Water plays a central role in the functioning of the biosphere and in supporting all life. Freshwater ecosystems are particularly important, providing a unique and diverse array of services upon which human society depends. These services include 'provisioning' services, such as the provision of water for agriculture and hydropower. They also include 'regulating' services, where water helps regulate our environment, such as by flood control or the breaking down of pollutants.
If our freshwater ecosystems are to continue to provide these services it is essential that there is water in sufficient quantity and of sufficient quality. This report primarily focuses on the problem of water quantity in Europe.
Water quantity varies naturally according to the seasons, the geography of Europe's regions, and the different types of water bodies (including lakes, rivers, wetlands and sub-surface groundwater bodies). This natural variation can be seen in periodic flooding and droughts, both of which have long been a feature of Europe's landscapes. Many ecosystems, habitats and species types have evolved to deal with precisely this type of variation in the hydrological cycle.
Today's threaths to water's natural variability
However this natural cycle of water availability is now coming under threat from a variety of different pressures, exposing water ecosystems and societies to man-made shortages and excesses of water, a situation known as 'water vulnerability'.
The first major driver of alterations to the hydrological system is change in land use. The growth of urban areas has several effects on the water cycle. Urban development usually leads to soil sealing by asphalt and concrete, meaning that water cannot seep naturally into the earth. Land use change also often places pressure on existing sewage and drainage systems. These two developments mean that in periods of heavy rain water can neither seep into the ground or be carried away by sewers, resulting in flooding.
Water abstraction is another cause of water vulnerability. Agricultural land is generally better at absorbing water than urban land, but this does not mean that agriculture always protects the soil and water beneath it. In many regions of Europe, agriculture is highly dependent on irrigation. Agriculture accounts for 33 % of total water use in Europe, and this dependence on water can reach up to 80 % in parts of Southern Europe. Usually, the periods of peak demand for irrigation come during the summer, when rainfall is already low and when regions are already suffering from drought.
The third main cause of water vulnerability is climate change. Climate change has a more indirect effect on water quantity than land use change or abstraction. Its effects are also more difficult to discern given the natural variability in the hydrological cycle. Nevertheless, the effects are increasingly visible. Since 1880, the average length of summer heat waves has doubled in Europe. It is predicted that climate change will exacerbate the frequency and severity of both droughts and floods in Europe over the coming decades. Climate change and its effects did not feature explicitly enough in the first round of River Basin Management Plans prepared by the Member States in 2009. However, the next round of River Basin Management Plans, which will be published in 2015, will consider the effects of climate change on river basins.
These human-induced changes in land use, climate, and water abstraction are combining to alter the natural 'flow regimes' that exist in water bodies. For this reason, it is important that human water use seeks to avoid creating situations of water vulnerability. We can do this by respecting the local 'ecological flow' — the quantity of water needed at different times of the year to maintain a water ecosystem.