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Ensemble projections of future changes in discharge over Europe show large variation. Several methods for performance-based weighting exist that have the potential to increase the robustness of the change signal. Here we use future projections of an ensemble of three hydrological models forced with climate datasets from the Coordinated Downscaling Experiment - European Domain (EURO-CORDEX). The experiment is set-up for nine river basins spread over Europe that hold different climate and catchment characteristics. We evaluate the ensemble consistency and apply two weighting approaches; the Climate model Weighting by Independence and Performance (ClimWIP) that focuses on meteorological variables and the Reliability Ensemble Averaging (REA) in our study applied to discharge statistics per basin. For basins with a strong climate signal, in Southern and Northern Europe, the consistency in the set of projections is large. For rivers in Central Europe the differences between models become more pronounced. Both weighting approaches assign high weights to single General Circulation Models (GCMs). The ClimWIP method results in ensemble mean weighted changes that differ only slightly from the non-weighted mean. The REA method influences the weighted mean more, but the weights highly vary from basin to basin. We see that high weights obtained through past good performance can provide deviating projections for the future. It is not apparent that the GCM signal dominates the overall change signal, i.e., there is no strong intra GCM consistency. However, both weighting methods favored projections from the same GCM.

Target 6.4 of the recently adopted Sustainable Development Goals (SDGs) deals with the reduction of water scarcity. To monitor progress towards this target, two indicators are used: Indicator 6.4.1 measuring water use efficiency and 6.4.2 measuring the level of water stress (WS). This paper aims to identify whether the currently proposed indicator 6.4.2 considers the different elements that need to be accounted for in a WS indicator. WS indicators compare water use with water availability. We identify seven essential elements: 1) both gross and net water abstraction (or withdrawal) provide important information to understand WS; 2) WS indicators need to incorporate environmental flow requirements (EFR); 3) temporal and 4) spatial disaggregation is required in a WS assessment; 5) both renewable surface water and groundwater resources, including their interaction, need to be accounted for as renewable water availability; 6) alternative available water resources need to be accounted for as well, like fossil groundwater and desalinated water; 7) WS indicators need to account for water storage in reservoirs, water recycling and managed aquifer recharge. Indicator 6.4.2 considers many of these elements, but there is need for improvement. It is recommended that WS is measured based on net abstraction as well, in addition to currently only measuring WS based on gross abstraction. It does incorporate EFR. Temporal and spatial disaggregation is indeed defined as a goal in more advanced monitoring levels, in which it is also called for a differentiation between surface and groundwater resources. However, regarding element 6 and 7 there are some shortcomings for which we provide recommendations. In addition, indicator 6.4.2 is only one indicator, which monitors blue WS, but does not give information on green or green-blue water scarcity or on water quality. Within the SDG indicator framework, some of these topics are covered with other indicators.

Water managers in the Rhine basin are increasingly confronted with information on the impact of climate change and climate variability on the discharge regime of their river system. The river Rhine has a long history of flooding events that caused casualties and severe damage. The question remains whether measures that are currently implemented upstream in Germany have either positive or negative effects on peak water levels downstream. Adaptation can significantly reduce impacts of climate change and is seen as an important part of societal response to global climate change. Planned adaptation implies decisions and measures within society that help to anticipate to climate related risks. The overall aim of ACER is to investigate the impact of climate change and to explore adaptation strategies for the Rhine basin under climate change, for both basin wide as well as regional water managers. The ACER project follows a so-called scenario analysis whereby solution trajectories are analyzed and compared, under the assumption of various long-term climate change and socio-economic scenarios. At the core of the ACER scenario approach are a group of stakeholders representing water managers at different levels in the Rhine basin. The results can be grouped in two themes: 1) Modeling processes - a trade-off. Instead of creating an overall new "Rhine model" for this project, we realized there is a trade-off between model complexity and the ability to run long time series and/or large ensembles of climate change scenarios. Considering model performance, focus and scale of the problem, a unique model set-up had to be optimized for each project objective. We coupled two complex models to simulate and investigate land surface - atmosphere feedback mechanisms. However, to simulate the combined effect of climate change and flood management measures, another model was developed that can be forced with output from a rainfall generator (10.000 year series of meteorological daily data).

Toelichtend artikel op het promotieonderzoek, dat onderdeel uitmaakt van het project "Developing adaptive capacity to extreme events in the Rhine basin (ACER). Een belangrijke vraag in het project is hoe te anticiperen op toekomstige klimaatverandering en in het bijzonder hoe men het huidige beleid klimaatbestendig kan maken. Specifiek gaat dit artikel in op de relevantie van recycling van neerslag als proces binnen de hydrologische kringloop. De voorlopige resultaten laten zien dat horizontaal watertransport een belangrijke factor is voor neerslag afkomstig uit lokale verdamping en dat er binnen Europa verschillen zijn in de herkomst van neerslag

Continental-scale models of malaria climate suitability typically couple well-established temperature-response models with basic estimates of vector habitat availability using rainfall as a proxy. Here we show that across continental Africa, the estimated geographic range of climatic suitability for malaria transmission is more sensitive to the precipitation threshold than the thermal response curve applied. To address this problem we use downscaled daily climate predictions from seven GCMs to run a continental-scale hydrological model for a process-based representation of mosquito breeding habitat availability. A more complex pattern of malaria suitability emerges as water is routed through drainage networks and river corridors serve as year-round transmission foci. The estimated hydro-climatically suitable area for stable malaria transmission is smaller than previous models suggest and shows only a very small increase in state-of-the-art future climate scenarios. However, bigger geographical shifts are observed than with most rainfall threshold models and the pattern of that shift is very different when using a hydrological model to estimate surface water availability for vector breeding.