Mountains are essential sources of freshwater for our world, but their role in global water resources could well be significantly altered by climate change. How well do we understand these potential changes today, and what are implications for water resources management, climate change adaptation, and evolving water policy? To answer above questions, we have examined 11 case study regions with the goal of providing a global overview, identifying research gaps and formulating recommendations for research, management and policy. <br><br> After setting the scene regarding water stress, water management capacity and scientific capacity in our case study regions, we examine the state of knowledge in water resources from a highland-lowland viewpoint, focusing on mountain areas on the one hand and the adjacent lowland areas on the other hand. Based on this review, research priorities are identified, including precipitation, snow water equivalent, soil parameters, evapotranspiration and sublimation, groundwater as well as enhanced warming and feedback mechanisms. In addition, the importance of environmental monitoring at high altitudes is highlighted. We then make recommendations how advancements in the management of mountain water resources under climate change could be achieved in the fields of research, water resources management and policy as well as through better interaction between these fields. <br><br> We conclude that effective management of mountain water resources urgently requires more detailed regional studies and more reliable scenario projections, and that research on mountain water resources must become more integrative by linking relevant disciplines. In addition, the knowledge exchange between managers and researchers must be improved and oriented towards long-term continuous interaction

Abstract:Snow cover and glaciers are the most important long-term forms of water storage and, hence, the main sources of runoff during the ablation period for many alpine headwater basins. We therefore investigated the application of the conceptual, distributed hydrological precipitation runoff evapotranspiration hydrological response unit model (PREVAH) to the alpine glacierized headwater basin of the Upper Salzach (593 km 2 , 5% glacierized) river in Austria. Hourly meteorological data from 17 stations for a 6-year period were available for the calibration and validation of the hourly runoff simulations. Multi-criteria validation included hourly discharge, snow covered area (SCA), and glacier mass balances. SCA maps were generated from optical satellite images for six dates. These maps were compared to simulated maps of SCA to (1) calculate differences in SCA, (2) calculate altitudinal differences, and (3) show the ability to accurately model snow cover on different aspects. The differences between observed and simulated SCA for glacierized areas were between 1 and 9% during June and July, and between 10 and 36% during August and September observations. In general, the model overestimated SCA, which is the result of PREVAH not including redistribution of snow by wind or avalanches. The temporal variability of the simulated mass balance agreed well with observations from surrounding glaciers. Nash-Sutcliffe Efficiency Criteria (R 2 ) of the hourly discharge simulations were between 0Ð83 and 0Ð89 with the exception of the extreme summer of 2003 which had an R 2 of 0Ð74. Contributions of glacier melt (firn/ice melt) to annual total runoff were between 1 and 4%. Again, the exception was 2003, when glaciers contributed 15% of the annual runoff and 60% to the August runoff alone.

Abstract:The model for mountain surface processes, Alpine 3D, was applied to the Goldbergkees basin (2Ð7 km 2 , 52% glacierized) in the central Austrian Alps to model hourly discharge and glacier mass balance. Alpine 3D is a physically based model which focuses on snow-ice-soil energy and mass fluxes (without lateral, gravity driven flows) in rugged terrain. From the records of the Sonnblick observatory, located in the study area, a high-quality set of meteorological, glaciological and hydrological data could be provided to force and evaluate the model. A 1-year period was simulated starting from September 2004. The model results were evaluated using observations of the glacier mass balance and discharge at the catchment outlet. The spatial variation of modelled annual net mass balance of Goldbergkees shows good agreement to observed data. Significant deviations occur mainly at locations, which are presumably influenced by avalanche events or drifting snow. The quality of runoff simulation was estimated using the Nash-Sutcliffe model efficiency and the explained variance number. Both criteria demonstrate that the modelled catchment discharge is of satisfactory quality, despite the fact that the local mass balance is not well represented at all grid points.

This paper describes a trend analysis performed on 177 streamflow time series collected over the Alps in Central Europe. The analysis covers several facets of the Alpine hydrologic regimes, including winter droughts and spring snowmelt flows, both in terms of severity and timing of occurrence. Statistical trend tests are applied at a local scale (i.e. on a site-by-site basis) and at a regional scale (seeking a common trend for sites within the same hydroclimatic region). The overall results indicate a trend toward less severe winter droughts, and consistent changes in the timing of snowmelt flows. However, a more in-depth analysis at the scale of hydro-climatic regimes reveals more contrasted changes. While most glacial-and snowmelt-dominated regimes show a decreasing trend in the severity of winter droughts, contrasted trends are found for mixed snowmelt-rainfall regimes in the Southeastern Alps. Changes in the timing of snowmelt flows (earlier start and increased duration of the snowmelt season) mostly affect glacial-and snowmelt-dominated regimes. Lastly, glacial regimes show an increase in the volume and the peak of snowmelt flows.

