What can we learn from comparing glacio-hydrological models?

Glacio-hydrological models combine both glacier and catchment hydrology modeling and are used to assess the hydrological response of high-mountain glacierized catchments to climate change. To capture the uncertainties from these model combinations, it is essential to compare the outcomes of several model entities forced with the same climate projections. For the first time, we compare the results of two completely independent glacio-hydrological models: (i) HQsim-GEM and (ii) AMUNDSEN. In contrast to prevailing studies, we use distinct glacier models and glacier initialization times. At first glance, the results achieved for future glacier states and hydrological characteristics in the Rofenache catchment in ötztal Alps (Austria) appear to be similar and consistent, but a closer look reveals clear differences. What can be learned from this study is that low-complexity models can achieve higher accuracy in the calibration period. This is advantageous especially when data availability is weak, and priority is given to efficient computation time. Furthermore, the time and method of glacier initialization play an important role due to different data requirements. In essence, it is not possible to make conclusions about the model performance outside of the calibration period or more specifically in the future. Hence, similar to climate modeling, we suggest considering different modeling approaches when assessing future catchment discharge or glacier evolution. Especially when transferring the results to stakeholders, it is vital to transparently communicate the bandwidth of future states that come with all model results. © 2020 by the authors

The importance of snowmelt spatiotemporal variability for isotope-based hydrograph separation in a high-elevation catchment

Seasonal snow cover is an important temporary water storage in high-elevation regions. Especially in remote areas, the available data are often insufficient to accurately quantify snowmelt contributions to streamflow. The limited knowledge about the spatiotemporal variability of the snowmelt isotopic composition, as well as pronounced spatial variation in snowmelt rates, leads to high uncertainties in applying the isotope-based hydrograph separation method. The stable isotopic signatures of snowmelt water samples collected during two spring 2014 snowmelt events at a north- and a south-facing slope were volume weighted with snowmelt rates derived from a distributed physicsbased snow model in order to transfer the measured plotscale isotopic composition of snowmelt to the catchment scale. The observed δ$^{18}$O values and modeled snowmelt rates showed distinct inter- and intra-event variations, as well as marked differences between north- and south-facing slopes. Accounting for these differences, two-component isotopic hydrograph separation revealed snowmelt contributions to streamflow of 35±3 and 75±14% for the early and peak melt season, respectively. These values differed from those determined by formerly used weighting methods (e.g., using observed plot-scale melt rates) or considering either the north- or south-facing slope by up to 5 and 15 %, respectively

Modeling of mountain snow and ice water resources at the human-environment system interface

