Water
Water is a unique component of our planet. It is also a commodity to manage and sell, and the object of many controversial economic interests and complex social interrelations.
Water supports life on our planet. Its constant motion from the Earth to the atmosphere and back is known as the hydrological cycle. The sun and wind cause water to evaporate from soil, plant leaves and animals, and from the surfaces of rivers, lakes and oceans. This process changes water to a gaseous form called water vapour. Water vapour condenses under certain conditions and falls back to Earth as rain or snow. Precipitation that ultimately reaches streams and rivers, often transporting other material with it, is known as runoff. Rain fills up rivers and lakes. Rivers flow into the oceans. Some precipitation penetrates the ground and forms groundwater.
Water quality is of vital importance to humans and other living beings. Human activities are the main cause of water pollution, and thus of the increasing shortage of good-quality drinking water. A growing number of countries are facing water stress, which now affects more than 2 billion people worldwide. Water stress affects countries on every continent, hindering the sustainability of natural resources as well as economic and social development.
Water resources include annually renewable surface waters and groundwater supplies that are renewed very slowly.
- Surface waters and groundwater are an essential component of the Earth’s water cycle. Surface waters include rivers, lakes and glaciers. Many European river flow regimes are heavily affected by human activities such as water abstraction and damming. In Southern Europe, many rivers dry up in the summer. Surface water is the main source for water abstraction in Europe – about 70 percent of total abstraction on average.
- Groundwater is mainly found in aquifers – that is, underground layers of water-bearing permeable rock or materials such as sand that are contained by layers of water-resistant rock (such as clay). The main characteristics of groundwater systems include their lack of visibility and relatively inaccessible locations; low flow rates; long residence times; and slow reactions to changes on the surface.
Groundwater plays a number of important economic and ecological roles, as well as being essential to human health. Groundwater systems are normally very stable, in terms of both quantity and quality. However, the effects of pollution and overexploitation could lead to drastic changes, with a recovery period lasting centuries.
Overall, there is no water shortage problem in Europe. However, the amount of water available for sustained consumption is very unevenly distributed across the continent. Many European countries are heavily dependent on external contributions of water through transboundary rivers to meet their demand.
