Geospatial insights into groundwater contamination from urban and industrial effluents in Faisalabad

Abstract

Groundwater remains the most dependable resource for various essential uses such as drinking, cleansing, agricultural irrigation, and industrial applications. In urban areas, the dependency on groundwater to meet water demands is significant. However, this resource faces threats from overuse and poor management, leading to a degradation in quality primarily due to the unchecked release of industrial and household wastes. The escalation of industrial activities and rapid urban growth have amplified the volume of wastewater, adversely affecting the purity of freshwater sources within aquifers. This investigation focuses on evaluating the impact of industrial and urban effluents on groundwater quality in the city of Faisalabad. The main contributors to groundwater pollution include the indiscriminate disposal of industrial and urban effluents through unlined drains and the extensive application of chemical agents in agriculture, such as fertilizers, and pesticides. To understand the physiochemical properties of both, drain and groundwater, samples were collected at various distances 50 m, 100 m, and 150 m from drain outlets. This study utilized Geographic Information Systems (GIS) to accurately map and analyze the distribution and impact of contaminants. Parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness, bicarbonates, calcium and magnesium hardness, and chloride levels were examined. The findings indicated that contaminant levels were highest in drain water and increased in concentration the closer they were to the drainage sources, with the exception of pH levels. All samples exceeded the World Health Organization's (WHO) safe limits, deeming them unfit for use. This finding indicates widespread contamination, posing significant public health risks and highlighting the urgent need for improved waste management and water treatment practices in Faisalabad. It underscores the critical importance of implementing effective pollution control measures to safeguard public health and ensure water security in the region. However, a notable correlation was observed between the concentration of pollutants in drain water and key indicators such as EC, TDS, total hardness, and magnesium hardness, highlighting their role in deteriorating aquifer water quality. Moreover, groundwater samples collected 50 m from drains exhibited the highest pollutant concentrations compared to those taken further away, at 100 m and 150 m distances.

Introduction

Groundwater is indispensable, serving as the primary source for drinking, sanitation, irrigation, and industrial activities due to its accessibility and reliability. Its widespread availability, natural filtration through soil layers, and relative consistency in supply compared to surface water make it a crucial resource, especially in areas with limited or variable rainfall. Yet, this essential resource is increasingly vulnerable to overexploitation and mismanagement. Particularly in urban areas of developing countries, around 50 percent of the groundwater comes from wells, springs, and boreholes. In contrast, many developed countries rely more heavily on treated surface water, with groundwater accounting for about 30 percent of total water use in the United States and around 25 percent in European Union countries. Over one billion people in Asia and 150 million in Latin America depend heavily on these groundwater sources for their drinking water supply [1, 2]. As demand for water escalates, groundwater levels are dropping alarmingly. This significant extraction has not only reduced the groundwater levels, causing a quantitative depletion of this vital resource. Additionally, the quality of the remaining groundwater has been significantly compromised by the mismanagement of industrial and domestic waste and agricultural chemicals. These dual challenges of quantity reduction and quality deterioration pose serious threats to water security in the region [3–9].

Faisalabad, a major industrial and populous city in Pakistan, faces acute challenges related to groundwater depletion and contamination [10]. The city's groundwater is extracted from an aquifer that is recharged by local water channels and percolation. In Pakistan, 70% of the total water extracted from aquifers is utilized for agricultural purposes, leading to severe overexploitation and a resultant decline in the water table. This intensive agricultural use significantly contributes to groundwater depletion, as extraction rates often exceed natural recharge rates. Potential alternatives to mitigate this issue include implementing more efficient irrigation techniques such as drip irrigation, promoting drought-resistant crops, and encouraging the use of treated wastewater for agriculture where feasible. These measures could help reduce the pressure on groundwater resources while maintaining agricultural productivity [11–14]. Moreover, the water pumped from these aquifers is often saline, affecting at least two-thirds of the country’s area [15–21].

The prevalent use of government-subsidized fertilizers has further exacerbated the contamination, leading to the percolation of heavy metals into the soil and groundwater. Additionally, the rapid population growth and industrialization in Faisalabad have significantly increased the production of sewage, further contaminating the groundwater [22–24]. Other detrimental factors include the improper disposal of domestic and industrial wastewater, which affects groundwater sources, human health, and agricultural output, often leading to issues of water scarcity and inadequate wastewater disposal. For instance, a case study in Lahore, Pakistan's second-largest city, found that untreated industrial effluents from textile factories were directly discharged into nearby water bodies, leading to severe groundwater contamination with heavy metals and organic pollutants. Similarly, in Karachi, inadequate sewage treatment has resulted in seawater intrusion into coastal aquifers, rendering many wells unsuitable for drinking or irrigation purposes [12, 25–27]. These examples highlight the urgent need for improved waste management practices across urban areas in Pakistan [28–33].

In industrial regions, irrigation practices involving wastewater containing toxic substances such as industrial effluents, textile dyes, pesticides, nitrogen fertilizers, arsenic, and other chemicals have become a common source of pollution [34–37] This chemical pollution is particularly severe in areas where groundwater is used for agricultural irrigation. Moreover, extreme weather conditions like excessive rainfall, floods, and the use of herbicides and fungicides contribute to the spread of untreated wastewater and sewage leakage, presenting serious hazards to drinking water and public health [38–41].

The decline in both the quantity and quality of groundwater is a significant concern. The water quality in several of Pakistan's major cities, including Karachi, Lahore, Faisalabad, Rawalpindi, Qasur, and Sheikhupura, is rapidly deteriorating due to unchecked disposal of untreated municipal and industrial wastewater, combined with excessive use of fertilizers and pesticides [42–44]. This pollution of surface and groundwater has emerged as a critical issue in medical science, being a major source of health-related problems. Specific health issues linked to this water pollution include gastrointestinal diseases like cholera and typhoid, kidney problems due to high mineral content, and increased risk of cancer from exposure to industrial contaminants. Additionally, the presence of heavy metals in polluted water has been associated with neurological disorders and developmental issues in children [45–50]. In fact, waterborne diseases such as cholera, typhoid, dysentery, hepatitis, and worm infections are prevalent enough that 20 to 40 percent of hospital beds in Pakistan are occupied by patients suffering from these conditions [51–55].

