Assessment of Water Quality of Key Dams in Jordan for Irrigation Purposes with Insights on Parameter Thresholds

Abstract

Dams play a vital role as a primary water supply for irrigation in Jordan, necessitating an assessment of their water quality. This study aimed to evaluate the suitability of irrigation water in a key number of Jordanian dams, namely Al Kafrain, Al Waala, King Talal (KTD), Mujib, Shuaib, and Sharhabil. Monthly readings of major water parameters (EC, Cl⁻, SO₄²⁻, HCO₃⁻, Na⁺, Ca²⁺, and Mg²⁺) were recorded for seven years (2015–2021) for each dam. The assessment criteria included the sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium adsorption ratio (MAR), kelley ratio (KR), total hardness (TH), and water quality index (WQI) using both average (APL) and maximum permissible limits (MPL). Additionally, USSL, Wilcox, Doneen, Piper, and Gibbs diagrams were applied. The findings indicate that all the dams demonstrated suitability for irrigation based on the SAR, SSP, RSC, MAR, and KR values. The USSL diagrams showed most samples falling under C2S1 and C3S1, except KTD, which fell under C3S2. According to the Wilcox diagram, the water was either Excellent to Good or Good to Permissible, while the KTD water was classified as Permissible to Doubtful. Furthermore, the water chemistry was found to be mainly influenced by rock weathering, as revealed in the Gibbs diagram, and has no restriction on permeability, according to the Doneen diagram. The WQI showed that all the dams fall in the Good and Excellent category for irrigation using APL, while applying MPL, all the dams were in the Excellent category, which demonstrates the necessity of considering extreme events and regulatory thresholds.

1. Introduction

Jordan is regarded as one of the most water-scarce countries in the world. The total annual water share is estimated to be less than 100 m³ per capita [1,2]. The quantity of renewable water resources accessible in Jordan per capita has fallen over time, from 1000 m³ in 1960 to 500 m³ in 1975 and less than 100 m³ in 2018 (the global threshold of absolute water scarcity is 500 m³) [3]. Furthermore, Jordan faces several challenges in meeting the rising demand for water resources necessary for household, industrial, and agricultural purposes.

The rapid growth in population, the abuse of water resources, the extensive use of pesticides and fertilizers in agriculture, and the discharge of residential and industrial waste have led to changes in the chemical, physical, and biological aspects of surface water. As a result, the quality of water resources has gradually worsened over time [3].

People rely on surface water, which comprises rivers, lakes, dams, and wells, to meet their water demands [4]. Dams are regarded as one of the major water sources in arid and semiarid regions, including Jordan. These dams were built to be used for different purposes such as recharge wells, electricity generation, industry uses, collecting water from streams, and irrigation [5]. However, the quality of water stored in these dams can be influenced by various factors, such as inflow sources, the geochemistry and geomorphology of the areas that surround the dams, climate changes, as well as any human activities in the vicinity of the dams [6].

The issues generated by poor water quality differ based on the contaminants and accompanying dangers. The suitability of surface water (e.g., dams) for irrigation purposes is determined by its physical, chemical, and biological characteristics, which can have substantial impacts on the growth and health of crops. For example, salinity can lead to soil salinization, which can lower crop yields by limiting the water supply to the roots [7]. Alkalinity, on the other hand, can influence soil pH, thus impeding nutrient uptake by crops and hence diminishing crop yield [8]. Elevated levels of suspended solids in irrigation water can block irrigation systems and hinder crop growth. Nutrient content, including nitrogen, phosphorus, and potassium, is another important factor that can influence crop growth and production. Finally, heavy metals, and organic compounds, can have a significant impact on crop quality and safety [9].

The water quality index (WQI) is the most widely used to assess water quality for irrigation purposes and is a tool used to evaluate the quality of surface water or groundwater based on various physicochemical, biological, and other parameters. The index provides a single value that reflects the overall water quality (based on a rating scale), which can be used to make informed decisions about water management and protection [10].

To ensure that irrigation water meets the necessary quality standards for optimal crop productivity, water quality testing is required. Therefore, the primary objective of this study is to evaluate the water quality of six dams, namely Al Kafrain, Al Waala, King Talal (KTD), Mujib, Sharhabil bin Hasna (Ziqlab) and Shuaib, to determine their suitability for irrigation purposes using the water quality index (WQI). This study introduces a novel approach by calculating a version of the WQI that incorporates both the average and maximum permissible limits of key parameters. While existing methodologies often rely solely on average values to assess water quality, our approach recognizes the importance of considering extreme events and regulatory thresholds.

