Serena Ceola

The Ebro River Basin is one of the most intensively managed and climatically sensitive basins in the Mediterranean region, where increasing water demands, pronounced climate variability, and environmental constraints pose major challenges for sustainable water resources management. Addressing these challenges requires hydrological models capable of consistently representing both natural processes and anthropogenic water use. In this context, the INTERROGATION project, funded by the Italian Ministry of Universities and Research, examines the interactions between climatic and anthropogenic factors in the development and recovery of major hydrological droughts that have affected the Ebro River Basin in recent decades (1990-2023).In this study, we present a comprehensive reconstruction of the water cycle in the Ebro River Basin, explicitly accounting for both natural processes and human water use. For this purpose, three different precipitation datasets are used as input data to the flexible conceptual hydrological model MISDc (Modello Idrologico Semistribuito in Continuo): long-term (2000-2023) daily in situ observations and two versions of a daily integrated dataset obtained by merging GPM and SM2RAIN products at low (10 km) and high (1 km) spatial resolutions.The hydrological model is calibrated against observed river discharge and validated through a multi-variable comparison with satellite-based estimates of soil moisture, evapotranspiration, snow water equivalent, and irrigation, which were developed within the framework of the European Space Agency Digital Twin Earth (DTE) Hydrology Next project. The results of this work demonstrate the significance of employing a suitable hydrological model in conjunction with accurate satellite information for capturing the spatiotemporal evolution of the hydrological cycle within highly managed basins. These results will be the basis for developing a decision support system that will guide stakeholders toward an integrated management of water resources in the Ebro River Basin.

Sub-daily extreme precipitation can trigger severe flooding in urban catchments due to short hydrological response times. Although recent evidences show heterogeneous trends in magnitude and frequency across different regions of the world, rapid soil sealing from urban expansion – outpacing population growth – may significantly amplify pluvial flood risk. This study evaluates projected changes in pluvial flood risk for four megacities (population >10 million in 2010) under the Shared Socioeconomic Pathway-Representative Concentration Pathway (SSP-RCP) 2-4.5 and 5-8.5 from 2020 to 2100. Megacities are selected globally based on geomorphic flood-prone areas, identified through digital elevation and floodplain datasets, and on population hotspots derived from historical gridded data. Pluvial flood hazard is assessed using a DEM-based hierarchical filling-and-spilling algorithm, and compared against detailed hydrodynamic modeling. Vulnerability assessment is conducted at present-day for simplicity, while a data-driven algorithm for predicting future building footprints associated with future demographic scenarios is under development. Results provide insights into how climate and urbanization interact to cast future pluvial flood risk in the world’s largest cities, informing adaptation strategies for sustainable urban planning.

In 2023 and 2024, Italy experienced severe flooding events with substantial environmental and socio-economic consequences. As climate change increases the frequency and intensity of extreme weather events, understanding individuals’ flood risk perceptions, preparedness, and responses to risk communication is crucial for effective climate adaptation and mitigation policies. In this work we assess preparedness against floods and risk perceptions, and examines whether targeted flood risk information can enhance risk awareness, pro-environmental behavior, and support for climate policies. To this aim, an original survey instrument was designed and administered to a representative sample of 3,423 residents in Emilia-Romagna and Tuscany in July 2024, following the 2023 flood events. The survey collected detailed information on socio-demographic characteristics, flood risk perceptions, preparedness and mitigation measures, awareness of municipal response strategies, information sources, and policy expectations. A key contribution of the study is the integration of survey responses with official flood hazard data, enabling a comparison between perceived and actual flood risk exposure. In December 2024, after new devastating floods in Italy, we conducted a follow-up survey, to allow us examining changes in preparedness and perceptions over time.Across both surveys, we implemented pre-registered randomized experiments to assess the causal impact of flood risk communication. In the first survey, treated respondents received municipality-specific flood risk information after reporting their place of residence. In the second one, treated respondents watched a 75-second video explaining the causes, consequences, and dangers of floods. Results show that overall preparedness is low, with around 70% of respondents reporting no adaptive actions, but that targeted risk information delivered through effective visual messages significantly increases flood risk awareness, pro-environmental behavior, and support for climate-related policies. These findings highlight the importance of using direct, visually effective, and context-specific risk communication in fostering climate adaptation and public support for mitigation efforts.

