Study Area

Yanbu Al Nakhal, located in the Medina region of western Saudi Arabia, is of great historical and geographical significance due to its strategic location along ancient trade routes and natural freshwater springs. It is situated at approximately 24°19′32″N latitude and 38°25′30″E longitude; the elevation is between 500 and 1814 m above sea level. Located near the Red Sea, Yanbu Al Nakhal has historically been a vital stopover for merchants, pilgrims, and travelers moving between the Levant, Egypt, and the Arabian Peninsula. The city’s oasis-like environment, created by its abundant springs, has supported human settlement and agricultural practices, particularly the cultivation of date palms.

Yanbu Al Nakhal’s water springs are one of the most prominent natural features of the region. For centuries, these freshwater springs have provided essential resources for local agriculture, making the city an agricultural center, particularly for date cultivation. The springs originate from natural aquifers in the surrounding mountains and valleys, forming streams and ponds that irrigate the fertile lands. Historically, the springs not only supported agriculture but were also a vital water source for travelers and pilgrims on their way to the holy cities of Mecca and Medina. The springs transformed Yanbu al-Nakhal into a green oasis in an otherwise barren area, making it a major settlement for centuries.

Over the past 50 years, the springs of Yanbu al Nakhal have faced complete depletion due to a combination of over-extraction, rapid urbanization, and prolonged droughts [40]. With high population growth and agricultural demand, unsustainable water management practices have placed significant pressure on the region’s natural aquifers, nearly depleting them. However, recent environmental changes have led to a gradual revival of these springs. A major factor has been increased regional rainfall, contributing to the natural replenishment of groundwater sources. Additionally, improved conservation efforts, such as implementing modern irrigation techniques and stricter regulations on water extraction, have played a critical role in restoring the springs. Together, these factors have begun to reverse the decline of this essential resource, offering hope for a sustainable future for Yanbu al Nakhal’s water system.

Water samples were collected from four springs, Ain Ajlan (A), Ain Ali Al-Harbiyah (H), Ain Al-Jabriyah, and Ain Al-Algamiyah (L), as shown in Fig. 1.

Data Collection and Analysis

Water samples from the water springs of Yanbu al Nakhal were collected in October 2023 via a standard water sample collection procedure. Specialized laboratory water sample collection bottles were used. Samples were collected from four different points labeled A, H, J, and L. Sample bottles were rinsed with deionized water thoroughly before use, and all collected samples were kept at 4ºC until use.

Fig. 1.

Study area, Ain Ajlan (A), Ain Ali Al-Harbiyah (H), Ain Al-Jabriyah, and Ain Al-Algamiyah (L), Yanbu Annakhal, Saudi Arabia.

The physicochemical parameters of the collected groundwater samples were analyzed using laboratory standard methods. The parameters analyzed include pH, F⁻,Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻, Na⁺, K⁺, Mg²⁺, Ca²⁺, and TDS (mg/L).

The collected samples were analyzed following standard methods described by the American Public Health Association [41]. TDS and pH were measured in situ using a portable instrument (HANNA, HI98194). Cations and anions were analyzed in the laboratory using an ion chromotrope instrument (Palo Alto, CA, USA, model: 720 ICP-OES Axial).

Physicochemical Parameters

The statistical results for the analysis of the sixteen groups of groundwater samples from four different points (labeled as A, J, H, and L) of the study area are presented in Table 4. The concentrations of the physicochemical parameters pH, TDS, F⁻, Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻, Na⁺, K⁺, Mg²⁺, and Ca²⁺ are in the range of 7.83-8.23, 820-1113, 1.506-1.541, 303.29-518.68, 1.937-3.228, 68.36-79.179, 0.002-0.04, 423.68-578.31, 200.81-292.89, 13.22-8.027, 39.083-54.324, and 155.65-228.95 mg/L, with an average mean of 8.03, 976, 1.524, 410.985, 2.583, 73.77, 0.021, 500.99, 246.85, 10.675, 46.704, and 192.30 mg/L, respectively. Based on the average concentration, Cl⁻ and Na⁺ were the most abundant parameters, exceeding the WHO permissible limits for drinking water quality, followed by NO₃⁻ and Br⁻ ions. All the collected samples from the four collection points (A, J, H, and L) exceeded the permissible limits for Br⁻, NO₃⁻, and Na⁺ concentrations. Moreover, the groundwater TDS of all samples also exceeded the permissible limit of 700 mg/L with a mean average of 976 mg/L. Groundwater pH is an important hydrogeological parameter that indicates its suitability for drinking. According to the WHO drinking water quality standard, a pH of 6.5 to 8.5 is considered safe for potable use. The pH values of the groundwater samples from the study area ranged from 7.83 to 8.23 (Table 4). None of the groundwater samples from the four sampling points show a pH value below or more than the permissible limits. This indicates the absence of possible water pollution containing acidic or basic concentrations within the study area.