2. Materials and Methods

2.1. Study Area

The aim of this study is to evaluate the suitability of water quality for irrigation purposes in six selected dams (Al Kafrain, Al Waala, KTD, Mujib, Shuaib, and Sharhabil) across the middle and northern parts of Jordan (Figure 1). Al-Kafrain Dam, situated about 35 km west of Amman, stands at 37 m tall and boasts a storage capacity of 8.5 million cubic meters, and is primarily fed by perennial springs and local side valleys. Al-Waala Dam, located approximately 40 km south of Amman, is characterized by its 52 m height and 9.3 million cubic meters storage capacity, with water utilized for supplementary irrigation and groundwater replenishment. KTD, positioned 70 km north of Amman on the Zarqa River, rises to 108 m high, storing up to 75 million cubic meters of water and serving irrigation needs in the central and southern Jordan Valley. Mujib Dam, situated 80 km south of Amman on Wadi Mujib, reaches a height of 62 m and has a storage capacity of 29.8 million cubic meters, benefiting areas like Amman and tourist resorts along the Dead Sea. Ziqlab Dam, also known as Sharhabil Bin Hasna Dam, is located 85 km north of Amman on Wadi Ziqlab, has a storage capacity of 4 million cubic meters and serves irrigation purposes in the northern Jordan Valley. Finally, Shuaib Dam, positioned about 45 km west of Amman on Wadi Shuaib, stands at 32 m high and has a storage capacity of 1.4 million cubic meters, facilitating irrigation for the Shuna region and groundwater recharge. These dams play crucial roles in water resource management and agricultural sustainability across Jordan’s diverse landscapes.

2.2. Sample Collection and Chemical Analysis

Over a span of seven years (2015–2021), a comprehensive dataset was built comprising 415 monthly readings of all dams (on average 96 per dam). For each monthly reading, 15 key water quality parameters (EC, pH, B, PO₄-P, NO₃-N, NH₄-N, TDS, Cl⁻, SO₄²⁻, HCO₃⁻, CO₃²⁻, Na⁺, Ca²⁺, and Mg²⁺) were collected and analyzed. Additionally, eight indices (SAR, SAR-adj, RSC, PI, KR, MAR, and TH) and five diagrams (USSL, Wilcox, Doneen, Piper, and Gibbs) were also generated using Grapher (Golden software, LLC, Golden, CO, USA) and Python to further characterize the water quality and its suitability for irrigation purposes. A total of 44,500 data points were used in this study.

2.3. Irrigation Water Quality Evaluation

The irrigation water quality was evaluated using several indices, which were determined using the following equations:

$$\mathrm{SAR}=\frac{{\mathrm{Na}}^{+}}{\sqrt{\frac{\left({\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}\right)}{2}}}$$

(1)

$$\mathrm{SSP}=\frac{{\mathrm{Na}}^{+}+{\mathrm{K}}^{+}}{{\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}+{\mathrm{Na}}^{+}+{\mathrm{K}}^{+}}\times 100$$

(2)

$$\mathrm{RSC}={(\mathrm{HCO}}_3^{-}+{\mathrm{CO}}_3^{2-})-\left({\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}\right)$$

(3)

$$\mathrm{MAR}=\frac{{\mathrm{Mg}}^{2+}}{{\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}}\times 100$$

(4)

$$\mathrm{KR}=\frac{{\mathrm{Na}}^{+}}{{\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+}}$$

(5)

$$\mathrm{PI}=\frac{{\mathrm{Na}}^{+}+\sqrt{{\mathrm{HCO}}_3^{-}}}{{\mathrm{Na}}^{+}+{\mathrm{Mg}}^{2+}+{\mathrm{Ca}}^{2+}}\times 100$$

(6)

$$\mathrm{TH}=2.5\times \mathrm{Ca}+4.12\times \mathrm{Mg}$$

(7)

$$\mathrm{Adj}. \mathrm{SAR}=\frac{{\mathrm{Na}}^{+}}{\sqrt{\frac{\left({\mathrm{Ca}}_{\mathrm{x}}^{2+}+{\mathrm{Mg}}^{2+}\right)}{2}}}$$

(8)

SAR is the sodium adsorption ratio, and the remaining indices include the soluble sodium percentage (SSP), residual sodium carbonates (RSC), magnesium adsorption ratio (MAR), Kelley ratio (KR), permeability index (PI), total hardness (TH) and adjusted SAR (Adj. SAR). These indices reflect the water suitability for irrigation purposes (

Table 1. Classes of water quality indices.

