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Reproducing the hydrological process of river runoff is a fundamental part of water resources planning and management. Finding a mathematical model to reproduce the runoff time series aims not only to extract maximum information from the limited available data, but also to extrapolate into the future by representatively generating the historical runoff process. Almost all management decisions are based on forecasts. Our present is characterized by the increasingly frequent occurrence of hydrometeorological process...

A classical approach to the assessment of the available water resources for different users, including environmental, in Europe is the Catchment Abstraction Management Strategy (CAMS). An assessment has to be made of the extent, to which natural runoff regime could be changed without affecting the sustainable functioning of the environment. The aim of the Restoring Sustainable Abstraction (RSA) is to identify over-abstraction in rivers and wetland sites and make the abstraction sustainable again. In this regard, t...

Climate factors are already exerting negative pressure on water resources, society and ecosystems. The analysis of trends and identification of vulnerable water supply areas is related to the River Basin Management Plans. For this end, a methodology for assessment of water resources vulnerability, developed in international projects of the National Institute of Meteorology and Hydrology (NIMH), is adapted. The methodology is further developed by drought risk assessment. The main stages are: 1) Assessment of the cl...

The results of many research projects and studies report that landuse/ landcover change (LULCC) is a major driver of the changes in the hydrological processes within a watershed. Landuse induced landcover changes, e.g., urbanization, deforestation, have a direct impact on the hydrological regime of watersheds thus increasing their vulnerability to extreme hydrological events. In this research the Soil and Water Assessment Tool (SWAT) was used to study the landuse/landcover change impact on the hydrological dynamic...

Accurate river flow forecasting is an extremely important issue for proper management and optimal use of water resources as well as for warnings of extreme hydrometeorological events. Rainfall-runoff simulation is essential for short and longterm forecasting of the river discharge. Determining the relationship between rainfall and runoff is one of the most important tasks faced by hydrologists. This relationship is a nonlinear and extremely complex process influenced by many factors such as watershed topology, veg...

Water resource of a given river basin is the main component of the ecosystem and water resources management system as well. Ecological flows are considered within the context of the Water Framework Directive (WFD) as -a hydrological regime consistent with the achievement of the environmental objectives of the WFD in natural surface water bodies as mentioned in Article 4(1). The so-called Heavily Modified Water Bodies (HMWB) or -regulated rivers- have modified flow, which is influenced by reservoir compensation rel...

Future climate scenarios of the Global Circulation model (GCM) show an increased frequency of heavy rainfall events, which may lead to more severe floods. It is also expected that more and more areas will suffer due to flooding as a result of growing urbanization. Public attention has increased in many parts of the world in recent years and calls have been made to improve flood warnings, including the United States, the European Union and Australia (Hapuarachchi, H.A.P, and Q.J. Wang 2008). To respond and manage f...

The development of indicator systems for drought identification is part of the Drought Management Plans. The analysis of the correlation between the different indices is an essential part of the indicator systems. That research is part of a task related to the developed at NIMH system (http://hydro.bg) of drought indicators and the development of recommendations for their simultaneous use. For this purpose, the influence of climatic factors on the hydrological cycle components and the role of the characteristics o...

Drought indicator systems help decision-makers to understand how and where the drought occurred and to take measures from the Drought Management Plans. The main goal in the Water Framework Directive (WFD) is the achievement -good ecological status-, but the Article 4.6 allows temporary deterioration of the status, occurred as a result of so called -prolonged drought-. Reduction of natural water resources such as rivers, lakes, aquifers, is associated with the reduction in available water resources for water supply...

Flash floods are defined as rapidly developing extreme events caused by heavy or excessive amounts of rainfall. Flash floods usually occur over a relatively small area within six hours or less of the extreme event with quite a rapid streamflow rise and fall. Increased occurrence of flash flood events is expected due to climate change and increase in extreme precipitation events [1]. Flash flood forecasting is still a challenge for hydrologists and water professionals due to the complex nature of the event itself. ...

