Assessment of groundwater quality in Piryaloi, Pakistan: integrating GPI, SPI, and GIS for comprehensive analysis

Water is essential for humans, plants, and animals (Gil-Rodas et al. 2023; Solangi et al. 2024). It is not easy to survive without water. People are looking at the various sources of drinking water supply because most life processes are directly or indirectly dependent upon water (Koohbanani et al. 2018; Iddrisu et al. 2023a). Despite being a basic necessity, an estimated 1.1 billion of the world's population lack access to safe drinking water (Hossain et al. 2020). This scarcity of clean drinking water presents a serious problem, especially for developing countries (Oftadeh et al. 2021; Solangi et al. 2024). As a result, many people in such areas turn to drinking untreated water from wells, streams, rivers, and boreholes (Oyelude et al. 2013). According to reports from the UNICEF and the WHO, about 2.3 billion people living in various locations worldwide are consequently afflicted by water-related diseases due to the consumption of polluted water (Solangi et al. 2017; Solangi et al. 2018; Solangi et al. 2019a). Unfortunately, human and natural activities are contributing to the contamination of drinking water resources (Nassery et al. 2017; Niyongabo et al. 2023).

The most typical water sources for domestic and other purposes are groundwater and surface water. Groundwater is the primary source of drinking water in many areas of the world, including Pakistan. About one-third of the world's population uses groundwater for drinking purposes. More than 70% of Pakistan's drinking water is unsuitable for human consumption (Azizullah et al. 2011; Jalees et al. 2023; Bahraseman et al. 2024). With about 250 million people, Pakistan has the sixth-highest population globally. The country's water supplies are under threat due to excessive population growth and rapid urban and industrial development (Panhwar et al. 2022). Many people living in various parts of the country depend on groundwater. According to WHO recommendations, almost 90.0% of water resources do not comply with drinking water guidelines (Al-Othman et al. 2012; Yeganeh et al. 2024). About 36.0% of Sindh, Pakistan's second-most populous province, uses contaminated water (Uqaili et al. 2012). Meanwhile, 68% of people who live in rural areas of the province drink water of low quality (Solangi et al. 2022). Rural and many urban regions in underdeveloped countries must have access to enough clean drinking water (Iddrisu et al. 2023a). However, both man-made and natural causes have an impact on groundwater quality. Groundwater quality is negatively impacted by anthropogenic activities such as open defecation, agriculture, and improper waste disposal (Ostad-Ali-Askari 2022; Iddrisu et al. 2023b; Jamshidi & Naderi 2023).

One of the leading causes of waterborne diseases worldwide, especially in Pakistan's Sindh region, is thought to be contaminated water (Memon et al. 2011). According to the WHO's 2005 report, 1.8 million people worldwide die each year from a waterborne diarrheal disease, and most of such diseases are caused by drinking contaminated water. According to a UNICEF report in 2010, 884 million people worldwide do not have access to clean drinking water (Solangi et al. 2019a). Groundwater contamination is a significant issue everywhere in the world. Ultimately, it harms people's health. According to Patel et al. (2023) and Elahi et al. (2022), the quality of water resources should be monitored regularly. Iddrisu et al. (2023a) have also suggested that regular monitoring and testing are necessary to guarantee that water is safe for consumption and other purposes.

To accurately determine the quality of water used for drinking and domestic uses, more research needs to be done (Iddrisu et al. 2023a), and it is imperative to assess the drinkability of water. Groundwater contamination poses a significant threat to the health of residents in U.C. Piryaloi, Pakistan. This study aims to comprehensively analyze groundwater quality in the region by integrating dual indices, GPI, and SPI, with geospatial tools. According to the literature, no study of this kind has ever been conducted before within the study area. Thus, this study has been undertaken to fill this research gap.