Parameters	Range	Water Class	Reference
SAR	<10	Excellent	[11]
	10–18	Good
	18–26	Doubtful
	>26	Unsuitable
SSP	<20	Excellent	[12]
	20–40	Good
	40–60	Permissible
	60–80	Doubtful
	>80	Unfit
RSC	<1.25	Good	[13]
	1.25–2.5	Doubtful
	>2.5	Unfit
PI	>75	Class-I	[14]
	25–75	Class-II
	<25	Class-III
KR	<1	Suitable	[15]
	>1	Unsuitable
MAR	<50	Suitable	[16]
	>50	Unsuitable
TH	0–75	Soft	[17]
	75–150	Moderately Hard
	150–300	Hard
	>300	Very Hard

). While TH is in mg/L, all the other index concentrations are expressed in milli-equivalents per liter (meq/L).

The categorization of water for irrigation purposes are presented using the US Salinity Laboratory (USSL), Wilcox, Doneen, Piper, and Gibbs diagrams. These diagrams provide a visual representation of the data to analyze and assess the water quality data in terms of the appropriateness for irrigation and can be further used for decision making and irrigation practices. The USSL and Wilcox diagrams categorize irrigation water quality based on the relationship between SAR and EC, providing insights into salinity and sodicity levels for irrigation suitability and determining the potential soil degradation and crop tolerance to irrigation water. The Doneen diagram evaluates water suitability for irrigation by considering SAR and the PI, offering guidance on potential soil infiltration and drainage issues associated with water quality. Finally, the Piper diagram is used to analyze the chemical composition of water by plotting the concentrations of major ions to identify dominant water types and to understand the geochemical processes influencing water quality.

2.4. Water Quality Index (WQI)

The WQI was calculated to assess the suitability of water quality of the studied dams for irrigation purposes. The WQI was calculated based on the following six water quality parameters: pH, Electrical conductivity (EC), Sodium (Na⁺), Bicarbonate (HCO₃⁻), Chloride (Cl⁻), and SAR. These parameters have been assigned based on their importance to irrigation water.

In the first step, each one of these six parameters was ranked from the most to least important parameter for irrigation purposes. EC was assigned as the most important and pH the least important parameter for irrigation purposes. In the second step, the sub-index (si) of each parameter was calculated to convert the parameter concentrations into unitless values, known as the parameter sub-index (si), using Equation (9):

$$\mathrm{Sub}-\mathrm{Index} \left(si\right)=\frac{{\mathrm{P}}_{\mathrm{c}}}{{\mathrm{M}}_{\mathrm{pl}}}\times 100$$

(9)

where ${\mathrm{P}}_{\mathrm{c}}$ is the measured value obtained by laboratory measurement, and ${\mathrm{M}}_{\mathrm{pl}}$ is the maximum permissible guideline limit of the water quality parameter proposed by the Jordanian Standard for irrigation.

Table 2. Guidelines of water quality for irrigation purposes [18].

Quality Parameter	Degree of Restriction
	Slight	Slight to Moderate	Severe
Electrical conductivity (EC)	<1.7	1.7–3.0	>3.0
Sodium Adsorption Ratio (SAR)	<3	3–9	>9
Bicarbonate (HCO3−)	<90	90–520	>520
Sodium (Na+)	<69	69–207	>207
Chloride (Cl−)	<142	142–355	>355
pH	Normal Range 6–9

shows the guidelines of water quality for irrigation purposes.

In the third step, the weight of each parameter was calculated. One way to calculate the relative weight of each parameter is through the Rank Order Centroid (ROC) weights method. The ROC provides a simple and efficient approach to weight assignment. The ROC technique is a relatively uncomplicated manner of giving weights to a list of items that have been ranked by taking the ranks as input and turning them into weights. The ROC weights of a set of N variables, ranked from i = 1 to N, were calculated using Equation (10) [19]:

$$w_i=\frac{1}{N} {\displaystyle \sum }_{i=1}^N\frac{1}{i}$$

(10)

Then, the water quality index (WQI) was calculated using Equation (11):

$$\mathrm{WQI} ={\displaystyle \sum }_{i=1}^n{s}_i\times w_i$$

(11)

where ${\mathrm{s}}_{\mathrm{i}}$ represents the sub-index of the ith parameter, n is the number of parameters and $w_i$ refers to the weight based on the rank of the ith parameter.

Table 3. Ranks and weight values of water quality parameters.

