## 4 Results and Discussion
### Correlation Matrix Evaluation and Seasonal Variation
Strong negative correlations were observed between the values of DO and TDS, EC, and Na\({}^{+}\) (r = \(-\)0.819, r = 0.817, r = \(-\)0.826; \(p<0.05\)), moderate negative correlations were observed between DO and TN, TP, BOD, K\({}^{+}\), and temperature values (r = \(-\)0.577, r = \(-\)0.568, r = \(-\)0.687, r = \(-\)0.639 r = \(-\)0.729; \(p<0.05\)), and a moderate negative correlation was observed between DO and NO\({}_{3}-\)N, with r = \(-\)0.464 at \(p<0.005\)). Strong positive correlations were found between temperature and EC and TDS (r = 0.839, r = 0.842; \(p<0.05\)), and moderate positive correlations were found for temperature with TP and PO\({}_{4}-\)P(r = 0.730, r = 0.532; \(p<0.05\)). There was also a moderate negative correlation observed between temperature and DO, with r = \(-\)0.729 at \(p<0.005\). NH\({}_{3}-\)N had a moderate positive correlation with COD, TP, temperature, and Na\({}^{+}\) (r = 0.476, r = 0.484, r = 0.550, r = 0.343; \(p<0.005\)). A strong positive correlation was found between PO\({}_{4}-\)P and TP, with r = 0.921 at \(p<0.005\), moderate positive correlations were found for PO\({}_{4}-\)P with BOD, COD, TP, Na\({}^{+}\), and temperature (r = 0.749, r = 0.647, r = 0.680, r = 0.76; \(p<0.05\)), and a moderate negative correlation was found between PO\({}_{4}-\)P and DO values r = \(-\)0.626; \(p<0.05\)) (Table 5). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline
**Parameters** & **TDS** & **EC** & **NH\({}_{3}-\)NNO\({}_{3}-\)NPO\({}_{4}-\)P** & **DO** & **BOD** & **COD** & **TN** & **TP** & **Tem** & **Mg\({}^{2+}\)** & **Ca\({}^{2+}\)** & **Na\({}^{+}\)** & **K\({}^{+}\)** \\ \hline TDS & **1** & & & & & & & & & & & & & & \\ EC & **0.999** & **1** & & & & & & & & & & & & & \\ NH\({}_{3}-\)N & 0.433 & 0.419 & **1** & & & & & & & & & & & & \\ NO\({}_{3}-\)N & 0.208 & 0.212 & \(-\)0.10 & **1** & & & & & & & & & & & \\ PO\({}_{4}-\)P & **0.814** & **0.815** & 0.383 & \(-\)0.04 & **1** & & & & & & & & & & \\ DO & \(-\)**0.82** & \(-\)**0.82** & \(-\)0.31 & \(-\)**0.46** & \(-\)**0.63** & **1** & & & & & & & & & \\ BOD & **0.686** & **0.686** & 0.450 & \(-\)0.12 & **0.749** & \(-\)**0.58** & **1** & & & & & & & & \\ COD & **0.561** & **0.564** & **0.476** & \(-\)0.19 & **0.647** & \(-\)0.41 & **0.871** & **1** & & & & & & & \\ TN & **0.645** & **0.642** & 0.410 & 0.184 & **0.680** & \(-\)**0.57** & **0.520** & **0.619** & **1** & & & & & & \\ TP & **0.899** & **0.899** & **0.848** & \(-\)0.03 & **0.921** & \(-\)**0.69** & **0.804** & **0.683** & **0.535** & **1** & & & & & \\ Temperature & **0.839** & **0.842** & 0.343 & 0.237 & **0.532** & \(-\)**0.73** & 0.436 & 0.344 & 0.291 & **0.730** & **1** & & & & & \\ Mg\({}^{2+}\) & \(-\)0.27 & \(-\)0.27 & \(-\)0.25 & \(-\)0.13 & \(-\)0.04 & 0.305 & \(-\)0.13 & \(-\)0.20 & \(-\)0.20 & \(-\)0.16 & \(-\)0.13 & \(-\)0.42 & **1** & & & & \\ Ca\({}^{2+}\) & 0.385 & 0.3 The pH of rivers was 7.4 (7.1 to 7.6) in the dry season and 8.2 (7.5 to 8.7) in the wet season, and the pH of lake was 8.2 (7.3 to 8.9) in the dry season and 8.5 (7.5 to 9) in the wet season. The pH of point sources was 8.3 (7.1 to 9) in the dry season and 8.3 (8.1 to 8.7) in the wet season. The recommended pH as per the standard for drinking, irrigation, and aquatic life is 6.5-8.6, and the pH of LHW was within the accepted limit (Table 6). The EC (TDS) of rivers was 148 mg/L (297 \(\upmu\)S/cm) in dry seasons and 89 mg/L (179 \(\upmu\)S/cm) in wet seasons, and EC (TDS) of lakes was 453 mg/L (877 \(\upmu\)S/cm) in dry season and 421 mg/L (829 \(\upmu\)S/cm) in wet seasons. The EC (TDS) of point sources was 1655 mg/L (3509 \(\upmu\)S/cm) in dry season and 1395 mg/L (2809 \(\upmu\)S/cm) in wet seasons. This shows that the EC (TDS) of rivers, lakes, and point sources increases significantly with increasing temperature (Table 6). The NO\({}_{3}-\)N concentration of rivers was 0.5 mg/L, NO\({}_{3}-\)N concentration of Lake Hawassa was 1.4 mg/L, and that of point sources was 1.5 mg/L for the dry season.