4. Results and discussion

#### 4.1 Descriptive statistics

The statistical summary of the data used in this study is represented in Table 1. The results show that pH values varied from 7.4 to 7.8 with a mean of 7.5, indicating that the water is consider as a slightly alkaline water [10]. Electrical conductivity values express the amount of dissolved solids in the water sample. Water samples has EC values that ranged from 1040 to 1800 μS/cm with an average of 1349 μS/cm. EC of the surface water samples was above the fixed value of 1000 μS/cm by WHO [11]. The average values of Ca, Mg, Na and K are 94.04, 42.72, 93.92 and 1.01 mg/L, respectively. The order abundance of the major cations as follows Ca > Na > Mg > K, where the calcium and sodium are the dominate cations in surface water. The calcium values are generally upper than the limits set in WHO guides [11]. The high concentrations of Ca and Na are explained by the ion exchange process between sodium and calcium elements which leads to the precipitation of CaCO3 in the soil profile. The order abundance of the major anion from the highest to the lowest is HCO3 > Cl > SO4 > NO3, indicating that bicarbonate and chloride are the dominants anions in the surface water. The concentration of HCO3 is varied from 134.2 to


#### Table 1.

Summary of the statistical analyses of the physicochemical parameters.

201.3 mg/L with an average of 173.21 mg/L, high concentration of this element related to the water-rock interaction process.

#### 4.2 Determination of the origin of dissolved solids

In order to determine the origin of the highest values of some parameters in surface water the relationships between some parameters are studied.

Figure 2 shows the relationship between total cations and Ca + Mg, we see that all sample points are located below the equilibrium line 1/1 which confirms the alteration process and the exchange of alkaline ions [13].

Total cations versus Na + K is presented in Figure 3, we see that the samples are located below the equilibrium line 1/1, indicating that the excessive concentrations of Na and K are due to the accumulated salts in the soil during the evaporation process [13].

Na versus HCO3 plot shows that there is a distribution of samples below and above the equilibrium line 1/1 indicating the presence of dissolution of the rocks during the infiltrations (Figure 4).

The chloride versus sodium plot (Figure 5) is employed to verify the relationship and sources of the ions in surface water. A Cl/Na ratio equal one is typically characteristic of halite dissolution, whereas values <1 implies the alkali metal is released from silicate weathering reactions [12, 13].

#### 4.3 Suitability of surface water for irrigation

The evaluation of the water surface suitability of the study area for irrigation was carried out using total dissolved solids (TDS), total hardness (TH), electrical conductivity (EC), the sodium adsorption rate (SAR), the percentage of sodium (%Na), residual sodium carbonate (RSC), the permeability index (PI), the salinity index (PS), the soluble sodium percentage (SSP), the magnesium adsorption rate

.

(MAR), and Kelly's ratio (KR). The results are presented in Tables 2–4.

Total dissolved solids (TDS) is calculated by the following equations:

4.3.1 Total dissolved solids (TDS)

Relations between the total cations and Na<sup>+</sup> with K+

Figure 2.

Figure 3.

7

Relations between the total cations and Ca2+ with Mg2+.

Suitability and Assessment of Surface Water for Irrigation Purpose

DOI: http://dx.doi.org/10.5772/intechopen.86651

Suitability and Assessment of Surface Water for Irrigation Purpose DOI: http://dx.doi.org/10.5772/intechopen.86651

Figure 2. Relations between the total cations and Ca2+ with Mg2+.

Figure 3. Relations between the total cations and Na<sup>+</sup> with K+ .

index (PS), the soluble sodium percentage (SSP), the magnesium adsorption rate (MAR), and Kelly's ratio (KR). The results are presented in Tables 2–4.
