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Awareness of the potential threat of significant natural hazards necessitates the introduction of appropriate procedures allowing for effective and systematic actions aimed at eliminating, or at least partially limiting the effects of such events. Due to the nature of drought and the complex process of its development, the cause and effect approach is widely used in assessing droughts. Naturally, this leads to the treatment of drought in terms of risk, which is defined as a derivative of hazards and consequences. Thus formulated definition of drought leads, in a broader context, to endeavours at minimizing the effects and reducing the size of losses, taking into account the prioritization of activities. An active drought risk management policy is necessary to achieve the safety of water resources in the face of current climate threats and expected further changes. The aim of this work is to present the original concept of drought risk assessment for the needs of strategic risk management as an integrated approach to the implementation of the drought management plan. Risk management is crucial and necessary to effectively reducing the effects of drought in a sustainable manner, in the context of meeting the needs of the population, the environment, and the economy. Risk management is a continuous process, consisting of logically arranged, consecutive events, actions, decisions and approvals, repeated cyclically in the course of monitoring the achieved results and implementing optional adaptations to the observed and forecasted changes. The risk management system presented in the work creates an organizational, methodical and functional framework, the implementation of which in the form of structural and IT solutions may be a tool for effective operation of plans aimed at counteracting the effects of drought on the level of particular water regions and river catchments. The proposed approach, based on strategic management in pursuit of sustainable assurance of water safety for social and natural systems, ensures durability of services of freshwater ecosystems responsible for maintaining biodiversity, maintaining life processes and regeneration of the environment, as well as providing people with economic benefits. The integrated SPI-SRI index of coexistence of humidity conditions was used to assess the risk of drought. The aforementioned index made it possible to determine the likelihood of a drought in probabilistic terms, including the phase of atmospheric and hydrological drought in a given basin, which is a key element in drought risk assessment. The estimated period of repeatability of the threat of dry or very dry meteorological conditions leading to hydrological drought in the Nysa Kłodzka catchment was calculated as once every 7.2 years, and in the Prosna catchment, once every 8 years. This information can be used in planning actions aimed at minimizing the effects of drought, and in water management (for instance, on reservoirs) aimed at reducing these effects.
Oszacowanie wysokości opadów wywołujących letnie wezbrania w dorzeczu środkowej Odry wykonano na podstawie dobowych sum opadów z 53 stacji opadowych w wieloleciu 1971-2005. Krytyczną wartość opadu poszukiwano spośród wartości 5-dniowych sum opadów o prawdopodobieństwie przewyższenia (p) od 10% do 0,1%. Wyznaczono zależności funkcyjne pomiędzy prawdopodobieństwem przewyższenia danej sumy opadu a wysokością nad poziomem morza. Uzyskane zależności pozwoliły na ocenę częstości przewyższeń danej sumy opadów w określonym piętrze wysokościowym. W poszczególnych latach badanego wielolecia wyznaczono ilość 5-dniowych epizodów opadowych w poszczególnych przedziałach p: >10%, [10% –5%), [5% – 2%), [2% – 1%), [1% – 0,1%), ≤ 0,1%. Uporządkowując uzyskane zestawienie według ilości epizodów o prawdopodobieństwie p ≤ 1%, wyselekcjonowano lata, w których wystąpiły znaczne obszarowo wezbrania w dorzeczu środkowej Odry. Z analizy zależności pomiędzy średnią wartością opadu a stopniem zagrożenia obszaru oszacowano wysokości opadu, które mogą powodować średnie i poważne zagrożenia wezbraniowe.
Flooding in East-Central Europe in May and June 2010 also affected the Odra River Basin. Unlike a typical summer flood scenario, in 2010 intensive precipitation was observed as early as May. Also, the location of the most intensive rainfall shifted to the catchments of the right bank tributaries of the Odra River. This paper presents the climatological assessment of the precipitation totals that caused two flood waves on the Odra River. The assessment was carried out with the use of selected indicators: monthly precipitation totals, daily precipitation totals, number of days exceeding given precipitation levels, number of days with precipitation of a given probability of exceedance and intensity, duration and accumulation of precipitation for a number of consecutive wet days. The reference values for climatological indicators were developed for the period 1966-2009. The values of the selected indicators were analyzed in terms of flood hazard in relation to the hazard gradation. The results show that the observed precipitation had the character of an extreme event with respect to its magnitude, duration and spatial extent. The catchments with recognized high levels of flood hazard were affected by the flood wave. The flood situation caused by the extreme precipitation was evaluated in the context of the largest floods in this region during recent decades.
Global climate change is anticipated to have consequences on water resources and the envi-ronment both at global and local/regional levels. Efforts towards proper management of future water resources and resolving potential water-related conflicts require the formulation of appropriate techniques to downscale the output of global climate models (GCM) to local conditions for hydrologic prediction. The paper presents an integrated framework for modeling the impact of climate change on river runoff that combines methodology for downscaling climate change scenarios for a basin scale with a hydrological model to estimate the impact of climate change on a river runoff. The modeling framework uses long-term observations of meteorological and hydrological variables together with a climate change scenario to provide a projection of future flows for the specified time horizon. The framework is based on a spatial weather generator and a distributed rainfall-runoff model. Such a configuration enables a reflection of the uncertainty of future conditions by running multiple realizations of future conditions, and also take into account the spatial variability of hydrological properties in the catchment by maintaining the physical details at a given grid size. The performance of the framework was presented for the Kaczawa basin that is one of the main left bank tributaries of the Odra River – the second biggest river in Poland. The results show simulated changes of the future river flow regime caused by climatic changes for two time horizons: 2040 and 2080.
The overall objective of the ongoing work is to develop the computational environment HY DRO-PATH as a flexible tool for forecasting runoff from catchment areas for various hydrometeorological conditions while taking into account the information available on a real-time basis. Ensuring the model’s operational reliability and reducing the uncertainty of generated forecasts is accomplished through the adjustment of both the internal structure of the model and the spatial representation of the computational grid to the physiographical, hydrological and climatological characteristics of a given basin. The research focused on the development of methods for selecting the optimal model structure and parameters by analysing the results obtained for different model structures. This is achieved through the computational environment, in which it is possible to implement different types of hydrological rainfall-runoff models. These models have a unified system of data input, parameter optimisation rules, and procedures for result generation. The developed elements of the computational environment correspond to generation potential of models with a given structure and complexity. Furthermore, within the framework of HY DRO-PATH the following components were developed: an application programming interface (API), a data assimilation module, a module for computational representation of a real object, and a module for the estimation and optimisation of model parameters. The developed computational environment was applied to prepare a version of TOPO-Flex and perform hydrological validation of the model’s results. The hydrological validation was performed for selected flood events in the Bystrzyca Dusznicka subbasin of the Nysa Kłodzka River.
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