Search

GENERAL INFORMATION The data and scripts used for the analysis of the manuscript "Coupling a large-scale glacier and hydrological model (OGGM v1.5.3 and CWatM V1.08) – Towards an improved representation of mountain water resources in global assessments" When using this dataset, please refer to the original publication in addition to this Zenodo repository.

Mountain areas provide disproportionally high runoff in many parts of the world, but their importance for water resources and food production has not been clarified from the viewpoint of the lowland areas downstream. Here we quantify the extent to which lowland inhabitants potentially depend on runoff contributions from mountain areas (39% of the global land mass). We show that ~1.5 billion people (24% of the world’s lowland population) are projected to depend critically on runoff contributions from mountains by the mid-twenty-first century under a ‘middle of the road’ scenario, compared with ~0.2 billion (7%) in the 1960s. This striking rise is mainly due to increased local water consumption in the lowlands, whereas changes in mountain and lowland runoff play only a minor role. We further show that one-third of the global lowland area equipped for irrigation is currently located in regions that both depend heavily on runoff contributions from mountains and make unsustainable use of local blue water resources, a figure that is likely to rise to well over 50% in the coming decades. Our findings imply that mountain areas should receive particular attention in water resources management and underscore the protection they deserve in efforts towards sustainable development.

Mountains are the water towers of the world, supplying a substantial part of both natural and anthropogenic water demands1,2. They are highly sensitive and prone to climate change3,4, yet their importance and vulnerability have not been quantified at the global scale. Here, we present a global Water Tower Index, which ranks all water towers in terms of their water-supplying role and the downstream dependence of ecosystems and society. For each tower, we assess its vulnerability related to water stress, governance, hydropolitical tension and future climatic and socio-economic changes. We conclude that the most important water towers are also among the most vulnerable, and that climatic and socio-economic changes will affect them profoundly. This could negatively impact 1.9 billion people living in (0.3 billion) or directly downstream of (1.6 billion) mountain areas. Immediate action is required to safeguard the future of the world’s most important and vulnerable water towers.

Despite precipitation intensities may greatly vary during one flood event, detailed information about these intensities may not be required to accurately simulate floods with a hydrological model which rather reacts to cumulative precipitation sums. This raises two questions: to which extent is it important to preserve sub-daily precipitation intensities and how long does it effectively rain from the hydrological point of view? Both questions might seem straightforward to answer with a direct analysis of past precipitation events but require some arbitrary choices regarding the length of a precipitation event. To avoid these arbitrary decisions, here we present an alternative approach to characterize the effective length of precipitation event which is based on runoff simulations with respect to large floods. More precisely, we quantify the fraction of a day over which the daily precipitation has to be distributed to faithfully reproduce the large annual and seasonal floods which were generated by the hourly precipitation rate time series. New precipitation time series were generated by first aggregating the hourly observed data into daily totals and then evenly distributing them over sub-daily periods (n hours). These simulated time series were used as input to a hydrological bucket-type model and the resulting runoff flood peaks were compared to those obtained when using the original precipitation time series. We define then the effective daily precipitation duration as the number of hours n, for which the largest peaks are simulated best. For nine mesoscale Swiss catchments this effective daily precipitation duration was about half a day, which indicates that detailed information on precipitation intensities is not necessarily required to accurately estimate peaks of the largest annual and seasonal floods. These findings support the use of simple disaggregation approaches to make usage of past daily precipitation observations or daily precipitation simulations (e

Die zur Abschätzung seltener Hochwasserabflüsse eingesetzten Methoden lassen sich in drei Verfahrensgruppen unterteilen: Extremwertstatistik, regionalhydrologische Ansätze und Niederschlag-Abfluss-Modellierung. Bei allen Verfahren bestehen jeweils spezifische Vor- und Nachteile, welche im Folgenden kurz erläutert werden sollen.

Das Bundesgesetz über den Wasserbau hält u.a. fest, dass in allen Landesteilen der Schweiz gleiche Sicherheitsstandards für den Hochwasserschutz garantiert sein müssen, dass die Bevölkerung in den Planungsprozess von Hochwasserschutzmassnahmen eingebunden werden muss und dass nachhaltige Schutzmassnahmen geplant und ausgeführt werden sollen. Ausgehend von diesem Gesetz hat die Nationale Plattform Naturgefahren (PLANAT) einen Vorschlag für den Prozess des integrierten Hochwasserschutzes in der Schweiz mit Grundlagenbereitstellung, Intervention nach Hochwasserereignissen, Instandstellung, Prävention und Vorsorge erstellt. In der vorliegenden Publikation werden ausgewählte Beispiele von Massnahmen im integralen Hochwasserschutz der Schweiz vorgestellt. Prioritär wurden dabei Grundlagen, Methoden und Beispiele aus den Bereichen der Hochwasserabschätzung und des Sedimenttransportes ausgewählt, welche vom Bundesamt für Umwelt in irgendeiner Form unterstützt wurden. Im Kapitel 1 finden sich einige generelle Angaben zum Hochwasserschutz in der Schweiz. Im Kapitel 2 werden Dienstleistungen der Abteilung Hydrologie beim Bundesamt für Umwelt dargestellt. Es wird kurz auf die Messgeräte und Messmethoden eingegangen und dann das Produkt Hochwasserstatistik vorgestellt. Abschliessend werden Hinweise zur Datenverfügbarkeit und Güte von Hochwassermessungen gegeben. In Kapitel 3 folgt ein Überblick über Tätigkeiten auf dem Gebiet der Feststoffbeobachtung in der Schweiz mit Angaben zum Geschiebesammlermessnetz der GHO und Verfahren zur Abschätzung des Geschiebetransportes in Wildbachgebieten. Das Kapitel 4 befasst sich mit dem Problem der Erfassung, Häufigkeit und Analyse von historischen Hochwassern. Daraus werden Konsequenzen abgeleitet. Im Kapitel 5 werden Erkenntnisse aus dem Bereich Umweltveränderungen und deren Auswirkungen auf die Hochwasserabflüsse in der Schweiz aufgezeigt. Ausgegangen wird von Veränderungen die in der Vergangenheit stattgefunden haben und dann wird auf zukü

Floods have broad impacts on nature, society, and the economy. The frequency and intensity of flood events are generally believed to increase with the anticipated changes in temperature and precipitation. Trend analyses are important tools to quantify these changes, but often, they provide inconclusive results, partly because of the limited data availability. One way to overcome this limitation is to pool data from different gauging stations. However, pooling data from different stations may lead to misleading results. For example, using pooled flood data Allamano et al. (2009a) found a considerable increase of flooding risks for Switzerland. Here we demonstrate that the previous finding of increased flooding risks was an artifact of the pooling of stations and the fact that the longer time series came from larger catchments, which tend to have lower values for specific peak flows than smaller catchments. Our results demonstrate the risk of obtaining incorrect statistical conclusions when statistical analyses and data selection are not considered with due care.