The sampling sites' locations were tracked using GPS. Different physicochemical parameters, including pH, turbidity, TDS, EC, Cl-, TH, Ca²⁺, Mg²⁺, ⁠, ⁠, F, and heavy metals, including Ca, Mg, Na, K, Fe, Mn, Ni, Zn, Mo, B, As, Cu, Co, Cd, Pd, and Cr, were examined in water samples. The turbidity, pH, TDS, and EC were observed using respective meters. However, Ca²⁺, Mg²⁺, TH, Cl⁻, ⁠, were determined using the standard titration method, and fluoride was observed using the 4500-F SPANDS APHA method. Moreover, Ca, Mg, Na, K, Fe, Mn, Ni, Zn, Mo, B, As, Cu, Co, Cd, Pd, and Cr content in the sampled groundwater was assessed using the ICP-MS.

The overall drinkability of collected groundwater was analyzed by applying two standard water quality indices, the groundwater pollution index (GPI) and the synthetic pollution index (SPI). The step-by-step calculation procedures of both indices are explained here.

Here, C represents the concentration of water quality parameters in each sample, R_w is the assigned weight or relative weight parameter, and D_s the allowable WHO guideline for each variable. According to the GPI model, evaluated groundwater is to be divided into five categories: excellent (50), good (>50–100), poor (>100–200), very bad (>200–300), and unfit for drinking (>300).

Table 1 specifies the allocated weights (R_w) and relative weights (W_p) of each water quality parameter for calculating the GPI values for each analyzed water sample.

Table 1

Parameters considered in the GPI model evaluation

Parameter .	Unit .	Ds (WHO guidelines) .	Rw .	Wp .
pH	–	8.5	3	0.047
Turbidity	NTU	5	2	0.031
TDS	mg/L	500	4	0.063
EC	dS/m	0.75	3	0.047
Cl	mg/L	250	4	0.063
TH	mg/L	500	3	0.047
Ca2+	mg/L	75	2	0.031
Mg2+	mg/L	50	2	0.031
	mg/L	15	1	0.016
	mg/L	120	2	0.031
Ca	mg/L	300	2	0.031
Mg	mg/L	30	2	0.031
Na	mg/L	200	3	0.047
K	mg/L	200	2	0.031
Fe	mg/L	0.3	3	0.047
Mn	mg/L	0.4	2	0.031
Ni	mg/L	0.07	2	0.031
Zn	mg/L	3	1	0.016
Mo	mg/L	0.07	1	0.016
B	mg/L	0.5	1	0.016
As	mg/L	0.01	5	0.078
Cu	mg/L	2	3	0.047
Co	mg/L	0.05	1	0.016
Cd	mg/L	0.003	2	0.031
Cr	mg/L	0.05	3	0.047
F (Fluoride)	mg/L	1.5	5	0.078
			ΣRw = 64	ΣWp = 1.0

Parameter .	Unit .	Ds (WHO guidelines) .	Rw .	Wp .
pH	–	8.5	3	0.047
Turbidity	NTU	5	2	0.031
TDS	mg/L	500	4	0.063
EC	dS/m	0.75	3	0.047
Cl	mg/L	250	4	0.063
TH	mg/L	500	3	0.047
Ca2+	mg/L	75	2	0.031
Mg2+	mg/L	50	2	0.031
	mg/L	15	1	0.016
	mg/L	120	2	0.031
Ca	mg/L	300	2	0.031
Mg	mg/L	30	2	0.031
Na	mg/L	200	3	0.047
K	mg/L	200	2	0.031
Fe	mg/L	0.3	3	0.047
Mn	mg/L	0.4	2	0.031
Ni	mg/L	0.07	2	0.031
Zn	mg/L	3	1	0.016
Mo	mg/L	0.07	1	0.016
B	mg/L	0.5	1	0.016
As	mg/L	0.01	5	0.078
Cu	mg/L	2	3	0.047
Co	mg/L	0.05	1	0.016
Cd	mg/L	0.003	2	0.031
Cr	mg/L	0.05	3	0.047
F (Fluoride)	mg/L	1.5	5	0.078
			ΣRw = 64	ΣWp = 1.0

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Many researchers worldwide are using the SPI, a contemporary instrument, to assess the overall quality of groundwater (Gautam et al. 2015; Egbueri & Unigwe 2019; Solangi et al. 2019a, b, c). SPI divides the water into five groups. As a result, the value of the SPI model for each water sample was determined using observed concentrations of several physiochemical indicators, including turbidity, Mg, Cl, pH, Ca, TH, TDS, and EC.

