# Integrated Assessment of Surface Water Quality in Danube River Chilia Branch
## 4 Conclusions  
Regular water quality evaluation may be complicated for large rivers due to the high number of monitored parameters in a huge volume of samples, which makes it difficult to express water quality status in a specific area. The results of this study represent a first step in assessment of water quality of Danube River branches at individual and integrated levels, while also giving a general overview of different pollution classes at the longitudinal level. A total of 106 samples of surface water were collected in the period 2013-2019 from the Danube River Basin, Chilia branch, from five sites (Periprava, Coastal Chilia, Izmail downstream, Bastroe upstream, and Bastroe downstream). The spatial distribution of the Chilia branch water quality at integrative level was carried out using GIS techniques. From the nutrients' point of view, Danube water in the Chilia branch is not polluted with ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, ortho- and total phosphorus. In 2015, the Chilia branch was polluted with organic nitrogen, a component of total nitrogen. CCME WQI method integrates the nutrient concentrations and the standard limits for second quality class, and it is a very useful tool for surface water managers, local and national authorities and inhabitants to evaluate the surface water quality in a selected sampling point and time. From a nutrient point of view, Coastal Chilia had an excellent quality in 2013, 2017, 2019, good quality in 2016, and fair quality in 2014 and 2015. Izmail downstream had an excellent water quality only in 2018 and a good quality in the rest of the monitoring years. Periprava had excellent quality in 2017 and 2019, good quality in 2015, 2016 and 2019, and fair quality in 2013 and 2014. Due to geographical position, Bastroe upstream and downstream showed the same trend, with excellent quality in 2013, 2017, 2019 and good quality in 2015, 2016, 2018. The accomplishment of this study started from the fact that in the literature there are very few studies related to the water quality of the Chilia branch from the chemical point of view. Our results showed different degrees of homogeneity for nutrient concentrations and also different concentration distributions. The next step is to include the other physico-chemical parameters in the CCME WQI, and to perform a comparison with other integrated indicators, targeted in international projects carried out in the Lower Danube and Black Sea Basins, in order to provide an overview on the Danube water quality of the Chilia branch at the longitudinal level. Conceptualization, L.T. and A.E. ; data curation, L.T. and A.E. ; formal analysis, L.T. and D.S.-O. ; funding acquisition, A.E. ; investigation, L.T., A.E., A.B., C.D., D.S.-O., C.T., O.I., E.B., M.-I.T., M.T., I.C., L.P.G. and C.I. ; methodology, L.T., A.E., A.B., C.D., D.S.-O., C.T., O.I., E.B., M.-I.T., M.T., I.C., L.P.G. and C.I. ; project administration, L.T. and A.E. ; resources, L.T. and M.T. ; software, L.T., A.E. and C.T. ; supervision, L.T. and M.T. ; validation, L.T., A.E., A.B., C.D., D.S.-O., O.I., E.B., M.-I.T., I.C., L.P.G. and C.I. ; visualization, C.T. ; writing-original draft, L.T. and A.E. ; writing-review and editing, L.T. and A.E. All authors have read and agreed to the published version of the manuscript. The APC is funded by \"Dunarea de Jos\" University of Galati, Romania. Not applicable. Data Availability Statement: The data that support the findings of this study are available from the first (LT) and corresponding (AE) authors, upon reasonable request. This research was funded by Romanian National Authority for Scientific Research and Innovation within the framework of Danube Delta Nucleus Programme and Joint Operational Programme Black Sea Basin 2014-2020 through the project with code BSB27 (MONITOX). The authors acknowledge the infrastructure and support of Danube Delta National Institute for Research and Development at Tulcea, Romania and INPOLDE research center of Dunarea de Jose University of Galati, Romania.