Lake Erenciuc is situated in the Danube Delta (Romania) and was created in the abandoned riverbed of the Sfântu Gheorghe arm. It is the largest meander lake in Romania. During spring–summer, the physico-chemical parameters of water have been measured in seven lake sampling points and one at the Sfântu Gheorghe branch, which supplies the lake through Erenciuc channel. The area around Lake Erenciuc belongs to the category of strictly protected areas within the Danube Delta Biosphere Reserve. The following water quality parameters were measured: temperature (T: °C); pH (pH units); Luminescent Dissolved Oxygen (LDO: mg dm−3); Dissolved Oxygen saturation (DO: %); water tension (U: mV); Electrical Conductivity (EC: μS cm−1); Total Dissolved Solids concentration (TDS: mg dm−3). The recorded values are easily differentiated across the entire length of the elongated lake path, especially between inflow (upstream) and outflow (downstream). The parameters recorded during the spring–summer period, with high flow rates and high water levels, demonstrate good lake water quality, especially oxygenation. The study also demonstrates that high waters refresh and recalibrate the water quality in isolated lake basins.
In this paper a class consisting of 8 environmental toxicants were selected to assess Danube River water quality between Calarasi-Silistra sector until the river flow into the Black Sea, the Romanian Monitox Network Area. A comprehnsive comparison between 2 years of investigations in terms of nutrients contribution, such as different forms of nitrogen (ammonium nitrogen (N-NH4+), nitrite nitrogen (N-NO2-), nitrate nitrogen (N-NO3-), organic nitrogen, total nitrogen (TN)) and phosphorus (orthophosphate phosphorus (P-PO4 -3), total phosphorus (TP)), was made in order to provide information on the spatial and temporal variations of this river water quality. Sampling was performed according to European standards and quantitatively analysed using molecular spectrophotometry using UV VIS spectrophotometer Perkin Elmer Lambda 650S. The obtained results showed differences in nitrite nitrogen loads in surface water samples with higher values in the samples collected from the sampling points situated at the mouths of the Danube River into the Black Sea in 2020. Regarding quality classes, the surface waters were generally framed, in good quality class. The nutrients concentrations, combined in CCME WQI index, give an overview on surface water quality assessement in Romanian Monitox Network Area, with a good quality of Lower Danube (Constanta in 2019 and 2020) and fair quality of Danube Delta in 2020, but very closed to good quality.
The Chilia branch is the north branch of the Danube River at the Romania-Ukraine border in the Danube Delta; it is a complex system with economic and ecological values. The surface water quality is a major concern and monitoring programs have been developed at the national and international level. The objective of this study was to evaluate the water quality of the Chilia branch in different sampling points from the mouth to the discharge in the Black Sea. The assessment of water quality was done at the individual level taking into account the nutrient concentrations and the standard limits for good ecological status and at integrative levels, using CCME WQI. The longitudinal distribution of Chilia branch water quality was done using GIS method. A total of 106 water samples were collected between 2013 and 2019 from five sampling points. At the individual level, the Chilia branch has a good ecological status except for its levels of total nitrogen, due to the organic nitrogen contribution in 2015. In 90% of nutrient concentrations, low values predominate and high values are considered extreme; only in 10% do high values predominate and low values are considered extreme concentrations. In equal percentages, 50% of the nutrient concentrations have a high degree of heterogeneity and the other 50% of concentration values are very close to the average values, with a high degree of homogeneity. CCME WQI method indicated that 39.93% of surface waters from the Chilia branch had an excellent quality, 45.45% a good quality, and only 14.62% a fair quality.
The hydrotechnical works on Sf. Gheorghe arm in Danube Delta was done by Institute for Research and Planning for Water Management. The work was part of the framework scheme for the Dobrogea hydrographic area and was nominated in the investment plan of the National Water Council. The regularization works, started in 1988, consists in the rectification of the main meanders of the arm in the following sectors: lvancea, Dranov, Dunavăț and Murighiol. The total length of the rectification is 15 km and the shortening of the natural course is 32 km. These works impose changes in the balance of the hydrological regime on the main course, along the meanders and on the channels connecting the arm waters and the aquatic complexes within the delta. By altering the fractal dimension of the arm, fluviatile processes are intensified and have irremediable long-term repercussions. This leads to the eutrophication of lakes in the aquatic complexes by low water intake, then clogging of the channels and, also, of the lakes resulting in diminishing / changing the habitats. As clear evidence are these two channels: Ivancea and Erenciuc north (completely clogged). Now, other 4 channels are threatened, which already show very low depths at the confluence with the Sf. Gheorghe arm. This is an exhaustive study of the current situation of the meanders of the Sf. Gheorghe arm from the morphological point of view and the fragile longitudinal and lateral connectivity through morphometric analysis methods using geomatics techniques. The foundation of this study will be based on existing literature, field data, historical and current data, in collaboration with other institutes and universities capable of providing important data such as sediments, hydro-technical works, etc.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.