## 4 Results and Discussion
### Pollution Source Identification of Monitored Variables
The second factor (F2) explained 16% of the total variance and had a strong negative loading of turbidity (\(-0.781\)), a moderate negative loading of NO\({}_{2}-\)N and Mg\({}^{+2}\) (\(-0.567\), \(-0.531\)), and a moderate positive loading of NO\({}_{3}-\)N and Ca\({}^{+2}\) (0.599, 0.524). NO\({}_{3}-\)N could be mainly from point sources, and the role of domestic waste is also strong. Hence, this component can be explained by the \"nutrient\" factor, which represents influences from non-point sources such as the domestic pollution factor [24; 27; 32; 35; 66; 69]. A moderately positive loading of K\({}^{+}\) and a moderately negative loading of Mg\({}^{2+}\) in this factor likely originate from industrial discharges into the Tikur\(-\)Wuha River and Lake Hawassa. This PC is more influenced by industrial discharges, and monitoring stations from the LHW, where industry is predominant, are more pronounced. This factor is more pronounced in monitoring stations in the upper catchment (MS2) and the monitoring stations in the eastern and western sides of Lake Hawassa (MS11, MS12, MS13, and MS18), where domestic, industrial, and agricultural activities are predominant in the upper stream due to irrigation. The third factor (F3), explaining 8.8% of the total variance, had a strong positive loading of pH (0.775), suggesting the dominance of physical reactions by aquatic plants and natural weathering of the basin, and attributed to industrial impact from different sources [22]. A moderate positive loading of NH\({}_{3}-\)N (0.7) indicates the biodegradation of organic matter causing concentrations of waterborne factors such as NH\({}_{3}-\)N. This variable originated primarily from wastes from point sources of pollution from domestic and industrial areas. Furthermore, NH\({}_{3}-\)N is triggered by organic matter decomposition, indicating the discharge of domestic sewage to surface water. Reports elsewhere support the findings of this study [42; 44; 45; 70]. This factor is more pronounced in monitoring stations on the eastern side of Lake Hawassa (MS7 and MS8), where domestic sewage, industrial effluents, and agricultural activities are prevalent. The bi-plot of PCs on key parameters TDS, EC, PO\({}_{4}-\)P, DO, BOD, COD, TN, TP, temperature, Na\({}^{+}\), K\({}^{+}\), Turbidity, NO\({}_{2}-\)N, NO\({}_{3}-\)N, Mg\({}^{2+}\), and Ca\({}^{2+}\) that characterize monitoring stations from rivers in the upper and middle catchment, point sources in the middle catchment, and the eastern and western sides of Lake Hawassa are presented in Figure 5a,b for dry and wet seasons. In fact, the average values of EC, TDS, BOD, COD, Na\({}^{+}\), K\({}^{+}\), Mg\({}^{2+}\), Ca\({}^{2+}\), and NH\({}_{3}-\)N of point sources were exceedingly higher than that of rivers in the upper and middle catchment (MS1-MS3, and MS6) and Lake Hawassa (MS7-MS14, MS16 and MS18) in Table 6. In addition, NO\({}_{3}-\)N, NO\({}_{2}-\)N, TN, TP, and PO\({}_{4}-\)P were the main parameters characterizing the stated monitoring sites in both seasons. These stations predominantly include rural areas, urban and peri-urban areas, and industrial sites from which domestic sewage, urban runoff, and effluents are discharged into the lake. Furthermore, the influence of agricultural activities in the upper catchment and Tikur-Wuha River feeding the lake was evident. The results of this investigation were comparable to the findings of the studies conducted by [PERSON] et al. [71] and [PERSON] et al. [72] on Lake Ziway. In particular, higher EC and TDS values were recorded for similar monitoring stations in both seasons (Table 6). In an aquatic environment, EC is used to categorize the pollution status of surface waters, and an increase in conductivity indicates the presence of dissolved ions that can affect aquatic life and water quality [73].