Long-Term Trends in Water Quality Indices in the Lower Danube and Tributaries in Romania (1996–2017)

Abstract

The Danube River is the second longest in Europe and its water quality is important for the communities relying on it, but also for supporting biodiversity in the Danube Delta Biosphere Reserve, a site with high ecological value. This paper presents a methodology for assessing water quality and long-term trends based on water quality indices (WQI), calculated using the weighted arithmetic method, for 15 monitoring stations in the Lower Danube and Danube tributaries in Romania, based on annual means of 10 parameters for the period 1996–2017. A trend analysis is carried out to see how WQIs evolved during the studied period at each station. Principal component analysis (PCA) is applied on sub-indices to highlight which parameters have the highest contributions to WQI values, and to identify correlations between parameters. Factor analysis is used to highlight differences between locations. The results show that water quality has improved significantly at most stations during the studied period, but pollution is higher in some Romanian tributaries than in the Danube. The parameters with the highest contribution to WQI are ammonium and total phosphorus, suggesting the need to continue improving wastewater treatment in the studied area. The methodology and the results of the study may be very useful instruments for specialists and decision makers in updating river basin management plans and prioritising intervention measures.

Danube Delta: Water Management on the Sulina Channel in the Frame of Environmental Sustainability

“…In order to have an overview on the water quality status in different locations along the Danube River, including the monitored area of this study (highlighted in Bold), the average concentrations for the selected indicators (nutrients and organic load (COD)) during (2013)(2014)(2015)(2016)(2017)(2018), are presented in Table 1 [40,41].…”

“…This could be explained taking into consideration the pollution generated by the anthropogenic activities, especially brought by the tributary rivers from the Romanian territory, which are more polluted than the Danube River. In order to support this information we will present a very recent study [41], including the map of the Lower Danube basin with 15 sampling points (related to both Danube River and respectively in the tributary rivers at the discharged points), which is presented in Figure 19.…”

“…This study presents a complex methodology for assessing water quality based on WQI (Water Quality Index), applied at 15 monitoring points from the Lower Danube and Romanian tributaries for a period of 10 years. The water quality has improved in time at the most sampling points, but some of the Romanian tributary rivers are more polluted than the Danube and still require efforts to improve wastewater treatment from urban agglomerations [41].…”

“…Based on the same database [41], in order to have an overview on the water quality discharged into the Black Sea by Danube Delta trough each branch (Chilia, Sulina, Sfantu Gheorghe), including the monitored area of this study (highlighted in Bold), the average concentrations for the selected indicators (nutrients and organic load (COD)) during (2013-2018) are presented in Table 2. 13-Chilia (at the Black Sea); 14-Sulina (at the Black Sea); 15-Sfantu Gheorghe (at the Black Sea); Danube River-Black points, tributary rivers-Blue points [41,42]. A very good correlation of AE0.01 mg/L was found between our results and these reported by [41], for all water quality indicators, except the value for NH4-N which was higher with 0.05 mg/L and for Total-P which was higher with 0.01 mg/L.…”

“…13-Chilia (at the Black Sea); 14-Sulina (at the Black Sea); 15-Sfantu Gheorghe (at the Black Sea); Danube River-Black points, tributary rivers-Blue points [41,42]. A very good correlation of AE0.01 mg/L was found between our results and these reported by [41], for all water quality indicators, except the value for NH4-N which was higher with 0.05 mg/L and for Total-P which was higher with 0.01 mg/L.…”