• Energy Research

La gestion des risques a réduit la vulnérabilité aux inondations et aux sécheresses dans le monde1,2, mais leurs impacts continuent d'augmenter3. Une meilleure compréhension des causes de l'évolution des impacts est donc nécessaire, mais a été entravée par un manque de données empiriques4,5. Sur la base d'un ensemble de données mondiales de 45 paires d'événements qui se sont produits dans la même zone, nous montrons que la gestion des risques réduit généralement les impacts des inondations et des sécheresses, mais fait face à des difficultés pour réduire les impacts d'événements sans précédent d'une ampleur jamais connue auparavant. Si le deuxième événement était beaucoup plus dangereux que le premier, son impact était presque toujours plus élevé. En effet, la gestion n'a pas été conçue pour faire face à de tels événements extrêmes : par exemple, ils ont dépassé les niveaux de conception des digues et des réservoirs. Dans deux cas de réussite, l'impact du deuxième événement, plus dangereux, a été plus faible, en raison de l'amélioration de la gouvernance de la gestion des risques et des investissements élevés dans la gestion intégrée. La difficulté observée à gérer des événements sans précédent est alarmante, étant donné que des événements hydrologiques plus extrêmes sont projetés en raison du changement climatique3. La gestión de riesgos ha reducido la vulnerabilidad a las inundaciones y sequías a nivel mundial1,2, pero sus impactos siguen aumentando3. Por lo tanto, se necesita una mejor comprensión de las causas de los impactos cambiantes, pero se ha visto obstaculizada por la falta de datos empíricos4,5. Sobre la base de un conjunto de datos global de 45 pares de eventos que ocurrieron dentro de la misma área, mostramos que la gestión de riesgos generalmente reduce los impactos de inundaciones y sequías, pero enfrenta dificultades para reducir los impactos de eventos sin precedentes de una magnitud no experimentada anteriormente. Si el segundo evento era mucho más peligroso que el primero, su impacto era casi siempre mayor. Esto se debe a que la gestión no fue diseñada para hacer frente a tales eventos extremos: por ejemplo, superaron los niveles de diseño de diques y embalses. En dos casos de éxito, el impacto del segundo evento, más peligroso, fue menor, como resultado de una mejor gobernanza de la gestión de riesgos y una alta inversión en la gestión integrada. La dificultad observada para gestionar eventos sin precedentes es alarmante, dado que se proyectan eventos hidrológicos más extremos debido al cambio climático3. Risk management has reduced vulnerability to floods and droughts globally1,2, yet their impacts are still increasing3. An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data4,5. On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change3. أدت إدارة المخاطر إلى تقليل التعرض للفيضانات والجفاف على مستوى العالم1,2، ومع ذلك لا تزال آثارها تتزايد3. لذلك هناك حاجة إلى فهم أفضل لأسباب تغير التأثيرات، ولكن أعيق ذلك بسبب نقص البيانات التجريبية4، 5. على أساس مجموعة بيانات عالمية مكونة من 45 زوجًا من الأحداث التي وقعت داخل نفس المنطقة، نظهر أن إدارة المخاطر تقلل عمومًا من آثار الفيضانات والجفاف ولكنها تواجه صعوبات في الحد من آثار الأحداث غير المسبوقة ذات الحجم الذي لم تشهده من قبل. إذا كان الحدث الثاني أكثر خطورة من الأول، فإن تأثيره كان دائمًا أعلى. وذلك لأن الإدارة لم تكن مصممة للتعامل مع مثل هذه الأحداث المتطرفة: على سبيل المثال، تجاوزت مستويات تصميم السدود والخزانات. في قصتي نجاح، كان تأثير الحدث الثاني، الأكثر خطورة، أقل، نتيجة لتحسين حوكمة إدارة المخاطر والاستثمار العالي في الإدارة المتكاملة. إن الصعوبة الملحوظة في إدارة الأحداث غير المسبوقة تنذر بالخطر، بالنظر إلى أنه من المتوقع حدوث المزيد من الأحداث الهيدرولوجية المتطرفة بسبب تغير المناخ3.