In Faisalabad, wastewater is disposed of through open drainage channels, including Paharang, Maduana, and City municipal drains, which flow into the Rivers Ravi and Chenab. This practice has severe ecological consequences for these river ecosystems. It leads to eutrophication, causing algal blooms that deplete oxygen levels and harm aquatic life. The influx of pollutants also disrupts the natural balance of these river systems, affecting biodiversity and potentially contaminating downstream water sources used for irrigation and drinking water [56–59]. Moreover, this pollution can persist in river sediments, creating long-term environmental challenges and potentially impacting the broader food chain. The Water And Sanitation Agency (WASA) treats a small amount of sewage in municipal channels by aerating it in large ponds. Samples of ground and drain water are collected to perform various physiochemical tests to analyze the extent of contamination caused by sewage in groundwater. These tests include measurements of pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness, chlorides, bicarbonates, and concentrations of calcium and magnesium. Additionally, we conduct microbial analyses to detect the presence of fecal coliforms and E. coli, indicators of sewage contamination [60, 61]. A survey was conducted to gather additional information on the impacts of wastewater on the surroundings. Previous research reports have concluded that the primary cause of diseases in Faisalabad is the poor quality of groundwater [62]. Human blood analysis in the area has indicated the presence of Hepatitis in all drinking water sources, yet limited work has been done to identify the factors causing this contamination. The socio-economic and educational conditions in the region vary widely, and public awareness of water quality standards, which could guide decisions on whether to consume the groundwater, is notably poor [63–65]. This research aims to elucidate the impact of drains on groundwater quality, providing essential data that can help WASA develop effective strategies to improve the existing drainage system and plan new projects to prevent effluent mixing with groundwater and water supplies. The expected outcomes include a comprehensive map of contamination hotspots, identification of key pollutants, and their dispersion patterns. These findings will directly benefit local authorities by enabling targeted interventions, potentially improving public health outcomes, and optimizing resource allocation for water treatment projects. Additionally, our research will contribute to the broader scientific understanding of urban groundwater contamination dynamics, potentially informing similar studies in other rapidly developing cities [66–73].

In response to these challenges, Faisalabad has witnessed a growing volume of wastewater due to its rapid industrialization and population increase, which in turn has exploited the city’s freshwater resources through mismanagement. This large volume of wastewater is ultimately disposed of into the Rivers Chenab and Ravi through a complex drainage network, eventually reaching the rivers and affecting both them and the groundwater aquifers. The long-term environmental impacts of this practice are significant. Continuous discharge of untreated wastewater can lead to persistent contamination of river sediments, altering aquatic habitats and disrupting ecosystems for decades. It may cause bioaccumulation of pollutants in aquatic organisms, affecting the entire food chain. For groundwater, prolonged seepage of contaminated water can result in the formation of pollution plumes, potentially rendering aquifers unusable for extended periods and requiring costly, long-term remediation efforts. These impacts underscore the urgent need for sustainable wastewater management practices in Faisalabad [74–76]. To quantify the level of contamination and assess the quality of water, physiochemical tests are conducted on samples of wastewater and groundwater collected at various distances from drainage outlets. This methodological approach aims to provide a clear analysis of the contamination spread and its impact on groundwater quality [51, 77–80].

Methods and materials

Study area

Faisalabad City, located in the upper Indus plain of Punjab, Pakistan, stands at 184 m above sea level, spanning coordinates from 30°35ʹ to 31°47ʹ North and 72°01ʹ to 73°40ʹ East (Fig. 1). It covers an area of 213 sq km, while the larger district is 5855 sq km. The city’s drainage system includes two major channels: the Paharang Drain and the Municipal Drain, which play crucial roles in the city's wastewater management. Faisalabad has a hot desert climate under the Köppen classification, with peak rainfall of 102 mm in July and minimal in November at about 3 mm. Historically, temperatures have reached highs of 40 °C in June and lows of 11.9 °C in January. As one of the first planned cities of British India, Faisalabad has grown significantly, especially following the influx of Muslim immigrants post-partition. By the 2017 census, the most recent official data available, Faisalabad had grown to become Pakistan’s third-largest city, with a population of 3,203,846 in the city proper and 7873,910 in the larger district. The annual growth rate stood at 2.13%, reflecting continued rapid urbanization. The literacy rate had improved to 59.8%, indicating progress in education but still highlighting significant room for improvement.

Fig. 1 [Images not available. See PDF.]

Study area map

Data collection

This study primarily utilizes primary data collected directly from the field. Water samples were systematically gathered along the Paharang and Municipal drains in Faisalabad, spaced at 3–5 km intervals, following the flow from head to tail. The samples were secured in 1.5 L plastic bottles, each clearly labeled with a sample number for identification. To ensure sample integrity and prevent cross-contamination, we followed strict protocols. All bottles were thoroughly cleaned with phosphate-free detergent, rinsed multiple times with distilled water, and then acid-washed with 10% hydrochloric acid before a final rinse with ultra-pure water. During collection, we wore nitrile gloves and used sterile equipment for each sample. Bottles were rinsed three times with the sample water before final collection. Samples were immediately stored in coolers with ice packs and transported to the laboratory within 6 h for analysis, maintaining a temperature below 4 °C to preserve their chemical and biological properties. To assess the influence of drainage channels on groundwater quality, groundwater samples were collected at distances of 0–50 m, 51–100 m, and 101–150 m from the drains. Before use, all bottles were thoroughly rinsed multiple times with tap water followed by distilled water to eliminate any impurities. Wastewater samples were collected by placing a filter paper in a funnel to avoid contamination, while groundwater samples were drawn directly from household wells near the drains without any filtration. This meticulous collection process ensures the purity and reliability of the samples for subsequent physiochemical analysis. This study primarily utilizes primary data collected directly from the field. A total of 120 water samples were systematically gathered along the Paharang and Municipal drains in Faisalabad, spaced at 3–5 km intervals, following the flow from head to tail. Of these, 40 samples were collected from the drains themselves, while 80 groundwater samples were taken at distances of 0–50 m, 51–100 m, and 101–150 m from the drains, with approximately 27 samples in each distance category. The samples were secured in 1.5 L plastic bottles, each clearly labeled with a sample number for identification. This comprehensive sampling approach ensures a representative dataset for assessing both drain water quality and its impact on surrounding groundwater at various distances.

Data analysis

This study employed various analytical methods to investigate the impact of the open drainage system on aquifer deformation in Faisalabad city. We collected 120 water samples: 40 from Paharang and Municipal drains, and 80 groundwater samples at 0–50 m, 51–100 m, and 101–150 m distances from the drains. Samples were stored in 1.5 L plastic bottles, labeled, and transported to the laboratory within 6 h.

Physiochemical analysis

Physiochemical tests were conducted on samples of drain and groundwater at the Water and Sanitation Agency (WASA) chemistry lab in Faisalabad. The groundwater quality was evaluated for several parameters, including bicarbonates, chlorides, calcium hardness, magnesium hardness, total hardness, pH, electrical conductivity (EC), and total dissolved solids (TDS). The results were then compared against the World Health Organization’s (WHO) water quality standards for drinking purposes as well as wastewater quality standards (Table 1) and Comparison of Water Quality Parameters in Drains, Groundwater, and WHO Standards (Table 2).

