A river is like a living “organism.” It is a complex system of plants, animals, nutrients, movement, and habitats. It includes all the living organisms of the entire basin, from the small aquatic beings (bacteria, algae, larvae, shellfishes, fish) to the larger terrestrial vertebrates (reptiles, amphibians, mammals, and birds) and humans.
A natural-flowing river creates abundant habitats which host a great number of living species. The variation in the waterscape (environmental differences) enables the river to shelter a large number of living species: for a river to keep its normal balance and to perform its natural functions, environmental diversity and biodiversity are fundamental conditions. One of the most important functions of the river is its self-cleansing ability, which refers to the process in which micro-organisms, macro-invertebrates and vertebrates literally break down both natural and human-created organic and inorganic waste in the water and purify the riverine environment.
Water is essential for life and for the survival of all creatures, and therefore, the management of this precious gift is one of the greatest challenges of our time. As the demand for water spirals upward, the inevitable need for adequate supply networks and sanitary services must be satisfied.
The distribution of fresh water reserves (supply) on our planet is unequal: many regions are subject to flooding in particular periods of the year, while other regions suffer from frequent drought periods. The consumption of fresh water is likewise unequal: it borders on waste in rich countries, and is a limiting factor for survival in poor countries. At present 80 countries and more than 1 billion of the world’s population lack access to potable (suitable for drinking) water. These figures also indicate that 40% of the world’s population suffer from lack of fresh drinking water. The consequence of this painful situation is, as the World Health Organization affirms, that millions die every year because of lack of water or bad water quality.
The presence of water strongly influences life on our planet. This is not only because water represents a vital element for all life forms of life on earth, but also because it creates environments such as rivers, lakes and wetlands which, in turn, constitute natural habitats for an enormous variety of plant-, and animal species.
Vegetation in marshes and ponds is distributed in relation to the depth of the waters: as one moves from the centre of a water body (e.g. a pond) to the outer edges of the riparian zone, populations of plant species change and blend from one into another. Thus, in a small area one can observe an exceptional variety of habitats which is also the reason that moist, damp areas are characterised by such high biodiversity.
Rivers are ecosystems which are characterised by the flow of water itself (as an abiotic factor), as well as by the sum of all organisms within the river basin (biotic constituents). A river is an ecological continuum of environments that can differ from one to another, and it functions best when there has been little or no human intervention along the river-bed and flood areas.
In Europe very few rivers are free to flood (e.g. the Loire in France). Luckily, in other regions of the world there are more numerous rivers which, at least in part, still experience periodical inundations leading to temporary wetland habitats like damp prairies, grassy swamps, alluvial forests, or stretches of water formed out of abandoned meanders.
Lakes are formed whenever there is a depression of the ground characterised by a waterproof substrate or by one which, in any event, does not possess good drainage. Most of the lakes in Europe are permanent, freshwater lakes. However, in Southern Europe where there is a more Mediterranean climate or in the regions of the former Soviet Union salty lakes (even temporary ones) are very widespread. Along the shallow lakesides light penetrates easily to the bottom and enables the development of rooted plants which create the biologically rich transition-zones between the stretch of water and the dry land.
The availability of natural resources, especially water, has a strong influence on human society. Today water is one of the biggest obstacles to development in many countries. History illustrates the often close and dramatic connection between the lack of drinkable water and the level of poverty in a country.
Water is not only essential for human health and quality of life, but also for the development of communities, for agriculture (farming and breeding), and industry.
Now at the turn of the century, the state of the earth’s water reserves is quite alarming: population growth, natural resource use and increased consumption have almost exhausted available water resources. The symptoms of this dramatic situation have unfortunately been underestimated for too long: water has been considered a free inexhaustible gift, and it has been wasted and used inefficiently. Water resources, even in countries with plenty of water, are endangered by pollution, overbuilding, increased consumption, irrational exploitation of resources, unsustainable economic growth and climatic changes.
Today, rivers risk becoming the symbol of the effects of man’s alteration of the environment: rivers are blockaded into resevoirs and forced into channels to create water supplies for agriculture, industry, public uses. Rivers are threatened by pollutants and by development along the banks and beds, and ravaged by the scarce and inefficient maintenance of river beds.
These alterations will inevitably have an effect on the natural balances of many rivers with many negative consequences for animals, plants and man, which all depend on them.
Solutions are not simple, but it is clear that increasing our effort to build dams, embankments and deviations on rivers is not the best way. However, there is an alternative: the sustainable management of fresh water resources. In other words: maximizing the rivers’ benefits and, at the same time, preserving the natural processes to guarantee the long term enjoyment and use of water resources.