Climate controls upland habitats, soils and their associated ecosystem services; there- fore, understanding possible changes in upland climatic conditions can provide a rapid assessment of climatic vulnerability over the next century. We used 3 different climatic indices that were optimised to fit the upland area classified by the EU as a Severely Disadvantaged Area (SDA) 1961-1990. Upland areas within the SDA covered all altitudinal ranges, whereas the maximum altitude of low- land areas outside of the SDA was ca. 300 m. In general, the climatic index based on the ratio between annual accumulated temperature (as a measure of growing season length) and annual pre- cipitation predicted 96% of the SDA mapped area, which was slightly better than those indices based on annual or seasonal water deficit. Overall, all climatic indices showed that upland environments were exposed to some degree of change by 2071-2100 under UKCIP02 climate projections for high and low emissions scenarios. The projected area declined by 13 to 51% across 3 indices for the low emissions scenario and by 24 to 84% for the high emissions scenario. Mean altitude of the upland area increased by +11 to +86 m for the low scenario and +21 to +178 m for the high scenario. Low alti- tude areas in eastern and southern Great Britain were most vulnerable to change. These projected climatic changes are likely to affect upland habitat composition, long-term soil carbon storage and wider ecosystem service provision, although it is not yet possible to determine the rate at which this might occur.

AbstractWater resources in semi‐arid regions like the Mediterranean Basin are highly vulnerable because of the high variability of weather systems. Additionally, climate change is altering the timing and pattern of water availability in a region where growing populations are placing extra demands on water supplies. Importantly, how reservoirs and dams have an influence on the amount of water resources available is poorly quantified. Therefore, we examine the impact of reservoirs on water resources together with the impact of climate change in a semi‐arid Mediterranean catchment. We simulated the Susurluk basin (23.779‐km2) using the Soil and Water Assessment Tool (SWAT) model. We generate results for with (RSV) and without reservoirs (WRSV) scenarios. We run simulations for current and future conditions using dynamically downscaled outputs of the MPI‐ESM‐MR general circulation model under two greenhouse gas relative concentration pathways (RCPs) in order to reveal the coupled effect of reservoir and climate impacts. Water resources were then converted to their usages – blue water (water in aquifers and rivers), green water storage (water in the soil) and green water flow (water losses by evaporation and transpiration). The results demonstrate that all water resources except green water flow are projected to decrease under all RCPs compared to the reference period, both long‐term and at seasonal scales. However, while water scarcity is expected in the future, reservoir storage is shown to be adequate to overcome this problem. Nevertheless, reservoirs reduce the availability of water, particularly in soil moisture stores, which increases the potential for drought by reducing streamflow. Furthermore, reservoirs cause water losses through evaporation from their open surfaces. We conclude that pressures to protect society from economic damage by building reservoirs have a strong impact on the fluxes of watersheds. This is additional to the effect of climate change on water resources.

Abstract To mitigate against future changes to estuaries such as water quality, catchment and estuary models can be coupled to simulate the transport of harmful pathogenic viruses, pollutants and nutrients from their terrestrial sources, through the estuary and to the coast. To predict future changes to estuaries, daily mean river flow projections are typically used. We show that this approach cannot resolve higher frequency discharge events that have large impacts to estuarine dilution, contamination and recovery for two contrasting estuaries. We therefore characterise sub-daily scale flow variability and propagate this through an estuary model to provide robust estimates of impacts for the future. River flow data (35-year records at 15-min sampling) were used to characterise variabilities in storm hydrograph shapes and simulate the estuarine response. In particular, we modelled a fast-responding catchment-estuary system (Conwy, UK), where the natural variability in hydrograph shapes generated large variability in estuarine circulation that was not captured when using daily-averaged river forcing. In the extreme, the freshwater plume from a ‘flash’ flood (lasting

SummaryClimate impact studies focused on the projection of changing flood risk are increasingly utilized to inform future flood risk policy. These studies typically use the output from global (GCMs) and regional climate models (RCMs). However the direct application of GCM/RCM output is controversial as often significant biases exist in predicted rainfall; instead a number of alternative ‘correction’ approaches have emerged. In this study an ensemble of RCMs from the ENSEMBLES and UKCP09 projects are applied, via a number of application techniques, to explore the possible impacts of climate change on flooding in the Avon catchment, in the UK. The analysis is conducted under a continuous simulation methodology, using a stochastic rainfall generator to drive the HBV-light rainfall run-off model under a parameter uncertainty framework. This permitted a comparison between the projections produced by differing application approaches, whilst also considering the uncertainty associated with flood risk projections under observed conditions.The results from each of the application approaches project an increase in annual maximum flows under the future (2061–2099) climate scenario. However the magnitude and spread of the projected changes varied significantly. These findings highlight the need to incorporate multiple approaches in climate impact studies focusing on flood risk. Additionally these results outline the significant uncertainties associated with return period estimates under current climate conditions, suggesting that uncertainty over this observed record already poses a challenge to develop robust risk management plans.