Calculating the Value of the constant of proportionality (K)

Calculating the value of relative weight/Weight coefficient (W_i).

The letter D represents each analyzed physicochemical parameter's observed value.

According to the SPI model, evaluated groundwater is to be divided into five categories: suitable (<0.2), slightly contaminated (0.2 ≤ SPI < 0.5), moderately contaminated (0.5 ≤ SPI < 1.0), highly contaminated (1 ≤ SPI < 3.0), and unfit for drinking (>3) (Solangi et al. 2019b; Jamali et al. 2022).

This section describes the groundwater quality of the study area for drinking purposes, based on the analysis results of physicochemical parameters and GIS interpolation maps.

Table 2 describes a statistical summary of the analysis results of physicochemical parameters in terms of minimum, maximum, average, standard deviation (SD), WHO guidelines, and percentage of samples beyond WHO guidelines.

Table 2

Statistical summary of physicochemical parameters of analyzed water

Parameter .	WHO guidelines .	Min. .	Max. .	Average .	Standard deviation .	Samples beyond guidelines .
pH	8.5	7.10	7.96	7.44	0.25	0.00
Turbidity	5	0.81	29.40	5.30	7.29	26.67
TDS	500	118	1,034	421.87	214.98	33.33
EC	0.75	0.18	1.62	0.66	0.34	33.33
Cl−	250	50	775	193	185.82	20.00
TH	500	120	680	348	152.40	13.33
Ca2+	75	48	272	139.20	60.96	80.00
Mg2+	50	17.28	97.92	50.11	21.95	53.33
	15	0	0	0	0	0.00
	120	100	400	254	102.88	80
F	1.5	0.2	4	0.72	0.91	6.67

Parameter .	WHO guidelines .	Min. .	Max. .	Average .	Standard deviation .	Samples beyond guidelines .
pH	8.5	7.10	7.96	7.44	0.25	0.00
Turbidity	5	0.81	29.40	5.30	7.29	26.67
TDS	500	118	1,034	421.87	214.98	33.33
EC	0.75	0.18	1.62	0.66	0.34	33.33
Cl−	250	50	775	193	185.82	20.00
TH	500	120	680	348	152.40	13.33
Ca2+	75	48	272	139.20	60.96	80.00
Mg2+	50	17.28	97.92	50.11	21.95	53.33
	15	0	0	0	0	0.00
	120	100	400	254	102.88	80
F	1.5	0.2	4	0.72	0.91	6.67

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Analysis showed that the turbidity of the water samples for the current study ranged from 0.81 to 29.40 NTU (nephelometric turbidity unit) with an average value of 5.31 NTU. Samples with a turbidity of 26.66% were determined to be over the WHO recommendation of 5 NTU (Ali et al. 2023). Figure 4(b) shows how the turbidity in the groundwater is distributed spatially.

