• Energy Research

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.

Cities are hotspots of commodity consumption, with implications for both local and systemic water resources. Water flows “virtually” into and out of cities through the extensive cross-boundary exchange of goods and services. Both virtual and real water flows are affected by water supply investments and urban planning decisions, which influence residential, commercial, and industrial development. This form of water “teleconnection” is being increasingly recognized as an important aspect of water decision-making. The role of trade and virtual water flows as an alternative to expanding a city’s “real” water supply is rarely acknowledged, with an emphasis placed instead on monotonic expansion of engineering potable water supplies. We perform a literature review of water footprint studies to evaluate the potential and importance of taking virtual flows into account in urban planning and policy. We compare and contrast current methods to assess virtual water flows. We also identify and discuss priorities for future research in urban water footprint analysis.

AbstractRisk 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.

Regional climate change impacts show a wide range of variations under different levels of global warming. Watersheds in the northeastern region of the United States (NEUS) are projected to undergo the most severe impacts from climate change in the forms of extreme precipitation events, floods and drought, sea level rise, etc. As such, there is high possibility that hydrologic regimes in the NEUS may be altered in the future, which can be absolutely devastating for managing water resources and ecological balance across different watersheds. In this study, we present a comprehensive impact analysis using different hydrologic indicators across selected watersheds in the NEUS under different thresholds of global temperature increases (1.5, 2.0 and 3.0 °C). Precipitation and temperature projections from fourteen downscaled Global Circulation Models (GCMs) under the representative concentration pathway (RCP) 8.5 greenhouse gas concentration pathway are used as inputs into a distributed hydrological model to obtain future streamflow conditions. Overall, the results indicate that the majority of the selected watersheds will enter a wetter regime, particularly during the months of winter, while flow conditions during late summer and fall indicate a dry future under all three thresholds of temperature increase. The estimation of time of emergence of new hydrological regimes show large uncertainties under 1.5 and 2.0 °C global temperature increases; however, most of the GCM projections show a strong consensus that new hydrological regimes may appear in the NEUS watersheds under 3.0 °C temperature increase.

Abstract The importance of climate in water resources management is well recognized, but less is known about how climate affects water access at the household level. Understanding this is crucial for identifying vulnerable households, reducing health and well-being risks, and finding equitable solutions. Using difference-in-differences regression analyses and relying on temporal variation in interview timing from multiple, cross-sectional surveys, we examine the effects of monsoon riverine flooding on household water access among 34 000 households in Bangladesh in 2011 and 2014. We compare water access, a combined measure of both water source and time for collection, among households living in flood-affected and non-flood-affected districts before and after monsoon flooding events. We find that households in monsoon flood-affected districts surveyed after the flooding had between 2.27 and 4.42 times higher odds of experiencing low water access. Separating geographically, we find that while households in coastal districts have lower water access than those in non-coastal districts, monsoon flood exposure is a stronger predictor of low water access in non-coastal districts. Non-coastal districts were particularly burdened in 2014, when households affected by monsoon flooding had 4.71 times higher odds of low water access. We also find that household wealth is a consistent predictor of household water access. Overall, our results show that monsoon flooding is associated with a higher prevalence of low water access; socioeconomically vulnerable households are especially burdened.