8. Drinking and irrigation water quality

The assessment of suitability of the groundwater for drinking and irrigation purposes can be determined through the parameters such as EC, TDS, pH, SAR, %Na, RSC, Kelley's ratio, MgR, CAI-1, P.I, and P.S as displayed in Table 3.

#### 8.1. Drinking water quality

The suitability of the groundwater in the study area is evaluated for drinking by comparing with the standard guideline values [25]. According to WHO specifications, TDS up to 500 mg/l is the highest desirable and up to 1500 mg/l is the maximum permissible level. Based on this classification, the TDS of the groundwater of the study area ranges between 3504 and 6366 mg/l with an average value of 4441 mg/l, which exceeds the recommended limit. However, the major cations and anions composition of the study area are all above the standard guideline of the WHO for drinking purposes. Water hardness causes more consumption of detergents at the time of cleaning, and some evidences indicate its role in heart disease [26]. The total hardness was determining by the following equation according to [27]:

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$$\text{TH} = 2.5 \,\text{Ca}^{2+} + 4.1 \,\text{Mg}^{2+}.\tag{3}$$

where Ca2+ and Mg2+ concentrations are expressed in mg/l as CaCO3. Hardness of water is due to the precipitation of Ca2+ and Mg2+ salts like carbonate, sulfates, and chlorides. Hardness of water causes scaling of pots, boilers, and irrigation pipes. However, the total hardness of the study area is varying from 1326 to 4040 mg/l as CaCO3, with an average value of 1826.22 mg/l as shown in Table 2. The analytical result of TH indicates that the groundwater of the study area is exceeding very hard water type according to [28] as shown in Table 4. Therefore, according to TDS and TH standards the groundwater is not suitable for drinking purposes.

#### 8.2. Irrigational suitability

minerals (gypsum and anhydrite). However, most of the points are placed in Ca2+ + Mg2+ side, which indicates excess calcium and magnesium derived from other processes such as reverse ion exchange reactions. In Ca2+ versus alkalinity diagram, Figure 7b indicates the contribution of both calcite and dolomite weathering on groundwater chemistry of the study

calcium over sulfate, which reveal that the groundwater samples seem to be derived from gypsum or anhydrite dissolution. Moreover, excess sulfate over calcium in few samples expresses the removal of calcium from the system likely by calcite precipitation. Therefore, silicate weathering and carbonate dissolution are the prevailing geochemical processes in the

Ion exchange is one of the important processes responsible for the concentration of ions in

CAI � <sup>1</sup> <sup>¼</sup> Cl� � Na<sup>þ</sup> <sup>þ</sup> <sup>K</sup><sup>þ</sup> ð Þ

Where all values are expressed in meq/l. When there is an exchange between Ca2+ or Mg2+ in groundwater with Na+ and K+ in the aquifer material, the CAI-1 is negative, and if there is a reverse ion exchange, CAI-1 will be positive [24]. The values of CAI-1 of the study area are positive in most wells, and very few wells show negative, and the CAI-1 ranges from �0.05 to 0.39 with an average value of 0.19 as presented in Table 3. Thus, it reveals that reverse ion exchange is the dominant process in the groundwater, whereas normal ion exchange is also

The assessment of suitability of the groundwater for drinking and irrigation purposes can be determined through the parameters such as EC, TDS, pH, SAR, %Na, RSC, Kelley's ratio,

The suitability of the groundwater in the study area is evaluated for drinking by comparing with the standard guideline values [25]. According to WHO specifications, TDS up to 500 mg/l is the highest desirable and up to 1500 mg/l is the maximum permissible level. Based on this classification, the TDS of the groundwater of the study area ranges between 3504 and 6366 mg/l with an average value of 4441 mg/l, which exceeds the recommended limit. However, the major cations and anions composition of the study area are all above the standard guideline of the WHO for drinking purposes. Water hardness causes more consumption of detergents at the time of cleaning, and some evidences indicate its role in heart disease [26]. The total hardness was

<sup>2</sup>� diagram (Figure 7c), most of the sample show excess

Cl� (2)

area. Moreover, in Ca2+ versus SO4

aquifer of the study area.

noticed in a very few wells.

8.1. Drinking water quality

8. Drinking and irrigation water quality

MgR, CAI-1, P.I, and P.S as displayed in Table 3.

determining by the following equation according to [27]:

7.1. Ion exchange

122 Aquifers - Matrix and Fluids

groundwater.