Parameter	Rank	Weight
EC	1	0.41
SAR	2	0.24
HCO3−	3	0.16
Na+	4	0.10
Cl−	5	0.06
pH	6	0.03
Sum of weights		1.0

summarizes the weights (${\mathrm{w}}_{\mathrm{i}}$) of the water parameters for the studied dams in Jordan.

Then the WQI scores of the water samples were classified into five categories, as shown in (

Table 4. Ranks and weight values of water quality parameters.

WQI Index Value	Water Quality Category
0–50	Excellent
50–100	Good
100–200	Poor
200–300	Very Poor
>300	Not Suitable for Irrigation

).

3. Results

3.1. Physicochemical Characterization and Irrigation Quality Indices of Water Samples

Notable variations were observed in the EC and SAR values of all the dams (

Table 5. Average ± standard deviation of major studied parameters and calculated indices of all dams.

	Al Kafrain	Al Waala	KTD	Mujib	Sharhabil	Shuaib
EC	0.95 ± 0.15	0.39 ± 0.1	1.87 ± 0.19	0.76 ± 0.32	0.81 ± 0.09	1.1 ± 0.24
Cl−	147.75 ± 38.59	33.76 ± 15.47	309.56 ± 43.34	83.75 ± 52.59	79.64 ± 21.14	146.37 ± 45.27
SO42−	124.98 ± 86.02	17.13 ± 20.94	216.22 ± 57.7	106.85 ± 77.87	62.83 ± 81.64	113.8 ± 99.23
HCO3−	140.04 ± 51.66	137.33 ± 44.8	271.75 ± 40.25	165.6 ± 46.05	272.61 ± 51.97	227.64 ± 52.9
Na+	87.31 ± 23.86	32.57 ± 11.48	230.44 ± 33.57	64.69 ± 32.39	45.36 ± 15.31	87.94 ± 28.13
Ca2+	44.24 ± 17.75	32.14 ± 9.96	90.6 ± 11.6	55.34 ± 23.11	53.05 ± 15.6	70.8 ± 15.15
Mg2+	38.31 ± 12.76	8.71 ± 11.03	39.54 ± 17.77	23.11 ± 15.28	43.07 ± 12.17	40.2 ± 18.65
SAR	2.37 ± 0.74	1.33 ± 0.35	5.15 ± 0.9	1.83 ± 0.5	1.14 ± 0.45	2.1 ± 0.67
SSP	42.8 ± 9.03	41.43 ± 7.04	58.15 ± 5.65	39.47 ± 6.02	25.22 ± 6.74	37.54 ± 8.27
RSC	−2.97 ± 0.99	−0.04 ± 0.8	−3.43 ± 1.93	−1.94 ± 1.64	−1.7 ± 1.01	−3.04 ± 1.63
PI	57.84 ± 8.38	80.84 ± 13.45	67.73 ± 6.94	61.7 ± 9.82	50.38 ± 6.94	54.71 ± 8.97
KR	0.75 ± 0.29	0.65 ± 0.18	1.33 ± 0.32	0.62 ± 0.17	0.34 ± 0.18	0.59 ± 0.22
MAR	58.75 ± 13.92	26.5 ± 17.86	40.37 ± 10.31	38.79 ± 13.67	57.17 ± 11.19	46.28 ± 12.42
TH	268.42 ± 56.59	116.22 ± 51.04	389.39 ± 76.88	233.58 ± 96.94	310.08 ± 54.63	342.65 ± 92.38

). The average EC values ranged from 0.39 to 1.87 dS/m, with Al-Waala exhibiting the lowest and KTD the highest.

The standard deviations indicated moderate to high variability within these averages, underscoring the diverse water compositions among the studied dams. Similarly, the SAR values fluctuated between 1.14 and 5.15, showing substantial differences in sodicity levels. KTD recorded the maximum SAR, reflecting potentially higher sodium concentrations, while Al-Waala displayed the minimum. Furthermore, the highest Cl⁻, SO₄²⁻, HCO₃⁻, Na⁺, Ca²⁺, and Mg²⁺ concentrations (mg/L) were found in KTD, while the lowest values were in Al Waala Dam.

