The geographical position of the Bistrita River favours a rich liquid run-off and great hydrotechnical potential. The Bistrita drainage basin is strongly developed from the hydrotechnical point of view. Within the drainage basin, numerous dams and storage reservoirs are installed with the purpose of producing electricity and reducing flood hazards. However, these structures could not stop floods at the drainage basin level. The most powerful floods from Bistrita River basin and the role in flood control of each of the storages are analysed in this paper. The hydrological data have been collected from the monitoring network, where the researchers elaborating this study are performing their daily activity. The most powerful floods in the last century took place in 1970, 1991, 2005 and 2010. An intensification of the floods can be noticed after the year 1990, a period which coincides with large-scale deforestation of the small drainage basins. Disastrous floods occurred as a consequence of summer heavy rains, with amounts of 100-200 mm within 24 h. The most powerful floods were recorded in 2005 and registered discharges up to 1,200 m 3 /s. Izvoru Muntelui reservoir, the biggest in the system, can take most of the waters in excess. The reservoirs located downstream are silting up, and the supplementary flows cannot be absorbed entirely by storage. The exact knowledge of flooding phenomena requires studies that can prevent and diminish the damages caused by extreme hydrological events.

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The issue of water management as well as its impact on the community has been both a challenge and a concern of the European Union, which lead to adopting the Directive 2007/60/EC with the purpose of establishing a framework for the assessment and management of flood risks, by which the member states had to identify the areas for which they conclude that potential significant flood risk exist or likely to occur and to develop flood risk management plans and measures to reduce the consequences of flooding. In this respect, the Siret Water Basin Administration has declared the area of the Tazlău river, as a significant flood risk area (A.P.F.S.R.) (*** A.B.A Siret). The Tazlău River is a left-bank tributary to the Trotuș River, passing through the ten communes and partially through the outside the built-up areas of Onești city. Recent studies have shown the benefits of reservoirs and floodplains, as these provide the most effective way to buffer the effect of floods by slowing and spreading the discharge of a river (Băloi, 1980). By restoring and improving an existing lateral floodplain in the Tazlău River basin, in order to store part of the floodwaters that cause significant adverse consequences, will reduce the flood vulnerability of its crossings.

This study aims to analyze the surface waters of the Trebes River. The Trebes-Negel River Basin is also known as the representative basin and it is the right tributary of the Bistrita River. The monitoring of this river reflects in a database necessary for the analysis of the long-term tendency of the hydrological regime, both in natural conditions and influenced by anthropogenic activities. The contact area between the Eastern Sub-Carpathians, in their middle part, and the Central Moldavian Plateau present a series of morphological peculiarities determined by a corrugated and varied structure, by an alternation of tough hard rocks and the action of the flowing water. These morphohydrographic peculiarities corroborated with climatic conditions dependent on the latitude, orientation and altitude of the major relief forms are determinant for genesis and flow regime. The first advantage in studying small river basins is that the results can be extrapolated for larger basins. Also, the magnitude of the analyzed data is smaller. The results of this study can certainly provide important information and can contribute to the implementation of effective measures in order to protect and prevent floods. The results of this study play an important role in the elaboration of hydrological prognosis of immediate or long-term utility because it is necessary to know in detail the variability in time and space of some hydrological parameters. The current period is characterized by an economic distinguished soar that requests for increasingly more water as a component of technological processes or as an indispensable part of sanitation for large human agglomerations.

The increase in most components of the climate over the past 50 years, including air and water temperature, is a real phenomenon, as attested by the numerous specialized researches according to IPCC (2013). The water temperature is one of the most important climatic components in analyzing the hydrological regime of the Bistrita River (Romania). The thermal regime of the Bistrita River basin and the frost phenomena associated with the risk factor are particularly important and frequently appear in this area. In recent years, under the Siret Water Basin Administration, this parameter was permanently monitored, so we could do an analysis, which shows that the water temperature fluctuations, influenced by air temperature, lead to the emergence of the ice jam phenomenon. The present study aims to analyze the water temperature, as compared to the air temperature, and the effect of these components on the liquid flow regime (the values were recorded at the hydrological stations on the main course of the Bistrita River). The negative effects resulted from the ice jam phenomenon require developing methods of damage prevention and defense. The frost phenomena recorded after the construction of the Bicaz dam are analyzed in this article