The suitability of groundwater for irrigation depends on the effect of mineral composition of water on the soil and plants. The effect of the salt on soils causes change in soil structure, permeability, and hence it effects on plant growth.

#### 8.2.1. Residual sodium carbonate

Residual sodium carbonate has been calculated to determine the hazard effects of carbonate and bicarbonate on the quality of water for irrigation and is expressed by the equation:

$$\text{RSC} = \left(\text{HCO}\_3^- + \text{CO}\_3^{2-}\right) - \left(\text{Ca}^{2+} + \text{Mg}^{2+}\right) \tag{4}$$

Where all ionic concentrations are expressed in meq/l. The classification of irrigation water according to the RSC presents in Table 5 after [29], where water containing more than 2.5 meq/l of RSC are not suitable for irrigation, while those having <1.25 meq/l are good for irrigation. Eaton (1950) indicated that if waters which are used for irrigation contain excess of HCO3 � + CO3 <sup>2</sup>� than its equivalent Ca2+ + Mg2+, there will be a residue of Na+ + HCO3 � when evaporation takes place and the pH of the soil increases up to 3 [30]. When total carbonate levels exceed the total amount of calcium and magnesium, the water quality diminished [31]. The calculated RSC values of the groundwater samples of the study area are ranged from �52.63 to


Table 4. Water classes (After [28]).


Table 5. Water classes based on RSC (after [29]).

�24.52 meq/l with an average value of �34.31 meq/l. Negative RSC indicates that sodium buildup is unlikely, since sufficient calcium and magnesium are in excess of what can be precipitated as carbonates [32]. Hence, the groundwater of the study area is safe for irrigation.

## 8.2.2. Permeability index

The permeability of soil is affected by long-term use of irrigation water and is influenced by sodium, calcium, magnesium, and bicarbonate contents in soil. Doneen (1964) set a criteria for assessing the suitability of water for irrigation based on permeability index; accordingly, waters can be classified as Class I, Class II, and Class III. The Class I and Class II waters are suitable for irrigation with 50–75% or more of maximum permeability, whereas Class III water is unsuitable with 25% of maximum permeability. Therefore, soil permeability is affected by consistent use of irrigation water which increases the presence of sodium, calcium, magnesium, and bicarbonate in the soil [33].

The permeability index is used to measure the suitability of water for irrigation purpose when compared with the total ions in meq/l, and it is expressed as follows:

$$\text{PI} = \frac{\text{Na}^+ + \sqrt{\text{HCO}\_3^-}}{\text{Ca}^{2+} + \text{Mg}^{2+} + \text{Na}^+} \ast 100\tag{5}$$

Figure 8. Permeability index diagram of the study area.

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Table 6. Classification of irrigation water based on potential salinity.

In the present study, the P.I of the groundwater samples ranged from 37.86 to 56.63% with a mean value of 49.1%, and it is observed that all the groundwater samples fall in Class II category of Doneen Chart (Figure 8). Therefore, the groundwater of the study area is good for use in irrigation.

#### 8.2.3. Potential salinity

Doneen as in Ref. [17] introduced an important parameter "Potential Salinity" for assessing the suitability of water for irrigation uses, which defined as chloride concentration plus half of the sulfate concentration expressed in meq/l.

Potential salinity = Cl� + ½ SO4 <sup>2</sup>�. On the basis of the potential salinity, Doneen [17] subdivided the irrigation water into three classes as presented in Table 6. The potential salinity of the majority of the analyzed groundwater samples of the study area ranges between 36.55 and 83.56 meq/l with an average value of 54.17 meq/l, indicating high values of potential

Figure 8. Permeability index diagram of the study area.

�24.52 meq/l with an average value of �34.31 meq/l. Negative RSC indicates that sodium buildup is unlikely, since sufficient calcium and magnesium are in excess of what can be precipitated as carbonates [32]. Hence, the groundwater of the study area is safe for irrigation.

