraded water quality mainly in the central part of the basin, where the landfill was. Also, 293.7ha of the study area possessed poor and very poor water quality, unsuitable for drinking. This study implicated multiple approaches for groundwater quality assessment and estimated its spatial structure as an effort toward effective groundwater quality management in Shur river basin.

Statistical Tool to Address the Influence of Urbanization in Groundwater Quality in Colombo District, Sri Lanka

Management of groundwater quality is becoming a key feature of a sustainable future while implementing sustainable development goals which are given by United Nations. During past decades, rapid land-use changes, urbanization, and population expansion are highly influenced the groundwater quality. To provide policymakers and water managers with reliable information on groundwater quality is a challenge to achieving sustainable development goals in developing countries. Therefore, this study intended to assess the spatial variability of groundwater quality using selected physicochemical parameters at the 39 available groundwater wells during the southwest monsoon period. Spatial variability is explained in 13 Divisional Secretariat Division (DSD) levels in Colombo district due to easier interpretation and management purposes. Afterward, groundwater quality was related to urbanization using population density and built-up density in 13 DSD levels in Colombo district, Sri Lanka. PCA (Principal Component Analysis) shows that 08 DSD levels are urban and 05 DSD levels are rural. pH (3.22–6.73), COD (8.91–52.9 mg/L), BOD5 (1.2–9.9 mg/L), and DO (2.17–5.05 mg/L) showed deviations from the given standards by local authorities in Sri Lanka. A significant relationship ( p < .05) was found between urbanization and physicochemical parameters in regression analysis. The water quality index shows poor water quality indices in urban areas and vice versa in rural areas which is similar to the results obtained by statistical analysis. A sustainable urban development plan with continuous groundwater quality monitoring is necessary to protect groundwater resources in Sri Lanka.

Groundwater Quality Assessment Using Water Quality Index, Principal Component and Cluster Analyses: A Case Study

This study assessed groundwater quality in Can Tho city, Vietnam using groundwater quality index (GWQI), principal component analysis (PCA), and cluster analysis (CA). Groundwater samples were collected in April (dry season) and October (rainy season) in 2019 and then analyzed for thirteen parameters: pH, color, total hardness, chloride, sulfate, chemical oxygen demand, magnesium, total iron, nitrate, arsenic, lead, mercury, and coliforms. The results showed that the values of these parameters were mainly within the Vietnamese regulations on groundwater quality, except for coliform density. Computed GWQI values in all monitoring sites were lower than 50 and suitable for potable purposes. The GWQI values in the dry season were slightly higher than in the rainy season because of higher concentrations of Cl-, SO42-, COD, As, Pb, and coliforms in the southeast of Can Tho. The results of CA revealed that 27 monitoring sites can be divided into nine clusters in the dry season and five clusters in the rainy season, which means that more noticeable spatial variation in groundwater quality occurred in the dry season. The PCA results can explain 63.4% and 73.9% of the total variation in the dry season via 4PCs and in the rainy season via 3PCs, respectively. It also indicated that this water resource could be affected by different sources such as industrial and agricultural activities, domestic wastewaters, and saltwater intrusion. These findings can be useful for policymakers in assessing current groundwater status and recognizing threats to its quality, and then developing long-term management policy.

Spatial Variability of Groundwater Quality for Freshwater Production in a Semi-Arid Area

Presenting groundwater quality assessment for different usages using one index is helpful to monitor the quality of this invaluable resource and reduce the cost of freshwater production, particularly in arid and semi-arid regions. The drinking groundwater quality index (DGWQI) is one the best indicators for groundwater quality assessment. Therefore, the purpose of the present research was to assess and map the groundwater quality of an aquifer for freshwater production in a semi-arid region, using GIS-based spatial analysis of DGWQI. For this goal, mean data from 70 wells collected during 2010–2018 were used. Results showed that total dissolved solids (TDS), electrical conductivity (EC), and total hardness (TH) had the highest impact on groundwater quality that exceed the permissible range for drinking purposes. Results also revealed that 42% of samples had a DGWQI value between 0 and 100 (appropriate quality class). Sensitivity analysis determined that Mg2+, EC, and TDS with highest mean variation indexes of 18.98, 20.68, and 19.04, respectively, were the most sensitive parameters in the calculation of DGWQI. According to R2 and RMSE, the ordinary kriging and spherical semi-variogram model had good performance for spatial analysis for all DGWQI, Mg2+, EC, and TDS. The DGWQI map showed that in the southern parts the groundwater (50% of the area) had unsuitable quality for drinking.