The findings of this study align with global concerns regarding groundwater contamination and its implications for drinking and irrigation. For instance, Tegegne et al. (2023) utilized EWQI and SAR indices to evaluate groundwater quality in Ethiopia’s Gunabay watershed and reported medium to poor quality due to agricultural runoff and geogenic factors [5]. Similarly, Rajmohan et al. (2022) employed multivariate statistical analysis to assess heavy metal contamination in the Hada Al-Sham region of Saudi Arabia, highlighting the significant role of salinity and anthropogenic activities [63]. These parallels underscore the global applicability of the EWQI and SAR indices in assessing groundwater quality and their potential in regions such as Yanbu Annakhal, where agricultural practices and natural geochemical factors contribute to elevated contaminant levels. Integrating these indices into the current study provides a robust framework for identifying key contaminants and informing mitigation strategies.

Moreover, this study’s focus on Yanbu Annakhal’s spring water addresses an essential knowledge gap, as research on groundwater quality assessment in this region remains limited. Previous studies, such as those by Pradipta et al. (2024) and El Yousfi et al. (2023), highlight the significance of using the EWQI for evaluating groundwater contamination. Pradipta et al. (2024) utilized multiple datasets to assess groundwater risks in the Arabian Basin of Saudi Arabia, demonstrating the applicability of EWQI in understanding contamination dynamics in arid environments [64]. Similarly, El Yousfi et al. (2023) applied the EWQI to predict and assess groundwater quality in the Ghiss-Nekkor Basin of northeastern Morocco, underscoring its effectiveness in identifying pollution levels in semi-arid regions [65]. These studies reinforce the global relevance of the EWQI as a robust tool for groundwater quality management, providing a strong foundation for its application in the Yanbu Annakhal.

Through the application of these methodologies, the present study not only validates their effectiveness in a new context but also highlights the unique challenges posed by high concentrations of chloride, nitrate, and bromide in Yanbu Annakhal. This research contributes to a growing body of literature emphasizing the need for targeted interventions and advanced monitoring techniques to ensure groundwater sustainability in similar arid environments.

Total Coliform

Total coliform is an important water quality parameter indicating the biological contamination of a water sample, where the acceptable WHO standard requires a total coliform of zero [66, 67]. Therefore, the bacterial count indicating the level of total coliform from groundwater was also evaluated based on their MPN (most probable number), a known statistical analysis used to evaluate the viable numbers of bacteria in a sample [68]. The total coliform count was detected in all four sample stations containing a total of 16 samples, indicating 100% of the total water samples, as summarized in Table 5b). Meanwhile, the MPN description for the majority of the water samples, except the average of samples collected at station H, was highly unsatisfactory, with MPN values of 315, 107, and 93 for stations A, J, and L, respectively. The MPN value of samples from station H can be ranked as suspicious and doubtful for potable and irrigational use due to the mean average MPN value of 7, as displayed in the data from Table 5b). Hence, it can be concluded that the total coliform level detected from the springs of the study area highly exceeds the permissible limit for drinking and irrigation purposes. A probable cause for increased total coliform from this region can be cross-connections with contaminated water sources from animals, human waste, and seasonal openings due to rainfall and agricultural runoff [69]. Meanwhile, a negligible strain of bacterial coliforms can likely cause illness up to serious health complications [70, 71]. However, the groundwater quality still meets the permissible limit for total coliform set by the WHO. As indicated earlier in Table 1, the WHO permissible limit for total coliform does not exceed 500-1500 CFU/mL, a unit equivalent to the MPN value per 100 mL [72]. It has been reported that E. coli contaminated manures and waters used for irrigation and contaminated the field crops, as they can survive for long periods in manure and water [73].