As the negative impacts of hydrological extremes increase in large parts of the world, a better understanding of the drivers of change in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is a lack of comprehensive, empirical data about the processes, interactions and feedbacks in complex human-water systems leading to flood and drought impacts. To fill this gap, we present an IAHS Panta Rhei benchmark dataset containing socio-hydrological data of paired events, i.e. two floods or two droughts that occurred in the same area (Kreibich et al. 2017, 2019). The contained 45 paired events occurred in 42 different study areas (in three study areas we have data on two paired events), which cover different socioeconomic and hydroclimatic contexts across all continents. The dataset is unique in covering floods and droughts, in the number of cases assessed and in the amount of qualitative and quantitative socio-hydrological data contained. References to the data sources are provided in 2023-001_Kreibich-et-al_Key_data_table.xlsx where possible. Based on templates, we collected detailed, review-style reports describing the event characteristics and processes in the case study areas, as well as various semi-quantitative data, categorised into management, hazard, exposure, vulnerability and impacts. Sources of the data were classified as follows: scientific study (peer-reviewed paper and PhD thesis), report (by governments, administrations, NGOs, research organisations, projects), own analysis by authors, based on a database (e.g. official statistics, monitoring data such as weather, discharge data, etc.), newspaper article, and expert judgement. The campaign to collect the information and data on paired events started at the EGU General Assembly in April 2019 in Vienna and was continued with talks promoting the paired event data collection at various conferences. Communication with the Panta Rhei community and other flood and drought experts identified through snowballing techniques was important. Thus, data on paired events were provided by professionals with excellent local knowledge of the events and risk management practices.

Résumé. Alors que les impacts négatifs des extrêmes hydrologiques augmentent dans de nombreuses régions du monde, une meilleure compréhension des facteurs de changement des risques et des impacts est essentielle pour une gestion efficace des risques d'inondation et de sécheresse et pour l'adaptation au climat. Cependant, il existe actuellement un manque de données empiriques complètes sur les processus, les interactions et les rétroactions dans les systèmes homme-eau complexes conduisant à des impacts d'inondation et de sécheresse. Nous présentons ici un ensemble de données de référence contenant des données socio-hydrologiques d'événements appariés, c'est-à-dire deux inondations ou deux sécheresses survenues dans la même zone. Les 45 événements appariés se sont produits dans 42 zones d'étude différentes et couvrent un large éventail de conditions socio-économiques et hydro-climatiques. L'ensemble de données est unique en ce qu'il couvre à la fois les inondations et les sécheresses, le nombre de cas évalués et la quantité de données socio-hydrologiques. L'ensemble de données de référence comprend : 1) des rapports de style d'examen détaillés sur les événements et les processus clés entre les deux événements d'une paire ; 2) le tableau de données clés contenant des variables qui évaluent les indicateurs qui caractérisent les lacunes de gestion, le danger, l'exposition, la vulnérabilité et les impacts de tous les événements ; 3) un tableau des indicateurs de changement qui indiquent les différences entre le premier et le deuxième événement d'une paire. Les avantages de l'ensemble de données sont qu'il permet des analyses comparatives entre tous les événements appariés sur la base des indicateurs de changement et permet des évaluations détaillées spécifiques au contexte et à l'emplacement sur la base des données et des rapports détaillés des