## 4 Results and Discussion
### Pollution Source Identification of Monitored Variables
The high loading of metals demonstrates the influences of industrial effluents and agriculture activities. Phosphorus and nitrogen can originate from point sources such as sewage pollution, industrial facilities and livestock, as well as from non-point sources, mainly from agricultural activities, runoff from rural and urban areas, soil erosion, and livestock. These results are consistent with findings of other reports elsewhere [27; 68]. Consequently, the component is more likely to be explained by the combination of domestic pollution and industrial factors. These factors are characteristic of the monitoring stations in the upper catchment (MS1 and MS2), in the middle section including point sources (MS5 and MS15), along Tikur-Wuha River (MS6), and on the eastern side of Lake Hawassa (MS7, MS9, MS12, MS13, and MS14), where domestic and industrial effluents and agricultural runoff are predominant. The strongly positive loadings of Na+ and weak positive loadings of K+ are likely due to industrial effluents discharged into the river Tikur-Wuha and Lake Hawassa. Reports also indicate that the sources of Na+ and K+ might be domestic sources, fertilizers, and residential waste in addition to industrial effluents [69]. During field observation, it was found that the major industries are discharging their treated and untreated effluents directly into the Tikur-Wuha River and the lake during the rainy period when the flow rate is high, resulting in high dilution, but during the dry period, the dilution effect is lower and consequent pollution is higher. On the other hand, the strong loadings of TN and TP in F1 suggest higher contribution from point sources in industry and non-point sources such as agricultural land use, urban drainage, and residential areas during the rainy season. In general, these factors are symbolic of a blended source of contamination, encompassing industrial discharges, urban runoff, and agricultural land use. The results are in agreement with those of other studies [5; 24; 67; 69]. Hence, they can be considered as the contamination index for surface water [44; 45]. The second factor (F2) explained 13.4% of the total variance. It had a moderately negative loading of Mg2+ and Ca2+ (\(-\)0.654, \(-\)0.627) and a moderately positive loading of NH3-N (0.516). This factor's moderately negative loading of Mg2+ and Ca2+ is likely to originate from industrial wastewater discharged into the Tikur-Wuha River and Lake Hawassa, usually from carbonate minerals, which are naturally present in the soils of the Lake Hawassa watershed. This factor is more pronounced at monitoring stations affected by point sources, agricultural lands, and rural and urban runoff, such as MS3 in the upper catchment, MS19 in the middle section (point source), and MS8, MS11, MS16, and MS18 monitoring stations on both eastern and western sides of Lake Hawassa. A moderately positive loading of NH\({}_{3}-\)N (0.7) indicates biodegradation of organic matter. This variable is primarily from runoff, with high loading of solids and wastes from point sources of pollution from domestic and industrial areas. Furthermore, NH\({}_{3}-\)N is triggered by the decomposition of organic matter, indicating the discharge of domestic sewage to surface water. Studies elsewhere have showed comparable results [42; 44; 45; 69; 70]. The third factor (F3), explaining 12.3% of the total variance, had a moderately negative loading for pH (\(-\)0.710), suggesting the dominance of physical reactions by aquatic plants and natural weathering of the basin, possibly due to industrial impact from different sources [22]. It had weak positive loading of turbidity (0.452), moderate negative loading of NO\({}_{2}-\)N (\(-\)0.620), and moderate positive loading of NO\({}_{3}-\)N (0.507).