Description: Glaciated high-alpine areas are fundamentally altered by climate change, with well-known implications for hydrology, e.g., due to glacier retreat, longer snow-free periods, and more frequent and intense summer rainstorms. While knowledge on how these hydrological changes will propagate to suspended sediment dynamics is still scarce, it is needed to inform mitigation and adaptation strategies. To understand the processes and source areas most relevant to sediment dynamics, we analyzed discharge and sediment dynamics in high temporal resolution as well as their patterns on several spatial scales, which to date few studies have done. We used a nested catchment setup in the Upper Ötztal in Tyrol, Austria, where high-resolution (15 min) time series of discharge and suspended sediment concentrations are available for up to 15 years (2006–2020). The catchments of the gauges in Vent, Sölden and Tumpen range from 100 to almost 800 km2 with 10 % to 30 % glacier cover and span an elevation range of 930 to 3772 m a.s.l. We analyzed discharge and suspended sediment yields (SSY), their distribution in space, their seasonality and spatial differences therein, and the relative importance of short-term events. We complemented our analysis by linking the observations to satellite-based snow cover maps, glacier inventories, mass balances and precipitation data. Our results indicate that the areas above 2500 m a.s.l., characterized by glacier tongues and the most recently deglaciated areas, are crucial for sediment generation in all sub-catchments. This notion is supported by the synchronous spring onset of sediment export at the three gauges, which coincides with snowmelt above 2500 m but lags behind spring discharge onsets. This points at a limitation of suspended sediment supply as long as the areas above 2500 m are snow-covered. The positive correlation of annual SSY with glacier cover (among catchments) and glacier mass balances (within a catchment) further supports the importance of the glacier-dominated areas. The analysis of short-term events showed that summer precipitation events were associated with peak sediment concentrations and yields but on average accounted for only 21 % of the annual SSY in the headwaters. These results indicate that under current conditions, thermally induced sediment export (through snow and glacier melt) is dominant in the study area. Our results extend the scientific knowledge on current hydro-sedimentological conditions in glaciated high-alpine areas and provide a baseline for studies on projected future changes in hydro-sedimentological system dynamics.

Description: The state of Ceará is located in the semi-arid northeast of Brazil, where droughts and uncertain water supply threaten people living in one of the most densely populated dryland regions in the world. To store and supply water during dry periods, tens of thousands of (small) dams have been built over time. Except for 155 strategic reservoirs, there is hardly any systematic monitoring and management of water resources. In addition to comprehensive monitoring, a hydrological forecasting tool is also needed to better manage water resources in Ceará and reduce the impact of future droughts. We developed an innovative system for monitoring and forecasting hydrological dynamics in Ceará. The system is based on the integrated use of climate modeling, process-based hydrological modeling, remote sensing, and existing databases. Specifically, it consists of three complementary products: (1) Satellite-based monitoring of reservoir water storage: Water storage in reservoirs is monitored by evaluating weekly updating Sentinel-1 images together with satellite derived bathymetric information for 〉 40,000 reservoirs. (2) Modeling and forecasting of hydrological dynamics: The process-based hydrological model WASA-SED was adapted for the state area of Ceará. Information from satellite-based monitoring is dynamically assimilated in the simulations. Based on an ensemble of bias-corrected ECHAM4.6 climate simulations, seasonal hydrological forecasts with six months lead time are issued every month. (3) Web-based visualization of monitoring and forecast results: The results of satellite-based monitoring and dynamic hydrological forecasting are centrally managed in a database. Specific information is visualized online as maps and graphics for different user groups and decision makers.