The permeability of soil is affected by long-term use of irrigation water and is influenced by sodium, calcium, magnesium, and bicarbonate contents in soil. Doneen (1964) set a criteria for assessing the suitability of water for irrigation based on permeability index; accordingly, waters can be classified as Class I, Class II, and Class III. The Class I and Class II waters are suitable for irrigation with 50–75% or more of maximum permeability, whereas Class III water is unsuitable with 25% of maximum permeability. Therefore, soil permeability is affected by consistent use of irrigation water which increases the presence of sodium, calcium, magne-

The permeability index is used to measure the suitability of water for irrigation purpose when

p

In the present study, the P.I of the groundwater samples ranged from 37.86 to 56.63% with a mean value of 49.1%, and it is observed that all the groundwater samples fall in Class II category of Doneen Chart (Figure 8). Therefore, the groundwater of the study area is good for use in irrigation.

Doneen as in Ref. [17] introduced an important parameter "Potential Salinity" for assessing the suitability of water for irrigation uses, which defined as chloride concentration plus half of the

subdivided the irrigation water into three classes as presented in Table 6. The potential salinity of the majority of the analyzed groundwater samples of the study area ranges between 36.55 and 83.56 meq/l with an average value of 54.17 meq/l, indicating high values of potential

HCO� 3

Ca2<sup>þ</sup> <sup>þ</sup> Mg2<sup>þ</sup> <sup>þ</sup> Na<sup>þ</sup> <sup>∗</sup><sup>100</sup> (5)

<sup>2</sup>�. On the basis of the potential salinity, Doneen [17]

PI <sup>¼</sup> Na<sup>þ</sup> <sup>þ</sup> ffiffiffiffiffiffiffiffiffiffiffiffiffiffi

compared with the total ions in meq/l, and it is expressed as follows:

8.2.2. Permeability index

124 Aquifers - Matrix and Fluids

8.2.3. Potential salinity

sium, and bicarbonate in the soil [33].

Table 5. Water classes based on RSC (after [29]).

sulfate concentration expressed in meq/l.

Potential salinity = Cl� + ½ SO4


Table 6. Classification of irrigation water based on potential salinity.

salinity. However, it is found that the classification of the groundwater of the study area for irrigation purposes fall in Class III; therefore, the groundwater should be used in case of a soil of high permeability.

#### 8.2.4. Sodium adsorption ratio

Sodium concentration is considered an important factor to express reaction with the soil and reduction in its permeability. Therefore, sodium adsorption ratio is considered as a better measure of sodium (alkali) hazard in irrigation water as it is directly related to the adsorption of Na<sup>+</sup> on soil and is the important criteria for estimating the suitability of the water for irrigation. SAR can be computed as follows:

$$\text{SAR} = \frac{\text{Na}^+}{\sqrt{\frac{\text{Ca}^{2+} + \text{Mg}^{2+}}{2}}} \tag{6}$$

Mg ratio <sup>¼</sup> Mg<sup>2</sup><sup>þ</sup>

In the study area, the magnesium hazard values fall in the range value of 25.65–40.46% with an average value of 32.48%, that is, magnesium hazard ratio is <50%, which is recognized as

Hydrogeology and Groundwater Geochemistry of the Clastic Aquifer and Its Assessment for Irrigation, Southwest…

Sodium is an important ion used for the classification of irrigation water due to its reaction

Ca<sup>2</sup><sup>þ</sup> <sup>þ</sup> Mg<sup>2</sup><sup>þ</sup> <sup>þ</sup> <sup>K</sup><sup>þ</sup> <sup>þ</sup> Na<sup>þ</sup> !

Where all ionic concentrations are expressed in meq/l. According to [15], in all natural waters, %Na<sup>+</sup> is a common parameter to assess its suitability for irrigation purpose as shown in Table 8. If the concentration of Na+ is high in irrigation water, Na+ gets absorbed by clay particles, displacing Mg2+ and Ca2+ ions. This exchange process of Na+ in water for Ca2+ and Mg2+ in soil reduces the permeability of soil and eventually results in poor internal drainage of

%Na<sup>þ</sup> <sup>¼</sup> ð Þ Na <sup>þ</sup> <sup>K</sup> <sup>þ</sup>

Where all ionic concentrations are expressed in meq/l.

with soil, reduces its permeability. The %Na is computed as:

suitable for irrigation.

8.2.7. Sodium percentage (%Na)

Table 7. Classification of waters based on EC [35].