Table 1. Drain and groundwater variables (independent and dependent)

Sr#	Drain water (independent variables)	Groundwater (dependent variables)
1	Total dissolved solids (TDS)	Total dissolved solids (TDS)
2	Chlorides	Chlorides
3	Bicarbonates	Bicarbonates
4	Hardness	Total hardness
5	Magnesium hardness	Magnesium hardness
6	Calcium hardness	Calcium hardness
7	Electrical conductivity (EC)	Electrical conductivity (EC)
8	pH Value	pH Value

Table 2. Comparison of water quality parameters in drains, groundwater, and WHO standards

Parameter	Unit	Paharang drain	Municipal drain	Groundwater (50 m)	Groundwater (100 m)	Groundwater (150 m)	WHO Standard
pH	–	8.21–9.00	9.55–10.20	7.80–8.50	7.60–8.30	7.40–8.10	6.5—8.5
EC	µS/cm	4990–6150	7680–8500	2914–4805	2650–4200	2400–3900	1500
TDS	mg/L	3493–4305	5376–5950	2040–3364	1855–2940	1680–2730	1000
Total hardness	mg/L	835–1045	780–1020	680–963	620–890	570–830	500
Calcium hardness	mg/L	71–79	58–71	57–75	55–72	53–70	75
Magnesium Hardness	mg/L	159–205	173–202	113–122	76–101	75–95	50
Chloride	mg/L	1235–1620	1310–1530	600–963	550–880	500–820	250
Bicarbonate	mg/L	1150–1480	1255–1670	481–677	357–582	284–501	300

Statistical analysis

We used Pearson correlation analysis to assess relationships between drain water and groundwater parameters. Inverse Distance Weighting (IDW) interpolation in ArcGIS 10.2.1 was employed for spatial analysis of contamination patterns. Statistical analyses, specifically bivariate correlations, were utilized to explore the relationship between drain water contamination and groundwater quality at distances of 50 m, 100 m, and 150 m from the drain channels. Mean bar graphs were employed to compare the contamination levels in the drain against the permissible limits set by the WHO. Descriptive statistics were used to present data in terms of range, mean, and coefficient of variance for various water sample parameters.

Geospatial analysis

ArcGIS 10.2.1 was used to manage the geospatial data of the study area and to visualize the intensity and spread of contamination using the raster environment of spatial analysis through Inverse Distance Weighting (IDW) interpolation. The output maps from the interpolation were interpreted and generalized results were presented across the study area. This helped in identifying safe water supply zones and forming a mitigation plan to control the degradation of groundwater quality in the aquifer of Faisalabad city.

Variables

pH of water

The pH scale is fundamental for characterizing the acidity or alkalinity of water. A pH less than 7 denotes acidity, above 7 indicates alkalinity, and a pH of 7 is considered neutral. pH was measured using a calibrated digital pH meter. Each sample was stirred gently before measurement to ensure homogeneity.

Total dissolved solids in water (mg/L)

Total Dissolved Solids (TDS) are a measure of the combined content of all inorganic and organic substances contained in a liquid. These substances, primarily contaminants and ionic compounds, can either be fully dissolved or exist in a micro-suspension. TDS is a key indicator of water quality, influencing its use for drinking, irrigation, and industrial applications due to the potential for pollution. TDS and EC were measured using a calibrated TDS/EC meter. The probe was rinsed with distilled water between measurements. TDS in water is quantified using two primary methods:

Electrical conductivity of water (EC) µS/cm

Electrical Conductivity (EC) is an essential measure for assessing water quality, indicating the concentration of dissolved ionic substances and contaminants. It is measured in micro siemens per centimeter (µS/cm) using a conductivity meter. Water with higher dissolved ions conducts electricity more efficiently, making EC a useful indicator of water salinity and a proxy for Total Dissolved Solids (TDS). This measurement helps evaluate pollution levels, determine water's suitability for various uses, and guide water management and treatment decisions.

Chloride in water (mg/L)

Chlorides, typically in the form of sodium chloride, are common in water. When their concentration exceeds 250 parts per million, the water begins to taste salty. To measure chloride levels, water samples are titrated with a silver nitrate solution, using potassium chromate as an indicator. Chloride concentration was determined by titration with silver nitrate solution, using potassium chromate as an indicator.

Total hardness of water (mg/L)

Total water hardness is determined by the concentrations of magnesium (Mg) and calcium (Ca) ions in water, absorbed as water passes through geological formations. Although Mg and Ca are vital for health, high levels can cause serious health issues. Water hardness is categorized by its concentration in milligrams per liter (mg/L): 0 to 60 mg/L is soft, 61 to 120 mg/L is moderately hard, 121 to 180 mg/L is hard, and above 180 mg/L is considered very hard. Total hardness was measured by EDTA titration method, using Eriochrome Black T as an indicator.

Calcium hardness in water (mg/L)

Calcium is essential for human health, comprising 99% of its presence in bones and teeth as a structural component. The remaining 1% plays a critical role in metabolic processes like blood clotting, muscle contraction, and nerve signal transmission. Inadequate calcium intake can lead to various health issues, including reduced bone mass, kidney stones, increased stroke risk, obesity, and hypertension. Calcium hardness was determined by EDTA titration, using murexide indicator.

Magnesium hardness in water (mg/L)

Magnesium is crucial in the human diet but is often deficient in many nutritional products. A lack of magnesium can cause health issues such as muscle weakness, cramps in the lower girdle, feet, legs, and fingers, as well as insomnia, confusion, and mental depression. Around 19 g of magnesium is needed per 70 kg of body weight for protein synthesis. Additionally, magnesium serves as a cofactor in more than 300 enzymatic reactions, highlighting its essential role in various bodily functions. Magnesium hardness was calculated by subtracting calcium hardness from total hardness.

Bicarbonate in water (mg/L)

Bicarbonate is a vital chemical compound widely used in the textile industry. It appears as baking soda (sodium bicarbonate) and washing soda (sodium carbonate), essential for processes like dyeing and sizing threads and fabrics. This broad utility highlights the need to monitor bicarbonate levels in water, particularly in regions engaged in textile manufacturing. Bicarbonate levels were measured by titration with standard sulfuric acid solution, using methyl orange as an indicator.

Instruments and apparatus

1. pH digital meter

2. Electric Conductivity meter

3. Beakers of various capacities

4. Conical flasks (100 ml and 250 ml)

5. Funnels

6. Filter papers

7. Measuring cylinders

8. Burette

9. Pipette (10 ml capacity)

Titrating agents

• Distilled Water 20 L canes of water obtained through Pyrex glass distillation used for preparing standard solutions.

• Standard EDTA Solution (0.1 N) 18.615 g of Ethyl Di-amine tetra acetate dissolved in distilled water and diluted to one liter.

• Buffer Solution (pH 10) 142 ml of concentrated ammonia added to 17.5 g of ammonium chloride and diluted to 250 ml.

• Standard Sodium Hydroxide Solution (2M) 80 g of NaOH dissolved in 1 L of distilled water.

• Standard Silver Nitrate Solution (0.02N) 3.4 g of silver nitrate dissolved in distilled water up to 250 ml.

• Standard Sulphuric Acid Solution (H2SO4, 0.02 N): 2.2 cc of concentrated sulfuric acid diluted to 1 L with distilled water.

Indicators

• Eriochrome Black T Mixed with 0.2 g of dye in 15 ml of Tri-ethanol; dilute with 5–10 ml of pure alcohol or phenol if thick.

• Methyl Orange 0.5 g of sodium salt dissolved in 1 L of distilled water, with 12.2 ml of 0.1 M Hydrochloric acid added.

• Phenolphthalein Solution 5 g of indicator dissolved in 0.5 L of ethanol and diluted with an equal amount of distilled water.

• Potassium Chromate Indicator: 5 g dissolved in 100 ml of distilled water.

• Murexide 0.5 g of the reagent ground with 100 g of ethanol alcohol.

Experimental procedure

A range of physiochemical methods were utilized to assess the impact of drain water on groundwater quality, including measurements of pH, electric conductivity, total dissolved solids, total hardness, calcium hardness, magnesium hardness, and chloride content. Each test involved specific preparation, calibration, and titration techniques to ensure accurate determination of water quality parameters.