zones d'étude individuelles. L'ensemble de données peut être utilisé par la communauté scientifique pour des analyses de données exploratoires, par exemple axées sur les liens de causalité entre la gestion des risques, les changements de danger, l'exposition et la vulnérabilité et les impacts des inondations ou de la sécheresse. Les données peuvent également être utilisées pour le développement, l'étalonnage et la validation de modèles socio-hydrologiques. L'ensemble de données est accessible au public via les services de données de GFZ (Kreibich et al. 2023, lien pour examen : https://dataservices.gfz-potsdam.de/panmetaworks/review/923c14519deb04f83815ce108b48dd2581d57b90ce069bec9c948361028b8c85/). Resumen. A medida que aumentan los impactos adversos de los extremos hidrológicos en muchas regiones del mundo, es esencial comprender mejor los impulsores de los cambios en el riesgo y los impactos para una gestión eficaz del riesgo de inundaciones y sequías y la adaptación al clima. Sin embargo, actualmente existe una falta de datos empíricos exhaustivos sobre los procesos, interacciones y retroalimentaciones en sistemas complejos de agua-humanos que conducen a los impactos de inundaciones y sequías. Aquí presentamos un conjunto de datos de referencia que contiene datos sociohidrológicos de eventos emparejados, es decir, dos inundaciones o dos sequías que ocurrieron en la misma área. Los 45 eventos emparejados ocurrieron en 42 áreas de estudio diferentes y cubren una amplia gama de condiciones socioeconómicas e hidroclimáticas. El conjunto de datos es único en cuanto a la cobertura tanto de inundaciones como de sequías, en el número de casos evaluados y en la cantidad de datos sociohidrológicos. El conjunto de datos de referencia comprende: 1) informes detallados de estilo de revisión sobre los eventos y procesos clave entre los dos eventos de un par; 2) la tabla de datos clave que contiene variables que evalúan los indicadores que caracterizan las deficiencias de gestión, el peligro, la exposición, la vulnerabilidad y los impactos de todos los eventos; 3) una tabla de los indicadores de cambio que indican las diferencias entre el primer y el segundo evento de un par. Las ventajas del conjunto de datos son que permite análisis comparativos en todos los eventos emparejados basados en los indicadores de cambio y permite evaluaciones detalladas específicas del contexto y la ubicación basadas en los amplios datos e informes de las áreas de estudio individuales. El conjunto de datos puede ser utilizado por la comunidad científica para análisis de datos exploratorios, por ejemplo, centrados en los vínculos causales entre la gestión de riesgos, los cambios en los peligros, la exposición y la vulnerabilidad y los impactos de inundaciones o sequías. Los datos también se pueden utilizar para el desarrollo, calibración y validación de modelos sociohidrológicos. El conjunto de datos está disponible para el público a través de GFZ Data Services (Kreibich et al. 2023, enlace para revisión: https://dataservices.gfz-potsdam.de/panmetaworks/review/923c14519deb04f83815ce108b48dd2581d57b90ce069bec9c948361028b8c85/). Abstract. As the adverse impacts of hydrological extremes increase in many regions of the world, a better understanding of the drivers of changes in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is currently a lack of comprehensive, empirical data about the processes, interactions and feedbacks in complex human-water systems leading to flood and drought impacts. Here we present a benchmark dataset containing socio-hydrological data of paired events, i.e., two floods or two droughts that occurred in the same area. The 45 paired events occurred in 42 different study areas and cover a wide range of socio-economic and hydro-climatic conditions. The dataset is unique in covering both floods and droughts, in the number of cases assessed, and in the quantity of socio-hydrological data. The benchmark dataset comprises: 1) detailed review style reports about the events and