Convective storms frequently trigger flash floods, debris flows, and urban flooding, making robust sub-hourly precipitation statistics essential for risk assessment and infrastructure design. The TENAX model (TEmperature-dependent Non-Asymptotic statistical model for eXtreme return levels) offers a physically-based framework to estimate future extreme rainfall by linking precipitation intensity to near-surface air temperature. Its standard configuration adopts a 24-hour temperature window with zero offset preceding the rainfall event, which is mainly driven by compatibility with daily climate model outputs rather than empirical optimization. Yet, its sensitivity to alternative configurations remains largely unexplored. We hereby analyze 145 rain gauges from Arpae Emilia-Romagna (106) and ARPA Lombardia (39), from the Po plains to the Alpine forelands, spanning 2003–2024, each with at least 15 years of precipitation records at 10- to 15-minute resolution. Temperature data come from VHR-REA_IT reanalysis at 2.2 km resolution. We test twelve model configurations obtained by combining three alternative window durations (1, 12, and 24 h) with four temporal offsets (0, 1, 5, and 12 h). The analysis is performed both at the annual and at the seasonal levels, and model performance is assessed through repeated split-sample validation (50–50 random temporal splits), where the optimal configuration is selected by minimizing the mean squared error with respect to empirical return levels derived using Weibull plotting positions. Our annual analysis shows that the 24 h window with 12 h offset consistently outperforms the default configuration. In contrast, seasonal analyses reveal marked differences: summer extremes show a clear preference for short (1-h) temperature windows, consistent with convective storm dynamics, whereas autumn and winter exhibit higher variability with no single dominant configuration. Moreover, we identify a statistically significant relationship (p < 0.05) between the optimal temperature window configuration and station elevation, suggesting that elevation-dependent thermodynamic and convective processes modulate the temperature–precipitation link. The findings provide practical guidance for calibrating TENAX in data-rich regions and support more physically consistent applications to future climate projections.

Extreme rainfall and its temporal evolution critically influence flood hazard, slope stability, and infrastructure resilience. Yet in Italy, where complex topography and diverse climates shape precipitation, studies of rainfall extremes have produced conflicting outcomes, with neighboring sites often showing opposite trends. Much of this inconsistency stems from differences in data length, baseline period selection, and orographic context.This study builds upon and extends the recent national-scale analysis by Mazzoglio et al. (2025), which, for the first time, quantified trends in rainfall extremes across Italy for the 1960–2022 period. Using the Improved Italian - Rainfall Extreme Dataset (I2-RED), which compiles data of thousands of rain gauges, we apply distributed quantile regression to annual maximum precipitation for short (1 h) and long (24 h) durations. Trends are expressed as percentage variations per decade and evaluated over multiple baseline windows (1960–2022, 1970–2022, 1980–2022, and 1990–2022) to test the sensitivity of results to the observational timeframe. Elevation effects are assessed by stratifying rain-gauge samples into low- and high-altitude groups and by comparing the regression slopes obtained for each.Results reveal that short-duration extremes exhibit widespread and coherent positive trends, while 24-hour events show more heterogeneous and regionally variable patterns. Shortening the analysis period strengthens the positive signal, indicating that the intensification of sub-daily rainfall is largely a recent phenomenon. The most pronounced increases occur at higher elevations, especially in the Alps and Apennines. By contrast, lowlands and coastal areas show weaker or negligible changes. The geographic segmentation further demonstrates that spatial patterns of change align closely with major Italian physiographic structures, highlighting the combined roles of orography and regional geography in shaping rainfall evolution.These findings suggest that trends in rainfall extremes in Italy cannot be interpreted through a single national lens: both methodological choices (baseline period and rainfall duration) and environmental factors (topography and geography) fundamentally shape the detected signals. The combined sensitivity to time window and elevation highlights the importance of accounting for Italy’s physiographic diversity when assessing hydrological risk and designing climate-resilient infrastructure. ReferenceMazzoglio P., Viglione A., Ganora D., Claps P. (2025). Mapping the uneven temporal changes in ordinary and extraordinary rainfall extremes in Italy. Journal of Hydrology: Regional Studies, 58, 102287. https://doi.org/10.1016/j.ejrh.2025.102287