Die in den Gebirgsregionen der Erde als Schnee und Eis gespeicherten Wasserressourcen sind von enormer Wichtigkeit für eine Reihe betroffener sozioökonomischer Bereiche. Zwei prominente Beispiele dafür sind die Wasserkraftproduktion sowie der Wintertourismus. Während die Wasserkraftproduktion aus Speicherkraftwerken von der Menge des festen Winterniederschlags sowie dem zeitlichen Ablauf der daraus folgenden Schnee- und Eisschmelze abhängt, ist der Wintertourismussektor sowohl von natürlichem Schneefall als auch von adäquaten Bedingungen zur Produktion technischen Schnees abhängig. Hydrologische Modellsimulationen erlauben die Abschätzung der Menge und räumlichen Verteilung der im Gebirge gespeicherten Schnee- und Eisressourcen sowie deren Veränderung in kurz- bis langfristigen Zeitskalen. Bei der Anwendung solcher Modelle in gekoppelten Mensch-Umwelt-Systemen ist jedoch eine integrative Perspektive notwendig, d. h. die Interaktionen zwischen Wasser und der Gesellschaft müssen berücksichtigt werden. Diese Arbeit beschäftigt sich mit der physikalisch basierten Modellierung der Schnee- und Eisressourcen in gekoppelten Mensch-Umwelt-Systemen in Gebirgsregionen. Ein konzeptuelles Framework, welches Schnittstellen zwischen quantitativen numerischen Modellergebnissen und qualitativen sozioökonomischen Informationen definiert, stellt die Grundlage für mehrere Untersuchungen dar, die die sozioökonomischen Bereiche Wintertourismus und Wasserkraft in zwei Regionen der Österreichischen Alpen adressieren. Für diese Untersuchungen wird das vollverteilte hydroklimatologische Modell AMUNDEN angewendet. Zur Simulation der technischen Beschneiung werden zwei Ansätze zur Schneeproduktion im Modell implementiert: ein einfacher Ansatz, welcher leicht übertragbar auf verschiedene Skigebiete ist und sich für die Anwendung auf der regionalen Skala eignet, und ein sehr detaillierter Ansatz, welcher explizit die im Skigebiet vorhandene Beschneiungsinfrastruktur sowie lokale Beschneiungsstrategien berücksichtigt. Beide dieser Ansätze werden in der Region Schladming angewendet. Während der einfachere Ansatz verwendet wird, um Klimawandelauswirkungen auf Natur- und Kunstschneebedingungen in der Region abzuschätzen, werden mittels des detaillierten Ansatzes die Infrastruktur und die Beschneiungspraktiken eines einzelnen Skigebiet in der Region abgebildet. Die Ergebnisse dieser Studien zeigen, dass das gekoppelte System in der Lage ist sowohl quantitative in qualitative Informationen (in der Form von sozioökonomischen Indikatoren wie der Länge der Skisaison) als auch umgekehrt (in der Form von Beschneiungsstrategien und Managementpraktiken) zu übersetzen. Die Simulation des zukünftigen Wasserkraftpotentials wird für das vergletscherte Gebiet der Ötztaler Alpen durchgeführt. Ein neues, allgemein anwendbares Konzept zur systematischen Validierung von Umweltmodellen wird entwickelt und verwendet, um das Modellsetup für vergangene Bedingungen zu validieren. Anschließend werden die Auswirkungen des Klimawandels im 21. Jahrhunderts auf die Schneedecke, die Gletscher und die hydrologischen Regime in der Region mittels aktueller Klimaprojektionen analysiert. Die Ergebnisse, die sich stark zurückziehende Gletscher und verringerte Abflussmengen in Kombination mit deutlichen Verschiebungen in den Abflussregimen bis zum Ende des Jahrhunderts zeigen, stellen eine Basis für zukünftiges Management und Planung von Wasserkraftanlagen in der Region dar.Snow and ice water resources stored in the mountain regions of the world are of enormous importance for a variety of affected socioeconomic sectors, two very prominent examples being hydropower and winter tourism. While hydropower operations are dependent on the amount of winter precipitation falling as snow and the timing of the generation of snow and ice meltwater contributing to the reservoirs, the winter tourism sector is reliant on both natural snowfall and adequate conditions for producing technical snow. Hydrological model simulations allow to assess the amount and distribution of mountain water resources stored as snow and ice and their short- to long-term changes. However, when applied in coupled human-environment systems, an integrative perspective is required, i. e., the interactions between water and people must be considered. This thesis aims at the physically based modeling of snow and ice resources in coupled human-environment systems in mountain regions. A conceptual framework defining interfaces between quantitative numerical model calculations and socioeconomic qualities lays the foundation for several modeling case studies addressing the socioeconomic systems winter tourism and hydropower in two regions of the Austrian Alps. For these studies, the fully distributed hydroclimatological model AMUNDSEN is applied. To simulate snowmaking operations, two approaches for technical snow production are implemented in the model: one simple method which is easily transferable and applicable on the regional scale, and one very detailed approach which explicitly takes snowmaking infrastructure including technical and environmental constraints as well as human-environment interactions in terms of snow production strategies into account. Both of these approaches are applied in the Schladming region the former to assess the effects of climate change on both natural and artificial snow conditions in the region, and the latter to simulate real-world snowmaking operations for a single ski area. The results of these studies demonstrate the skill of the coupled model in translating quantitative to qualitative data (in the form of socioeconomic indicators such as the length of the ski season) and vice versa (in the form of rules when and where to produce snow). Future hydropower potential is simulated for the glacierized region of the Ötztal Alps. A novel, generically applicable concept for systematically validating environmental models is developed and utilized to validate the model setup for past conditions. Subsequently, the impacts of 21st century climate change on snow, glaciers, and hydrological regimes in the region are investigated using state-of-the-art climate projections. The results indicate strongly receding glaciers and declining runoff volumes throughout the century, accompanied by considerable shifts in runoff regimes, and provide a basis for future hydropower management and planning in the area.by Florian HanzerZusammenfassung in deutscher SpracheKumulative Dissertation aus fünf ArtikelnUniversity of Innsbruck, Dissertation, 2017OeBB(VLID)196600