The current study found that the mean TDS content in the groundwater sampled ranged from 421.870 to 214.98 mg/L, with a range of 118.0 to 1,034.0 mg/L. Five samples out of 15 were found to have TDS concentrations over the permissible WHO standard of 500.0 mg/L, or 33.33% of the samples. The groundwater at position S-10 (Village Haji Ghulam Hussain Kandhir) had the highest TDS content, whereas water at location S-4 (Village Haji Jadal Khan Burdi) had the lowest TDS concentration. The groundwater aquifer was being continuously replenished, and dissolved contaminants were being eliminated by aquifer recharge, which is likely the cause of the lowest TDS. The water source was constructed on the side of a canal named West Feeder, and the groundwater aquifer was being recharged continuously and dissolved impurities were removed through aquifer recharge. Water, with TDS concentrations greater than 500 mg/L, is considered unsuitable for human consumption. Ewaid & Abed (2017) also reported that water containing TDS greater than 500 mg/L is not suitable for water supply schemes. With the increase in TDS, hardness and the corrosive nature of water increases (Devi et al. 2003; Solangi et al. 2019a). The spatial distribution of TDS in the groundwater of the study area is depicted in Figure 4(c). A similar trend of TDS values has been reported by Ansari et al. (2021) and Jamali et al. (2022) for the groundwater of Sukkur City and Taluka Larkana, Pakistan, respectively.

According to the current study, EC concentrations ranged from 0.184 to 1.616 dS/m, with an average of 0.660 ± 0.340 dS/m. Out of 15, five samples, or 33.33%, exhibited EC levels that were higher than the WHO-permitted limit of 0.75 dS/m. According to analysis, 66.67% of samples had EC concentrations that were within the WHO's recommended range of 0.75 dS/m. The water at position S-10 (Haji Ghulam Hussain Kandhir village) had the highest concentration of EC, whereas the water at location S-4 (Haji Jadal Khan Burdi village) had the lowest concentration of EC.

Figure 4(d) shows the regional distribution of EC in the research area's groundwater. A similar trend of EC values for groundwater of Sukkur City Pakistan was reported by Ansari et al. (2021).

The calcium (Ca) level of the groundwater samples ranged from 48 to 272 mg/L, with an average of 139.2 ± 60.96 mg/L. About 80% of samples had calcium concentrations higher than the WHO recommendation of 75 mg/L. The highest and lowest Ca values were recorded at sites S-10 and S-4, respectively. Figure 5(b) shows the spatial distribution of Ca in the study area. A similar trend of lime calcium concentration in the groundwater of Pano Akil City of Pakistan was reported by Solangi et al. (2024).

Magnesium hardness shows an excessive amount of magnesium (Mg) in water. The increased level of calcium and magnesium in water makes it hard (Al-Ahmadi & El-Fiky 2009). Abbasnia et al. (2018) reported that high amounts of calcium and magnesium could cause abdominal ailments in the human body. According to the current study, Mg concentration in the water samples ranged from 17.28 to 97.92 mg/L, with a mean value of 50.11 ± 21.95 mg/L. As per the WHO-recommended limit of 50 mg/L (Ali et al. 2023), Mg beyond the limit was found in about 53.33% of samples. Figure 5(c) shows the spatial distribution of Mg in the analyzed groundwater. Also, a similar trend of Mg concentration in the groundwater of Sukkur City, Sindh, Pakistan has been reported by Ansari et al. (2021).

Analysis showed that the collected water's total hardness (TH) concentration ranged from 120 to 680 mg/L, with a mean value of 348 ± 152.40 mg/L. The hardness level between 150 and 300 mg/L also adversely affects human health; it causes heart and kidney problems (Ramesh & Elango 2006; Solangi et al. 2019c).

Only 13.33% of samples contained amounts beyond the WHO's recommended limit of 500 mg/L. The water at position S-10 (village Haji Ghulam Hussain Kandhir) had the highest content of TH, whereas water at location S-4 (village Haji Jadal Khan Burdi) had the lowest concentration.

Figure 5(d) shows the spatial distribution of TH in the study area's groundwater. Also, the TH values reported here are like those of Jamali et al. (2022) and Ansari et al. (2021) for the groundwater of Larkana taluka and Sukkur City of Pakistan, respectively. However, the reason could be that the water source is located in areas with soft soils, loose sediments, or high erosion rates, and runoff during rainfall, agricultural runoff, urbanization construction, and industrial effluents. If past studies (Ansari et al. 2021; Jamali et al. 2022) found lower TH values, it might indicate changes in human activities or natural conditions over time.