EWQI Assessment for Drinking Water Quality

As presented in Table 2, generally, when EWQI values of water samples are >100, such water is unfit for drinking purposes [74, 75]. To obtain a better understanding of the quality assessment, the EWQI values calculated for the study are presented in Table 6. The evaluated EWQI values ranged from 88.629 to 118.351 (Table 6), averaging 96.76. These results indicate that the groundwater quality of samples collected from Yanbu Annakhal Village, Saudi Arabia, can be considered medium to poor quality (ranking from III-IV), which is not recommended for drinking purposes unless with prior application of appropriate water treatment. The EWQI values indicate that three of the four (75%) groundwater collection points were of medium quality. Groundwater collected at sample points A, J, and H indicated medium quality with an EQWI of 89.280, 88.629, and 90.767, respectively. Meanwhile, the EQWI from station L indicates a poor-quality standard with an EQWI value of 118.351. This interpretation also indicates a groundwater quality ranking of III and IV for A, J, H, and L, respectively. Hence, based on the obtained EQWI, none of the samples can be graded as good (ranking II) or excellent (ranking I). The high EQWI values ranking the medium and poor quality of the groundwater from the study might be due to the high-level concentrations of some chemical ions (particularly Cl⁻, Br⁻, NO₃⁻, and Na⁺ ions) exceeding the permissible limits [76]. High-level bromide and nitrate in groundwater indicate the possible impacts of agricultural activities and seawater intrusion [77]. Bromide assessment is crucial for groundwater quality assessment and has been reported as a tracer to identify possible intrusion of seawater into coastal aquifers. This is because, naturally, groundwater bromide levels lie below 0.1 mg/L unless contaminated due to various factors, including oil field brine and seawater intrusion [78, 79]. On the other hand, a high nitrate concentration indicates the occurrence of organic matter pollution, possibly due to manure and synthetic fertilizer application [80, 81]. General industrial waste materials, fertilizers, and animal husbandries all contain nitrogen compounds that can be soluble in water streams. Continuous agricultural cultivation may potentially lead to high nitrate concentrations in groundwater. Similarly, Menció and his co-workers (2016) researched the hydrochemistry and qualities of Catalonia groundwater samples from Northeastern Spain and observed high nitrate concentrations and positive linear relationships with some ions, indicating the magnitude of the fertilization [82]. Additionally, Rahman et al. (2018) observed a similar scenario in their study investigating nitrate concentration in the groundwater from the central coastal region of Bangladesh. They concluded that nitrate concentration can be elevated from the ground due to the huge amount of nitrate released every year from agricultural and other anthropogenic sources [83]. An increasing number of studies have reported that the potential health implications due to high nitrate intake include increased heart rate, abdominal pains, headaches, and nausea [84]. The average mean nitrate concentration from the study area is 73.8 mg/L, while the permissible limit for nitrate in drinking water, according to the WHO, is ≤50 mg/L. Hence, evaluating the possible contamination source for these ions in the groundwater will be essential to prevent their health implications.

However, it has been proven that one of the greatest importance of chlorination in water is the effective disinfection of microbial contamination due to bacteria and viruses [85-87]. On the other hand, it has been referenced as a trace element that may have either adverse or beneficial effects on humans based on its concentration level from drinking [88]. Possible health implications from chloride salt pollution may include direct effects on human body systems, especially respiratory and cardiovascular systems [89, 90]. The mean average chloride concentration in the study area is about 410.1 mg/L, while the WHO permissible limit is just ≤250 mg/L. Although chloride is a naturally occurring form of ion salt found in both fresh and salt water, its high-level concentration can be due to geogenic and anthropogenic sources. Geogenic sources may include geological formation of the study area, weathering and deposition of salts, etc. [91, 92]. The anthropogenic activities include the infiltration of salty ocean water, de-icing of roads from snow-bearing areas, and wastewater disposal [93]. These usually result from a dissolved form of salts, especially sodium and magnesium chlorides [94].

Correlation Analysis of Physicochemical Parameters

Correlation analysis, such as the Pearson correlation test, is an important statistical tool commonly used to show the degree of linear association between certain variables. Hence, it can be used to indicate the level of relationship between the physicochemical parameters and the quality of groundwater [17, 95]. A range between 1 and -1 interprets the degree of closeness of the chosen variables. The closer the correlation coefficient (r) is to a value of 1, the closer the linear association of the two variables and vice versa [96]. The Pearson correlation analysis of the major ions studied from the study area is displayed in Table 7. Based on the analysis, there is a significant positive interrelation between TDS and the concentration of major ions, particularly F⁻, Cl⁻, Br⁻, NO₃⁻, Na⁺, SO₄^2- K⁺, Mg²⁺, and Ca²⁺ ions. This suggests that the high-level concentrations of these ions significantly contribute to the spatial distribution of TDS. The correlation coefficient shows TDS is positively correlated with Cl⁻, Na⁺, K⁺, Mg²⁺, SO₄²⁻, and Ca²⁺ ions, with a correlation coefficient of 0.996, 0.996, 0.988, 0.989, 0.988, and 0.957, respectively, at confidence levels of 0.01. Furthermore, a strong interrelation also exists between Mg²⁺ and SO₄²⁻ ion concentrations, with a correlation coefficient of 1. In the meantime, these ions constitute the component of major ground mineral evaporates such as mirabilite (Na₂SO₄), halite (NaCl), and gypsum [97]. Hence, their subsequent dissolution may be the reason for the high TDS level and salinity of the groundwater in the study area.

