Managing Flood Hazard in a Complex Cross-Border Region Using Sentinel-1 SAR and Sentinel-2 Optical Data: A Case Study from Prut River Basin (NE Romania)

In this study, an alternative solution for flood risk management in complex cross-border regions is presented. In these cases, due to different flood risk management legislative approaches, there is a lack of joint cooperation between the involved countries. As a main consequence, LiDAR-derived digital elevation models and accurate flood hazard maps obtained by means of hydrological and hydraulic modeling are missing or are incomplete. This is also the case for the Prut River, which acts as a natural boundary between European Union (EU) member Romania and non-EU countries Ukraine and Republic of Moldova. Here, flood hazard maps were developed under the European Floods Directive (2007/60/EC) only for the Romanian territory and only for the 1% exceeding probability (respectively floods that can occur once every 100 years). For this reason, in order to improve the flood hazard management in the area and consider all cross-border territories, a fully remote sensing approach was considered. Using open-source SAR Sentinel-1 and Sentinel-2 data characterized by an improved temporal resolution, we managed to capture the maximum spatial extent of a flood event that took place in the aforementioned river sector (middle Prut River course) during the 24 and 27 June 2020. Moreover, by means of flood frequency analysis, the development of a transboundary flood hazard map with an assigned probability, specific to the maximum flow rate recorded during the event, was realized.

Dynamics of microelements (B, Al) in the water samples from the Prut river during the 2020 year

The purpose of this research was to study the dynamics of microelement content, the correlation between the main forms of migration of microelements (B, Al) - dissolved and suspended forms, except colloidal, and to study their seasonal variation. The main form of migration of the metalloid B in the waters of the Prut river is the dissolved one, while the migration form of Al is the suspensions. In this research, the content of the mentioned microelements was investigated in the water samples collected from the Prut River in 2020 (winter, spring, summer, and autumn) from 7 collection points. The microelements were determined using atomic absorption spectrophotometry (Perkin-Elmer AAnalist 400 atomic absorption spectrophotometer). The importance of determining trace elements in natural waters is determined by a number of issues, including the need to monitor the environment and assess environmental risks and assess their influence on living systems. The results of studying these forms of migration (dissolved and suspended) allow us a fuller understanding of their role in the migration of microelements in aquatic ecosystems in the system "water-suspensions-underwater deposits-hydrobionts".

Ihtiofauna lacurilor de acumulare Dubăsari și Costești Stânca în anul 2020

The present work presents the results of the research of the ichthyofauna of the largest accumulation lakes in the Republic of Moldova (Dubăsari on the Dniester River and CosteștiStânca on the Prut River) under the conditions of climate changes and intensification of anthropogenic pressure. The state of profound change in the ichthyocenosis of the Dubasari reservoir is demonstrated, which is currently dominated by small species (gobius species, bleak, bitterling, blackstriped pipefish), and indicates the urgent need to carry out ameliorating measures of populating the ecosystems with economically valuable species of fish, among which a significant share shall be placed on ichthyophagous species of fish, such as pikeperch, northern pike, catfish, asp. The higher share of oxyphilic and reophilous fish species in the fish catches from the Costești-Stânca accumulation lake reveals a more favourable ecological status of this ecosystem compared to the Dubasari accumulation.

Mineralizarea și raportul între ionii principali în apele râului Prut

The paper includes the results of mineralization research and the ratio of hydrogen carbonate and carbonate ions – HCO3 - + CO3 -, sulphates – SO4 -, chlorides – Cl-, calcium – Ca2+, magnesium – Mg2+, sodium – Na+ and potassium – K+, in the waters of the Prut River downstream of Costesti-Stinca reservoir (Braniste, Sculeni, Leuseni, Cahul, Cislita Prut, Giurgiulești) in 2020.

Consumul chimic de oxigen în apele râului Prut

Chemical oxygen demand (COD) was determined in water samples from the Prut River during 2020. Mean values of CODMn and CODCr ranged from 3.5 to 9.0 mg O2/L (5.5 ± 1.2 mg O2/L) and from 12 to 45 mg O2/L (22 ± 8.7 mg O2/L) respectively. The analysis of the results demonstrates the existence in the waters of the Prut River of easily degradable organic substances (an indicator of fresh and permanent pollution) and those that are difficult to degrade. According to the requirements of the Regulation on the quality of surface waters, the water from the Prut River for the period studied in accordance to the chemical oxygen demand with manganese is assigned to quality class I-II (very good – good), and after chemical oxygen demand with chrome – to class II-III (good – moderately polluted).

Potențialul producțional-destrucțional al bacterioplanctonului în ecosistemul Prutului de jos în anii 2015-2020

The results of studies on the production and destruction of organic matter by bacterioplankton, the relationship between them in the period of 2015-2019 in the Prut River, within the borders of the Republic of Moldova, are presented.

Dinamica efectivului numeric al bacteriilor amonificatoare și denitrificatoare în sectorul inferior al râului Prut în perioada a. 2015-2019

This paper reflects the seasonal and spatial dynamics of the number of microorganisms of the nitrogen cycle (ammonifiers and denitrifiers) in the lower areas of the Prut River.

Starea macrobentosului rîului Prut în anul 2020

In this study the author presents data on the density, biomass and diversity of macrobenthos along the Prut River in 2020. There are data on groups more sensitive to environmental changes and anthropogenic impact, collection points of interest in terms of species conservation due to the presence of rare species, the potential impact of invasive species.

Dinamica compușilor azotului mineral în apele râului Prut

In this article the results on the content of mineral nitrogen compounds (ammonium ions, nitrites and nitrates) during 2020 year in the Prut River Braniște – Giurgiulesti sector are presented. In the study is examinated the seasonal dynamics of these parameters in the winter – spring – summer – autumn period. The range of ammonium ions in the waters of the Prut River varies from 0.002 to 0.26 mgN /L, of nitrite – from 0.002 to 0.02 mgN /L and of nitrates – from 0.002 to 0.73 mgN /L, the maximums being lower than in 2009-2010, and much lower than in the 80s-90s of the last century.

The seasonal dynamics of phytoplankton and water quality in the Prut River lower sector

The article presents the results on qualitative and quantitative indicators of phytoplankton of the Prut River lower sector within the Republic of Moldova in 2018-2020. In phytoplankton compositions 72 species were identified. Seasonal and long-term patterns of phytoplankton development have been established in Prut River lower sector. The numbers of phytoplankton changed within the limits 1,06 to 20,32 mln. cell/l, with biomass 1,23-21,64 g/m3. The values of saprobic indexes, estimated on the basis of species-indicators (52 species) from phytoplankton composition, which are in proportion of 58% typically β-mezosaprobic, confirm the following: the water quality of lower Prut River sector in the period 2018-2020 was satisfactory for the development of phytoplankton and was attributed mainly to II-III (good-moderately polluted) quality classes.