Comparison and Assessment of Intelligent and Geostatistical Models for Analysis of Spatial Variations of Groundwater Quality (Komijan Plain)

Comparison and Assessment of Intelligent and Geostatistical Models for Analysis of Spatial Variations of Groundwater Quality (Komijan Plain)

Optimizing Rural Drinking Water Supply Infrastructure to Account for Spatial Variations in Groundwater Quality and Household Welfare in Coastal Bangladesh

AbstractAchieving water security requires reconciling multiple objectives while prioritizing scarce resources for the provision of safe drinking water supplies. We examine decision‐making to invest in drinking water infrastructure in coastal Bangladesh where increasing saline intrusion in aquifers intersects with high levels of poverty for the 20 million people living in the coastal region. Multi‐objective optimization is used to explore the trade‐offs between two public policy goals: (a) maximizing overall access to improved water supplies (the greater good) and (b) maximizing access for the population with the lowest welfare (the greater need). To elucidate this trade‐off, we make use of groundwater salinity measurements, an extensive household survey and an audit of drinking water infrastructure in 1 out of Bangladesh’s 139 polders, which is home to nearly 60,000 people. We quantify the costs of a variety of drinking water supply options including deep tube wells, desalination plants, and piped systems. The recommended solutions are sequences of investments in water supply assets that are optimized to specified locations within the polder. The method is potentially scalable and transferrable to inform investments to achieve the Sustainable Development Goal (Target 6.1) of universal access to safe and affordable drinking water.

Assessment of groundwater quality and human health risk related to arsenic using index methods and GIS: A case of Şuhut Plain (Afyonkarahisar/Turkey)

In this study the spatial variation of groundwater quality and the potential health risk situation arising were evaluated determining Water Quality Index (WQI and IWQI) for drinking and irrigation water in Şuhut Plain (Afyonkarahisar, Turkey). A total of 27 groundwater samples were collected from wells in May-2019 and physicochemical analysis results were evaluated.According to analysis results of the water samples, the orders of anion and cations are HCO3>SO4-2>Cl- > CO3-2 and Ca+2 > Mg+2 > Na+>K+, respectively. It has been determined that groundwater samples are generally in “excellent” and “good” water class according to the WQI and IWQI assessment. At the same time, groundwater in the study area is suitable for agricultural irrigation water. However, many water samples cannot be used as drinking water in terms of TDS, Mg, NO3 and AsT according to limit values of TSI-266 (2005) and WHO (2011). Health risk assessment indicate that, the risk of developing cancer due to arsenic exposure in healthy adults or children is very low. But, arsenic has a high non-carcinogenic and carcinogenic potentially harmful effect.

ASSESSMENT OF GROUNDWATER QUALITY IN TEHSIL GOJRA BY USING GEOGRAPHICAL INFORMATION SYSTEM

Groundwater is imperative for the continuance of life and sustainability of ecosystem. Contamination of the water is the well-recognized danger to the public health in Pakistan. Hence, this study was conducted to assess and map the spatial variation of groundwater quality in the surroundings of Dijkot Branch Drain by using the Geographical Information System(GIS). For this purpose, sixty samples of groundwater, ten samples of wastewater and five samples of sludge were collected along with their coordinates from the study area. The collected samples were analyzed for chemical parameters and heavy metals, such as pH, EC, TDS, Carbonates, Bicarbonates, Arsenic, Lead, Chromium, Cadmium, Zinc. The results obtained from the study were compared with WHO guidelines. Then, the values of these water quality parameters were mapped by using GIS software. Arc GIS V 10.2 was used for raster interpolation. To exhibit the spatial variation of groundwater quality scenario of the study area, Kriging method was adopted. on. It was generally observed that none of the parameters in the wastewater samples was found to be within the permissible limit. The research study resulted that the groundwater of the study area is deteriorated by Dijkot Branch Drain and is not fit for drinking purpose.

Spatial variability of ground water quality: a case study of Udupi district, Karnataka State, India

Groundwater is a reliable source of fresh water for domestic and agricultural water users. It supports subsurface ecosystem by balancing the geo-biological and bio-geochemical processes at micro- and macro-scales of the ecosystem. Overexploitation, anthropogenic activities and improper agricultural practices have contributed to the pollution of groundwater sources all around the globe. The water quality index (WQI) is the most extensively used indicator which transforms the water quality information derived from several parameters into a single value/rating to categorize and provide a general perception of water quality standard. Groundwater quality analysis and mapping via geographical information system (GIS) proves to be beneficial in identifying the locations where the groundwater quality is deteriorating. In the current study, the WQI of groundwater was determined for the samples collected from open and tube wells located within the Udupi district of Karnataka state, India. The groundwater quality parameters such as pH, hardness, calcium, chlorides, nitrates, iron, fluoride, sulfates, manganese, sodium, magnesium, potassium, turbidity, and phosphate were analyzed for water samples collected from 112 randomly chosen open/tube wells in order to determine the WQI. Interpolation approaches such as inverse distance weighting (IDW) and kriging were adopted in the GIS environment to quantify the spatial variability of groundwater quality over the entire geographical area. The groundwater quality maps were generated using the best fit models. The results portray that, the accuracy of interpolation using IDW and kriging methods was dependent on the measures of central tendency and variability of water quality data of different parameters. The kriging interpolation was much accurate for most of the groundwater quality parameters compared to IDW maps. The WQI maps, perhaps signposted the poor quality of groundwater quality in about 1.88% of the geographical area of Udupi district. Further, about 21.69% of the area was affected by poor quality of groundwater where suitable strategies for replenishment of groundwater resources should be taken up by the concerned authorities. The spatial distribution maps of groundwater quality aid to locate vulnerable places where immediate action is required.