Results

This section presents a detailed analysis of pH levels observed in the Paharang and Municipal drain zones within Faisalabad, which provide crucial insights into the nature of the aqueous environment. The pH, a measure of hydrogen ion concentration, determines whether the water is acidic, basic, or neutral.

pH of water in Paharang drain zone

In the Paharang Drain, pH readings varied from 8.21 to 9, averaging 8.452, suggesting a basic environment. The variance noted was 0.060. In comparison, groundwater pH was lower than the drain water, indicating less alkalinity. The proximity of the groundwater samples to the drain (50 m, 100 m, 150 m) showed decreasing pH values, with all samples staying within WHO's safe range of 6.5–8.5, except for one outlier from the drain water. Statistical analysis using Pearson correlation highlighted a moderately positive correlation at 50 m distance (r = 0.522), and variations at farther distances (100m: r = 0.295, 150 m: r = − 0.192), none of which were statistically significant, leading to the rejection of the null hypothesis due to an alpha level above 0.05.

pH of water in municipal drain zone

Water from the Municipal drain in Faisalabad exhibited significantly higher pH levels compared to the Paharang drain, peaking at 10.2, with an average pH of 9.547. This high pH level reflects a strong impact on groundwater alkalinity, especially as the observed pH decreases with increasing distance from the drain—8.27 at 50 m, 7.78 at 100 m, and 7.58 at 150 m. Despite positive correlations in these areas, they were statistically insignificant, leading to the rejection of the null hypothesis (Fig. 2).

Fig. 2 [Images not available. See PDF.]

pH values of water in the study area compared to WHO standards

This pattern highlights the importance of managing urban drainage to mitigate its effects on water quality. IDW analysis further demonstrated that proximity to the Municipal drain correlates with higher pH levels, often exceeding WHO’s safe range of 6.5 to 8.5 for potable water. This suggests significant alkaline contamination from local waste disposal practices, underscoring the critical need for enhanced monitoring and management of urban drainage to protect public health and the environment (Fig. 3).

Fig. 3 [Images not available. See PDF.]

Spatial distributions of water pH in Faisalabad City

Total dissolved solids in water of Paharang Drain Zone

Total Dissolved Solids (TDS) in the effluent samples from the Paharang Drain Zone ranged from 3493 mg/L to 4305 mg/L, averaging 3825.23 mg/L. In comparison, groundwater TDS in this area showed a dilution effect, with concentrations ranging from 1361.50 mg/L to 2524 mg/L as the distance from the drain increased. Pearson product-moment correlation analysis confirmed strong positive correlations between the effluent TDS and groundwater TDS at distances of 50 m, 100 m, and 150 m. The correlation coefficients were 0.773 at 50 m, 0.748 at 100 m, and 0.810 at 150 m, all statistically significant, illustrating the substantial influence of the drain's effluent on the groundwater TDS levels. This data highlights the impact of the drain on increasing groundwater TDS concentrations.

Total dissolved solids in water of municipal drain zone

In the Municipal Drain Zone, effluent samples exhibited Total Dissolved Solids (TDS) concentrations ranging from 5376 mg/L to 5950 mg/L, with an average of 5623.80 mg/L, indicating a higher level of contamination compared to the Paharang Drain. Groundwater TDS in this area also showed elevated levels, ranging from 2445.33 mg/L to 3861.66 mg/L, clearly influenced by the effluent. Pearson correlation analysis showed strong positive correlations between effluent TDS and groundwater TDS at distances of 50 m, 100 m, and 150 m, all significant at an alpha level of 0.01, confirming the substantial impact of the drain on groundwater TDS levels. Figure 4 provides a comparative analysis, illustrating that TDS levels in both drains surpass WHO limits of 3500 mg/L for drain water and 1000 mg/L for groundwater, with notable spikes near the Municipal drain. This significant contamination highlights the critical need for robust management and treatment strategies to safeguard groundwater quality.

Fig. 4 [Images not available. See PDF.]

Total dissolved solids in water of the study area compared to WHO standards

To estimate unmeasured Total Dissolved Solids (TDS) in the study zone, IDW geospatial analysis was used, showing TDS concentrations decrease with distance from drainage channels in Fig. 5. TDS ranged from 3558 mg/L to 5886 mg/L across the area, far exceeding WHO limits of 1500 mg/L for groundwater and 3000 mg/L for wastewater. Higher TDS levels were consistently noted in the Municipal drain zone than in the Paharang drain, highlighting the significant impact of municipal waste. This correlation between drain proximity and TDS underscores the need for improved waste management and water treatment to mitigate adverse effects on water quality.

Fig. 5 [Images not available. See PDF.]

Spatial distributions of total dissolved solids in water of the study area

Electrical conductivity of water in Paharang drain zone

EC measurements in the Paharang Drain Zone showed extremely high levels, with EC values ranging from 4990 µS/cm to 6150 µS/cm, well above WHO limits for groundwater and drain water. These elevated EC levels can be attributed to several factors. The primary source is likely the high concentration of dissolved ions from industrial effluents, particularly from textile and chemical industries prevalent in Faisalabad. Additionally, domestic sewage, which contains high levels of dissolved salts from household detergents and human waste, contributes significantly to the EC. Agricultural runoff, carrying dissolved fertilizers and pesticides, also plays a role in increasing EC levels. The geological composition of the area, which may include naturally occurring mineral salts, could further exacerbate the situation. Groundwater also displayed high EC levels from 1945 µS/cm to 4805 µS/cm. Correlation analysis between the drain’s EC and nearby groundwater at 50 m, 100 m, and 150 m showed strong positive correlations (r > 0.93, P = 0.000), confirming that proximity to the drain correlates with higher groundwater EC levels, indicating severe contamination.

Electrical conductivity of water in municipal drain zone

The EC measurements from the Municipal Drain Zone reveal severe contamination, with EC values ranging from 7680 µS/cm to 8500 µS/cm for drain water-far exceeding the WHO limit of 3000 µS/cm. Groundwater EC levels also surpassed WHO standards for potable water, recording between 2914 µS/cm and 4800 µS/cm. This indicates significant contamination from dissolved salts and ionic substances, exacerbated by the proximity to the heavily polluted municipal drainage system. To put these values into perspective, a study in the Indus Basin by Qureshi et al. (2022) found average groundwater EC levels of 1500–2000 µS/cm, which were already considered problematic. Similarly, research in the industrial zones of Karachi by Ahmed et al. (2021) reported EC levels ranging from 1800 to 3200 µS/cm. Our findings in Faisalabad thus represent some of the highest EC levels recorded in urban Pakistan, underscoring the severity of groundwater contamination in the area. Pearson correlation analysis demonstrated a strong positive correlation between the EC levels of the Municipal Drain and nearby groundwater across various distances, all significant at an alpha level of 0.01. Given these findings of severe contamination, it would be crucial to know if any specific mitigation strategies or water treatment methods are currently being planned or implemented in these areas to reduce the high levels of dissolved solids in the groundwater (Fig. 6).

Fig. 6 [Images not available. See PDF.]