Analysis revealed that the assessed water contained bicarbonates in concentrations ranging from 100 to 400 mg/L, with a mean value of 254 ± 102.88 mg/L. The recommended upper limit for bicarbonate in drinking water is 120 mg/L. Concerning bicarbonates, over 80% (12 samples) were found to be poor for drinking.

In this section, the groundwater quality of the study area for drinking purposes considering analysis results of heavy metal concentrations such as Ca, Mg, K, Na, Mn, Fe, Ni, Zn, Mo, B, As, Co, Cu, Cd, Pd, and Cr is discussed.

A statistical summary of metal analysis results in the form of WHO guidelines, minimum value, maximum, average, SD, and percentage of samples beyond WHO guidelines is described in Table 3.

One important ingredient that is good for human health is calcium (metal). The calcium content in the current study ranged from 25.07 to 104.61 mg/L, with a mean of 71.06 ± 21.83 mg/L. The WHO recommendation of 300 mg/L for calcium concentration was found to be met in all samples. The current investigation found that the average concentration of magnesium in the analyzed water was 29.88 ± 12.30 mg/L, ranging from 5.76 to 52.56 mg/L. The WHO-recommended limit of 30 mg/L for magnesium was exceeded in about 46.67% of samples.

According to the current study, the potassium concentration in the water samples ranged from 3.94 to 94.27 mg/L, with a mean concentration of 20.47 ± 26.68 mg/L. Figure 6(b) depicts the spatial distribution of potassium in the sampled groundwater.

The maximum WHO recommendation for fluoride in drinking water is 1.5 mg/L. Excessive fluoride can cause changes in tooth enamel, ranging from barely noticeable white spots to staining and pitting. Skeletal and dental fluorosis is the ill effects associated with excess fluoride in drinking water (Barathi et al. 2019). According to the current study, there were between 0.20 and 4.0 mg/L of fluoride in the water samples, with an average value of 0.73 ± 0.91 mg/L. Figure 6(c) depicts the spatial distribution of fluoride in the study area's groundwater.

The significant water contaminant parameter is arsenic (As). The recommended arsenic (As) content for residential use is 0.01 mg/L, or 10 μg/L, according to the WHO's guidelines. Excess of arsenic concentration beyond the permissible range in water causes liver problems, cancer, cardiovascular, ocular, and neuropathies (Das et al. 2012; Solangi et al. 2019c).

In the analyzed water arsenic levels ranged from 2.0 to 7.0 g/L, with a mean of 5.0 ± 2.0 μg/L. Figure 6(d) depicts the spatial distribution of arsenic (As) in the groundwater of the study area.

The WHO recommends an iron concentration in drinking water between 0.3 and 2 mg/L. According to the current study, the iron concentration in the analyzed water ranged from 0.02 to 0.173 mg/L, with a mean concentration of 0.09 ± 0.05 mg/L.

The optimum manganese level for drinking water according to WHO guidelines is 0.4 mg/L. Manganese concentration in the observed water ranged from 0.013 to 0.28 mg/L, with an average concentration of 0.12 ± 0.07 mg/L.

For water used for human consumption, the WHO guidelines suggested a health-based guideline of 0.07 mg/L for molybdenum. Molybdenum analysis showed that the assessed water contained molybdenum in concentrations ranging from 0.036 to 5.12 mg/L, with a mean value of 0.52 ± 1.24 mg/L. Analysis revealed that 12 samples (80%) had molybdenum contents above the WHO recommendation of 0.07 mg/L. Samples from locations S-1 (village Allah Wadhayo Burdi) and S-15 (village Veeram Mahar) had the highest and lowest molybdenum concentrations, respectively.