key processes between the two events of a pair; 2) the key data table containing variables that assess the indicators which characterise management shortcomings, hazard, exposure, vulnerability and impacts of all events; 3) a table of the indicators-of-change that indicate the differences between the first and second event of a pair. The advantages of the dataset are that it enables comparative analyses across all the paired events based on the indicators-of-change and allows for detailed context- and location-specific assessments based on the extensive data and reports of the individual study areas. The dataset can be used by the scientific community for exploratory data analyses e.g. focused on causal links between risk management, changes in hazard, exposure and vulnerability and flood or drought impacts. The data can also be used for the development, calibration and validation of socio-hydrological models. The dataset is available to the public through the GFZ Data Services (Kreibich et al. 2023, link for review: https://dataservices.gfz-potsdam.de/panmetaworks/review/923c14519deb04f83815ce108b48dd2581d57b90ce069bec9c948361028b8c85/). الخلاصة: مع زيادة الآثار السلبية للظواهر الهيدرولوجية المتطرفة في العديد من مناطق العالم، يعد الفهم الأفضل لدوافع التغيرات في المخاطر والآثار أمرًا ضروريًا للإدارة الفعالة لمخاطر الفيضانات والجفاف والتكيف مع المناخ. ومع ذلك، هناك حاليًا نقص في البيانات التجريبية الشاملة حول العمليات والتفاعلات والتغذية المرتدة في أنظمة المياه البشرية المعقدة التي تؤدي إلى آثار الفيضانات والجفاف. نقدم هنا مجموعة بيانات مرجعية تحتوي على بيانات اجتماعية هيدرولوجية للأحداث المزدوجة، أي فيضانان أو موجتي جفاف وقعتا في نفس المنطقة. وقعت الأحداث الـ 45 المزدوجة في 42 منطقة دراسة مختلفة وتغطي مجموعة واسعة من الظروف الاجتماعية والاقتصادية والمائية المناخية. مجموعة البيانات فريدة من نوعها في تغطية كل من الفيضانات والجفاف، وفي عدد الحالات التي تم تقييمها، وفي كمية البيانات الاجتماعية الهيدرولوجية. تشتمل مجموعة البيانات المعيارية على: 1) تقارير أسلوب المراجعة التفصيلية حول الأحداث والعمليات الرئيسية بين حدثين للزوج ؛ 2) جدول البيانات الرئيسية الذي يحتوي على المتغيرات التي تقيم المؤشرات التي تميز أوجه القصور في الإدارة والمخاطر والتعرض والضعف وتأثيرات جميع الأحداث ؛ 3) جدول مؤشرات التغيير التي تشير إلى الاختلافات بين الحدث الأول والثاني للزوج. تتمثل مزايا مجموعة البيانات في أنها تمكن من إجراء تحليلات مقارنة عبر جميع الأحداث المقترنة بناءً على مؤشرات التغيير وتسمح بإجراء تقييمات مفصلة للسياق والموقع بناءً على البيانات والتقارير الشاملة لمناطق الدراسة الفردية. يمكن للمجتمع العلمي استخدام مجموعة البيانات لتحليل البيانات الاستكشافية، على سبيل المثال التركيز على الروابط السببية بين إدارة المخاطر والتغيرات في المخاطر والتعرض والضعف وآثار الفيضانات أو الجفاف. يمكن أيضًا استخدام البيانات لتطوير النماذج الاجتماعية الهيدرولوجية ومعايرتها والتحقق من صحتها. مجموعة البيانات متاحة للجمهور من خلال خدمات بيانات GFZ (Kreibich et al. 2023، رابط للمراجعة: https://dataservices.gfz-potsdam.de/panmetaworks/review/923c14519deb04f83815ce108b48dd2581d57b90ce069bec9c948361028b8c85/).

AbstractAscension Island is a remote South Atlantic equatorial site, ideal for monitoring tropical background CH4. In September 2014 and July 2015, octocopters were used to collect air samples in Tedlar bags from different heights above and below the well‐defined Trade Wind Inversion (TWI), sampling a maximum altitude of 2700 m above mean sea level. Sampling captured both remote air in the marine boundary layer below the TWI and also air masses above the TWI that had been lofted by convective systems in the African tropics. Air above the TWI was characterized by higher CH4, but no distinct shift in δ13C was observed compared to the air below. Back trajectories indicate that lofted CH4 emissions from Southern Hemisphere Africa have bulk δ13CCH4 signatures similar to background, suggesting mixed emissions from wetlands, agriculture, and biomass burning. The campaigns illustrate the usefulness of unmanned aerial system sampling and Ascension's value for atmospheric measurement in an understudied region.