Analysis of the water quality indices including SSP, RSC, PI, KR, MAR, and TH, further showed the diverse characteristics of water samples in each dam (Table 4). The SSP values ranged from 25.2 to 58.1%, with Mujib having the lowest (avg. 39.4 ± sd 6.0) and KTD the highest value (58.2 ± 5.65). The RSC values fluctuated between −3.43 and −0.04 meq/L, with Mujib exhibiting the most negative value (−1.94 ± 1.64) and Al Waala the closest to neutral (−0.04 ± 0.8), reflecting differences in alkalinity levels. Similarly, the PI values varied between 50.4 and 80.8, with Mujib displaying the lowest (61.7 ± 9.82) and Al Waala the highest value (80.8 ± 13.5). KR ranged from 0.34 to 1.33, with Al Kafrain showing the lowest (0.8 ± 0.3) and KTD the highest ratio (1.3 ± 0.3). The MAR values fluctuated between 26.5 and 58.7, reflecting differences in magnesium levels among the dams, and the TH values ranged from 116.2 to 389.4 mg/L, with Al Waala exhibiting the lowest (116.2 ± 51.0) and Sharhabil the highest (310.1 ± 54.6) value (Table 5).

The abundance of major ions in the studied dams is shown in the box-whisker plot in Figure 2. The abundance order was as follows: Cl⁻ > Na⁺ > Mg²⁺ > SO₄²⁻ > HCO₃⁻ > Ca²⁺ for Al Kafrain (Figure 2A), HCO₃⁻ > Ca²⁺ > Na⁺ > Cl⁻ > Mg²⁺ > SO₄²⁻ for Al Waala (Figure 2B), Na⁺ > Cl⁻ > Ca²⁺ > SO₄²⁻ > HCO₃⁻ > Mg²⁺ for KTD (Figure 2C), Na⁺ > Ca²⁺ > HCO₃⁻ > Cl⁻ > SO₄² > Mg²⁺ for Mujib (Figure 2D), HCO₃⁻ > Mg²⁺ > Ca²⁺ > Cl⁻ > Na⁺ > SO₄²⁻ for Sharhabil (Figure 2E), and Cl⁻ > Na⁺ > HCO₃⁻ > Ca²⁺ > Mg²⁺ > SO₄²⁻ for Shuaib Dam (Figure 2F). Descriptive statistics for each dam are shown in Tables S1–S6, in the Supplementary Materials.

The quality of irrigation water was also assessed using USSL, Wilcox, Doneen, and Piper diagrams. The USSL diagram (Figure 3) shows that 90.6% of EC values were between 0.75 and 1.3 μS/cm, and 100% of SAR < 5 for Al Kafrain; while 94% were between 0.25 and 0.75 μS/cm and 100% of SAR < 3 for Al Waala. For KTD, 100% were between 1.4 and 2.25 μS/cm (32% > 2 μS/cm), 50% of SAR < 5 and 50% of SAR < 7.2; for Mujib, 62% were between 0.25 and 0.75 μS/cm, 37% between 0.75 and 2.25 μS/cm and 97% of SAR < 3; for Sharhabil, 26% were in the range 0.25–0.75 μS/cm, 74% were between 0.75 and 1.1 μS/cm, and 97% of SAR < 3; and for Shuaib Dam, 9% were in the range 0.25–0.75 μS/cm, 91% were between 0.75 and 1.6 μS/cm and 91% SAR < 3 (99% < 4).

The Wilcox diagram (Figure 4) shows that 84% of Al Kafrain water samples lie between an EC of 0.76 and 1.3 mS/cm and have an SSP of 16.3–60.9% (Good to Permissible). For the other dams, the data were as follows: Al Waala, 100% 0.18–0.78 mS/cm and SSP 19.5–54.1% (Excellent); KTD, 66% 1.43–2.21 mS/cm and SSP 44.6–68.9% (Permissible to Doubtful); Mujib, 62% 0.43–0.75 mS/cm and SSP 20–56% (Excellent to Good), 36.4% 0.75–1.1 mS/cm (Good to Permissible) and SSP 25–45%; Sharhabil, 74% 0.75–0.97 mS/cm and 28.2–31.7% (Good to Permissible); and Shuaib, 91.0% 0.75–1.58 mS/cm and SSP 22–55% (Good to Permissible).

According to the Doneen diagram (Figure 5), 95.3% of water lies between 15 and 31.5 meq/L and 36.1 and 70% PI (Class I). In addition, (4.5, 100, 63.6, 96.9, and 95.5%) of water samples fall under class 1 for Al Kafrain, Al Waala, KTD, Mujib, Sharhabil, and Shuaib dams, respectively.

A Piper diagram was created for each dam to display the chemistry of the water samples. Al Kafrain Dam (Figure 6A) exhibits mixed type, primarily mixed anion and cation (66.1 and 71%). For Al Waala (Ca-HCO₃) (Figure 6B), bicarbonate dominates the anions (90.8%), while the cations are mostly mixed type (58.5%). KTD (Figure 6C) shows a predominance (92.1%) of sodium, whereas 55.0% of the anions were mixed and 44.94% chloride type. Mujib Dam (Figure 6D) displays mixed types of cations and anions (92.59 and 83.4%, respectively). Sharhabil (Figure 6E) shows bicarbonate (81.25%) and mixed types of cations (67.19%), while Shuaib (Figure 6F) shows mixed type of cations (87.7%) and anions (81.54%).

