## 3 Results
### Physicochemical Status
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{4}{c}{**Comparison of the Results of Upstream and Downstream HPs (Average Physicochemical Status)**} \\ \cline{2-7}  & \multicolumn{2}{c}{**Wroclaw II Hydropower Plant (HP)**} & \multicolumn{2}{c}{**Wroclaw I Hydropower Plant (HP)**} \\ \cline{2-7}  & **Improvement** & **Deterioration** & **No Changes** & **Improvement** & **Deterioration** & **No Changes** \\ \hline pH & 8.33\% & 2.78\% & 88.89\% & 0.00\% & 2.78\% & 97.22\% \\ \hline EC & 2.78\% & 2.78\% & 94.44\% & 0.00\% & 2.78\% & 97.22\% \\ \hline Temperature & 0.00\% & 0.00\% & 100.00\% & 0.00\% & 0.00\% & 100.00\% \\ \hline NH\({}_{4}\)-N & 0.00\% & 0.00\% & 100.00\% & 0.00\% & 0.00\% & 100.00\% \\ \hline NO\({}_{3}\)-N & 11.11\% & 0.00\% & 88.89\% & 8.33\% & 11.11\% & 80.56\% \\ \hline NO\({}_{2}\)-N & 2.78\% & 0.00\% & 97.22\% & 2.78\% & 5.56\% & 91.67\% \\ \hline PO\({}_{4}\)-P & 8.33\% & 19.44\% & 72.22\% & 19.44\% & 16.67\% & 63.89\% \\ \hline DO & 5.56\% & 8.33\% & 86.11\% & 2.78\% & 11.11\% & 86.11\% \\ \hline BOD\({}_{5}\) & 5.56\% & 16.67\% & 77.78\% & 8.33\% & 13.89\% & 77.78\% \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Detailed summary of the results of the average physicochemical status within the Wroclaw I and Wroclaw II hydropower plants. Figure 2: Average physicochemical status for the tested parameters within the Wroclaw I and Wroclaw II hydropower plants (HPs). Comparing the percentage of improvement and deterioration in the average physicochemical status for the Wroclaw II hydropower plant, an improvement was noted for NO\({}_{3}\)-N, pH, and NO\({}_{2}\)-N (by 11.11%, 5.56%, and 2.78%), and a deterioration was noted for BOD\({}_{5}\), PO\({}_{4}\)-P, and DO (by 11.11%, 11.11%, and 2.78%). For the Wroclaw I hydropower plant, an improvement was noted for PO\({}_{4}\)-P (by 2.78%), while a deterioration was noted for DO, BOD\({}_{5}\), pH, EC, NO\({}_{3}\)-N, and NO\({}_{2}\)-N (respectively by: 8.33 %, 5.56%, and 2.78% in the other six cases). The differences were, therefore, small and usually below 5%. Convergent results for both hydropower plants were obtained for DO and BOD\({}_{5}\). A deterioration in the average physicochemical status was noted for both of these parameters. In terms of the results against the limit values (Figure 3), there was an improvement for four out of the eight assessed parameters (BOD\({}_{5}\), NH\({}_{4}\)-N, DO, water temperature; changes from \(-\)2.21% to \(-\)60.00%), a deterioration for three out of eight parameters (PO\({}_{4}\)-P, NO\({}_{3}\)-N, EC; changes from 0.70% to 16.67%), and no change for one parameter, NO\({}_{2}\)-N.  
When analyzing the results separately for the Wroclaw I and Wroclaw II hydropower plants (Table 10), a greater percentage of improvements and deterioration of the calculated indicators related to the limit values of physicochemical parameters was observed than for the average physicochemical status. For the Wroclaw II hydropower plant, deterioration of values was noted for three out of eight parameters (EC, NO\({}_{3}\)-N, temperature, deterioration by 50.00%, 11.11%, and 8.33%, respectively, comparing the percentage of improvements and deteriorations) and an improvement was noted for five out of eight parameters (PO\({}_{4}\)-P, NH\({}_{4}\)-N, BOD\({}_{5}\), DO, and NO\({}_{2}\)-N by: 27.78%, 22.22%, 13.89%, 8.33%, and 2.78%, respectively). For the Wroclaw I hydropower plant, deterioration was noted for one of eight parameters (PO\({}_{4}\)-P, by 16.67%), improvement was noted for six of eight parameters (changes ranging from 8.33% to 30.56%), and no change (same number of improvements and deteriorations) was noted for one of eight parameters (BOD\({}_{5}\)). Convergent results were obtained in both hydropower plants for NH\({}_{4}\)-N, NO\({}_{2}\)-N, and DO. There were more cases of improvement than deterioration of values.