Drought Risk Management: Needs and Experiences in Europe
Jurgen V. Vogt, Paulo Barbosa, Carmelo Cammalleri, Hugo Carrao, and Christophe Lavaysse
The European Drought Observatory (EDO) was developed as a response to the need to better understand, monitor, and forecast the interlinked phenomena of water scarcity and drought (WS&D) in Europe and to provide input for the development of evidence-based policies in the field. A first attempt to address the WS&D problem in the European Union (EU) was included in the European Water Framework Directive (WFD 2000), which requires drought management plans to be developed in all river basin districts prone to prolonged droughts. However, this requires a clear definition of a "prolonged drought" and adequate monitoring and assessment systems. In 2007, the European Commission (EC) published a specific Communication to the European Parliament and the Council, Addressing the challenge of water scarcity and droughts in the European Union (European Commission 2007). This communication explicitly asks for the development of EDO and acknowledges its use for the enhancement of the knowledge of the issue. It further underlines the fact that efficient alert systems are an essential dimension of risk management and that an early warning system will, therefore, follow suit to improve the drought preparedness of the relevant authorities. It details the need for a system that "will integrate relevant data and research results, drought monitoring, detection and forecasting on different spatial scales, from local and regional activities to continental overview at EU level, and will make it possible to evaluate future events" (European Commission 2007, p. 9).
This communication and the general lack of harmonized drought information at the European level led the European Commission Joint Research Centre (JRC) to start the development of such a system in close collaboration with the EU member states, the European Environment Agency, Eurostat, and representatives from the electricity and water industries. EDO targets efficient methods to monitor and forecast meteorological, agricultural, and hydrological droughts at European scale and at the same time to benchmark the developed methods with national to subnational information systems. It is a distributed system, where data and indicators are handled at each spatial scale by the responsible authorities (stakeholders) and visualized through Web mapping services. This requires calculation of a suite of core indicators according to defined standards at all scales. With increasing detail, additional locally important indicators can be added by the responsible authorities. While JRC handles data and computes indicators at the continental level (so-called awareness-raising indicators), national, regional, and river basin authorities add more detailed information for their area of interest. As detail increases, indicators become more relevant for day-to-day water management. EDO can be accessed through JRC's web portal at http://edo. jrc.ec.europa.eu/ and at the same time it serves as the European node in the first prototype of a distributed global drought information system (GDIS) hosted by NOAA at https://www.drought.gov/gdm/ and developed as part of the Group on Earth Observation (GEO) work plan.
EDO provides a suite of drought indicators at different spatial and temporal scales, including 10-daily and monthly updated maps on the occurrence and evolution of drought events, as well as a 7-day forecast of soil moisture. Medium- to long-term forecasting is under development using probabilistic ensemble methods. Currently, EDO includes meteorological indicators (e.g., Standardized Precipitation Index [SPI] and temperature), soil moisture (output of a distributed hydrological model), vegetation condition (based on satellite-derived measurements of the photosynthetic activity of the vegetation), and river low flows. At the more detailed levels it includes, for example, indicators on groundwater levels and trends (France) and warning levels for water management in irrigated and non-irrigated areas (Ebro river basin).
The variety of indicators proved useful for the expert user and, in case of severe drought events, for the production of drought reports by the JRC drought team. The information content, including the drought reports, is well received by the stakeholder community, as shown by the number of web accesses and downloads. For the policymakers and high-level managers, however, this level of detail proved to be too complicated. They require synthetic high-level combined indicators, showing different alert levels, to be used for awareness raising as well as for policy and decision-making. Such combined indicators need to be developed by sector (e.g., for agriculture, public water supply, energy production, and waterborne transport).
The development of the first Combined Drought Indicator (CDI) for agriculture, therefore, was a major breakthrough in providing information on the drought propagation within the hydrological cycle, that is from the rainfall deficit to a deficit in soil moisture and the resulting impacts on the vegetation cover. The CDI provides easy-to-understand sector-specific information for decision makers in the form of alert levels. Like the North American Drought Monitor (NADM; see Chapters 7 and 19), EDO provides reports of exceptional drought events, albeit not in a regular manner. More recently, EDO has been extended to the global level in order to provide information to the Emergency Response Coordination Centre (ERCC) of the EC, which supports and coordinates a wide range of prevention and preparedness activities in the area of natural and manmade disasters. This extended system, called the Global Drought Observatory (GDO; http://edo.jrc.ec.europa.eu/gdo) adds the component of risk and impact assessment. A first drought risk assessment for food security has been implemented and a Likelihood of Drought Impact (LDI) indicator has been developed that serves as a high-level alert indicator combining the hazard with exposure and vulnerability to evaluate the evolving drought risk for that sector.
In the following sections, we provide more detail on various aspects of the EDO and GDO systems. In Section 18.2, we discuss the core indicators and the approach to forecasting drought events. Section 18.3 then details the current approach implemented for drought risk assessment at the global level, and Section 18.4 provides some information on the setup of the GDO. Section
18.5 provides conclusions and an outlook.