# Integrated Assessment of Surface Water Quality in Danube River Chilia Branch
## 3 Results and Discussion
Surface waters from Coastal Chilia (2014, 2015), Periprava (2013, 2014) and Bastroe Upstream (2018) are ranked in the fair quality class, the water quality being usually protected but occasionally threatened or impaired; conditions sometimes depart from natural or desirable levels [22]. Low values of CCME WQIs have been attributed to a high level of total nitrogen and nitrites. In our study area, using the QGIS interpolated data for CCME WQI, which integrated the nutrient concentrations, this global indicator was ranked in 10 graduated quantile classes, with different trends between 2013 and 2019 (Figures 4-10). It can be noticed that from the start (Ceatal Chilia) to the end of the branch (Bastroe Downstream), in 2013, 2017, and 2019 the CCME WQI has the same shape, with maximum values at the extreme points, corresponding to excellent water quality, and graduated lower values along the branch. In 2014, CCME WQI values did not reach the highest values. So, the quality of water collected from the Chilia mouth has the lowest values, corresponding to the fair water quality class and, for the rest of this branch, the water quality increases from Ceatal Chilia to Periprava. In 2018, the water quality of the Chilia branch decreases from west to east, from Ceatal \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sampling Point**} & \multirow{2}{*}{**Variables**} & \multicolumn{8}{c}{**Values**} \\ \cline{3-8}  & & **2013** & **2014** & **2015** & **2016** & **2017** & **2018** & **2019** \\ \hline \multirow{4}{*}{Ceatal Chilia} & F1 & 0.00 & 33.33 & 33.33 & 16.67 & 0.00 & 0.00 & 0.00 \\  & F2 & 0.00 & 9.52 & 11.11 & 4.17 & 0.00 & 0.00 & 0.00 \\  & nse & 0.00 & 0.05 & 0.21 & 0.01 & 0.00 & 0.00 & 0.00 \\  & F3 & 0.00 & 5.14 & 17.53 & 1.20 & 0.00 & 0.00 & 0.00 \\  & CCME WQI & 100.00 & 79.77 & 77.33 & 90.06 & 100.00 & 100.00 & 100.00 \\ \hline \multirow{4}{*}{Izmail Downstream} & F1 & 16.67 & 16.67 & 16.67 & 16.67 & 16.67 & 0.00 & 16.67 \\  & F2 & 5.56 & 12.50 & 8.33 & 8.33 & 5.56 & 0.00 & 5.56 \\  & nse & 0.01 & 0.02 & 0.03 & 0.04 & 0.01 & 0.00 & 0.02 \\  & F3 & 0.99 & 1.91 & 2.64 & 3.89 & 1.28 & 0.00 & 1.64 \\  & CCME WQI & 89.84 & 87.92 & 89.13 & 89.01 & 89.83 & 100.00 & 89.81 \\ \hline \multirow{4}{*}{Periprava} & F1 & 33.33 & 33.33 & 16.67 & 16.67 & 0.00 & 33.33 & 0.00 \\  & F2 & 11.11 & 13.89 & 11.11 & 12.50 & 0.00 & 8.33 & 0.00 \\  & nse & 0.22 & 0.10 & 0.04 & 0.04 & 0.00 & 0.03 & 0.00 \\  & F3 & 17.84 & 9.21 & 4.22 & 3.41 & 0.00 & 3.14 & 0.00 \\  & CCME WQI & 77.25 & 78.48 & 88.18 & 87.81 & 100.00 & 80.08 & 100.00 \\ \hline \multirow{4}{*}{Bastroe Downstream} & F1 & 0.00 & - & 16.67 & 16.67 & 0.00 & 33.33 & 0.00 \\  & F2 & 0.00 & - & 5.56 & 8.33 & 0.00 & 8.33 & 0.00 \\  & F2 & 0.00 & - & 5.07 & 4.74 & 0.00 & 3.10 & 0.00 \\  & CCME WQI & 100.00 & - & 89.44 & 88.90 & 100.00 & 80.08 & 100.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: CCME WQI evaluation values of the Chilia branch (2013–2019). Figure 8: CCME WQI trends in 2017 on the Chilia branch. Figure 7: CCME WQI trends in 2016 on the Chilia branch. Figure 9: CCME WQI trends in 2018 on the Chilia branch. Taking into account the classification of water quality based on CCME WQI and regular WQI calculation [3] (Tables 4 and 7), Table 8 presents a comparison between the results obtained by applying both indices. At the integrative level, on the whole Chilia branch, throughout the analyzed period, respectively 2013-2019, taking into account the nutrient concentrations both in dissolved and total form, we found a similarity of the quality classes established according to two complex indicators, respectively WQI and CCME WQI (Table 7). Thus, 38.72% of surface waters (according to WQI) and 41.94% (according to CCME QWI) are in very good ecological condition. In good ecological condition are 54.84% of the surface waters taken from the