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This paper aims to identify the impact of anthropogenic changes caused by the construction of the Bastroe Canal on the hydrology, hydrochemistry and biodiversity of the Danube Delta Biosphere Reserve (DDBR). The paper wants to provide a knowledge tooi that can be a working basis for government and local decision-makers due to the special importance of conserving the biodiversity of this area. The impact of the Bastroe Canal will be revealed through a synthesis of the conclusions of the main studies carried out by institutes in Romania in the period 2004 - 2020.

Located in the Danube Delta Biosphere Reserve, the Chilia branch serves as country boundary between Romania and Ukraine. The former state started in 2004 a project intended to increase the navigability capacity of Bystroe Channel, the environmental impact of the works carried out being discordantly considered by the Romanian and Ukrainian authorities. The Inquiry Commission established under the Espoo Convention, of which both countries are part of, delivered its final opinion that the project was likely to have a significant adverse transboundary impact on the hydrodynamic local conditions and habitat loss for fish and birdlife. Statistical analysis was operated on daily and monthly averaged water discharge values and the results were graphically displayed as hydrographs and probability curves and distribution. Addressing the in situ data measurements deficit for the Chilia branch - Bystroe Channel Area, measurement campaigns have been carried out in order to monitor the alterations of the hydrodynamic parameters. Using the specialized Acoustic Doppler Current Profilers technique, there have been recorded water flow parameters (water discharge and water current velocity vectors) and the data used for analysis and 2D and 3D representation of the hydrodynamic conditions.

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.

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