The Pearson correlation between various water quality parameters such as pH, turbidity, TDS, EC, Cl, TH, Ca²⁺, Mg²⁺, As, and fluoride was determined as shown in Table 4.

In Table 4, many metrics show a substantial trend, including EC and TDS (1.00), EC and Cl (0.91), TDS and Cl (0.91), TDS and TH (0.92), and TH and Cl (0.80). However, a moderate trend has been observed between Ca and TH (0.77) and Mg and TH (0.63).

The GPI and SPI values for each analyzed water sample are presented in Table 5.

Analysis based on the calculations of the GPI (Table 5), 46.67, 40, and 13.33% of groundwater samples were categorized as excellent, good, and poor, respectively. However, based on the SPI, 33.3, 40, 20, and 6.7% of groundwater samples were categorized as suitable, slightly polluted, moderately polluted, and highly polluted, respectively. The correlation between the outcomes of the indices showed a moderate correlation with a coefficient of determination of R² = 0.62.

The analysis results revealed that the pH of the water samples ranged from 7.10 to 7.96, with an average value of 7.44 ± 0.25. While turbidity was observed between 0.81 and 29.40 NTU. TDS was found from 118.0 to 1,034.0 mg/L, with an average of 421.87 ± 214.98 mg/L. EC was detected between 0.184 to 1.61 dS/m, with an average of 0.660 ± 0.340 dS/m. Between 50 and 775 mg/L of chlorides were found in the water samples, with an average value of 193 ± 185.82 mg/L. Ca²⁺ and Mg²⁺ ionic concentrations were found between 48 to 272 mg/L and 17.28 to 97.92 mg/L, respectively, with average values of 139.20 ± 60.96 mg/L and 50.11 ± 21.95 mg/L. TH was found between 120 to 680 mg/L, with an average concentration of 348 ± 152.40 mg/L. The concentration of bicarbonate (⁠⁠) varied between 100 and 400.0 mg/L with a mean content of 254 ± 102.88 mg/L. Fluoride was found between 0.2 to 4 mg/L, with a mean value of 0.73 ± 0.91 mg/L.

Based on heavy metals analysis, it was revealed that the calcium content ranged from 25.1 to 104.61 mg/L, with a mean concentration of 71.06 ± 21.83 mg/L. Magnesium concentrations ranged from 5.76 to 52.56 mg/L, with an average of 29.88 ± 12.30 mg/L. Between 22.88 and 198.21 mg/L of sodium was found, with an average value of 77.49 ± 46.06 mg/L. Between 3.94 and 94.27 mg/L of potassium was detected, with an average concentration of 20.47 ± 26.68 mg/L. With a mean value of 4.51 ± 2 μg/L, arsenic concentrations ranged from 2 to 7 μg/L. The overall results of the physicochemical and heavy metals showed that all parameters, including pH, ⁠, Ca, Na, K, Fe, Mn, Ni, Zn, B, As, Cu, Co, and Cr, were entirely within the prescribed WHO criteria. However, more than the permitted WHO standards were found for turbidity, TDS, EC, Cl⁻, TH, Ca²⁺ (as CaCO₃), Mg²⁺ (as CaCO₃), ⁠, Mg (metal), Mo, Cd, and fluoride in 27, 33, 33, 20, 13, 80, 53, 80, 47, 80, and 6.67% of the samples, respectively.

The GPI model showed that 46.67, 40, and 13.33% of the samples were rated as excellent, good, and poor, respectively. However, based on the SPI, 33.3, 40, 20, and 6.7% of groundwater samples were categorized as suitable, slightly polluted, moderately polluted, and highly polluted, respectively. Also, according to GIS interpolated maps, groundwater in some areas of the U.C. is unsuitable in terms of turbidity, TDS, EC, Cl-, TH, Ca²⁺, Mg²⁺, Na, K, As, and fluoride concentrations; thus, it should frequently be monitored, treated well before its use for domestic purposes.

The authors have not received grants for this manuscript.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.