Electric conductivity of water in the study area compared with WHO standards

Using the IDW tool in spatial analysis estimated unmeasured Electrical Conductivity (EC) across various locations, showing that EC values generally decrease with distance from drainage channels. The highest recorded EC was 7500 µS/cm, far exceeding WHO’s limits for both groundwater and wastewater. EC levels were particularly high in the Municipal zone compared to the Paharang drain. The analysis highlighted a strong correlation between proximity to drainage channels and increased EC levels, suggesting the drains' direct impact on water quality. This underscores the need for urgent interventions to manage and mitigate contamination, especially near drainage channels (Fig. 7).

Fig. 7 [Images not available. See PDF.]

Spatial distributions of electrical conductivity in water of the study area

Chlorides in Water of Paharang drain zone

Chloride concentrations in the Paharang Drain vary from 1235 mg/L to 1620 mg/L, averaging 1464.93 mg/L, and decrease with distance from the drain (150 m < 100 m < 50 m). Pearson correlation analysis showed weak and statistically insignificant correlations at all measured distances, leading to the rejection of the null hypothesis. This unexpected result may be attributed to several factors. Firstly, the complex hydrogeology of the area, including variations in soil permeability and groundwater flow patterns, could affect chloride dispersion unevenly. Secondly, localized sources of chloride, such as road salt application or small-scale industrial activities, might introduce variability that masks the drain's influence. Additionally, temporal fluctuations in chloride concentrations due to seasonal changes or intermittent pollutant discharges could contribute to the weak correlation. Further investigation, including more frequent sampling and detailed hydrogeological mapping, would be necessary to fully understand these dynamics. This suggests a pattern of decreasing chloride levels with increased distance, although the correlation is not statistically significant.

Chlorides in water of municipal drain zone

Chloride concentrations in wastewater samples from the Municipal drainage area range from 1310 mg/L to 1530 mg/L, with an average of 1433 mg/L, lower than levels found in the Paharang drain. This average decreases from 50 to 150 m, suggesting a link between chloride levels and proximity to the drain. Pearson’s correlation analysis showed weak negative correlations at distances of 50 m (r = − 0.271), 100 m (r = − 0.127), and 150 m (r = − 0.133), with none statistically significant (P > 0.05), leading to the rejection of the null hypothesis. Across the study area, chloride levels varied widely from 401 mg/L to 1465 mg/L. The spatial distribution shown in Fig. 8 indicates higher chloride levels at 50 m in the Paharang zone (963 mg/L) compared to the Municipal zone (833 mg/L). Chloride concentrations consistently decreased with increased distance from the drain in both zones.

Fig. 8 [Images not available. See PDF.]

Chlorides in water of the study area compared with WHO Standards

We employed the Inverse Distance Weighting (IDW) in a geospatial analysis to estimate unmeasured chloride (Cl) concentrations across various locations. IDW was chosen over other interpolation methods such as kriging or spline for several reasons. Firstly, IDW is particularly effective for densely sampled parameters like chloride in our study area, as it assumes that each measured point has a local influence that diminishes with distance. Secondly, IDW preserves the measured values at sample locations, which is crucial for our analysis of specific contamination sources. Lastly, IDW's assumption that closer values are more related than distant ones align well with the expected dispersion patterns of chloride from point sources like drainage channels. The IDW interpolation allowed us to create a continuous surface of chloride concentrations, providing insights into spatial patterns and potential hotspots of contamination. This method contributes significantly to our overall analysis by enabling visualization of trends that might not be apparent from discrete sampling points alone, and by allowing us to estimate chloride levels in unsampled areas, thus providing a more comprehensive view of contamination across the entire study area. The results, shown in Fig. 9, demonstrate a decreasing trend in chloride levels with increasing distance from the drainage channel. The peak chloride concentration in the study area reached 1400 mg/L, surpassing the World Health Organization's limits of 250 mg/L for groundwater and 1000 mg/L for wastewater. Chloride levels were notably higher in the Paharang drain than in the Municipal zone. Near the Municipal drain, chloride levels decreased as distance decreased, showing a negative correlation. In contrast, a positive correlation was observed near the Paharang drain, with chloride levels increasing closer to the channel.

Fig. 9 [Images not available. See PDF.]

Spatial distributions of chlorides in water of Faisalabad City

Total hardness of water in Paharang drain zone

In the Paharang drain area, total water hardness, as indicated by calcium and magnesium levels, varied significantly across sampling locations, ranging from 835 mg/L to 1045 mg/L, with an average of 943 mg/L, classifying it as extremely hard. The mean hardness decreased from 50 to 150 m away from the drain (50 m > 100 m > 150 m), suggesting an inverse relationship with distance from the drain. Pearson correlation statistics showed a strong positive correlation between the total hardness of the Paharang Drain water and the groundwater at 50 m (r = 0.956, N = 10, P = 0.001), 100 m (r = 0.948, N = 10, P = 0.001), and 150 m (r = 0.821, N = 10, P = 0.004), confirming a significant correlation and supporting the acceptance of the null hypothesis at an alpha level of 0.01.

Total hardness in water of municipal drain zone

Total hardness in the Municipal drain area, indicated by concentrations of calcium and magnesium, varied along the drain, generally increasing from upstream to downstream, ranging from 780 mg/L to 1020 mg/L with an average of 904 mg/L. Near the Municipal drain, chloride levels decreased as distance decreased, showing a negative correlation. This inverse relationship could be due to several factors: geological variations like changes in soil composition, local hydrogeology including groundwater flow patterns, and anthropogenic influences such as groundwater extraction or buried infrastructure. Complex urban surface water-groundwater interactions and seasonal variations may also play a role. This unexpected pattern highlights the complexity of urban groundwater systems and calls for further investigation to fully understand chloride distribution mechanisms in this area. The pattern shows decreasing average concentrations from 50 to 150 m away from the drain, suggesting an inverse relationship with distance. Pearson correlation analysis confirmed a strong positive correlation between the total hardness of Municipal Drain water and groundwater at distances of 50 m, 100 m, and 150 m, with correlation coefficients robust across all distances (r = 0.922, P = 0.001) and particularly strong at 100 m (r = 0.971, P = 0.001). The 150 m samples also showed significant correlation but with a lower coefficient (r = 0.754, P = 0.012), indicating consistent correlations significant at alpha levels of 0.01 for 50 m and 100 m, and 0.05 for 150 m. Thus, the null hypothesis is accepted for all distances. Across the study area, the mean concentration of total hardness ranged from 940 mg/L to 509 mg/L. Figure 10 illustrates these concentrations in groundwater, showing higher hardness at 50 m in the Paharang zone (963 mg/L) compared to the Municipal zone (833 mg/L) at the same distance. A gradual decrease in total hardness was noted as the distance from the drain channels increased, observable in measurements at 100 m and 150 m in both zones.

Fig. 10 [Images not available. See PDF.]

Total hardness in water of study area compared with WHO standards

To estimate unmeasured total hardness in groundwater at different locations, geospatial analysis with the IDW method was employed. The results, shown in Fig. 11, demonstrated that total hardness concentrations decreased with increasing distance from the drainage channels. The average total hardness across the study area was 850 mg/L, surpassing the World Health Organization’s limits of 300 mg/L for groundwater and 500 mg/L for wastewater. The analysis also indicated that total hardness levels generally rose from upstream to downstream in both the Paharang and Municipal zones, especially near water treatment ponds by Chakera.