Description: Alpine ski-touring and off-piste freeriding enjoy great popularity in recent years. Countless friends of winter sport activities enter uncontrolled terrain and relish moments in remote high-alpine landscapes. In addition to the requisite attentiveness for the surrounding flora and fauna, an awareness of the current snow and avalanche conditions is of great importance for safety reasons, prior to the engagement in winter sports activities. To improve the quality and availability of information on avalanche problems and danger levels, the European national avalanche warning services increasingly coordinate and pool information enabling the provision of systematic, transnational and multi-lingual reports and visualizations (e.g. www.avalanche.report). Out of this transnational effort, a database with detailed avalanche forecast information covering large parts of the European Alps comes into being. The standardized structure and descriptions of the reports enable a systematic analysis. First objective of this study is the development of an open-source software to download and extract avalanche forecast information for selected locations and time frames. The provision of the software in the form of a R package ensures easy access, re-usability and modifiability. In a second step, we assess the potential of meteorological and snow-hydrological observations including measurements of wind-driven snow-redistribution as well as dynamically downscaled ERA5 reanalysis data to detect critical avalanche conditions.

Description: We assess the potential of new remote sensing data products developed within the AlpSnow project (2020-2023), a science activity within ESA's Alpine Regional Initiative, to improve snow-hydrological modeling in the high alpine environment of the Rofental (Ötztal Alps, Austria). The satellite data products are optimized for scientific and operational applications and include snow covered area, surface albedo, grain size, snow water equivalent, snow depth, snowmelt area extent and liquid water content. The study area covers an elevation range of 1890 - 3770 m a.s.l. and is part of LTSER and INARCH research initiatives. In a first experiment, we force the snow hydrological model openAMUNDSEN with station-based meteorological data to evaluate and optimize the simulation results using the AlpSnow products with a focus on snowmelt and runoff timing. Specific targets of model optimizations are precipitation regionalization and the parameterizations for lateral snow redistribution, liquid water content, and albedo. In a second experiment, added values of assimilating the remote sensing products in the model are analyzed. We validate results against in-situ snow hydrological observations recorded by the station network in the research basin.

Description: The determination of inside-canopy micrometeorological conditions is an important preparatory step towards modelling the snow processes interception, sublimation, accumulation and melt in forests. Often, the required observations of the meteorological variables used in the modelling are lacking. Hence, transfer functions can be utilized to scale the meteorological observations from the open to the conditions inside the forest, depending on parameters which describe the relevant features of the trees important for their effect on the meteorological conditions. The study site in Berchtesgaden National Park offers a broad amount of forest measurements. Due to a difference in altitude of around 1500 m, meteorological variations are large. This is especially visible in spring and autumn, when the vegetation at higher regions still is snow covered while the temperatures in the lower regions are high enough for evapotranspiration to occur. We use the distributed physically-based snow hydrological model openAMUNDSEN to conduct the respective meteorological and snow simulations. The model can simultaneously consider both snow interception and subsequent sublimation and melt, as well as evapotranspiration processes inside the considered forests. We present and evaluate the simulation of the meteorological variables and first results for the combination of the different hydrological processes inside the canopies of the National Park area to demonstrate their spatial and temporal patterns. Ultimately, we aim to model the inside-canopy snow processes to identify potential effects of climate change refuges and hotspots in high mountain regions.

Description: Hochwasser in Flussgebieten werden in lokale und plötzliche Sturzfluten in kleinen Gebieten und in Hochwasser an größeren Flüssen unterschieden. Für verschiedene Hochwasserindikatoren und Flusseinzugsgebiete ergeben sich erhebliche Unterschiede, wobei sowohl überwiegend aus Regen als auch überwiegend aus Schmelzwasser gespeiste Hochwasserereignisse betrachtet werden. Besondere Aufmerksamkeit finden Hochwasserereignisse in den großen Flussgebieten von Rhein, Donau, Elbe, Weser und Ems in Deutschland sowie die Entwicklung von Sturzfluten infolge von Extremniederschlägen kurzer Dauer, wobei die Beobachtungen und Trends zu Modellierungsergebnissen in Beziehung gesetzt werden. Auch die Notwendigkeit von Anpassungsmaßnahmen wird diskutiert.