Ca<sup>2</sup><sup>þ</sup> <sup>þ</sup> Mg<sup>2</sup><sup>þ</sup> � � � <sup>100</sup> (7)

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127

� 100 (8)

Where all ionic concentrations are expressed in meq/l. The SAR of the study area ranges between 4.65 and 9.4, with an average value of 7.54. The SAR values of all the study area are found to be <10 and are classified as categories S1 and S2, as low and medium sodium water, respectively. Therefore, based on the sodium hazard class the groundwater of the study area is suitable for irrigation.

#### 8.2.5. Salinity hazard

The most important criteria regarding salinity and water availability to the plant is the total salt concentration. Since there exists a straight line correlation between electrical conductivity (EC) and total salt concentration of waters, the most expedient procedure to evaluate salinity hazard is to measure its electrical conductivity measured in (μmohs/cm) [34]. On the basis of salt concentration, the US Salinity Laboratory Staff divided the irrigation waters into four classes. Later on, another class was added to it [35] as given in Table 7. Waters having EC values above 1500 μmohs/cm can cause serious damage.

For rating irrigation waters, the US salinity diagram was used, in which the SAR is plotted against EC as shown in Figure 9, where the EC values of samples of the study area range from 4370 to 8230 with an average value of 5837 μmohs/cm and water exhibited very high to extensively high water salinity and medium sodium, high sodium type (C4-S2, C4-S3). Few samples are located on C4-S4 type. Therefore, the groundwater can be used with tolerant crops of clayey, sandy loam, and loamy sand soil texture, and special management for salinity control.

#### 8.2.6. Magnesium ratio

In most waters, calcium and magnesium maintain a state of equilibrium. A ratio namely index of magnesium hazard was developed by [36]. According to this, a high magnesium hazard value of >50% has an adverse effect on the crop yield as the soil becomes more alkaline, and effect on the agricultural yield, and a harmful effect on soil will appear.

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$$\text{Mg ratio} = \frac{\text{Mg}^{2+}}{\left(\text{Ca}^{2+} + \text{Mg}^{2+}\right)} \times 100\tag{7}$$

Where all ionic concentrations are expressed in meq/l.

In the study area, the magnesium hazard values fall in the range value of 25.65–40.46% with an average value of 32.48%, that is, magnesium hazard ratio is <50%, which is recognized as suitable for irrigation.

#### 8.2.7. Sodium percentage (%Na)

salinity. However, it is found that the classification of the groundwater of the study area for irrigation purposes fall in Class III; therefore, the groundwater should be used in case of a soil

Sodium concentration is considered an important factor to express reaction with the soil and reduction in its permeability. Therefore, sodium adsorption ratio is considered as a better measure of sodium (alkali) hazard in irrigation water as it is directly related to the adsorption of Na<sup>+</sup> on soil and is the important criteria for estimating the suitability of the water for

SAR <sup>¼</sup> Na<sup>þ</sup>

Where all ionic concentrations are expressed in meq/l. The SAR of the study area ranges between 4.65 and 9.4, with an average value of 7.54. The SAR values of all the study area are found to be <10 and are classified as categories S1 and S2, as low and medium sodium water, respectively. Therefore, based on the sodium hazard class the groundwater of the study area is

The most important criteria regarding salinity and water availability to the plant is the total salt concentration. Since there exists a straight line correlation between electrical conductivity (EC) and total salt concentration of waters, the most expedient procedure to evaluate salinity hazard is to measure its electrical conductivity measured in (μmohs/cm) [34]. On the basis of salt concentration, the US Salinity Laboratory Staff divided the irrigation waters into four classes. Later on, another class was added to it [35] as given in Table 7. Waters having EC

For rating irrigation waters, the US salinity diagram was used, in which the SAR is plotted against EC as shown in Figure 9, where the EC values of samples of the study area range from 4370 to 8230 with an average value of 5837 μmohs/cm and water exhibited very high to extensively high water salinity and medium sodium, high sodium type (C4-S2, C4-S3). Few samples are located on C4-S4 type. Therefore, the groundwater can be used with tolerant crops of clayey, sandy loam, and loamy sand soil texture, and special management for

In most waters, calcium and magnesium maintain a state of equilibrium. A ratio namely index of magnesium hazard was developed by [36]. According to this, a high magnesium hazard value of >50% has an adverse effect on the crop yield as the soil becomes more alkaline, and

effect on the agricultural yield, and a harmful effect on soil will appear.

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Ca<sup>2</sup>þþMg2<sup>þ</sup> 2

<sup>q</sup> (6)

of high permeability.

