# Hydrochemical Characteristics and Suitability Assessment of Groundwater Quality for Irrigation
## 3 Results and Discussion
### Hydrochemical Characteristics
Specifically, it separated the years 2017 and 2020, which are characterized by higher values of these elements, from the other observed years. In relation to the PC1 axis, the years 2012 and 2014 were the most similar. The second axis of PC2 separated the years according to higher values of Cl\({}^{-}\) (0.94) and lower values of Na\({}^{+}\) (\(-\)0.79) in water, i.e., 2012, 2015, 2018, and 2020 from the other observed years. In relation to PC2, the years 2015 and 2020 were the most similar. Figure 4: Biplot diagram of irrigation groundwater parameters and years (PCA analysis). The cluster analysis grouped the water parameters in all three locations into 3 clusters, where the first cluster is electrical conductivity, the second cluster is dry residue and HCO\({}_{3}\), while all other investigated water parameters are grouped into the 3 rd cluster (Figure 5). At the Nikinci site, the most similar were NO\({}_{3}\) and pH, followed by K and Ca, and Mg, Na, and Cl (Figure 5a). At the Sid locality, K and pH were the most similar, then Mg and Cl, and Na, SO\({}_{4}\), and NO\({}_{3}\) (Figure 5b), while at the Lacarak locality, K and NO\({}_{3}\), and Cl and pH were the most similar (Figure 5c). Indices such as soluble sodium percentage (SSP), sodium absorption ratio (SAR), residual sodium carbonate (RSC), permeability index (PI), Kelly's ratio (KR), magnesium adsorption ratio (MAR), and total hardness (TH) provided a detailed assessment of the groundwater's impact on soil sodicity and magnesium hazard as well as total hardness (Table 6). While most samples showed suitability for irrigation, occasional deviations emphasized the need for continuous monitoring. The formula for sodium percentage (SSP) is given in the Table 2 (Formula (1), and the values ranged from 6.54-17.83 (Nikinci), 6.31-13.24 (Sid), and 4.77-31.87 (Lacarak), indicating high variations (Table 6). The average values were 11.91% at Nikinci, 8.90% at Sid, and 24.17% at Lacarak. These values classify the water at Nikinci and Sid as excellent (SSP < 20%) and at Lacarak as good (SSP 20-40%). Figure 5: Cluster analysis of irrigation groundwater parameters at the monitoring localities for the period 2011–2020: (**a**) Nikinci, (**b**) Sid, (**c**) Lacarak. Residual sodium carbonate (SAR) is a well-known value used for irrigation water quality and it is calculated according to Formula (2) [32], given in the Table 2. In this study area, results indicated generally low SAR values, with averages of 0.58 (Nikinci), 0.37 (Sid) and 1.59 (Lacarak) (Table 6), which indicates that the irrigation water quality, according to this index, falls into the category of good quality (SAR \(<\) 3). The value of RSC was calculated according to Formula (3) as shown in Table 2[33]. As indicated in Table 6, at the measuring point at Sid, there was no deviation from the first class (RSC \(<\) 1.25). At the Nikinci point, the second class (RSC 1.25-2.5) was observed during the measurement in two years, and at the measuring point at Lacarak, the first class occurred during measurements in two years, the third unsuitable class (RSC \(>\) 2.5) occurred during only one year, and the other samples belonged to the second doubtful class. Soil irrigated with water having a high RSC and presumably high pH can become infertile due to NaCO\({}_{3}\) deposition and reduced internal drainage [34]. Such results indicate the necessary monitoring of water quality. The permeability index (PI) was calculated based on Equation (4) from Table 2, which is given by [PERSON] (1964) [35]. With a range of between 25 to 75%, all analyzed samples at all monitoring locations belong to the second group, indicating good quality. These results indicate that water in this area is suitable for irrigation. [PERSON]'s ratio (KR) is given by Formula (5) in Table 2[36]. It is a very important indexe that reveals the level of sodium relative to calcium and magnesium ion concentrations in irrigation water. All analyzed samples at all monitoring locations of irrigation water were suitable.