Groundwater Quality Assessment for Irrigation

Assessing groundwater quality for irrigation purposes is another essential procedure that determines the suitability of groundwater for agricultural use. This is because the application of groundwater quality assessment may attempt to minimize possible negative impacts on the irrigation plants and the soil at large. For example, soil content is affected by high sodium concentration, which can eventually lead to low plant productivity. Thus, sodium and magnesium absorption ratios were regarded as a common approach to assess the quality of groundwater suitability for irrigation purposes [98]. The results of the calculated SAR and MAR values for the study area are presented in Table 8.

The analysis found that all the samples from the four stations indicated poor quality based on their SAR value. Their individual SAR values evaluated were 20.392, 20.195, 19.497, and 24.610 epm for the A, J, H, and L stations, respectively. This result shows the unsuitability of the groundwater quality for irrigational purposes. On the other hand, the MAR evaluation result also shows 20.270, 19.169, 18.987, and 19.177 epm for the A, J, H, and L stations, respectively. Here, all the samples indicate a permissible limit for irrigation based on their individual and mean value of <25 epm. Therefore, this study found that the groundwater quality of Yanbu Annakhal collected at stations A, J, and H was of medium quality for both drinking purposes with reference to their EWQI assessment. Meanwhile, groundwater from station L is of poor quality and unsuitable for drinking purposes due to its high EWQI. The general quality assessment based on the SAR and MAR evaluation shows that the groundwater from the study area is unsuitable for irrigation due to its high concentration of sodium ions. High sodium concentration and potential salinity hazards may restrict proper plant growth because of reduced soil permeability and water circulation [99-101].

Spatial Analysis of Groundwater Physicochemical Parameters

Fig. 2(a-i) present the spatial contour map distributions of the physicochemical parameters (pH, TDS, F⁻, Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻, Na⁺, K⁺, Mg²⁺, and Ca²⁺) based on their concentrations from the study area. The proof of contour maps shown in these figures shows an excellent relationship between the observed and estimated data according to the correlation coefficient (R), which ranged from 0.88 to 0.99 from the Pearson correlation analysis. The pH values tend to look spatially heterogeneous and increase towards the northern part, while most other parameters increasing towards the western part of the region indicate pinker to reddish contour coloration. Station J in the top north and L in the northeast have indicated excellent pH (neutral) and alkaline water quality at stations A and H (pH values ranging from 8.12 to 8.23). The southwestern portion of Yanbu Annakhal is typically dense with a high concentration of F⁻, Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻, Na⁺, K⁺, Mg²⁺, and Ca²⁺. In contrast, NO₃⁻ and PO₄³⁻ have a different geographical distribution pattern where low concentrations of the NO₃⁻ and PO₄³⁻ have been observed towards this region, indicating light to dark greenish colorations. In fact, a greater portion of the study area, indicating stations A, H, and J, have shown greener coloration for most of the parameters, indicating their low concentrations except for F⁻, NO₃⁻, and PO₄³⁻. Hence, it is obvious that these areas might have groundwater contamination on the concentration of these parameters due to geochemical properties or anthropogenic activities. Furthermore, the decrease in the concentration of these ions demonstrates that the groundwater stream possibly flows towards the west. In general, poor groundwater quality is emerging in station L upstream of Yanbu Annakhal Springs to the west in the study area due to its high concentrations of the physicochemical parameters. Long-term consumption of contaminated groundwater containing high concentrations of physicochemical water parameters beyond acceptable might impact human health, leading to various tissue and organ disorders. Therefore, appropriate assessment and pre-treatment of polluted groundwater are necessary before residents use it for drinking and/or irrigation purposes.

Limitations of the Study

Due to funding limitations and access to advanced laboratory facilities, the study has not included research on assessing trace elements, particularly heavy metals, which have a significant public health impact. Similarly, no assessment study on the boron concentration for irrigational purposes has been reported. Nevertheless, the most significant WHO physicochemical parameters required for assessing groundwater quality for drinking and irrigation have been appropriately considered under standard guidelines. Further research may focus on assessing the potential trace elements from the groundwater of the study area to determine its complete suitability for both human drinking and agricultural use.

Fig. 2.

Spatial contour map distribution of physicochemical parameters of the study area. a) pH, b) TDS (mg/L), c) Fluoride (F⁻), d) Chloride (Cl⁻), e) Bromide (Br⁻), f) Nitrate (NO₃⁻), g) Phosphate (PO₄³⁻), h) Sulfate (SO₄²⁻), i) Sodium (Na⁺), j) Potassium (K⁺), k) Magnesium (Mg²⁺), l) Calcium (Ca²⁺).