126 Aquifers - Matrix and Fluids

suitable for irrigation.

8.2.5. Salinity hazard

salinity control.

8.2.6. Magnesium ratio

8.2.4. Sodium adsorption ratio

irrigation. SAR can be computed as follows:

values above 1500 μmohs/cm can cause serious damage.

Sodium is an important ion used for the classification of irrigation water due to its reaction with soil, reduces its permeability. The %Na is computed as:

$$\% \text{Na}^{+} = \left(\frac{(\text{Na} + \text{K})^{+}}{\text{Ca}^{2+} + \text{Mg}^{2+} + \text{K}^{+} + \text{Na}^{+}}\right) \times 100\tag{8}$$

Where all ionic concentrations are expressed in meq/l. According to [15], in all natural waters, %Na<sup>+</sup> is a common parameter to assess its suitability for irrigation purpose as shown in Table 8. If the concentration of Na+ is high in irrigation water, Na+ gets absorbed by clay particles, displacing Mg2+ and Ca2+ ions. This exchange process of Na+ in water for Ca2+ and Mg2+ in soil reduces the permeability of soil and eventually results in poor internal drainage of


Table 7. Classification of waters based on EC [35].

Figure 9. Wilcox diagram illustrating the groundwater quality of the study area.

the soil, and such soils are usually hard when dry [37]. The values of %Na<sup>+</sup> of the study area varies from 35.28 to 54.23% with an average value of 46.73% which fall in good to permissible category, showing that the groundwater of the study area is suitable for irrigation; meanwhile, the EC ranges between 4370 and 8230 μmohs/cm, in which the groundwater salinity is classified as very extensively high as presented in Figure 10; therefore, the groundwater can be used for irrigation under specific conditions.

8.2.8. Kelly's ratio

Kelly's ratio is used for the classification of water for irrigation purposes. A Kelly's index (>1) indicates an excess level of sodium in waters [38]. Therefore, water with a KR (<1) is suitable for irrigation. KR is calculated by using the formulae, where all the ions are expressed in meq/l.

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Figure 10. A plot of percentage of sodium vs. electrical conductivity of groundwater of the study area.

s ratio <sup>¼</sup> Na<sup>þ</sup>

Ca<sup>2</sup><sup>þ</sup> <sup>þ</sup> Mg<sup>2</sup><sup>þ</sup> (9)

Kelly'

Table 8. Classification of groundwater based on %Na [15].

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Table 8. Classification of groundwater based on %Na [15].

Figure 10. A plot of percentage of sodium vs. electrical conductivity of groundwater of the study area.

#### 8.2.8. Kelly's ratio

the soil, and such soils are usually hard when dry [37]. The values of %Na<sup>+</sup> of the study area varies from 35.28 to 54.23% with an average value of 46.73% which fall in good to permissible category, showing that the groundwater of the study area is suitable for irrigation; meanwhile, the EC ranges between 4370 and 8230 μmohs/cm, in which the groundwater salinity is classified as very extensively high as presented in Figure 10; therefore, the groundwater can be used

for irrigation under specific conditions.

128 Aquifers - Matrix and Fluids

Figure 9. Wilcox diagram illustrating the groundwater quality of the study area.

Kelly's ratio is used for the classification of water for irrigation purposes. A Kelly's index (>1) indicates an excess level of sodium in waters [38]. Therefore, water with a KR (<1) is suitable for irrigation. KR is calculated by using the formulae, where all the ions are expressed in meq/l.

$$\text{Kelly's ratio} = \frac{\text{Na}^+}{\left(\text{Ca}^{2+} + \text{Mg}^{2+}\right)}\tag{9}$$

The values of the KR in the present study varied between 0.55 and 1.2 with an average value of 0.89 which is <1. It is found that 87.32% of the groundwater samples have KR <1, and 12.68% KR > 1. Accordingly, the groundwater of the study area is suitable for irrigation.

Acknowledgements

Author details

References

Fawzia Mohammad Al-Ruwaih

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Address all correspondence to: farhdana@yahoo.com

The author would like to thank the Ministry of Electricity and Water for providing the chem-

Hydrogeology and Groundwater Geochemistry of the Clastic Aquifer and Its Assessment for Irrigation, Southwest…

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131

Department of Earth and Environmental Sciences, Kuwait University, Safat, Kuwait

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