# Integrated Assessment of Surface Water Quality in Danube River Chilia Branch  
[PERSON]  
1 Danube Delta National Institute for Research and Development Tulcea, 16 Babadag Street, 820112 Tulcea, Romania; [EMAIL_ADDRESS] (L.T. ); [PERSON]S] (A.B. ); [PERSON](C.D. ); [PERSON]D.S.-O. ); [PERSON].T. ); [PERSON]ESS] (O.I. ); [PERSON] (E.B. ); [PERSON]SS] (M.-LT.); [PERSON]SS] (M.T. ); [PERSON]SS] (I.C.) 2 INPOLE Research Center, Faculty of Sciences and Environment, Dunarea de Jose University of Galati, 47 Domnensac Street, 800008 Galati, Romania  
European Center of Excellence for the Environment, Faculty of Sciences and Environment, Dunarea de Jose University of Galati, 800201 Galati, Romania; [PERSON](L.P.G. ); [PERSON]C.I.) [PERSON]  
1 Danube Delta National Institute for Research and Development Tulcea, 16 Babadag Street, 820112 Tulcea, Romania; [EMAIL_ADDRESS] (L.T. ); [PERSON]S] (A.B. ); [PERSON](C.D. ); [PERSON]D.S.-O. ); [PERSON].T. ); [EMAIL_ADDRESS] (O.I. ); [PERSON] (E.B. ); [PERSON]SS] (M.-LT.); [PERSON]SS] (M.T. ); [PERSON]SS] (I.C.) [PERSON]  
1 Danishce Delta National Institute for Research and Development Tulcea, 16 Babadag Street, 820112 Tulcea, Romania; [EMAIL_ADDRESS] (L.T. ); [PERSON]S] (A.B. ); [PERSON](C.D. ); [PERSON]D.S.-O. ); [PERSON].T. ); [PERSON]ESS] (O.I. ); [PERSON] (E.B. ); [PERSON]SS] (M.-LT.); [EMAIL_ADDRESS] (M.T. ); [PERSON]SS] (I.C.) Marian Tudor  
impacts on aquatic life, biomass growth, oxygen concentrations, water clarity, and sedimentation rates [1; 2; 6; 7]. They play an important role in the eutrophication process and pose a serious problem for the monitoring and estimation of their effects on water quality in a riverine environment, being difficult to control [2; 8; 9; 10]. The Danube is the second largest river in Europe and twenty-first in the world, passing through Europe from west to east, flowing through or forming a part of the borders of ten countries-Germany, Austria, Slovak Republic, Hungary, Croatia, Serbia, Bulgaria, Romania, Moldova, and Ukraine. In addition, its drainage basin includes areas of nine more countries: Italy, Poland, Switzerland, Czech Republic, Slovenia, Bosnia and Herzegovina, Montenegro, Republic of Macedonia, and Albania [11] (Figure 1a). The Danube River has been an important link in Central Europe as well as the border between EU and the Balkans and Black Sea Region [12; 13]. In the lower part, before reaching the Black Sea, the Danube River is divided into three main branches: Chilia, Sulina, and Sfantu Cheorghe (St. George), forming a remarkable delta, the Danube Delta (Figure 1a). Water pollution caused by the high population density and heavy industrialization in the catchment area is a major problem in the Danube [11]. Through its three branches, the Danube is by far the most important contributor to the regional nutrient pollution and is directly responsible for eutrophication processes within the river and in the Black Sea [10; 14; 15]. Having a length of 104 km, the Chilia branch, a natural border between Romania and Ukraine, is a very dynamic ecosystem in terms of biological activities, with  
Figure 1: Geographical location of: (**a**) Danube River basin, Danube Delta, and the three branches (Chilia, Sulina, and Sfantu Cheorghe), and (**b**) sampling points from Danube River Chilia branch. temporal and spatial variations of nutrient concentrations [13]. In the last few decades, local and national authorities raised concerns regarding the Danube water quality, including the Chilia branch, determined by the fact that it is an important source of drinking water for the riparian population, in most cases without being subjected to any processes of drinking water extraction [14]. During regular monitoring and assessment of water quality, large datasets could be collected, which contain rich information about the water characteristics in a huge volume of samples [16; 17].