Glacier snowline determination from Terrestrial Laser Scanning intensity data

Accurately identifying the extent of surface snow cover on glaciers is important for extrapolating end of year mass balance measurements, constraining the glacier surface radiative energy balance and evaluating model simulations of snow cover. Here, we use auxiliary information from Riegl VZ-6000 Terrestrial Laser Scanner (TLS) return signals to accurately map the snow cover over a glacier throughout an ablation season. Three classification systems were compared, and we find that supervised classification based on TLS signal intensity alone is outperformed by a rule-based classification employing intensity, surface roughness and an associated optical image, which achieves classification accuracy of 68–100%. The TLS intensity signal shows no meaningful relationship with surface or bulk snow density. Finally, we have also compared our Snow Line Altitude (SLA) derived from TLS with SLA derived from the model output, as well as one Landsat image. The results of the model output track the SLA from TLS well, however with a positive bias. In contrast, automatic Landsat-derived SLA slightly underestimates the SLA from TLS. To conclude, we demonstrate that the snow cover extent can be mapped successfully using TLS, although the snow mass remains elusive

Projected cryospheric and hydrological impacts of 21st century climate change in the Ötztal Alps (Austria) simulated using a physically based approach

A physically based hydroclimatological model (AMUNDSEN) is used to assess future climate change impacts on the cryosphere and hydrology of the Ötztal Alps (Austria) until 2100. The model is run in 100 m spatial and 3 h temporal resolution using in total 31 downscaled, bias-corrected, and temporally disaggregated EURO-CORDEX climate projections for the representative concentration pathways (RCPs) 2.6, 4.5, and 8.5 scenarios as forcing data, making this - to date - the most detailed study for this region in terms of process representation and range of considered climate projections. Changes in snow coverage, glacierization, and hydrological regimes are discussed both for a larger area encompassing the Ötztal Alps (1850 km2, 862-3770 m a.s.l.) as well as for seven catchments in the area with varying size (11-165 km2) and glacierization (24-77 %). Results show generally declining snow amounts with moderate decreases (0-20 % depending on the emission scenario) of mean annual snow water equivalent in high elevations (> 2500 m a.s.l.) until the end of the century. The largest decreases, amounting to up to 25-80 %, are projected to occur in elevations below 1500 m a.s.l. Glaciers in the region will continue to retreat strongly, leaving only 4-20 % of the initial (as of 2006) ice volume left by 2100. Total and summer (JJA) runoff will change little during the early 21st century (2011-2040) with simulated decreases (compared to 1997-2006) of up to 11 % (total) and 13 % (summer) depending on catchment and scenario, whereas runoff volumes decrease by up to 39 % (total) and 47 % (summer) towards the end of the century (2071-2100), accompanied by a shift in peak flows from July towards June. © Author(s) 2018

Retrospective forecasts of the upcoming winter season snow accumulation in the Inn headwaters (European Alps)

This article presents analyses of retrospective seasonal forecasts of snow accumulation. Re-forecasts with 4 months' lead time from two coupled atmosphere-ocean general circulation models (NCEP CFSv2 and MetOffice GloSea5) drive the Alpine Water balance and Runoff Estimation model (AWARE) in order to predict mid-winter snow accumulation in the Inn headwaters. As snowpack is hydrological storage that evolves during the winter season, it is strongly dependent on precipitation totals of the previous months. Climate model (CM) predictions of precipitation totals integrated from November to February (NDJF) compare reasonably well with observations. Even though predictions for precipitation may not be significantly more skilful than for temperature, the predictive skill achieved for precipitation is retained in subsequent water balance simulations when snow water equivalent (SWE) in February is considered. Given the AWARE simulations driven by observed meteorological fields as a benchmark for SWE analyses, the correlation achieved using GloSea5-AWARE SWE predictions is r D0.57. The tendency of SWE anomalies (i.e. the sign of anomalies) is correctly predicted in 11 of 13 years. For CFSv2-AWARE, the corresponding values are r D0.28 and 7 of 13 years. The results suggest that some seasonal prediction of hydrological model storage tendencies in parts of Europe is possible

Simulation of snow management in Alpine ski resorts using three different snow models

International audienceSnow management, i. e., snowmaking and grooming, is an integral part of modern ski resort management. While the current snow cover distribution on the slopes is often well known thanks to the usage of advanced monitoring techniques, information about its future evolution is usually lacking. Management-enabled numerical snowpack models driven by meteorological forecasts can help to fill this gap.In the frame of the H2020 project PROSNOW, the snowpack models AMUNDSEN, Crocus, and SNOWPACK/Alpine3D are applied in nine pilot ski resorts across the European Alps for forecasting snow conditions in time scales from days to several months ahead. We present the integration of detailed snowmaking and grooming practices implemented in the three models and show how they can be adapted to individual ski resorts. An ensemble of snow management configurations accounting for a comprehensive set of possible tactical and strategic operational choices is introduced, along with an approach to homogeneously spatialize the results of the three snow models over different areas of the ski resorts. First simulation results are presented for the nine pilot ski resorts in the form of distributed snow water equivalent (SWE) maps along with SWE and snow depth time series for two selected seasons in the past