Four of the largest river basins in Europe – Rhine, Rhône, Po, and Danube – rely heavily on Alpine headwaters. Recently, these basins have experienced intensifying hydroclimatic fluctuations, including catastrophic floods and prolonged droughts, highlighting the vulnerability of these basins to climatic variability. Understanding the potential drivers behind changes in streamflow patterns, particularly the relative contributions of precipitation and temperature, is essential for improving the attribution of extreme hydrological events and informing sustainable freshwater resource management. However, relatively short instrumental hydroclimatic records in the European Alps limit our understanding of the long-term influence of climate variability on hydrological extremes. This research integrates proxy-based reconstructions with paleo-climate reanalysis to assess streamflow variations over an extended timeframe. Through statistical regression, we quantify how changing rainfall and temperature patterns contribute to the onset of extreme events, with a specific focus on recent droughts. By comparing historical trends with future projections across different climate scenarios, we aim to identify the primary climatic drivers of hydrological extremes and their evolution over time. This work emphasizes the necessity of long-term perspectives in attributing extreme events and securing water resources in the Alps.

Droughts in Europe are becoming increasingly frequent and severe, with the 2022 drought surpassing previous records and causing widespread socio-economic impacts. Using a Europe-wide survey (n = 481 across 30 countries) combined with hydroclimatic data (i.e., Standardized Precipitation Evapotranspiration Index; SPEI), we quantify how forecasting systems and Drought Management Plans (DMPs) affected response timing and perceived effectiveness. It specifically assesses the role of forecasting systems and Drought Management Plans (DMPs) in improving preparedness and in facilitating more effective and timely responses. Our findings show that organisations with forecasting systems or DMPs in place implemented drought response measures on average two and one months earlier respectively than those without, and rated their effectiveness higher. Additionally, the study investigates how drought management practices and awareness have evolved as a consequence of the 2018 European drought and how recent experiences shape water managers' perceptions, with 35 % of the respondents indicating introducing or updating their DMPs after the 2018 drought. The findings emphasize the necessity of a standardized, continent-wide drought risk management coordination to address the multifaceted nature of drought risk by integrating climatic and societal factors, and advocates for a Drought Directive as a means to achieve this. This research aims to inform policy development towards sustainable and holistic drought risk management, highlighting the crucial roles of preparedness, awareness, and adaptive strategies in mitigating future drought impacts. This study and its companion paper The 2022 drought needs to be a turning point for European drought risk management are the result of a study carried out by the Drought in the Anthropocene (DitA) network, an IAHS initiative.

The 2022 European drought has underscored critical deficiencies in European water management. This paper explores these shortcomings and suggests a way forward for European drought risk management. In particular, we focus on four key aspects: the increasing drought risk, its spatial and temporal impacts, current management approaches, and how these differ across Europe. We base our findings on a continent-wide survey of water managers involved in responding to the 2022 drought. The survey collected 481 responses from 30 European countries and contained 19 questions on perceived sectorial impacts and the drought risk management practices implemented by the respondents' organizations. Information from the survey was supported with climate-related data on drought severity as quantified by the Standardised Precipitation Evapotranspiration Index, to offer a comprehensive overview of how extreme historical droughts are managed across Europe. Our findings reveal a consensus on the growing risk of drought, driven by droughts' rising frequency and intensity. While the 2022 event affected most of the continent, our findings show significant regional disparities in management capacity. In many countries – particularly those with agriculture-dominated economies – drought responses remain short-term and reactive, often leading to potentially maladaptive practices. Despite these challenges, we also observe a positive shift, with organizations showing increased awareness and preparedness. Hence, the lessons learnt from the 2022 event may provide an ideal opportunity to mainstream European-wide drought risk management. To seize this opportunity, we advocate for a European Drought Directive, to harmonize and enforce risk management policies across the continent. This directive should promote a systemic, integrated, and long-term risk management perspective. It should also set clear guidelines at the national and sub-national level, and for cross-boundary drought collaboration. This study and its companion paper, “From Crisis to Capacity: Institutional Preparedness and Response During the 2022 European Drought”, result from work carried out by the Drought in the Anthropocene network, an initiative of the International Association of Hydrological Sciences (IAHS).