All this is conspiring to unravel the ecological functioning of the world's river basins, in effect destroying the very systems that gather and convey freshwater for life.
Dynamic, living systems
Experts agree that the best approach to conserving the world's freshwater resources is through managing river basins sustainably. This means making wise choices about resource use, based on an understanding of how to maintain dynamic, living systems in the long term.
Any activity that takes place in a river basin such as the disposal of waste water or the cutting of forests, has impacts downstream. A vivid example of this was the cyanide spill in the River Tisza (a tributary of the Danube) from a mine in Romania in January 2000. The highly toxic chemical swept downstream through Hungary, devastating aquatic life along the course of the river and contaminating the drinking water of hundreds of thousands of people.
Source of life, food and power
River basins are important from hydrological, economic and ecological points of view. They absorb and channel the run-off from snow-melt and rainfall which, when wisely managed, can provide fresh drinking water as well as access to food, hydropower, building materials (e.g. reeds for thatching), medicines and recreational opportunities.
They also form a critical link between land and sea, providing transportation routes for people, and making it possible for fish to migrate between marine and freshwater systems.
By acting as natural 'filters' and 'sponges', well-managed basins play a vital role in water purification, water retention and regulation of flood peaks. In many parts of the world, seasonal flooding remains the key to maintaining fertility for grazing and agriculture.
Mix of habitats = mix of life
Last but not least, these often very large-scale ecosystems combine both terrestrial and aquatic components, thereby providing a wide diversity of habitats for plants and animals.