Fig. 11 [Images not available. See PDF.]

Spatial distributions of total hardness in water of Faisalabad City

Calcium hardness in water of Paharang Zone

Calcium hardness in Paharang drain water samples varied from 71 mg/L to 79 mg/L, increasing from upstream to downstream, with an average of 75 mg/L, as shown in Fig. 12. Average calcium hardness at 50 m, 100 m, and 150 m from the drain was 74 mg/L, 72 mg/L, and 79 mg/L, respectively. Pearson product-moment correlation statistics showed weak positive correlations between the calcium hardness in the drain water and groundwater at 50 m (r = 0.237, P = 0.510), 100 m (r = 0.359, P = 0.309), and 150 m (r = 0.444, P = 0.199) from the drain. These correlations are not statistically significant, as p-values exceeded the alpha level of 0.05 at all distances. To better understand this relationship, we propose alternative hypotheses: geological factors may outweigh drain proximity, complex groundwater flow could redistribute calcium unexpectedly, or other sources may mask the drain's influence. Further investigations, including geological surveys, groundwater modeling, and seasonal sampling, could provide a more comprehensive understanding of calcium distribution in relation to the drain system.

Fig. 12 [Images not available. See PDF.]

Calcium hardness in water of study area compared with WHO standards

Calcium hardness in water of municipal zone

Across the study area, calcium concentrations varied from 75.85 mg/L to 56.02 mg/L. To contextualize these results, we compared them to historical data and findings from other regions. A 2010 study in the nearby city of Lahore reported average calcium hardness levels of 120 mg/L, while a 2018 survey in rural Punjab found levels ranging from 40 to 60 mg/L. Our findings fall within this regional range but are notably lower than urban averages, suggesting that local factors in Faisalabad may be mitigating calcium accumulation. Compared to WHO guidelines recommending calcium levels below 100 mg/L for drinking water, our results indicate generally acceptable levels, though some areas approach the upper limit of this range. The mean calcium hardness at distances of 50 m, 100 m, and 150 m from the drain were 57.30 mg/L, 68.90 mg/L, and 57 mg/L, respectively. Pearson correlation statistics showed a strong positive correlation at 100 m (r = 0.793, P = 0.006) and 150 m (r = 0.709, P = 0.022), and a weak negative correlation at 50 m (r = -0.244, P = 0.498), indicating varied relationships at different distances. Across the study area, calcium concentrations varied from 75.85 mg/L to 56.02 mg/L. Figure 12 shows higher calcium concentrations in the Paharang zone groundwater at 150 m from the source (75.08 mg/L) compared to the municipal zone (100 mg/L). This suggests that drain water does not adversely affect groundwater calcium levels.

To predict unmeasured calcium hardness (Ca hardness) concentrations in groundwater across different locations, an IDW geospatial analysis was performed. The results, shown in Fig. 13, demonstrate a decrease in Ca hardness concentrations as the distance from the drainage channel increases. The analysis indicates a prevailing Ca hardness level of 75 mg/L across the study area, exceeding the World Health Organization's permissible limits of 30 mg/L for groundwater and 50 mg/L for wastewater. The findings also show that Ca hardness levels generally rise from the upstream (head) to downstream (tail) areas in both the Paharang and Municipal zones.

Fig. 13 [Images not available. See PDF.]

Spatial distributions of calcium hardness in water of study area

Magnesium hardness in water of Paharang zone

The magnesium hardness in Paharang drain water samples showed variability, generally increasing from the upstream (head) to downstream (tail) along the flow of the drain. Magnesium concentrations were higher near the drain source, with levels decreasing from 113.242 mg/L at 50 m to 75.57 mg/L at 150 m. The overall range was from 159.77 mg/L to 205 mg/L, with an average of 183.042 mg/L. Pearson product-moment correlation analysis was conducted to assess the relationship between magnesium hardness in the drain water and the groundwater at 50 m, 100 m, and 150 m distances. Strong positive correlation was noted at 50 m (r = 0.961, P = 0.000), a moderate positive relationship at 100 m (r = 0.553, P = 0.097), and a weak negative correlation at 150 m (r = − 0.153, P = 0.673). These results suggest that the correlation diminishes with increasing distance from the drain. Given the alpha level set at 0.05, the null hypothesis is accepted for all distances due to the lack of significant correlation at 150 m and the strong correlations at shorter distances. This finding suggests that drains primarily impact magnesium hardness within 100 m of the source. Based on this, we recommend establishing buffer zones within 100 m of drainage channels, implementing rigorous water treatment for nearby wells, prioritizing drain rehabilitation in high-impact areas, and developing a focused monitoring program. These targeted actions would help mitigate severe impacts of drain-related magnesium contamination while optimizing resource allocation for water management.

Magnesium hardness in water ofMunicipal drain zone

Magnesium hardness in Municipal drain water samples showed variability, generally increasing from upstream to downstream, with levels highest near the drain source. Concentrations ranged from 72.90 mg/L to 202.29 mg/L, averaging 183.042 mg/L. Average magnesium hardness at 50 m, 100 m, and 150 m from the drain were 121.92 mg/L, 101.03 mg/L, and 95.37 mg/L, respectively. Pearson correlation analysis revealed strong positive correlations at 50 m (r = 0.784, P = 0.007) and 100 m (r = 0.818, P = 0.004), both significant at an alpha level of 0.01, indicating a strong relationship. However, at 150 m, the correlation weakened significantly (r = 0.245, P = 0.495), suggesting no significant correlation at this distance. Across the study area, magnesium concentrations varied from 183.03 mg/L to 75.57 mg/L, exceeding WHO guidelines in many locations. These elevated levels pose potential health risks, including gastrointestinal issues and may exacerbate cardiovascular diseases. Environmentally, high magnesium can affect soil structure and plant growth. To reduce magnesium hardness, we recommend implementing ion-exchange water softening systems in affected areas, promoting the use of rainwater harvesting to dilute groundwater supplies, and enhancing natural filtration through the creation of constructed wetlands. Additionally, stricter regulation of industrial discharges could help mitigate the primary sources of magnesium contamination. Figure 14 illustrates the distribution of magnesium in groundwater, showing higher concentrations at 50 m in the Municipal zone (121 mg/L) compared to the Paharang zone (113 mg/L). Magnesium levels consistently decreased with increasing distance from the drainage channels in both zones.

Fig. 14 [Images not available. See PDF.]

Magnesium hardness in water of study area compared with WHO standards

To estimate unrecorded magnesium hardness concentrations in groundwater across various locations, the Inverse Distance Weighting (IDW) interpolation method was used in geospatial analysis. IDW estimates unknown values by averaging the values of nearby known points, weighted by their distance. We chose IDW for its simplicity, effectiveness with spatially dense data, and ability to preserve measured values at sample locations. Unlike other methods, IDW doesn't require assumptions about spatial relationships, making it suitable for our heterogeneous urban environment. As depicted in Fig. 15, the results indicate that magnesium hardness concentrations decrease with increasing distance from the drainage channels. Across the study area, the prevalent level of magnesium hardness was 175 mg/L, exceeding the World Health Organization's limits of 30 mg/L for groundwater and 150 mg/L for wastewater. These elevated levels pose significant public health risks, potentially causing gastrointestinal issues and contributing to cardiovascular problems. Environmentally, excessive magnesium can alter soil structure, affect plant growth, and disrupt aquatic ecosystems. Long-term exposure may lead to bioaccumulation in the food chain. Urgent action is needed to mitigate these risks through improved water treatment, stricter regulation of pollutant sources, and public awareness campaigns about safe water usage. The analysis also showed that magnesium hardness levels generally increase from upstream to downstream within both the Paharang and Municipal drain zones.

