## 4 Results and Discussion
### Pollution Source Identification of Monitored Variables
NO\({}_{3}-\)N may additionally have derived from agricultural areas in the region, where inorganic nitrogen fertilizers are in common use and the role of domestic waste is strong, and hence, this component can be best explained by a \"nutrient\" factor representing influences from non-point sources such as agricultural runoff and the domestic pollution factor. The reports of [PERSON] et al. [35] in Ethiopia and [PERSON] et al. [27] elsewhere were comparable with this result. This factor is typical of the monitoring stations in the middle section including point sources and eastern and western sides of Lake Hawassa (MS4, MS10, and MS17), where domestic sewage, industrial effluents, and agricultural runoff are predominant. The FA in LHW extracted three factors by retaining the PCs through varimax rotation that explained 70.5% of the total variance for the dry season. The first factor (F1), accounting for 45.7% of the total variance, showed strong positive loadings of TDS, EC, PO\({}_{4}-\)P, BOD, DO, TP, Na\({}^{+}\), and temperature, having factor loadings of 0.962, 0.961, 0.830, 0.796, 0.897, 0.783, and 0.973, respectively; moderate positive loadings of K+, COD, and TN (0.572, 0.721, 0.724); and strong negative loadings of DO (\(-\)0.847). Strong positive loadings of organic matter and strong negative loadings of DO might suggest the impact of seasonal variations. The strong and moderate positive loading of BOD and COD signify biodegradation of organic matters and negatively affect DO of water bodies. F1 stands clearly for pollution by BOD or COD, and nutrients and oxygen depletion is a consequence. High temperature increases biodegradation and reduces solubility of oxygen in the water. This PC was correlated with COD and BOD\({}_{5}\), indicating a group of purely organic pollution indicator parameters from uncontrolled domestic discharges caused by rapid urbanization and industrial effluents. Biodegradation of organic matter causes concentrations of BOD and dissolved oxygen in water [23; 27; 51]. A high loading of nutrients represents pollution from industrial setup and domestic wastewater. High loading of metals demonstrates the influences of industrial discharges. Phosphorus and nitrogen may originate from point sources such as sewage pollution, agricultural runoff in the upper stream due to irrigation, industrial facilities, and livestock. Consequently, this component is more likely to be explained by the combination of domestic pollution factors and industrial factors. Strongly positive loading of Na\({}^{+}\) and moderate positive loadings of K\({}^{+}\) are likely to originate from industrial effluents discharged directly into the Tikur-Wuha River and Lake Hawassa. These results are also supported by similar findings obtained elsewhere [27; 69]. This factor is more pronounced at monitoring stations in the upper catchment (MS1 and MS3), monitoring stations in the middle section including point sources (MS4, MS5, MS15 and MS19), Tikur-Wuha River (MS6), and monitoring stations from both eastern and western sides of Lake Hawassa (MS9, MS10, MS14, MS16, and MS17), where domestic sewage, industrial effluents, and agricultural activities are predominant. The major industries discharge their treated and untreated effluents directly into Tikur-Wuha River and the lake during the dry period when the flow is low, which might lead to higher pollution. On the other hand, the strong loadings of TN and TP at F1 suggest a higher contribution of point sources from industrial facilities and agricultural runoff in the upper stream due to irrigation. Generally, these factors suggest a blended source of contamination encompass ing municipal and industrial point source and livestock. This result is also confirmed by other studies [5; 23; 33; 67; 69]. Hence, it can be considered to be the contamination index for surface water [44; 45].