Adapting flood preparedness tools to changing flood risk conditions: The situation in Poland

Flooding is the most destructive natural hazard in the Baltic Sea Basin in general and in Poland in particular. The notion includes floods from rivers and mountain torrents, as well as floods from sea surges in coastal areas, and floods from sewage systems. There have been several large floods in Poland in the last century and in recent decades, with damage exceeding 1% of the Polish GDP. The spatial and temporal characteristics of the flood risk in Poland are reviewed and observations and projections of changes in the flood hazard in the country are discussed. Furthermore, flood defences and flood preparedness systems in Poland are examined, with particular reference to the European Union (EU) Floods Directive, which is being implemented in Poland, an EU country. Finally, the public debate on flood risk and flood preparedness is reviewed

Assessing the influence of the Merzbacher Lake outburst floods on discharge using the hydrological model SWIM in the Aksu headwaters, Kyrgyzstan/NW China

Glacial lake outburst floods (GLOF) often have a significant impact on downstream users. Including their effects in hydrological models, identifying past occurrences and assessing their potential impacts are challenges for hydrologists working in mountainous catchments. The regularly outbursting Merzbacher Lake is located in the headwaters of the Aksu River, the most important source of water discharge to the Tarim River, northwest China. Modelling its water resources and the evaluation of potential climate change impacts on river discharge are indispensable for projecting future water availability for the intensively cultivated river oases downstream of the Merzbacher Lake and along the Tarim River. The semi-distributed hydrological model SWIM was calibrated to the outlet station Xiehela on the Kumarik River, by discharge the largest tributary to the Aksu River. The glacial lake outburst floods add to the difficulties of modelling this high-mountain, heavily glaciated catchment with poor data coverage and quality. The aims of the study are to investigate the glacier lake outburst floods using a modelling tool. Results include a two-step model calibration of the Kumarik catchment, an approach for the identification of the outburst floods using the measured gauge data and the modelling results and estimations of the outburst flood volumes. Results show that a catchment model can inform GLOF investigations by providing ‘normal’ (i.e. without the outburst floods) catchment discharge. The comparison of the simulated and observed discharge proves the occurrence of GLOFs and highlights the influences of the GLOFs on the downstream water balance. © 2013 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd

Extreme hydrological events and security

proc-iahs.net/369/181/2015/ doi:10.5194/piahs-369-181-201

Climatic Change Impact on Water Resources - A Systems Review

Global climate change related to natural and anthropogenic processes has been the topic of many research projects and high-level debates. Despite the ongoing research efforts, the climate predictions cannot be rated any better than speculative or possible scenarios whose probability of occurrence is, at the present stage, impossible to assess. One of the most significant impacts of the "greenhouse effect" is anticipated to be on water resources management, including different elements of the hydrologic cycle, water supply and demand, regional vulnerability, and water quality. Thus, the impact of climate change appears to be an additional component on top of the large number of stressing (existing and likely future) water related problems. The existence of the greenhouse effect, the increase of greenhouse gas emissions, and the rise of corresponding concentrations are certain things. However, impacts become increasingly uncertain as we move towards hydrology and water management. For this analysis, we would need information on much smaller spatial and temporal scales (i.e. a basin, a subbasin, or an agglomeration and the duration of rare, short-lasting events, such as floods, droughts or low flow periods) than used in climate studies. The objective of the present paper is to analyze the climate change impact on water resources from a systems view, to discuss scientific gaps, and to identify the possible future role of IIASA in this subject area. The report discusses the role of different scales and uncertainties, as well as the hydrological perspective of global circulation models. An essential part of the analysis is devoted to the impact of climate change on the hydrologic cycle and water resources. Subsequently, our preparedness for probable global (climate) change is discussed in terms of assessment, planning, design, adaptation, and others. The focus is obviously on water-related response strategies. Finally, the paper identifies four challenging future research areas for IIASA as follows: (1) Central Europe as a case to study climate change impacts on water resources management; (2) The application of a pre-hydrological model to probabilistically assess the rainfall pattern of a river basin; (3) Methodological research to study water management vulnerability with a strong focus on uncertainties (including methods and concepts such as the Delphi technique, Bayesian statistics, reliability resilience, vulnerability, robustness, and surprises); and (4) The impact of climate change on water quality

