Future Projections of Water Scarcity in the Danube River Basin Due to Land Use, Water Demand and Climate Change

This paper presents a state-of-the-art integrated model assessment to estimate the impacts of the 2°C global mean temperature increase and the 2061-2090 warming period on water scarcity in the Danube River Basin under the RCP8.5 scenario. The Water Exploitation Index Plus (WEI+) is used to calculate changes in both spatial extent and people exposed to water scarcity due to land use, water demand, population and climate change. Despite model and data uncertainties, the combined effects of projected land use, water demand and climate change show a decrease in the number of people exposed to water scarcity during the 2°C warming period and an increase in the 2061-2090 period in the Danube River Basin. However, the projected population change results in a decrease of exposed people in both warming periods. Regions with population growth, in the northwestern part of the Danube River Basin experience low water scarcity or a decrease in water scarcity. The largest number of people vulnerable to water scarcity within the Danube River Basin are living in the Great Morava, Bulgarian Danube and Romanian Danube. There, the combined effects of land use, water demand and climate change exacerbate already existing water scarce areas during the 2°C warming period and towards the end of the century new water scarce areas are created. Although less critical during the 2°C warming period, adjacent regions such as the Tisza, Middle Danube and Siret-Prut are susceptible to experience similar exposure to water scarcity within the 2061-2090 period. Climate change is the most important driver for the increase in water scarcity in these regions, but the strengthening effect of water demand (energy sector) and dampening effect of land use change (urbanization) does play a role as well. Therefore, while preparing for times of increased pressures on the water supply it would be advisable for several economic sectors to explore and implement water efficiency measures

Addressing the Water–Energy Nexus by Coupling the Hydrological Model with a New Energy LISENGY Model: A Case Study in the Iberian Peninsula

As water is required for producing hydropower, and subsequently the water balance is changed for downstream areas, the linking of hydrological and energy models is needed to properly address the interactions among them. In this study, volume–depth-based water storage estimation models were proposed for individual lakes and reservoirs in the Iberian Peninsula using the 30-year Global Water Surface dataset and reservoir morphometry methodology which enables to evaluate reservoirs where data were not available before. The models were subsequently implemented within the new hydropower model called LISENGY that provides the first comprehensive assessment of the temporal and spatial dynamics of water storage, water depth and hydropower production in the Iberian Peninsula. The LISENGY model was coupled with the distributed LISFLOOD hydrological model. The seasonal and interannual changes in energy production were assessed for 168 studied reservoirs with diverse morphometries, which is unique. Conical, concave and convex regression reservoir relationships were distinguished, and optimized turbine discharge and power production were computed. A 10-year water–energy linked system for the 2007–2016 period has been established for the Iberian Peninsula which was not available before. The results showed that it is possible to connect those two models and that the timing and magnitude of simulated storage were well reproduced. The study represents the first step towards integrated pan-European water–energy modeling. Future climate scenarios and energy demands are to be fed into the linked model system to evaluate expected future hydropower generation and possible water scarcity issues

Independence of Future Changes of River Runoff in Europe from the Pathway to Global Warming

The outcomes of the 2015 Paris Agreement triggered a number of climate impact assessments, such as for floods and droughts, to focus on future time frames corresponding to the years of reaching specific levels of global warming. Yet, the links between the timing of the warming levels and the corresponding greenhouse gas concentration pathways to reach them remain poorly understood. To address this gap, we compared projected changes of annual mean, extreme high, and extreme low river discharges in Europe at 1.5 °C and 2 °C under Representative Concentration Pathways RCP8.5 and RCP4.5 from an ensemble of regional climate model (RCM) simulations. The statistical significance of the difference between the two scenarios for both warming levels was then evaluated. The results show that in the majority of Europe (>95% of the surface area for the annual mean discharge, >98% for high and low extremes), the changes projected in the two pathways were statistically indistinguishable. These results suggest that in studies of changes at global warming levels, the projections of the two pathways can be merged into a single ensemble without major loss of information. With regard to the uncertainty of the unified ensemble, the findings show that the projected changes of annual mean, extreme high, and extreme low river discharge were statistically significant in large portions of Europe

The Water-Energy-Food-Ecosystem Nexus in the Mediterranean: Current Issues and Future Challenges

The Mediterranean is an area where the balance between water demand and abstractions vs. water availability is often under stress already, as demonstrated here with the Water Exploitation Index. In this work, model estimates on how different proposed measures for water resources management would affect different indicators. After a review of the current water resources status in the Mediterranean and the definition of indicators used in this study, aspects interlinked with water in the Water-Energy-Food-Ecosystems Nexus are briefly discussed, focusing on problems linked with water scarcity and depletion of groundwater resources as well as with climate change projections. Subsequently, the proposed measures for water efficiency are detailed—irrigation efficiency, urban water efficiency, water reuse and desalination—that might be effective to reduce the growing water scarcity problems in the Mediterranean. Their effects that result from the LISFLOOD model, show that wastewater reuse, desalination and water supply leakage reduction lead to decreased abstractions, but do not affect net water consumption. Increased irrigation efficiency does decrease consumption and reduces abstractions as well. We deduct however that the current envisaged water efficiency measures might not be sufficient to keep up with the pace of diminishing water availability due to climate change. More ambition is needed on water efficiency in the Mediterranean to keep water scarcity at bay

Water-resource management

Africa contains three extremely dry regions: northern Africa (with the Sahara Desert at its heart), southwestern Africa (around the Kalahari and Namib deserts), and the Horn of Africa. The continent also covers several regions with abundant water resources, which are often called water towers. Africa’s water towers include the Ethiopian Highlands, the Congo Basin, the East African mountain region, the Angolan water plateau, the Lesotho Highlands, the Jos Plateau in central Nigeria and the Fouta Djallon mountains in Guinea (UNEP, 2010).Fil: De Roo, Ad. No especifíca;Fil: Brink, Andreas. No especifíca;Fil: Pekel, Jean François. No especifíca;Fil: Alfieri, Lorenzo. No especifíca;Fil: Naumann, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; ArgentinaFil: Rembold, Felix. No especifíca;Fil: Negre, Thierry. No especifíca;Fil: Bouraqui, Faycal. No especifíca;Fil: Bisselink, Berny. No especifíca;Fil: Ronco, Paolo. No especifíca;Fil: Dondeynaz, Celiné. No especifíca;Fil: Farinosi, Fabio. No especifíca;Fil: Pastori, Marco. No especifíca;Fil: Ameztoy, Iban. No especifíca;Fil: Markantonis, Vasileios. No especifíca;Fil: Cordano, Emmanuele. No especifíca;Fil: Sánchez González, David. No especifíca;Fil: Carmona Moreno, César. No especifíca;Fil: Belward, Alan. No especifíca