Abstract. The EU Flood Risk Management Directive 2007/60/EC aims at an active involvement of interested parties in the setting up of flood risk management plans and thus calls for more governance-related decision-making. This requirement has two perspectives. On the one hand, there is (1) the question of how decision-makers can improve the quality of their governance process. On the other hand, there is (2) the question of how the public shall be appropriately informed and involved. These questions were the centre of the ERA-Net CRUE-funded project IMRA (integrative flood risk governance approach for improvement of risk awareness) that aimed at an optimisation of the flood risk management process by increasing procedural efficiency with an explicit involvement strategy. To reach this goal, the IMRA project partners developed two new approaches that were implemented in three case study areas for the first time in flood risk management:1. risk governance assessment tool: An indicator-based benchmarking and monitoring tool was used to evaluate the performance of a flood risk management system in regard to ideal risk governance principles;2. social milieu approach: The concept of social milieus was used to gain a picture of the people living in the case study regions to learn more about their lifestyles, attitudes and values and to use this knowledge to plan custom-made information and participation activities for the broad public.This paper presents basic elements and the application of two innovative approaches as a part of an "involvement strategy" that aims at the active involvement of all interested parties (stakeholders) for assessing, reviewing and updating flood risk management plans, as formulated in the EU Flood Risk Management Directive 2007/60/EC.

Abstract. This paper quantifies the contribution of glacier melt to river runoff from compilation and statistical interpretation of data from available studies based on observations or glacio-hydrological modelling for the region of Austria (Austrian Salzach and Inn river basin). A logarithmic fit between the glacier melt contribution and the relative glacierized area was found not only for the long-term mean glacier contributions but also for the glacier melt contribution during the extreme hot an dry summer of 2003. Interestingly, the mean contributions of glacier melt to river runoff do not exceed 15 % for both river catchments and are uncorrelated to glacierization for glacierization values >10 %. This finding, however, has to be seen in the light of the general precipitation increase with altitude for the study region which levels out the increase of absolute melt with glacierization thus resulting in the rather constant value of glacier melt contribution. In order to qualitatively proof this finding another approach has been applied by calculating the quotient q A03 of the mean monthly August runoff in 2003 and the long-term mean August runoff for 38 gauging stations in Austria. The extreme summer 2003 was worth to be analysed as from the meteorological and glaciological point of view an extraordinary situation was observed. During June and July nearly the entire snow-cover melted and during August mainly bare ice melt of glaciers contributed to runoff. The q A03 quotients were calculated between 0.32 for a non-glacierized and 2.0 for a highly glacierized catchment. Using the results of this study the mean and maximum possible glacier melt contribution of catchments can be estimated based on the relative glacierized area. It can also be shown that the found correlation of glacierized area and glacier melt contribution is applicable for the Drau basin where yet no results of modelled glacier melt contributions are available.

Abstract:This paper gives an overview on the regional hydrological impact of the heatwave, which affected Europe in the summer of 2003. We investigated the small, glacierized Goldbergkees basin in the Austrian Alps, which is situated directly beneath the high Alpine Sonnblick observatory (3106 m a.s.l.). We analysed the long-term air temperature time series and quantified the extreme anomaly of the mean summer (JJA) air temperature for 4Ð4 times the standard deviation of the long-term mean . The mean summer air temperature was 4Ð7°C. In 2003, the solid fraction of precipitation was only 35%. This was the lowest value observed from 1927 to 2005. To quantify the impact of the warm temperatures on the Goldbergkees glacier positive degree-day sums were calculated. The 'hot' conditions of the summer of 2003 rapidly melted the snow covering the glacier and finally melted the ice beneath. The winter balance of the Goldbergkees did not show anomalies. The specific net balance of Goldbergkees was 1Ð8 m water equivalent (w.e.) for the 2002/2003 period and has been the most negative observed. Snowmelt was accelerated by low albedo, which was a result of Sahara dust-falls. The hydrological response unit (HRU)-based model PREVAH was applied to simulate hourly runoff, which was observed at the outlet of this small and topographically heterogeneous basin. All components contributing to runoff were separated. The model was driven using hourly meteorological data gained from the Sonnblick observatory. Snow-and icemelt were modelled based on an advanced temperature index-based approach. The model was validated using observed glacier mass balance data. The maximum simulated icemelt rate was 2Ð7 mm/h (4Ð9 mm/h assigned to the glacier surface). During August 2003, glaciermelt contributed 81% to the total runoff.

Mountains are essential sources of freshwater for our world, but their role in global water resources could well be significantly altered from anticipated climate change. How well do we understand these changes today, and what are implications for water resources management and for policy? <br><br> With these questions in mind, a dozen researchers – most of them with experience in collaborating with water managers – from around the world assembled for a workshop in Göschenen, Switzerland on 16–19 September 2009 by invitation of the Mountain Research Initiative (MRI). Their goal was to develop an up-to-date overview of mountain water resources and climate change and to identify pressing issues with relevance for science and society. <br><br> This special issue of Hydrology and Earth System Sciences assembles contributions providing insight into climate change and water resources for selected case-study mountain regions from around the world. The present introductory article is based on analysis of these regions and on the workshop discussions. We will give a brief overview of the subject (Sect. 1), introduce the case-study regions (Sect. 2) and examine the state of knowledge regarding the importance of water supply from mountain areas for water resources in the adjacent lowlands and anticipated climate change impacts (Sect. 3). From there, we will identify research and monitoring needs (Sect. 4), make recommendations for research, water resources management and policy (Sect. 5) and finally draw conclusions (Sect. 6)