3.2. Water Quality Index (WQI)

The WQI was determined for all dams and is presented in Figure 7, Figure 8, Figure 9 and Figure 10. Figure 7 and Figure 8 show the average WQI values of all years using APL (Figure 7) and MPL (Figure 8). The two approaches were implemented to determine which one provides greater flexibility in accommodating a wider range of water quality.

The evaluation of the WQI for the studied dams over a span of 7 years, utilizing both APL (Figure 7) and MPL (Figure 8), revealed intriguing insights. Initially, based on the APL, Al Waala, Mujib, and Sharhabil dams consistently demonstrated exceptional water quality, with all WQI measurements falling within the Excellent category throughout the study period. Al Kafrain, Mujib, and Shuaib also showed commendable results, with 69.64%, 97.96% and 37.29% of their respective WQI data classified as Excellent. However, KTD presented a mix of classifications, with 70.45% in the Good category and the remaining 29.55% in the Poor category.

However, when using MPL, all the dams, except KTD, maintained an Excellent water quality classification. Interestingly, there was a significant improvement in KTD’s water quality status, transitioning from 70.45% in the Good category and 29.55% in the Poor category to a remarkable 100% in the Good Quality category.

Figure 9 and Figure 10 show that Shuaib and KTD had the most notable changes in WQI when using APL compared to MPL. For example, using APL, Shuaib Dam shows Excellent category percentages as follows: 2015 (50%), 2016 (33.33%), 2017 (25%), 2018 (25%), 2019 (50%), and 2020 (100%). In contrast, employing MPL, the percentages, categorized as Excellent for Irrigation, were as follows: 2015 (100%), 2016 (100%), 2017 (75%), 2018 (100%), 2019 (100%), and 2020 (100%). For KTD, using APL, the Good category percentages across the years were as follows: 2015 (92.31%), 2016 (94.44%), 2017 (62.5%), 2018 (45.83%), 2019 (71.43%), 2020 (100%), and 2021 (25%). However, using MPL, the percentages of samples classified as Good for Irrigation were as follows: 2015 (100%), 2016 (100%), 2017 (93.75%), 2018 (95.83%), 2019 (100%), 2020 (100%), and 2021 (100%).

The range and averages of the WQI values using APL are depicted in Figure 7. For Al Kafrain Dam, the values ranged from 30.46 to 62.35% (average 46.76%); for Al Waala, the range was 14.23–38.30% (25.60%); for KTD, 37.54–114.07% (93.50%); for Mujib, 27.72–99.56% (39.07%); for Sharhabil, 30.27–60.92% (41.16%), and 31.77–74.34% (52.72%) for Shuaib Dam. Using MPL (Figure 8), the WQI ranges and average values (in brackets) were as follows: 21.86–44.22% (33.19%) for Al Kafrain, 10.29–26.65% (17.82%) for Al Waala, 29.56–79.85% (65.82%) for KTD, 19.37–70.60% (27.47%) for Mujib, 21.12–42.82% (28.51%) for Sharhabil, and 22.32–52.32% (37.08%) for Shuaib Dam.

Table 6. WQI scores, water quality categories, and percentage of water samples for studied dams using average permissible limit (APL).

WQI Score	Water Quality Category	Al Kafrain	Al Waala	KTD	Mujib	Sharhabil	Shuaib
0–50	Excellent	69.64	100	–	97.96	100	37.29
50–100	Good	30.36	–	70.45	2.04	–	62.71
100–200	Poor	–	–	29.55	–	–	–
200–300	Very Poor	–	–	–	–	–	–
>300	Not Suitable	–	–	–	–	–	–

and

Table 7. WQI scores, water quality categories, and percentage of water samples for studied dams using maximum permissible limit (MPL).

WQI Score	Water Quality Category	Al Kafrain	Al Waala	KTD	Mujib	Sharhabil	Shuaib
0–50	Excellent	100	100	–	100	100	100
50–100	Good	–	–	100	–	–	–
100–200	Poor	–	–	–	–	–	–
200–300	Very Poor	–	–	–	–	–	–
>300	Not Suitable	–	–	–	–	–	–

show the WQI scores, water quality categories, and percentage of water samples for the studied dams using APL and MPL, respectively.