Variability of snow cover and frost depth at the Potsdam station, Germany

The presented paper examines variability of characteristics of snow cover (snow cover depth, number of days with snow cover and dates of beginning and end of snow cover) and frost depth in Potsdam. The study makes use of a unique long time series of data from the secular meteorological station in Potsdam (Germany), covering the time interval from 1893 to date. The observed behaviour of time series of snow is complex, and not easy to interpret. Even if shrinking snow cover is typically expected in the warming climate of the moderate zone, the change in Potsdam is largely dominated by inter-winter and intra-winter variability, rendering trend detection difficult. Nevertheless, an increasing, statistically significant trend for winter precipitation was detected with almost no changes in the snow fall. A statistical link between the NAO index and the snow cover depth as well as the number of snow cover days was found

Regional projections of temperature and precipitation changes: Robustness and uncertainty aspects

This study presents the analysis of bias-corrected projections of changes in temperature and precipitation in the Vistula and Odra basins, covering approximately 90% of the Polish territory and small parts of neighbouring countries in Central and Eastern Europe. The ensemble of climate projections consists of nine regional climate model simulations from the EURO-CORDEX ensemble for two future periods 2021-2050 and 2071-2100, assuming two representative concentration pathways (RCPs) 4.5 and 8.5. The robustness is measured by the ensemble models' agreement on significant changes.We found a robust increase in the annual mean of daily minimum and maximum temperature, by 1-1.4 °C in the near future and by 1.9-3.8 °C in the far future (areal-means of the ensemble mean values). Higher increases are consistently associated with minimum temperature and the gradient of change goes from SWto NE regions. Seasonal projections of both temperature variables reflect lower robustness and suggest a higher future increase in winter temperatures than in other seasons, notably in the far future under RCP 8.5 (by more than 1 °C). However, changes in annual means of precipitation are uncertain and not robust in any of the analysed cases, even though the climate models agree well on the increase. This increase is intensified with rising global temperatures and varies from 5.5% in the near future under RCP 4.5 to 15.2%in the far future under RCP 8.5. Spatial variability is substantial, although quite variable between individual climate model simulations. Although seasonal means of precipitation are projected to considerably increase in all four combinations of RCPs and projection horizons for winter and spring, the high model spread reduces considerably the robustness, especially for the far future. In contrast, the ensemble members agree well that overall, the summer and autumn (with exception of the far future under RCP 8.5) precipitation will not undergo statistically significant changes

Trend detection in river flow indices in Poland

The issue of trend detection in long time series of river flow records is of vast theoretical interest and considerable practical relevance. Water management is based on the assumption of stationarity; hence, it is crucial to check whether taking this assumption is justified. The objective of this study is to analyse long-term trends in selected river flow indices in small- and medium-sized catchments with relatively unmodified flow regime (semi-natural catchments) in Poland. The examined indices describe annual and seasonal average conditions as well as annual extreme conditions—low and high flows. The special focus is on the spatial analysis of trends, carried out on a comprehensive, representative data set of flow gauges. The present paper is timely, as no spatially comprehensive studies (i.e. covering the entire Poland or its large parts) on trend detection in time series of river flow have been done in the recent 15 years or so. The results suggest that there is a strong random component in the river flow process, the changes are weak and the spatial pattern is complex. Yet, the results of trend detection in different indices of river flow in Poland show that there exists a spatial divide that seems to hold quite generally for various indices (annual, seasonal, as well as low and high flow). Decreases of river flow dominate in the northern part of the country and increases usually in the southern part. Stations in the central part show mostly ‘no trend’ results. However, the spatial gradient is apparent only for the data for the period 1981–2016 rather than for 1956–2016. It seems also that the magnitude of increases of river flow is generally lower than that of decreases

Changes in impacts of climate extremes: Human systems and ecosystems

In this chapter, two different types of impacts on human and ecological systems are examined: (i) impacts of extreme weather and climate events; and (ii) extreme impacts triggered by less-than-extreme weather or climate events (in combination with non-climatic factors, such as high exposure and/or vulnerability). Where data are available, impacts are examined from sectoral and regional perspectives