Abstract

An assessment for Europe on available water resources and a comparison with water demands from various economic sectors shows that freshwater availability over the European continent varies significantly. Large areas in Spain and Eastern Europe have on average less than 200 mm generated freshwater per year. At the same time, in parts of those areas annual water demand from the various sectors is equal or even larger than the freshwater generation. However, estimating water scarcity is not a straightforward exercise, since important parts of the ‘puzzle’ are missing, such as inter-river basin water transfers, detailed information on various storages in lakes and reservoirs, as well as the use of deep/fossil groundwater. Therefore, estimating water scarcity still includes many uncertainties, and the estimation made here needs further improvement. In addition, although data needed for water resources assessment do exist in Europe, the access to these data to make a pan-European overview could still be improved - the public availability of observed river flows is still a particular concern. The availability of meteorological observations, together with increased availability of satellite observations, has greatly improved already. An assessment of the African continent reveals large areas with less than 200 mm freshwater generation per year. Areas with freshwater generation larger than 200 mm are situated in Morocco, equatorial Africa, Southwest Ethiopia, Eastern South-Africa and Madagascar. Estimating water scarcity is again a challenging exercise. First of all, the most recent pan-African data on water abstractions date from the year 2000, which needs improvement. Next, as in Europe, information on large inter-river basin water transfers is not available. There are many future research challenges, knowledge gaps, and data gaps in the field of water resources estimation. The lack of available observed river flow data for Africa, for example, creates a major bottleneck in calibrating and verifying hydrological models for this continent. Satellite data provide improved meteorological data for Africa, but data on water abstractions need to be updated more frequently. In general, information on long-distance water transfers - intra river basin, inter-river basin, or cross-border - is largely unavailable at continental and global leve