4. Discussion

The Jordanian guidelines of water quality for irrigation purposes [18] are adopted from the FAO guidelines [20]. According to the FAO guidelines (restriction on use), water with EC in dS/m or (TDS in mg/L) values of <0.7 (450), 0.7–3.0 (450–2000), and >3.0 (>2000) has no problem (none), Slight to Moderate problems, and Severe problems, respectively. However, these guidelines should also be linked to the SAR of irrigation water. For example, for irrigation water with an SAR ranging from 0 to 3, the EC values should be >0.7, 0.2–0.7, and <0.2 dS/m, while for water with an SAR range of 3–6, the EC values should be <1.2, 0.3–1.3, and <0.3 dS/m and are categorized as no problem, Slight to Moderate problems, and Severe problems, respectively [20,21,22]. According to the FAO guidelines, all the water samples of Al Kafrain and KTD would have no restriction on use, Al Waala (Slight to Moderate), Mujib (50% None and 50% Slight to Moderate), Sharhabil, and Shuaib (96% none).

According to the USSL diagram, water with SAR < 10 indicates suitability for most crops (Excellent Quality), except those sensitive to sodium, whereas water with SAR 10–18 (Good Quality) indicates suitability for course textured soils with good permeability [11,23]. Classifications of irrigation water based on the USSL diagram are provided in Table S7, Supplementary Materials. Therefore, for Al Kafrain, Sharhabil and Shuaib, 90.6, 72.7 and 92.7% of water samples, respectively, fall under the C3S1 category (high salinity, low sodium hazard). Additionally, 93.8, 61.8, and 27.3% of Al Waala, Mujib, and Sharhabil samples, respectively, are categorized as C2S1 (medium salinity, low sodium hazard). In the case of KTD, 75.3% of water samples fall under the C3S2 (high salinity, medium sodium hazard).

It is apparent that most of the water samples from the studied dams have high salinity and low sodium risks. Long-term irrigation with such water can lead to salt accumulation in the soil, potentially harming both soil health and crop production. Effective management strategies are, therefore, necessary to mitigate these risks.

Furthermore, management of irrigated soils is particularly important in arid regions such as Jordan, where water scarcity poses a significant threat to the agricultural sector [20,24]. Agricultural practices should include one or more of the following options: (1) determination of the leaching fraction under different soil salinity and crop selection, (2) use of soil amendments to mitigate elevated levels of soil sodicity, (3) selection of crops that tolerate soil and irrigation water salinity, (4) applying different cropping schemes (adjustments in planting procedures and placement of seeds) that reduce the exposure to higher soil salinity levels, (5) alternating between continuous and intermittent irrigation, and (6) mixing or blending of different qualities of irrigation water.

The suitability of water for irrigation use can also be interpreted using the Piper diagram. Water with high levels of sodium and chloride can be detrimental to certain crops, whereas calcium and bicarbonate rich water is often more favorable.

The geochemical classification of water (Piper diagram) shows the major cation and anion compositions of the studied dams (Figure 6). It is clear that the predominant water types according to the cation and anion composition varied among these dams. Al Kafrain mainly shows mixed and sodium-type cations, and mixed and chloride-type anions (mixed and NaCl-type), suggesting that the water is influenced by a variety of sources and processes, possibly including the dissolution of minerals containing sodium and chloride, such as halite. The presence of mixed cations indicates a combination of different mineral inputs, making the water chemistry relatively complex. Al Waala shows mixed cations and calcium type, as well as bicarbonates dominance (Ca-HCO₃ type). This indicates that Al Waala water is likely to be influenced by the weathering of carbonate rocks, such as limestone and dolomite, that release calcium and bicarbonate ions into the water. The presence of bicarbonates suggests that the water has undergone significant interaction with carbonate minerals, which is typical in areas with extensive limestone geology [25].

KTD shows sodium, mixed anion and chloride-type anions (Na-Cl type). This points to the influence of evaporite minerals like halite or the presence of saline water sources. The dominance of sodium and chloride ions suggests limited contributions from other cations and anions, indicating a more straightforward geochemical pathway, likely influenced by the dissolution of sodium chloride minerals [6,26]. This dam also receives both runoff water from surrounding areas and treated wastewater (TWW) from Kherbit As-Samra wastewater treatment plant. Therefore, KTD is a mix of both types of waters (diluted water). In general, TWW often contains higher levels of salinity and sodicity, reflecting the influence of mixing runoff with TWW [27,28]. In addition, this water has elevated levels of cations and anions in addition to other calculated water indices (Table 5 and Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6).