Floods are one of the deadliest natural disasters in the world. According to the World Meteorological Organization (WMO), this is a consequence of the increasing frequency of heavy precipitation, changes in upstream land use, and a continuously increasing concentration of population and assets in flood-prone areas [1]. For this reason, flood prevention, and protection are a growing priority these days. Flood hazard mapping is a state-of-the-art tool for decision-makers and stakeholders when it comes to flood prote...

Floods are the most frequent and widespread natural disasters worldwide (WMO, 2013). In 2006 for instance, exceptionally high river levels caused loss of lives and considerable economic losses in Serbia, Bulgaria and Romania. Thus risk prevention strategies were reconsidered and the need for common solutions for the Danubian countries was outlined. Non-structural measures to mitigate flood risk as is the improvement of forecasting capabilities on a basin-wide scale are known to be highly effective. The DAREFFORT p...

During the last decades the extreme hydrometeorological events increased. Respectively the needs for more accurate estimation of the precipitation amounts have increased. One of the opportunities to get denser precipitation data in space and time is through the remote-sensing. Satellite-based products allow obtaining spatially distributed hydrologic variables and could be very useful in the modeling of the elements of the hydrological cycle. A big variety of hydrological models exist nowadays. In this study the fu...

In studying WRS that belong to complex probability systems, it is necessary first to make a mathematical description of the input process of the system - the process of changing the river flow. The use of the available series, which cover several decades of years (in Bulgaria about 30-70 years), cannot reflect the alternation of sequences of high-water and low-water years and the great diversity of the intra-annual runoff distribution, which characterizes the different water years. For these reasons, studies based...

Modeling is important for river system analysis and management. The aim of the research is to apply disaggregation models to data with recovered natural river flow of Osam River located in North Bulgaria. As a result river discharge synthetic sequences are generated on monthly and seasonal discretization. We want to test applicability of the models for specific climatic, hydrological and orographic conditions in Bulgaria. Disaggregation models are from the family of stochastic models. Disaggregation models could b...

The updating of the used inflow data to the reservoirs from Annex 1 of the Water Act has been developed for the needs of the Ministry of Environment and Water (MoEW) and for the annual schedules of their water use. Monthly inflow with a certain probability of exceedance (PE - 50%, 75%, 95%) were estimated. The results of the development are uploaded to the MoEW website(https://www.moew.government.bg).In the report are presented and new unpublished results of the annual security assessments - annually inflows with ...

Reservoirs are important hydraulic infrastructure for water use and flood control. Their impact on the hydrological regime of rivers downstream is significant. Accurate and reliable forecasting of flows in the rivers below the reservoirs is very important in cases of extreme meteorological events (heavy rains) for flood mitigation. The evolution of physically based hydrological models in recent years significantly improved the ability to describe and represent the hydrological processes at a basin scale. This pape...

Water resources are vulnerable not only from climate change, but from many other socio-economic drivers of change. According to the Intergovernmental Panel on Climate Change ?Vulnerability is the degree, to which a system is susceptible to, or unable to cope with adverse effects of climate change, including climate variability and extremes?. When a trend towards decreased precipitation and runoff coincides with a trend towards higher water consumption or deteriorated water quality, then the given region or river b...

The hydrological processes are very complex and the hydrological and hydraulic models are the main components of the flood forecasting and warning systems. They identify the dominant hydrological processes which influence water balance and result in conditions of extreme hydrological events. A variety of hydrological models exist nowadays. In this study the physically-based, fully distributed hydrological TOPKAPI (TOPographic Kinematic APproximation and Integration) model was applied on Aytoska river catchment. Th...

Climate change exerts influence on water resources and runoff directly ? by altering natural factors (precipitation, temperature, evapotranspiration) and indirectly ? by induced as a result of climate change land use alterations (forests, wetlands, etc.). The report presents the methodological approach for estimation of the cumulative impact of both climate and land use changes on the availability of water resources. For calculation of water balance a Model of monthly water balance, created in the United States Ge...

In terms of climate change and extreme events, the role of the complex water systems and reservoirs management is increasing. Under these conditions the management of the built water reservoirs is of primary importance for both: responding to high-wave and for ensuring the ecological flow and water consumption during drought periods. In order to improve the complex and significant reservoir management, it has been initiated a phased development of a Decision support system (DSS) with the appropriate modules. The u...