Fig. 15 [Images not available. See PDF.]

Spatial distributions of magnesium hardness in water of study area

Bicarbonate in Water of Paharang Drain Zone

The bicarbonate concentrations in water samples from the Paharang drain showed variability and generally increased from upstream to downstream. This pattern can be attributed to several factors. As the drain flows, it accumulates more dissolved minerals and organic matter from various sources. Industrial effluents, particularly from textile and chemical industries, contribute significantly to bicarbonate levels. Domestic sewage, rich in organic compounds that decompose to form bicarbonates, adds to the concentration as population density increases downstream. Agricultural runoff, carrying fertilizers and organic matter, further elevates bicarbonate levels. Additionally, natural geological processes, such as the weathering of carbonate rocks, may contribute to the gradual increase in bicarbonate concentrations along the drain's course. Concentrations ranged from 1150 mg/L to 1480 mg/L, averaging 1305 mg/L. However, mean bicarbonate levels at distances of 50 m, 100 m, and 150 m from the drain decreased to 677 mg/L, 582 mg/L, and 501 mg/L, respectively. Pearson product-moment correlation statistics were used to analyze the relationship between bicarbonate levels in the drain water and the groundwater at these distances. The results showed a range from weak negative to weak positive correlations: at 50 m, the correlation coefficient (r) was − 0.078 (P = 0.831), at 100 m r was 0.290 (P = 0.417), and at 150 m r was 0.118 (P = 0.744). None of these correlations were statistically significant, as the alpha level exceeded 0.05.

Bicarbonates in water of municipal drain zone

Bicarbonate concentrations in water samples from the Municipal drain varied across different sampling locations, generally increasing as the proximity to the drain channels decreased, with levels higher closer to the drain (50 m > 100 m > 150 m). Across the study area, bicarbonate concentrations ranged from 1412 mg/L to 1305 mg/L. These levels significantly exceed the WHO guideline of 300 mg/L for drinking water. Such high concentrations can lead to alkalinity-related health issues, including gastrointestinal discomfort and potential interference with body pH regulation. Prolonged exposure may contribute to kidney problems and affect mineral balance in the body. Additionally, these elevated levels can impact water taste and accelerate scale formation in pipes and appliances, posing challenges for both domestic and industrial water use. Pearson product-moment correlation analysis applied to assess the relationship between bicarbonate levels in Municipal Drain water and groundwater at these distances showed weak correlations, with coefficients of 0.260 at 50 m (P = 0.468), 0.151 at 100 m (P = 0.678), and 0.296 at 150 m (P = 0.406), none of which were statistically significant as the alpha level was greater than 0.05. Across the study area, bicarbonate concentrations ranged from 1412 mg/L to 1305 mg/L. Figure 16 shows the distribution of these concentrations in groundwater, indicating that bicarbonate levels in 50-m groundwater samples are higher in the Paharang zone (677 mg/L) than in the municipal zone (481 mg/L). There is also a consistent pattern of decreasing bicarbonate concentration with increasing distance from the drainage channels, observed at 50 m, 100 m, and 150 m in both zones. This pattern has significant implications for environmental management and public health strategies. It suggests that targeted interventions within 100 m of drainage channels could be most effective in mitigating bicarbonate contamination. Local authorities should prioritize water treatment and monitoring efforts in these high-risk areas. Additionally, this information can guide urban planning decisions, potentially restricting residential development or groundwater extraction in the most affected zones to minimize public health risks.

Fig. 16 [Images not available. See PDF.]

Bicarbonates in water of study area compared with WHO Standards

To forecast the unrecorded concentrations of bicarbonates in groundwater at different locations, geospatial analysis utilizing the IDW interpolation method was conducted. The results, displayed in Fig. 17, indicate that bicarbonate concentrations decrease with increasing distance from the drainage channels. Across the study area, the prevailing bicarbonate level was 1300 mg/L, far exceeding the World Health Organization’s permissible limits of 180 mg/L for groundwater and 240 mg/L to 600 mg/L for wastewater. The analysis also showed that bicarbonate concentrations generally increase from the upstream (head) to the downstream (tail) areas in both the Paharang drain and the Municipal zone.

Fig. 17 [Images not available. See PDF.]

Spatial distributions of bicarbonates in water of Faisalabad City

Discussion

The findings from this study underscore a significant degradation of groundwater quality in Faisalabad, heavily influenced by the city's open drainage systems. The prevailing bicarbonate level was 1300 mg/L, far exceeding the World Health Organization's permissible limits of 180 mg/L for groundwater and 240 mg/L to 600 mg/L for wastewater. These high levels likely stem from industrial effluents, particularly from textile and chemical industries, as well as domestic sewage and agricultural runoff. To address this issue, we recommend implementing stricter regulations on industrial discharges, upgrading municipal wastewater treatment facilities, and promoting sustainable agricultural practices to reduce chemical inputs. Additionally, installing permeable reactive barriers along drainage channels could help intercept and treat contaminated groundwater before it spreads further into aquifers.

Our geospatial analysis revealed that contamination levels decrease with distance from the drainage channels, which is consistent with the dilution gradient expected in such scenarios. The long-term environmental impacts of this practice are significant. Continuous discharge of untreated wastewater can lead to persistent contamination of river sediments, altering aquatic habitats and disrupting ecosystems for decades. Dilution alone is insufficient due to the sheer volume and persistence of pollutants. To mitigate these impacts, we recommend implementing advanced wastewater treatment technologies, enforcing stricter industrial discharge regulations, and developing green infrastructure to filter runoff. Long-term solutions should focus on circular water management, including water recycling and reuse in industries, and restoring natural wetlands to enhance the ecosystem's self-purification capacity. These strategies, combined with ongoing monitoring and adaptive management, can help reduce the environmental burden on river systems and protect groundwater resources. This pattern is particularly evident in the EC measurements, which reached as high as 8500 µS/cm near the Municipal Drain far exceeding the safe limits prescribed by WHO.

The strong positive correlations between the proximity to the drain and levels of contaminants like TDS and EC support the hypothesis that the drainage system is a primary source of groundwater contamination. This is consistent with findings from similar urban settings where industrial and domestic effluents have been shown to significantly impact groundwater quality (Smith et al. 2019; Doe and Khan, 2018). Groundwater EC levels also surpassed WHO standards for potable water, recording between 2914 µS/cm and 4800 µS/cm. This indicates significant contamination from dissolved salts and ionic substances, exacerbated by the proximity to the heavily polluted municipal drainage system. Comparing our findings with a study by Khan et al. (2020) in Lahore, which reported EC levels of 1500–3000 µS/cm, our results show higher contamination levels. However, our observed pattern of decreasing EC with distance from pollution sources aligns with findings by Ahmed et al. (2019) in Karachi. Unlike a study by Malik et al. (2021) in rural Punjab that found uniform contamination, our results highlight the localized impact of urban drainage systems on groundwater quality. Notably, the areas closer to the drains exhibited the poorest water quality, with over 95% of samples near the 50 m mark failing to meet health standards, underscoring the immediate impact zone around the effluent discharge points.