Mujib and Shuaib show mixed cations and anions (mixed type), reflecting a diverse range of geological sources contributing to the water chemistry. The mixed nature suggests that the water receives inputs from various mineral dissolution processes, including silicate and carbonate weathering, which introduce a variety of cations and anions. This complexity often points to heterogeneous geological formations in the catchment area [29].

Finally, water from Sharhabil Dam is dominated by magnesium and mixed cations, and bicarbonate and mixed anions (Ca-HCO₃ and mixed type). The presence of magnesium alongside calcium indicates that the water interacts with both carbonate and silicate minerals. The dominance of bicarbonates suggests significant weathering of carbonate rocks, but the mixed-cation type also points to contributions from other mineral sources [30].

To further support the above findings, a Gibbs diagram was used to show the main processes controlling the water chemistry (Figure S1, Supplementary Materials). The results indicate that water samples from all dams fall within the rock (weathering) dominance zone. This suggests that rock weathering or interactions with rocks are the major sources controlling the chemistry of water in all the studied dams. The water samples from KTD exhibited an inclination towards the evaporation-dominant zone, suggesting an increase in sodium and chloride ions, leading to higher total dissolved solids as a result of water contamination [31]. Therefore, surface water chemistry is influenced by geological conditions and chemical weathering of various rocks [32,33]. In addition, the classification of irrigation water and the respective percentages based on other indices are shown in Table S8 (Supplementary Materials).

Furthermore, the relation between EC and SAR underscores the necessity of understanding and managing water quality parameters within the permissible limits, with attention to both average trends and extremes, to ensure the sustainability of irrigation practices across Jordan’s agricultural landscapes. The results also underscore the need for comprehensive water quality assessments for sustainable irrigation practices across the sampled dams.

The WQI results underscore the varied water quality profiles, highlighting the importance of ongoing monitoring and targeted interventions to maintain and improve water quality in these vital reservoirs. Furthermore, such findings emphasize the impact of adopting different permissible limits in the assessment of water quality, indicating areas where improvements are necessary to meet stringent standards, particularly in KTD, where notable enhancements have been achieved.

The assessment of WQI for each year of all dams yielded consistent outcomes when both APL and MPL were applied. Notably, across the years, similar trends emerged with similar water quality levels observed using APL. However, it was particularly noteworthy that when evaluating the WQI using MPL, substantial improvements were evident for all dams, especially for KTD. This indicates a significant enhancement in the overall water quality status, underscoring the effectiveness of adhering to stringent limits in ensuring and maintaining healthier water conditions.

Using APL offers the option to use irrigation water for crops that are slightly to moderately tolerant to the salinity of irrigation water (broader options for crops), while using MPL enables the use of irrigation water of higher salinity (lower quality) if crops of higher tolerance to salinity are used. Expanding the range of crop selections to include varieties that exhibit greater tolerance to irrigation salinity presents a promising strategy for sustainable agriculture in regions facing water quality challenges. The integration of salt-tolerant crops into agricultural systems offers numerous benefits that contribute to enhanced productivity, resource efficiency, and environmental resilience. Economically, the diversification of crop selections to include salt-tolerant varieties can provide farmers with greater resilience to environmental fluctuations and market uncertainties [34,35]. Additionally, the ability to grow a wider range of crops increases farmers’ flexibility in responding to changing climatic conditions and water availability, reducing the risks associated with crop failures [36].

It is also important to note that other important parameters, such as organic contaminants and heavy metals, should be included in the WQI. However, such data were unavailable for this study. In Jordan, several studies have been conducted to measure organic contaminants and heavy metals in surface waters [37,38]. Persistent organic pollutants (POPs), semi-volatile organic chemicals, and xenoestrogen in surface waters were within acceptable limits. Monitoring of POPs highlighted the need for long-term surveillance programs to maintain water quality within these standards [37,38]. Furthermore, metal levels in soils of the Jordan valley did not exceed the maximum permissible limits after long-term irrigation with KTD water [9].

5. Conclusions

The quality of irrigation water of key dams in Jordan was assessed using traditional indices and diagrams as well as the calculation of WQI based on six main water quality parameters. The results showed that these dams have high salinity and low sodium hazard, with Excellent to Good WQI values. Incorporating both average and maximum limit values into the calculation of the WQI would result in an effective assessment, not only of the overall quality of water in the dams but also its resilience to fluctuations and its ability to meet regulatory standards under various conditions, thereby contributing to more robust water management strategies in Jordan.