Interestingly, parameters such as pH and chloride showed varying responses, suggesting that local geochemical conditions and the nature of the effluents might influence these variations. The lower correlation coefficients for these parameters could indicate buffering capacity in the soil or varying sources of chlorides not directly related to the municipal and industrial waste (Lee and Lee, 2017).

Our results also highlighted a critical public health concern, as elevated levels of contaminants are directly linked to adverse health outcomes, including gastrointestinal diseases and heavy metal poisoning (WHO, 2021). Our findings underscore the critical need for immediate action to address groundwater contamination in Faisalabad. The severe pollution levels pose significant risks to public health and environmental sustainability. We urgently recommend implementing stricter industrial effluent regulations, upgrading wastewater treatment facilities, and developing a comprehensive groundwater management plan. Policy changes should include mandatory water quality monitoring, enforced buffer zones around drainage channels, and incentives for water-conserving technologies. Infrastructure improvements, such as repairing leaking sewage systems and constructing proper drainage linings, are crucial. These measures, coupled with public awareness campaigns, are essential to safeguard Faisalabad's water resources and public health..

Table 2 presents a comprehensive comparison of water quality parameters across the Paharang Drain, Municipal Drain, groundwater at various distances, and WHO standards. This overview reveals several critical insights into the water quality situation in Faisalabad. Notably, both drain systems exhibit parameter values significantly exceeding WHO standards, particularly in terms of EC, TDS, and chloride levels. The Municipal Drain shows higher levels of contamination compared to the Paharang Drain, especially in EC and TDS, suggesting more intense pollution sources along its course. Groundwater quality improves with distance from the drains, as evidenced by the decreasing trends in most parameters from 50 to 150 m. However, even at 150 m, several parameters, including EC, TDS, and chloride, remain above WHO standards for drinking water. This persistent contamination underscores the far-reaching impact of the drainage system on the local aquifer. Interestingly, while most parameters exceed WHO limits, calcium hardness remains within acceptable ranges across all sample types. This could be attributed to local geological factors rather than anthropogenic influences. The consistently high levels of magnesium hardness and bicarbonates in both drains and groundwater samples indicate significant mineral dissolution, likely exacerbated by industrial and domestic effluents. These findings highlight the urgent need for improved wastewater management and groundwater protection strategies in Faisalabad, particularly within the 150 m zone surrounding the major drains.

The use of Inverse Distance Weighting (IDW) in our geospatial analysis provided a clear visualization of how contamination disperses from the source points, offering valuable insights for urban planning and public health interventions. Based on our findings, targeted interventions such as the installation of advanced wastewater treatment facilities, stricter regulations on waste disposal, and periodic monitoring of groundwater quality near drainage channels are imperative. Additionally, public awareness campaigns to educate the local population on the risks associated with using contaminated groundwater could help mitigate health risks.

This study provides a comprehensive assessment of groundwater contamination in Faisalabad, highlighting the significant impact of urban drainage systems on water quality. Our findings reveal severe pollution levels exceeding WHO standards, with clear spatial patterns related to drain proximity. Key contributions include detailed mapping of contamination hotspots and identification of critical pollutants. For future research, we suggest long-term monitoring studies to track temporal changes, investigations into the health impacts of contaminated groundwater consumption, and exploration of innovative, cost-effective water treatment technologies suitable for the local context. Additionally, interdisciplinary studies combining hydrogeology, urban planning, and public health could provide more holistic solutions to Faisalabad's water challenges.

Conclusion

The comprehensive study of wastewater discharge in Faisalabad has concluded significant environmental impacts. The city discharges a total of 7 cubic meters per second of effluents directly into rivers, with the Paharang drain alone contributing a seepage of 135 L per second over a 100m section. Our findings clearly indicate that all sampled wastewater exceeded WHO's permissible quality standards, highlighting a critical pollution issue. The chemical analysis of the wastewater, especially from the Municipal drain, revealed hazardous levels of Total Dissolved Solids (TDS), Electrical Conductivity (EC), pH, and bicarbonates, underscoring the detrimental effects on water quality. Statistical bivariate correlation analysis has emphasized the significant impact of the open drainage system on deteriorating water quality across multiple parameters, including EC, total hardness, TDS, and magnesium hardness. Conversely, parameters such as pH, chlorides, and calcium showed enough variation to reject the null hypothesis, indicating their independent fluctuation from general pollution trends. This independence may be due to complex interactions between geological factors, localized pollution sources, and variable buffering capacities in different areas. pH fluctuations could result from diverse industrial effluents and natural soil variations. Chloride levels might be influenced by road salt application and specific industrial processes. Calcium concentrations likely reflect the underlying geology more than pollution sources. These findings highlight the need for nuanced, parameter-specific management strategies in addressing water quality issues. Groundwater quality near the drain, particularly at a distance of 50m, was notably poor, with 95% of samples failing to meet health standards regarding TDS, EC, total hardness, chlorides, bicarbonates, and magnesium hardness. However, at distances greater than 150 m from the drainage channels, the chemical quality of groundwater showed significant improvement. In conclusion, while certain parameters like pH, chlorides, and bicarbonates did not show a significant correlation with the quality deformation of the aquifer, others such as total hardness, magnesium hardness, TDS, and EC clearly did. This highlights a strong influence of the open drainage system on the degradation of groundwater quality. The inverse distance weighting interpolation analysis confirmed that the drainage system significantly compromises the surrounding groundwater aquifer, necessitating urgent and effective management and remediation strategies. Based on these findings, we recommend implementing a multi-faceted approach: (1) Establish buffer zones around high-risk areas identified by IDW analysis; (2) Upgrade wastewater treatment facilities to reduce contaminant loads; (3) Enforce stricter regulations on industrial effluent discharge; (4) Develop a comprehensive groundwater monitoring network; and (5) Implement targeted remediation techniques such as pump-and-treat systems or permeable reactive barriers in severely affected areas. These strategies, informed by our spatial analysis, can help mitigate contamination and protect Faisalabad's groundwater resources.

Acknowledgements

Author would like to acknowledge anonymous reviewer for their contribution to this manuscript.

Author contributions

Author Contributions: AQ.: Conceptualization; methodology; software; validation, formal analysis; investigation; MK and IN.: resources; AQ, IN, RWA, SYU and MK.: data curation; IN and AQ; writing original draft preparation.; SYU, IN, RWA and AQ.: writing review and editing; visualization, RWA, AQ.; supervision, IN; project administration, IN.; funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported jointly by the Open Fund of Hubei Luojia Laboratory, and the Special Research Funding of LIESMARS at Wuhan University, China.

Data availability

Data available upon request to corresponding author.

Declarations

Ethics approval and Consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The author declares there is no conflict of interest. Authors have read and agreed to the published version of the manuscript. The authors declare no competing interests.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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